Escape Battery pack

[ronstew]

You get the about the same stored energy (amp-hours) from two similarly priced 12-V or 6-V batteries. Ron, you are correct that you put the 6-V batteries in series or the 12-V batteries in parallel, so in either case you get 12 volts. You would be able to get a higher peak current from the parallel 12s, but that makes no difference at all in our application.

I decided too late to go with twin batteries, so I am stuck with one 12-V on the bumper, and one mounted under my rear dinette in a sealed compartment that is vented outside.

An advantage of twin 12s would be that you could run on one, and when it gets low, switch to the other. But we do not really have this advantage, since the law requires that the carbon monoxide and propane detectors be constantly energised. Instead, we have one battery that can be swtiched off, and one that cannot.

I do not like the twin 12-V arrangement in my trailer. The switch to turn on and off the inside battery does not seem to be designed for large currents. When you connect two batteries of this type (batteries with low internal resistance) in parallel, if they do not have equal charge, there will be a short-lived high current while the batteries match voltage. This means that you should balance the load at all times. It also means that you ought to replace both batteries at the same time when they wear out, even if only one is defective.

So I say now, get twin 6-V batteries. If you go with twin 12-V, use them both - don't switch one off. But get twin batteries. The fan in the furnace draws the battery down fast on cold nights.