LITHIUM BATTERY UPGRADE, PART 3: CHARGING / INVERTER SYSTEM

Following on Part 1 which described the general configuration of our DIY electrical system, and Part 2 which dealt with the AC system, here's the diagram for the charging and inverter portions of our system.  Relevant forum cross-references:  My husband's original electrical system development Air Forums thread here, and a Sprinter Forum lithium thread here.

As with my first two posts, I'll recap the general operation by describing the components individually.  The superscripted component numbers on this diagram correspond to the numbered paragraphs below it.

Click or tap image to expand size for clarity.  Blogger downsamples embedded images. 

13.  Engine alternator - For as long as we retained the original OEM single-AGM Lifeline house battery in our rig, we had no need to change or upgrade the alternator.  Shortly after converting to lithium iron phosphate (LiFePO4) battery (described below), we installed a Bosch 200 A alternator which, when used with a battery-to-battery charger (also described below), theoretically should be able to integrate seamlessly and charge the lithium battery when the van's engine is running.  However, as is often the case in cutting-edge conversions, there have been complexities, most notably the premature failure of the alternator's clutch pulley, which I describe in this post.  I will have more to say about alternator management in the future.

14.  Chassis battery - Nothing fancy here, just an ordinary EverStart truck battery from Walmart.  Chassis batteries don't last in the deep south, and with their climate-limited lifespans, I've never seen fit to buy anything more expensive.

Welcome to the red zone.  Diagram courtesy of Tiresplus and yes, I've always found it to be accurate.  Not changing a battery at 30 months here is to risk being stranded.  I often do it at 24 months. 

15.  Battery relay - The purpose of this device is to isolate the house system from the chassis system when the engine is not running.  This is a Mercedes Benz (MB) component that was already present in the vehicle as OEM equipment.  It had been used by Airstream to isolate the original lead-acid single house battery.  These types of relays are sometimes called battery isolation modules (BIMs).

16.  Battery-to-battery charger - This Sterling limits the load to 60 A and bumps the voltage up to 14.6, which is what the lithium battery prefers to charge at.  There is sometimes uncertainty about which of Sterling's products we've used (they don't seem to number their products very clearly), so here is a close-up photo:

17.  Lithium charger - This Progressive Dynamics Inteli-Power PD9100L Series unit accepts 120V AC and converts it to 14.6V DC with a maximum input current of 60A (again, 14.6V DC is the voltage at which the lithium battery charges most efficiently).  We installed this to retain the option of charging the lithium battery from a shore power source.  As we have learned again and again, it is essential that off-grid vans incorporate as much systemic redundancy as possible.  Something will fail - it's just a matter of what and when - so you better have a Plan B.  In our case, we also have Plans C and D, because our system allows 4-way charging - solar, alternator, generator, and shore. When we originally installed this charger, we never actually intended to connect to shore power - it was just there for emergencies.  But, heh heh, we've done it, especially following the alternator clutch pulley failure described above.

18.  Solar Panels - Our Grape Solar GS-S-100-TS 100 watt monocrystalline panels are wonderful, and I'm very glad we managed to get them before supplies were exhausted.  They are no longer manufactured in the size (aspect ratio) that was ideal for installation on our roof.

They straddled our OEM stainless steel roof rack like they were made for it.

These monocrystalline panels were also noteworthy in the high efficiency that they offered (18.3%).  Knowing that they would be discontinued, we bought two extras and put them in storage for potential future use.

19.  Switches - The Blue Sea manual battery switches were inserted so that we would have the option to disable charging on PV1 or PV2 circuits on the BMS described below.  We like Blue Sea products, which are ruggedly made for marine applications and are good quality.

20.  Battery Management System (BMS) - This is an Electrodacus SBMS-100, currently out of production but its builder still offers comparable models.  This particular BMS was chosen because we were able to run every load except the inverter through it, a configuration which allows the BMS to disconnect the DC loads when the battery is in a low state of charge (SOC).  In other words, it would cut power to the whole DC circuit array (distribution) once the SOC fell to a predetermined level, or when an individual battery cell voltage becomes critically low to the point where battery damage could occur (lithium batteries are expensive and they cannot be discharged all the way down to 0%).  This load-shedding does not disconnect any of the charging circuits, so the SOC can be recovered while the system is in low-charge shut-down mode.  Some other commercially-available BMSs disconnect both charging and discharging when the SOC falls to unacceptable levels, triggering a greater demand for human interface.  The Electrodacus is programmed to protect the battery from both overcharging and undercharging conditions.  There is no need for manual re-set buttons to remedy these conditions.

There are two charging inputs on the Electrodacus:

• PV1 which accepts current from the alternator, shore power, and the propane generator
• PV2 which accepts current from the 3 x 100 watt solar panel array 

Each of these routes charging current to the lithium battery (described below).  PV1 and PV2 are configured so that all inputs can be handled simultaneously; the BMS can safely handle up to approximately 100 amperes total input (hence the "100" in its model name).  In other words, solar charging can (and does) continue while alternator charging is also occurring, and/or shore power, and/or generator charging (!).  However, in practice, it is typically not necessary to stack charging sources.

21.  Lithium battery - Three GBS 12V (4-Cell) 100Ah LiFeMnPO4 cells were used deconstructed and reconfigured into a 300 AH battery.  The cells were rearranged to fit available space under our closet floor.  Here's a pic of how that was done:

22.  Electrical inverter - Xantrex Freedom Xi 2000 watt Pure Sine Wave Inverter was chosen for two reasons.  First, this model doesn't have a charger, and it was important that we separate our charging and discharging circuits for better battery management.  Secondly, this model had a built-in automatic transfer switch (ATS) which saved space in our tight build area.  Thirdly, the device's form factor meant that it could be positioned conveniently in an available space between the top of the lithium battery and the underside of the closet floor.  This inverter, when coupled with an EasyStart (described in Part 2), also allows us to run our 11,000 BTU Dometic roof air conditioner using the lithium battery alone for up to approximately 2.5 hours at a time (i.e., with neither generator nor shore power) before battery recharge is required.

23.  Positive busbar - The positive busbar allows the connection of multiple high-amperage wires to a single device with multiple terminals.  Without this device, the wires would instead need to be crimped in a way that did not reflect optimal design.

24.  Remote battery switch - This is a Blue Sea ML-RBS switch that isolates the inverter for safety reasons.  A short circuit developing in the inverter or in the high-amperage cables feeding it could cause a fire in the van.   This switch is connected to a pair of manual buttons on the control panel.  When we are done using the inverter, we isolate it by punching the "off" button and creating an open circuit at this point in the system.

Do you see those red and green punch buttons in the center of this control panel?  That's the remote battery switch.

25.  Shunt - The shunt is a 50 milliohm resistor.  The BMS reads the voltage drop across this resistor to calculate how much current is being used by the inverter.  All other loads go through the BMS itself, so it already "knows" how much current is being consumed for the other van circuits.  However, the external load from the inverter does not go through the BMS, so this device is needed.

26.  Negative busbar - This is where the chassis is tied to the negative terminal and return legs of all the major loads.  The negative busbar is tied to the chassis in a location behind the black water tank, under the cabinetry.

27.  Chassis ground - My husband describes the chassis ground as "the pool of electrons for all circuits".  The alternator, chassis battery, house battery, and all loads directly or indirectly connect to a common ground.  A ground is the means by which electricity is able to complete its journey and get back to the current source.

For those of you who are still on the steepest portion of the electrical learning curve (as I am), I highly recommend this webinar which has been reproduced as an unlisted YouTube video below, especially for understanding issues of grounding (earthing) and electrocution generally (HT this Sprinter Forum thread).  The video describes on-water mobile scenarios (boats), but similar principles hold true with on-land mobile vehicles (vans and RVs).  The person who presents the information is a parent who lost a young child to electrocution.  He was not a technician, but rather learned electrical engineering after his personal tragedy.  He uses clear lay language to describe complex constructs as a result.

The direct link below has the video continuing from around the 1 hour 13 minute mark, where the presenter is talking about electricity getting back to its source.  But IMHO, the entire video is worth your time, so I've embedded the full video below the timed link.  There are a lot of valuable lessons in it.

https://www.youtube.com/watch?time_continue=4396&v=O7-s_mdEPb0

LITHIUM LOAD TESTING A 200 A BOSCH ALTERNATOR

This blog post is a placeholder containing two video clips of our 200 A Bosch alternator.  We took these as we were trying to ascertain why our previous alternator's clutch pulley failed at 17 months of age (original blog post here; Sprinter Forum discussion commences at post #110 on this page here).  Was it caused by the dynamics of the lithium charging?  Or was it an unrelated failure?

It's very difficult to tell.  These two tests do not represent actual vehicle operating conditions, which would include high engine RPMs, cab a/c cranking and placing its own load on the alternator, other vehicle systems engaged, road roughness contributing to vibrations, etc. 

The results are utterly inconclusive.  There is evidence of pitch changes when the lithium charging loads are applied and removed, but no obvious thrashing of the belts, or visible vibrations, or anything like that. 

I'll have more on what we plan to do about this failure in future posts, but in the meantime, here are the views from below and above.

PSA: ALTERNATOR CLUTCH PULLEY FAILURES ON LITHIUM SYSTEMS

I put this information on Instagram (@interstate.blog), but not everyone is on IG, so here is a regurg, starting with what I posted, upon which I will then expound in this blog post, because this is super-important.  For you guys who have a lithium system charged by a single engine alternator (plus or minus other charging options such as generator, shore power, or solar), if your alternator behaves as mine did, the outcome could be life-threatening.  DO NOT ASSUME THAT YOU ARE SAFE FROM THIS TYPE OF FAILURE IF YOU HAD A PROFESSIONAL INSTALL YOUR LITHIUM SYSTEM. 

My IG tile. 

Text: 

Our 17-month-old 200 A Bosch alternator began failing last month when I was on the road between Houston and Nova Scotia. This was a particularly pernicious problem because my first sign of trouble had nothing to do with our camper van’s lithium system - instead what happened is that I started losing the chassis electrical system, which would have developed into a middle-of-the-freeway potentially catastrophic breakdown if I hadn’t caught it in time. There’s a #vanlife myth floating around out there that if you have a Sterling battery-to-battery charger in your system, it will protect against engine alternator damage. This is not true - it will protect against SOME types of alternator damage, but it will NOT prevent your alternator’s clutch from wearing out grossly prematurely, which is what happened to ours (we had it diagnosed by a repair shop today; I estimate that this alternator did perhaps 20 hours of heavy-load lithium recharging spread across the 17 short months of its life before failing). Those of you who have single-alternator lithium rigs might be sitting ducks if you haven’t hardened your electrical system against this kind of weak-link-in-the-chain breakdown scenario. See vids by YouTuber Alternatorman for more detail on alternator clutches. Thanks once again to @million_mile_sprinter for helping me out last month.

OK, now the expound.  When I said "I started losing the chassis electrical system", what I meant was that I began noticing that I could no longer crank my air conditioner fan up to its highest setting.  I was driving through Mississippi in August - trust me, under those conditions, it's noticeable if the a/c starts to wane.  I literally had a panic attack when I realized that there's basically only one thing that could bring about that result - a failed or failing alternator.  I opened up the OBD Fusion app on my iPhone which bluetooths to a reader that we have permanently mounted in the van's OBD socket.  Sure enough, the chassis battery was reading 12.8 V, which is way below what it should have been.  The alternator was not charging the chassis battery.  The van was about to stop dead in the middle of IH-59 between Hattiesburg and Meridian (i.e., middle of nowhere). 

I pulled off the road and sprang to the back of the van to look at the lithium charging status.  I had done my usual thing that day by driving from Houston to Laf Louisiana, stopping for lunch, and running our roof air conditioner off our 300 AH lithium battery for about an hour while I took a nap.  I then got back on the road with the alternator engaged to bring the lithium battery back up to full charge (a heavy-load scenario for the alternator because I'd run it down to about 50% state of charge (SOC)).

Cue additional horror when I got to the back of the van, which is where our electrical control system is located:  my lithium was reading about 90%, which means that the alternator had been, and perhaps still was, charging the house battery at the expense of the chassis battery.  That should never, ever, EVER happen, and I didn't understand how it was even physically possible given the way we had configured our system. 

Immediately I de-loaded the alternator by isolating the lithium charging circuit.  (Yes, we'd had the foresight to install a kill switch for that when we DIY'd our electrical system). 

I then got back on the road, praying that whatever was remaining of the alternator functionality could then put its full contribution into the chassis battery, which was dangerously low at that point.  I had planned to stop for the night in Toomsuba MS, but I kept driving straight through to Tuscaloosa AL to give the battery time to recover.  That's a 615 mile run on the day, more than I prefer to do when driving solo, but it was necessary.

I got to Tuscaloosa (excellent boondocking Cracker Barrel there BTW), pulled out my voltmeter and measured the chassis battery directly, terminal to terminal (we don't rely on the OBD exclusively because it seems to not have foolproof accuracy; story omitted for brevity).  It was reading not ideal but reasonable.  I knew I'd have enough juice to get the van running properly in the morning. 

No more deep lithium discharges from that point forward.  No more alternator charging, period.  I was in a rare pocket of cooler summer air (a cool front had passed through) such that I could live without a/c, and rather than bailing on the trip and returning to Houston, I continued heading north, hoping to intercept Joel Sell (Million Mile Sprinter) in Philadelphia.  I had my husband (who was still back in Houston) make contact with him to see if he could replace the alternator while I was en route, and he said yes.  A Philly detour would add only an hour or two to my total route.

Here's the maddening part:  Through no fault of his own, Joel couldn't determine conclusively on the spot what was wrong with the alternator.  Of course he could take it off site and get it diagnosed, but that takes time.  I arrived at his place around 2 p.m. on a Friday afternoon and I didn't necessarily want to hang around until Monday morning.  So we made the decision to just go ahead and replace the existing alternator, which clearly had something wrong with it, so that I could get back on the road.

The replacement deed in progress.

As for what was wrong with the alternator, that would have to be determined later.  Joel and I did some preliminary testing just so that my engineer husband could have data to noodle on.  It looked like this:

Tap to expand for clarity.  If you are a less-technical person, know that higher voltages indicate a better-performing alternator. 

I continued to Nova Scotia without further incident, carrying the half-dead alternator with me.  A 200 A alternator is big and heavy and a pain to tote around in a small van.  After I off-loaded my meal-encapsulating solid ice blocks at my father's place, I used our hitch-mounted Yeti to carry it.

These were my 2018 ice blocks, 35 pounds apiece with vacuum-packed home cooking embedded in them.  Many good meals were had by at least seven adults courtesy of these, which I prepared in Houston and took with me. 

Five weeks after I set out, my husband and I returned to Houston, never having resumed alternator charging.  We had the old alternator diagnosed yesterday.  The clutch was worn out and was slipping under high-load usage scenarios.  It's being repaired as I speak, and I'll follow up with a separate blog post on that process.  And BTW, who even knew that alternators have clutches?!?!  They did not used to have this failure-prone add-on.  I'll also discuss that subsequently. 

First moral of this story:  NO MORE SINGLE ALTERNATOR OFF-GRIDDING.  We are going to reconfig our van for a second isolated alternator which will be dedicated to just the house lithium battery.  That way, even if we have another such failure, it won't kill the chassis battery and disable the Sprinter's native electrical system to boot. More on that later.

Second moral of this story:  This whole failure episode of mine is exactly why off-grid vans need as many redundant systems as they can support within their space limitations.  Many have asked why we'd go to all the trouble and expense to put solar on the roof when the alternator is going to outperform solar's recharging ability by a factor of somewhere between 3 to 4.  The answer is that STUFF BREAKS.  Sometimes it breaks in ways that nobody can predict.  Never before this had I heard about alternator clutches failing, and I've been following all of the vanning and off-gridding forums for four years now!!  Neither had my husband ever heard of this phenomenon, and he had done months of research on mobile lithium systems.

My boondocking property in Canada, where there was no crimp in our style.  We completed a 5-week off-grid trip even with this limitation of not being able to use our new alternator, because our solar alone took care of our lithium battery.  We had to be careful with our usage, because my property is surrounded by these high trees, limiting sun exposure.  But we spent 2 of our 5 weeks here without any recharging problems, running on solar alone. 

I'll close this post with this 3-minute video that describes alternator clutches.  Read it and weep.  Watch it and weep.  The manufacturers took a pretty good device (alternators have been around for a long, long time) and screwed it up by adding this failure-prone clutch part.  More on that later, too.

Link:  https://www.youtube.com/watch?v=QUs4Y5ZMiTU

Embed:

LITHIUM BATTERY UPGRADE, PART 2: AC SYSTEM

I will write these next three posts using the plainest language that I can muster.  My purpose here is to introduce readers to the components of our lithium system, and to how they work together, in a manner that non-technical people can understand.  Most people who want lithium battery systems in their RV or van are not engineers.  They don't necessarily need to learn enough to become system designers, but they should learn the principles behind the systems.  After all, lives are depending on proper system design.

^^ What HE said.
This quote is attributed to him.  The actual owner is uncertain.

If you really want to understand any van or RV electrical system, the best way to go about it is to break it down into the smallest possible pieces, and learn each one.

Dr. Feynman sorta took the original Einstein-attributed construct and, well, he Feynman-ized it.  

It's important to note, however, that there are no freebies with this process.  If you don't have a background in electrical design but you really want to learn a few things about this stuff anyway, be prepared to study hard.  It's time-consuming because it's not enough to simply gaze at this information passively.  You have to manipulate it in your head and visualize yourself applying it, or at least watching it in action.  You'll have to walk yourself through our design diagrams (I stop short of calling them schematics) repeatedly in order to solidify your understanding of this kind of system. 

As is genius, so is learning generally.  Especially when it comes to challenging content like this. 

The first thing we need to do is review the meanings of some words that are used to describe electrical systems.  This is not necessarily the best place to ask "Why?"  These are definitions that just need to be accepted as-is.  I'll try to minimize the extent to which these are needed, but they may come in handy before this post series is through. 

The plumbing analogy can be helpful because electricity cannot generally be "seen" but at the same time, it needs to be visualized.  People are generally familiar with how water moves through pipes or hoses, so this serves as a comparison of sorts.  

Three of those units in that table above relate to each other in a very specific defined way, as this diagram shows:  

The common instruction is to cover the third of the triangle that you are intending to derive, and then either multiply or divide based on the spatial relationship of the other two thirds.  

When describing the flow of electricity through a wire or certain devices, this handy diagram is often invoked:

Now that the internet has barfed up this wealth of handy electrical references, here's our basic simplified AC diagram below.

Tap or click to expand for clarity.
Blogger downsamples embedded images.

I'll generally describe each of the diagram's numerically-superscripted components in terms of:

(a) what the component is (with links, or, where specific models have been discontinued, I linked to the closest-available substitute), 

(b) how it gets the electricity that it receives, 

(c) what it does with that electricity, and 

(d) why. 

I've also set up this narrative to follow the general electrical flow from points of origin to the points where it is expended by doing work in a specific way.  Remember - if this material is unfamiliar to you, then it might help to return repeatedly to the analogy of water flowing through an interconnected series of devices and pipes. 

1.  Shore Power – Our van was wired by Airstream to receive 30 amp AC electrical service (larger RVs with more extensive electrical loads are usually designed around 50 amp service).  This is the electrical supply that is commonly referred to in the vernacular as “shore power”, a phrase borrowed from the boating industry.  It is obtained by connecting a heavy power cord from an electrical outlet (often mounted on a low pedestal in campgrounds) to the plug-in connector on the outside of the rig.

2.  Surge Suppressor - Some shore power sources supply voltage that is not held steady at 120V, which is normal household supply.  Voltage spikes and brown-outs can occur due to electrical storms, overloaded campgrounds, and problems with the grid where the electricity is originating. Allowing electrical fluctuations into a van or RV can cause serious damage to the internal components and appliances.  We installed an integrated surge suppressor (Surge Guard Model 34520) to protect against these events.  This device is mounted on an interior wall under the street-side rear couch.

3.  Generator - Our Airstream Interstate camper van was delivered with an Onan Microlite 2800 series propane generator installed.  Much like shore power, this device supplies 120V AC when it is running.  We were not the first owners of this vehicle, and we didn’t choose to have this generator.  We would not have ordered it given the limited ways in which it can be used - it is too noisy, plus our van's propane tank is not large enough to run it for long periods.  But given that it was functioning well and had low run-time hours on it, we decided to keep it as an active component of the electrical system for now.

4. Automatic Transfer Switch (ATS) – This device (a Parallax ATS301 switch) contains a toggle style of mechanical component called a relay that makes the choice to accept AC from either the generator or shore power, with priority given to the generator.  If an ATS were not present, then accidentally connecting shore power and turning on the generator at the same time would result in the combining  of two out-of-phase AC voltages. Each independent source would contribute 120V and, depending on how they alternated, they could double up to create a 240V difference between the shore source and the generator, and damage to the system would occur from the resulting rush of current.

Components 5 and 6 are first discussed separately and then in terms of how they share the incoming AC from the switch-selected source (either the generator or shore power).

5.  Lithium Charger – This Progressive Dynamics Inteli-Power PD9100L Series unit accepts 120V AC and converts it to 14.6V DC with a maximum output current of 60A (14.6V DC is the voltage at which the lithium battery charges most efficiently).  This process will be discussed in the future Charging / Inverter System blog post.

6.  Inverter – The model we chose is the Xantrex Freedom Xi 2000W unit.  An inverter is an device that changes direct current (DC) to alternating current (AC) – in other words, it does the opposite of what an electrical converter or charger does.  That being the case, you would be justified in your curiosity if you wondered why a source that was supplying AC to start with (shore or generator) would need to be routed through an inverter before it could ultimately be sent on to do its job in powering certain downstream AC appliances.  The answer is that the inverter is essentially serving as a “pass-through” device in this scenario.  It contains its own embedded ATS that chooses between issuing AC from one of those two upstream external supplies, versus issuing AC from its own self, via inversion from battery supply.  Priority is obviously given to the external supply, because it would make no sense to invert power from the battery if shore or generator current is available. If the Inverter didn’t have an internal ATS built in, an external transfer switch would be needed to safely connect it to the AC supply system.

If you look at Diagram 2 of 4 above, you can see a bifurcation issuing from component 4, the ATS.  So how does the incoming current “know” to split itself between the Lithium Charger and the Inverter? As they are wired in parallel, they both get equal priority, similar to multiple electrical outlets on the same circuit in your home.  In our van scenario, there is a maximum of 30A available on the circuit to be shared by the two appliances.  In a scenario in which the Lithium Charger draws 9A AC (the maximum it can accept) to convert to 60A DC for battery charging purposes, a remainder of 21A is then available to feed through the Inverter to the appliance(s) that are activated.  In some scenarios, charging may need to be disabled in order for higher-consuming appliances to be run.  More detail on this process will be given in the post that discusses the Charging / Inverter System.

7.  Circuit Breakers – The 30A and 20A circuit breakers act as safety mechanisms that prevent excess current from accidentally routing to any of the appliances that are either hard-wired or plugged into the AC outlets.  Most appliances have their own internal circuit protection, so the circuit breakers are primarily designed to protect the wiring from shorts and overheating.  As described above, the Inverter passes through shore power which feeds into the 30A circuit breaker first.  That limits maximum downstream loads on all circuits to a total of 30A (if more is added, the breaker will trip).  From the 30A breaker, the current proceeds to three 20A circuit breakers across which the appliance loads are distributed.

A ground fault circuit interrupt (GFCI) is a device that shuts off an electric power circuit when it detects that current is flowing along an unintended path, such as through water or a person to ground.  Some RV configurations, including our Airstream Interstate, had electrical systems designed to include GFCI-enabled circuit breakers, if those breakers delivered electricity to AC outlets in potentially wet areas.  In certain circumstances, an electrical inverter could interfere with the operation of GFCI breakers because of issues involving the configuration of ground and neutral wires (some technical detail is omitted here for brevity; this Xantrex Technical Note (PDF) provides discussion).  In lieu of maintaining the original GFCI breakers, we opted for individual GFCI outlets as described below.

8. AC Outlets – Our rig contains five AC outlets that were wired by Airstream (galley kitchen, bottom of the street-side overhead cabinet, refrigerator alcove, microwave cabinet, and curbside exterior van body).  When AC is being supplied, these work like regular household electrical outlets, with the caveat being that they are collectively limited to a maximum of 30A, as that limitation is imposed by the 30A circuit breaker.  If GFCI circuit breakers are not being used for the reason described above, GFCI outlets are advised.

Like this one, which we added above our galley kitchen. 

9.  Priority Switch – An Intellitec automatic energy select switch is installed because the available current is insufficient to run both the roof A/C and the microwave oven simultaneously.  The roof A/C (described below) requires approximately 13A to run, and the microwave needs 8.3A.  Both appliances also require start-up surges of greater current, so their total instantaneous demand can be far in excess of the 21.3A that results from simply adding their continuous current values.  Out of necessity, it is an either-or scenario when it comes to running them.  If we need to run our microwave, we switch off our roof A/C momentarily (the microwave and the A/C share a single 20A circuit breaker). 

10. Microwave – Our van came with a Dometic CDMW07 (PDF) series microwave oven which nominally requires 1,000W of power to operate (8.3A).  Some people question why anyone would need a microwave in an off-grid van, and our answer is because it reduces propane consumption by the hot water heater, saves fresh water, and conserves gray water tank space, all because of the extra dishes that we don’t have to wash (throw some tamales on a paper plate and pop them in that microwave and voila – no clean-up).

11. Roof A/C – A Dometic DuoTherm 11,000 BTU coach A/C unit (no longer manufactured) was installed by Airstream in our van’s roof.  The manufacturer represents that this A/C requires 13A of current to operate (3.5A for the fan and 9.5A for the compressor).

12.  Soft Starter – We installed an electronic device called a MicroAir EasyStart 364 into the body of the Dometic roof A/C for the purposes of modulating the amperage demands that are imposed on our electrical system.  Without a device of this type, starting the high-demand A/C would overwhelm the Inverter, exceeding what it is able to supply while it is drawing from the lithium battery, and shutting down the operation of the A/C as a result.  The Inverter is capable of providing power up to 2,000W (16.7A) continuously and up to 3,000W (25A) briefly, but the A/C start-up demands a surge that is greater and for a longer duration than the Inverter can accommodate.  The soft starter contains electronic components that essentially start the A/C compressor motor more slowly to prevent this kind of shut-down.  With the soft starter integrated into the system, our lithium battery can power our roof A/C for about 2 hours before becoming overly depleted. 

If you have questions on this section, please contact me via interstate.blog at gmail.

I had to have at least one dumb meme in here...

LITHIUM BATTERY UPGRADE, PART 1: GENERAL OVERVIEW

Over the next four posts, I'm going to present consolidated details regarding the DIY lithium battery system that we installed in our 2007 Airstream Interstate Class B van.  I've previously touched on some of the peripheral details in previous posts including the following:

(1) This post described some of the required lower cabinetry modification, and
(2) This post described upper cabinetry expansion, which was done in part to accommodate the new electrical control panel.

I've also interspersed anecdotal progress reports through various trip descriptions, but I've never pulled together any comprehensive description of the entire system in terms of either its components or its operation.

There's a reason for that - it's an enormous job to describe an incredibly intricate, one-of-a-kind long-term project.  As of this blog post, the chatter on the project's corresponding Air Forums thread, which my husband named "My Interstate Lithium Battery Adventures" stretches from its inception in June of 2016 though November of 2017 and includes over 450 comments, LOL.

The enormity of the job raises questions in the minds of people who are less familiar with lithium systems, mainly, why even do it?  Why go to all this kind of trouble and expense in the first place?

Route map from my September 2047 blog post titled "Top ten lessons from an off-grid month on the road".  We didn't hook up to campground utilities during any of that time because we no longer have a need. 

^^ That's why.  Because conventional RVs and camper vans were not designed with a "go anywhere" mentality.  They have limited battery capacity and their design assumes that the owners will be staying in full-service campgrounds every night during their travels.  That is an out-moded assumption that doesn't fit our chosen lifestyle and in our view, it rather negates the whole purpose of having a camper van in the first place.  An upgrade to a lithium-based electrical system can make pretty much every off-grid difficulty disappear, as it has in our case.

Anyway, first, a few necessary disclaimers.  Our general disclaimer applies - if you work on your van or RV without knowing what you are doing, you could get yourself killed -- and that is especially true when working with a dangerous commodity such as lithium battery cells, which can cause electrical fires if not managed safely.

In terms of a more specific disclaimer, if you imagine that this blog post series will teach you how to engineer a lithium battery system, here's what I have to say to that:

In other words, a big fat NO. 
Don't even think about it.

This series is for general information only, in order to give you a qualitative feel for how such a system can be designed and implemented in the context of a van.  There are approximately one million technical details that will not be included in this write-up for reasons of sheer practicality - if I tried to describe every wire and connector specification, for instance, I'd be sitting here writing for the next six years.

Rather, my point is to tell you how we did it, moreso than the nitty gritty of what we did.  Vans are tricky - the amount of space available for any given upgrade is extremely limited.  I can't tell you how many times I've seen an aftermarket lithium job presented on social media only to think to myself  "Congratulations owners - you now have extended boondocking capability courtesy of the lithium system which, by the way, happens to have consumed every cubic inch of space that you otherwise would have had for storing your boondocking supplies, duh."

But of course there's a good reason why even the best aftermarket installers tend to gobble up available storage space indiscriminately - it happens because the alternative is to have the labor costs mushroom out of control.  Every electrical component that has to be custom-fit to a van crevice here or there is going to require re-wiring, extra cabinetry work, etc.  So the installers tend to take the path of least resistance, which then causes secondary logistical problems for van owners.

My husband and I got around that problem by taking our time and meticulously splicing every electrical component into its own hand-picked individual void space, all of which were existing and not otherwise earmarked for other purposes.  We probably expended at least five times the average installation labor in the process.  But hey, it's DIY, so the only thing we spent was time, and it's a hobby, so we don't consider that to be a loss.

This first of the four posts presents the consolidated general lay-out that we achieved.  The three posts that will follow (and I'll back-link them here after publication) will break down the process to describe the construction of the AC System, the Charging/Inverter System, and the DC System respectively.

First, a brief review of where we started oh-so long ago.

Gross.

 That image above shows a view looking down into the van's closet beneath its raised floor, which was removed for the photo.  The area essentially began its life as a dog's breakfast of tangled wires and water lines as they were installed by Airstream - ugh, nothing creeps me out quite like mixing live electrical wires and questionably-constructed water lines in close proximity in a confined space.

Despite the obvious mess, this area proved to be a gold mine of recoverable space, because we realized that the two bulkiest components of a lithium system (the cells themselves and the electrical inverter) could be made to fit here without triggering exterior cabinetry modifications.  The battery cells could be regrouped and re-strapped into an assemblage that would conform to this shape, and the inverter plus certain associated components could be installed on a shelf suspended immediately above the lithium cells.

Furthermore, because we were working under a closet and adjacent to the street-side overhead cabinetry bulkhead, we realized that we could run all wires under the couch, to the top of the closet, and through to the bulkhead beside the closet without needing to add any external cabinetry elements.  The spaces were contiguous in other words.

Here is what the resulting lay-out looked like, after hundreds of hours of research and work:

Tap to expand for clarity, as Blogger still downsamples embedded images.
Diagram updated 20180207.

For those of you reading this on small devices, here is an enlargement of just the lower left portion which shows the general view inside the cabinetry and below the couch:

Tap image to expand for clarity.
Diagram updated 20180207.

Now that you've put eyeballs on this much, and have hopefully gotten a general feel for the components and the lay-out, the wiring diagrams to follow in the next series of posts should begin to make sense conceptually.  Stay tuned, because some of the corresponding narrative is complex, and it is taking me quite a bit of time to translate it into layman's terms, even if I am cutting necessary corners for brevity.

LITHIUM BATTERY CABINET MOD ON AN AIRSTREAM INTERSTATE

Inch by inch, life's a cinch.  Yard by yard, life is hard.

There are numerous versions of that quote floating around out there, and we may never know who coined the original phrase. Given that Ms. Giffords is married to an astronaut and lived a few miles from us, and given that my husband works as a Flight Controller for the International Space Station, I thought I'd use this one.  

"Inch by inch" is my best piece of advice where DIY is concerned, and I'm going to give an example of what I mean with this blog post.  It's fairly unlikely that there's another person out there who will need to do this exact mod to their Airstream Interstate, but that's not the point.  The point is to illustrate the general headspace associated with tackling modifications when you possess no formal skill in the area of issue, which is the case with me when it comes to woodworking and metalworking.  I hear from people who express reservations about their own ability to tackle DIY jobs and van modifications.  A lot of that can be overcome by simply taking things one small step at a time.

Let me start from the very beginning and proceed incrementally with successive photos to show you what I mean.

Originally, the space under our coach's closet contained this conventional electrical converter and a bunch of miscellaneous electrical and water lines kinda tossed back behind it.  You can see that there's a mounting panel cut out of cabinetry material, to which this converter was attached.  

This is what that mounting panel looked like when removed from the Interstate.  It's a piece of OEM cabinetry material, but it was cut very crudely by Airstream.  You can see that the cut lines are jagged and the right side leg is a conspicuously different width than the left side leg.  Despite these limitations, I had to find a way to re-adapt this piece during our lithium battery upgrade project (blog posts on the technical aspects of that project itself are still to be published).  I had to re-use this piece because we did not have access to any more of this cabinetry material. 

This is what the lithium install looked like with the closet door removed, closet floor removed, and that front mounting panel also removed.  You can see the shallow tray on top of the batteries, a frame painted white, but the new electrical inverter had not been installed in that spot when this photo was taken.  Nevertheless, you get the general idea of this lay-out.  

This was my temporary protective cover for that under-closet lithium chamber - it's simply a piece of black coroplast (plastic cardboard) with some mosquito screen covering two ventilation cut-outs, with the mosquito screen being held on the back side using duct tape.  The coroplast piece was then screwed into the mounting frame using the same screws and holes that had held the original electrical converter. But that wouldn't do as a long term solution.  It was strictly a stop-gap measure. 

I knew that the final modified panel had to include a kick plate on the bottom.  In the tiny space of the Interstate, stuff gets bumped, kicked, and generally smacked around - it happens.  I didn't want anything to accidentally punch itself through that opening and impact the lithium batteries or other electric components.  We have a miter saw and I've gotten reasonably good at making precise wood cuts using it.  So I cut a strip of half-inch furniture-grade plywood to be added across the bottom.  The plywood was left over from my custom closet shelf project.  

You might observe that it's a very thin kick plate that I added above - possibly not very strong.  But knowing that the original converter opening had been crudely cut by Airstream, I knew I'd have to make an overlay for the ventilation opening.  There was no way to re-cut that panel to make it visually presentable, especially given that one leg was wider than the other.  So I began to measure for a quarter-inch furniture-grade plywood overlay to hold the ventilation screen.  Together with the half-inch strip at the bottom, it would be strong enough when all attached together.  

At that point I needed to size the opening.  I wanted as large an opening as possible for maximum ventilation, but I had to account for the irregularity of the underlying cabinetry mounting piece.  I settled on this size as represented by the blue construction paper, and my husband and I worked together to cut the opening.  Basically, he used a jig saw freehand, with me standing on the workbench, standing on top of this piece of plywood to hold it steady as he cut (we don't own a lot of sophisticated woodworking tools).  

OK, so now I'm one more inch further along in this process, with the overlay cut.  Next I painted it and the underlying strip using a Sherwin Williams oil-based enamel color formulation that matched our Interstate's counter tops.  

Once the paint had dried, I needed to determine how large to order the perforated aluminum sheet, which was by far the most expensive part of this process (about $37 with tax, shipping, and handling).  For that reason, I wanted it to be as large as the opening would tolerate, knowing that we might do further mods down the road and maybe I'd want to re-purpose that piece on a different future cabinetry mod.  So here you see the overlay opening in blue, and the aluminum plate sizing in pink.  Given that we are not professionals, we always create project mock-ups out of cardboard and/or construction paper.  It's a practice that tends to eliminate both accidents and unforeseeable sizing mistakes, no matter what we are working on.  

I ordered the piece from Online Metals, which also supplied the same perforated aluminum sheet for my custom computer table and my under-cabinet shelving projects.  They have given me really good service.   

After the aluminum piece arrived, the next task was to attach it to the gray painted overlay.  This was more challenging than you might first assume, because I was using the existing perforations rather than drilling holes electively in locations of my choice.  As such, I had to drill the small bolt holes partially blindly from the back side.  You can see that I'm a couple of millimeters off being completely centered with those bolts.  As my husband would say, "If you could achieve better than that on a first try, then you wouldn't be called a DIYer.  You'd be called a professional instead and you'd be getting paid accordingly."  

I had originally planned to add a second quad of small bolts to hold the overlay to the original cabinetry mounting piece.  But once I realized that my first four bolts were slightly off center, I didn't want to add any more because it would visually amplify the imperfection.  For that reason, I decided to attach the overlay to the original cabinetry piece using 3M exterior grade double-sided tape, one of the few applications in which I would agree to use that product (adhesive products generally don't stand up well here in the Deep South).

However - next inch please - using the 3M tape caused a domino effect in that the overlay was now standing a bit proud of the cabinetry mounting piece.  Which means that my strapping for the bottom reinforcement strip was no longer flush.  So I added a spacer washer on either side in order to close the gap between the kick plate strip and the small mending plates I was using to attach it to the cabinetry mounting piece, as you can see above.  

In order to create a good seal along the bottom of this workpiece, I had to add something flexible and compressible to exclude dirt or spilled materials from potentially penetrating the bottom edge and entering the lithium chamber.  This is what I chose.  

And here you see it applied to the bottom edge. 

My husband wants to be able to pull off key cabinetry pieces quickly without having to mess with screw drivers and hardware.  For that reason, we've used neodymium magnets to attach certain structural pieces, rather than fixed screws.  Several of them were attached to the back of this workpiece to hold it in place against the cabinetry frame below the closet.  

This and the jig-saw cut to the overlay were the only parts of this project that my husband assisted with - I could have done the entire job without him, but two heads are better than one, and he decided that he wanted to counter-sink screws into the steel washers that would go on cabinetry frame, to which the neodymium magnets would attach.

"You don't have to make every last thing fancy," I noted to him as he was purchasing the counter-sink drill bit needed to do this.

"What's the point of doing any project if you're not learning at least one new thing in the process?" he asked.

I replied (paraphrased), "I've got four additional projects stacked up on the heels of this one.  I'd never get them all done if I don't simplify and choose a path of least resistance at times." 

Here's the counter-sunk screw sitting in its metal washer, stuck to the neodymium magnet in the workpiece.  

And this is what it looks like from above, peering down into the small gap created as the new front panel stands a bit proud of the existing cabinetry frame.  That small gap allows one's fingers to pry the piece off the cabinetry - in other words, we designed it this way intentionally.  Those neodymium magnets are very strong, and leverage is required to dislodge them.

The mat you see lining the closet floor is an IKEA Oplev which I cut to the shape of the closet.  Its purpose is to trap grit and dirt that falls off my folding bicycle which I store here.  I don't want that dirt making its way down into the lithium chamber.  

And after proceeding through this little project all those incremental inches one at a time, here's the final result.

I think it looks pretty good.  It does a good job of resurrecting a badly-cut cabinetry piece while meeting the ventilation and chamber protection goals.  

This project represents one more small step in the life of a couple of van DIYers.