I have always wondered why marine type ACRs or combiners aren't used in RVs. They work fine in boats and are generally a lot cheaper than Precision Circuits BIMs. The Blue Seas ACR referenced above is one, a line of combiners by
http://yandina.com/ is another.
These connect the two battery systems whenever one is at least at 13 or so volts, ie charging. The PC BIM waits until one battery is charging but also the other one is at roughly 12.5 vots, ie 80% SOC. This limits charging up the last 20% while driving. ACRs and combiners will easily charge the last 20% while driving.
One limitation, particularly for the Yandina combiners is the maximum current that can be transferred. Yandina specifies a minimum length of 6 gauge wire to connect them no doubt to cause a voltage drop at high currents to limit the current. This will limit current during aux start usage but that may not be critical. Holding down the aux start switch for a few minutes will probably transfer enough current to let the chassis engine start.
I installed a 200 amp Yandina combiner on my friend's 2005 Winnebago MH and it works well to combine the batteries while either is charging. I didn't hook up the aux start circuit to avoid the problem with high starting current when combined.
David
Thor Forums
