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ron_dittmer's avatar
ron_dittmer
Explorer III
Oct 13, 2014

Batteries: Two-6V In Series, or Two-12V In Parallel ???

Before spring I will be replacing our two 12V Walmart coach batteries. Our 7 year old rig has it's original Tripplite 2000 watt inverter/charger similar to THIS ONE. I was thinking of replacing the ...
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DiploStrat's avatar
DiploStrat
Explorer
Oct 16, 2014
map40 wrote:

Sorry, but no. In most (if not all) the starter battery is in a completely separate circuit. You can't drain your starter battery, no matter how much you drain your house batteries.
We isolate them so they don't pray on each other. You don't like diodes? Fine, use relays. But I can assure you, there are several of them already running in your RV, sucking your power as we speak....
Jokes aside, you can avoid this all together by using two 6 volt batteries.
As far as the 8 volt batteries, if you will use them, invite me for when you plug them in, I always enjoy a good firework show...


With deepest respect, you are mistaken, or at least unclear, on several points. At the very least, we are talking past each other.

-- Your camper batteries are almost always tied back to the vehicle alternator and the starter battery. GM, for example, specs that auxiliary batteries be tied to the positive terminal of the starter battery. There is, of course, some form of isolation at this point to avoid drawing down the starter battery. There are many reasons not to use a diode isolator for this function unless it is part of a secondary regulator. And there are many reasons why this type of gear may not be necessary.

-- Within a given battery bank, there are no theoretical advantages to using 6v over 12v batteries. (You are really only using a lot of 2v batteries in series anyway.) There are definite advantages to using deep cycle batteries for campers.

-- As a practical matter, most manufacturers make larger 6v deep cycle batteries than 12v deep cycle batteries. So, of course, two larger batteries will have greater capacity than two smaller batteries, but this has nothing to do with whether the battery is 6v or 12v. In fact, the battery bank on my truck consists of four 300Ah 6v batteries, wired in series/parallel. This gives me a battery bank of 600Ah. (300Ah usable if you follow the 50% rule.)

-- I assure you, there are no diodes in my camper battery charging circuit.

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