Originally Posted by markopolo
Thanks for posting the diagram. Looks well done and accurate.
The balancer is probably between the 24 volt battery bank and the 12 volt battery bank.
Like booster noted, it looks pretty straightforward. Dealer probably meant "unusual" instead of "odd". It is what I'd expect to see - I don't have an E-trek though. I think there was variance amongst the first builds. They may have standardized production now.
Looks like the battery capacity is 400 ah (approx) at 12 volts plus an additional 200 ah (approx) at 24 volts. The balancer would 'balance" the remaining capacity if one bank is drawn down quicker than the other I'd expect.
I am totally not up to speed on balancers, and how they work, so I may be way off base here. I am assuming they are a variant of battery to battery charger, that works both directions between two banks? In this case it would be 12 to 24v one way and 24 to 12v the other way. If that is the case, I think I would expect to see the balancer positive connections to the first of the batteries in the series change for each bank, rather than the last one. The diagram would not charge the forward two coach batteries with the balancer, it appears, either. It may be just a line to the wrong spot, I know how hard it is to figure out where a maze of wires go, even if I just created them.
Interesting about the battery overcharge failures mentioned by the Caped Crusader. One of the big questions that I had from the beginning was how they handled the very high charge rates available form the huge engine generator and fairly large stock Sprinter alternator. To be kind to the batteries, these outputs would have to go through a very very big battery to battery charger to get "safe" multistep charging. With the two systems shown, they very well may have the van alternator going to the 12v batteries, and the engine generator at 24v and to the inverter batteries. The 12v system would be the same as any Sprinter in that configuration, and 400AH is a lot of coach battery, so overcharging would be less likely than with the 3500 watt engine generator into the 24v system. If they are running that straight in without modulation, it could do some damage, I would think. I know the AGM makers claim very high, or no, limits on amperage into the batteries at charging, but AGMs are also very sensitive to overheating and high voltages once full.
I am very glad some of this information is showing up, it will help all of us to understand the etrek, and our own, homemade, "improved" charging systems.