NEODYM-SUSPENDED MULTI-PURPOSE SIDEBOARD FOR THE AIRSTREAM INTERSTATE

Every good project starts with an inspiration photo.  This cluttered and inefficient image from last summer was mine:

Dog be like, "Whut??"

That photo shows the laundry drying under the awning by being stuck to the side of the van with individual magnets.  And it shows a wilderness-built cooking table (which should be kept next to the fire pit) being used to hold what our little folding aluminum camp table is too small to accommodate.

You might wonder why, in an infinite sea of trees, I'd choose to stick laundry to the side of the van for drying.  Well, in that part of the world, rain showers come frequently and without warning.  It is simply more effective to stick it under the awning where I do not have to worry about it getting soaked unexpectedly.  

I decided I would build a sideboard to serve both of the identified needs - to provide more storage for pots, pans, drinks, condiments, etc. during meals, and to double as a drying rack for laundry.

There was no doubt in my mind about what material would comprise the sideboard - I used the same perforated aluminum out of which I'd constructed our under-cabinet suspended shelves, our Lagun table, and the ventilation cover on our lithium battery chamber.

Consistency is NOT the hobgoblin of little minds, thank you. 

Here's a photo tour of this project, including sourcing. 

That's the spec on the one-eighth aluminum, which I got in a 1' x 2' sheet from Online Metals. 

Given that this device was intended to hang on the exterior side of the van, there were a couple of unusual operational considerations.  

First, the sideboard had to be strong enough to support at least 10 pounds of stuff without either falling off or skidding down the side of the van under the weight.  To support the main mass, I used the same "skyhook" magnets as I had found to be effective for the awning screen surround that I designed a few years ago.  These are rubber-backed and, as long as you observe good neodym hygiene, your scratches should be minimal.  

By "hygiene" I mean, do NOT leave these things lying around.  They will pick up every speck of magnetize-able dust and every iron shaving that they can find within about a one-mile radius.  It's not really the magnet itself that has the potential to scratch your paint - it's what gets trapped between the magnet and the van.  They have to be kept very clean, which is a challenge given the power they exert on their surroundings.    

The pictured object is a Master Magnetics 7580 Magnetic Hook Organizer, which has a 65 pound pull force. The quote is from someone's hacked Wonka transcription. 

The hooks look like this in application - just a simple knotted loop to keep the suspension lines in place.

That's a brother from another mother in the reflection above the hook - an Amazon delivery Sprinter with its headlights on. 

Second, obviously I could not have a bare cut aluminum table edge bumping up against the side of the van - that would be a disaster for the paint.  The body contact had to be with a soft non-abrasive surface.  My husband and I first used a jigsaw to round the corners of this sheet (for visual consistency with the Lagun table) and then I edged in in Dritz 1" charcoal gray polyester belt webbing, which is the same treatment I had given to the Lagun top (belt webbing has about a million uses in a van).

Third, for similar scratch-prevention reasons, I could not allow any suspension hardware to touch the van, so it had to be inset.  The beauty of perforated aluminum is that it provides an infinite number of possible configurations without the need for drilling holes.

There's a close-up of the belt webbing which I bound into place with embroidery floss, and a Strapworks stainless steel D-ring with clip bolted behind it. 

I used one of those D-rings inset into each rounded corner.  In order to make for easy assembly, disassembly, and storage, I decided that the suspension lines needed to be detachable, so I used Strapworks' half-inch miniature bolt snaps at the four corners.  The tiny bolt snaps will remain connected to the lines at all times, whether in use or in storage. 

My suspension lines are made of orange paracord.  In the realm of artistic design, ordinarily one might not choose to combine orange with the garnet color of our rig's side stripe - those two don't necessarily go together.  But the orange design element was already present in the form of reflectors and the signal glasses on the van.  If you can't beat 'em, join 'em - I ran with safety orange in getting an CG Gear sand-free mat (I cut an 8' x 8' into two halves and re-edged the cut seams, also with belt webbing) and in using the paracord.  I also like the photo ops that this combo provides in cross-referencing camp fires.

Best orange ever.  Orange accessories would have made for a nice photo with this, if I'd had them at the time it was taken. 

Getting those lines the correct length took a long time and many careful iterations.  The van body is curved, plus in my driveway it was parked on a slope, so it was basically impossible to get it level in situ.

Nice try, but too many variables to be useful. 

I achieved level by hanging it on the side of my upright freezer and working on it there, given that the freezer was more conveniently plumb and level.

In order to keep the table from slipping fore and aft when it hangs on the side of the van, I used orthogonally-magnetized neodyms as "keepers" on the edge of the sideboard that fit into the van's lateral body groove.  By this I mean, the north and south poles of the magnets were oriented out the sides, not out the top and bottom face as they typically are.

See the little red and green cartoon at the upper right corner?  That's what I mean.
Image from KJ Magnetics.  

I needed two of those 2-hole countersunk block magnets to stabilize the edge that was up against the van body.  For better and for worse, each of those blocks has a 17-pound pull force (smaller ones were not available with sideways magnetization).  Trust me when I say that this table is not going anywhere.  I could probably drive at freeway speed with it in place, having 2 x 64-pound suspension hooks and 2 x 17-pound lateral stabilizing magnets on it!  

Here's what one of those countersunk blocks looks like in place.  Note that the edge of the table snugs into the Sprinter's body groove, as I mentioned above.  That allows the side-mounted neodym block to get close enough to grab the metal, but the majority of the force is exerted by the web-woven table edge, to minimize scratches.

Fun blog post for me, as these materials are so photogenic.

Here are a couple of money shots of the table in place.  

Dinner is not yet served, but it will be.  

Yeah, I can support all that weight, baby. Bring it!!

The sideboard is easy to reach from those "butt bucket" REI camp chairs (aka Flexlite chairs) that we typically carry lashed underneath our under-cabinet suspended shelves:

Yup, I can reach it easily.

When it's time to dry laundry, I simply raise this sideboard up and suspend it from the top of the van body.

Much better looking than having individual pieces of clothing strewn all over the side of the van.  More effective for drying, too. 

It was windy when that photo was taken; you can see the clothes being blown forward a bit.  I'm using well-rated folding travel hangers for this hanging purpose.  The points do not insert into the perforated aluminum holes, but they do catch in the edge of the holes, so in light winds, they won't blow off.

How often do you see 5 stars anywhere on Amazon?!

The sideboard's drying utility is not just limited to hanging.  Because the perforated aluminum is 40% open space, socks, gloves, etc. small items can be dried on top of it while the other items hang underneath.

When I raise the sideboard up high as shown above, the countersunk neodym side magnets will no longer touch the van's steel side body because the windows sit proud of the van.  I solved that issue by using a KJ Magnetics plastic-coated disc as follows, in order to keep the sideboard from swaying in the wind (the clothing could act as sails) and potentially scratching the windows:

The neodym black disc attracts to one of the two lateral magnets, which is enough to stop it from moving around. 

We used Slide-co spring-loaded mirror clips to mount this table for storage.  At long last, I have something to break up the monolithic appearance of the butt end of this galley cabinet.  I've always found that orange atrocity to be a visual distraction.  With its Lagun table big sister hanging nearby (the Lagun top stores on our wet bath door), the sideboard looks like it was intended to be in this space all along.  The space finally appears visually coherent and complete.

Close up:

Almost no other object could be stored in this space due to the sliding door clearance issue.  But this sideboard fits perfectly.

You'll notice that I detached the suspension lines and hung them a few inches right of this sideboard for storage.  The two neodym suspension hook magnets are right above them. 

Next will come the off-grid road testing of this new asset, but our big trip won't be for a few more months.  All of my current projects are in preparation for returning to this little piece of paradise:

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