REPLACING THE ELECTRICAL CONVERTER IN AN AIRSTREAM INTERSTATE

I mentioned in this post that we noticed a few things wrong with our 2007 Airstream Interstate (AI) even before we finalized our purchase.  One of those was that the house battery was obviously in bad shape, failing to hold charge and not having enough current to even start the on-board generator.

Meanwhile, on board the starship Interstate:  I don't know who created this original meme or why, but speaking of DIY, did you know that William Shatner has a new DIY television show premiering soon?  It's not DIY centered on an RV but rather his own house.  One of the series announcement commercials is hilarious, with him peering through a busted wall quipping, "HEEERE'S BILLY!" as he channels Jack Nicholson in "The Shining".  

We quickly found out why there was no power.

The Battle of the Bulge:  The battery wasn't that old - we have a receipt from the previous owner suggesting that it was purchased three years before we bought the vehicle.  But something was visibly wrong nevertheless.  It was important to determine the cause and remedy it, because this is a $300+ battery and we wouldn't want the same bulging thing to go wrong with a new one.  

As I mentioned in this other post, we don't have a large local Interstate knowledge base upon which to draw, because these vehicles are rare in our area.  However, what we do have here is about ten million boats, by virtue of our subtropical coastal location.  And with boats come brick-and-mortar boat shops.  And with boat shops comes practical knowledge about battery problems, because pleasure craft use the same deep cycle batteries as RVs.

A local salesperson took one look at this battery and told my husband that the bulge and degradation occurred because the battery had been overcharged.  My husband did a some online research and decided that the best way to guard against a repeat of the same problem was to upgrade the AI's original single-stage converter / charger to a three-stage device that includes a temperature compensation function.

He gleaned much of his research information from this Best Converter website and also from Handy Bob's accumulated wisdom on general RV electrical system functionality.  Ultimately he purchased the Parallax Power Supply Model TCRU with TempAssure retrofit kit from PPL because it was available in-store.  Off-the-shelf was a big plus because my husband wanted to get this project completed quickly; this particular unit was selling for about $240 in the PPL storefront as of October 2014 (the price may be somewhat lower via a few other online sellers, assuming you can wait for shipping).

BZZZT!!  I would rate this project as "DIFFICULT" in terms of the DIY skills required, for the three reasons given below (hubster disagrees with my assessment and would instead rate it as "EASY" except for the stringing of the temperature sensor):

(1) It involves removing and replacing a significant component of the electrical system.  If you screw it up, you could injure yourself or burn down your RV.

(2) It requires that a sensor wire be run from the house battery (which in our 2007 AI is located beneath the front passenger's seat) to this unit, which is located amidships near the fridge / microwave column.  That requires crawling beneath the RV to make the physical connections and also a lot of careful zip-tie of the new sensor wire to existing wire bundles and other secure chassis structures.

(3) The orifices in the underside of our AI were not large enough to accept the lead ends of the temperature sensor wire.  Rather than enlarging the holes (which would be bad for reasons having little to do with the electrical system), my husband cut off the end pieces and re-soldered them back together once they had been fed through, shrink-wrapping the connections as he went.  This requires yet another skill plus additional tools.

See our BIG FAT DISCLAIMER on RV DIY.  

Despite the complexity of this task, the retrofit unit is sold with extremely detailed step-by-step, plain-English instructions that include photographs and line diagrams, so a DIYer with sufficient skills could successfully execute this job.

It is an explicit instruction set, six pages long, which I will not repeat in this post.  Here is an example excerpt screengrabbed from the pamphlet provided in the box by Parallax Power Supply; I cannot locate an online PDF.  

We worked on this project as a husband and wife team, with my husband doing the wiring and me calling out each step in the instruction sequence so that he did not have to drop his tools and get off the floor (or out from under the dark underside of the vehicle) every time he needed to hear the next line.  Our AI did not display any deviation from the expected configuration as it was described in those manufacturer's instructions, although my husband recommended that I inject this pointer:

Come to Papa:  Those red and white wires connect to the new unit in a slightly different place than they were on the original board.  You might need more slack to connect them, and you might not realize that until other stuff is already connected.  So you might want to dry-fit them in advance to ensure they'll reach.   

Everything seemed to work just fine when we got done with this retrofit.

Meme the mighty:  The new battery worked as expected and the generator started up immediately.  Ever since we completed this project, the battery appears to be recharging normally, knock wood.   

This project took about six hours cumulatively, including my husband's time in getting up to speed on the technical requirements, plus the installation (the main time sink was the feeding and fishing of the sensor wire).

One of the complexities with the AI is that the converter is so far from the battery.  Furthermore, a battery isolator and other house wiring appears to be routed under the driver's seat whereas the house battery itself is under the passenger's seat.  There is a wire channel in the Sprinter body between the two seats but attempts to fish the wire wasted several hours of effort before we decided to route the line through a drain hole and under the chassis instead.   

The issue with these projects is always the time spent on the learning curve - we could probably do the same project again in just two hours, now that we know what to do.

Of course, none of this addresses the question as to how our original fairly-young battery got itself overcharged (and therefore dead) in the first place.

As I understand it from general knowledge, temperature plays into this because at higher temperatures, the charging voltage required by the battery is lower.  If the temperature increases while the voltage remains the same, apparently it can result in overcharging.  Or something.

Tell it like it is:  I can't say for sure what the danged problem is, but I do know that motor vehicle batteries have been an ongoing pain in my rear end since the very day I moved to the southern US (I'm originally from "up north" where we did not have such problems).  They just don't last here for whatever reason(s), and I can't tell you how many times I've been stranded by a young-ish battery that reportedly checked out OK by a dealer, only to die a few days or weeks later.

The illustration above was adapted from a wall display I saw a few months ago at our local NTB service center.  I took these pictures because this represented the first time I saw any retailer be really explicit about the consequences of this annoying issue.  There is a huge variation in expected battery lifespans between hot and cold climates.

As always, this is a noncommercial post expressing personal opinions only and incorporating a BIG FAT DISCLAIMER.  No manufacturer or service provider supplied any consideration in exchange for being cited.  By all means, if you have anything to add to or clarify with this post, please contact us via interstate.blog - at - gmail.  We would greatly appreciate your comments and feedback.