Battery guestion for a guru or two

"Why is two 6 volt batteries in series better than two 12 volt in parallel?"


Reminds me of the old Groucho Marx "You Bet Your Life" show...


When the duck used to come down...

The OP has a single battery so two 6V would give him a LOT more capacity then he has now. Also, no one puts deep cycle 12's in RV's. They are nearly 100% Walmart, Interstate, or Costco hybrids.

Flyfasteddie wrote:
Actually, if you have 2 12v batteries in parallel now, you would be using 4 6v batteries in a series/parallel configuration. They will likely take up a bit more room as well, so measure before you buy.

Depends on what OP's original 12V batteries are: A pair of group 24s will give approximately 160 AH (80 X 2) a pair of group 27s, about 200 AH and group 31s about 210.

It is also possible though unlikely that OP has true Deep Cycle 12V batteries and not the popular Deep Cycle/Marine-RV type.

A pair of 6V GCs will yield anywhere from 220 to 242 AH.

(note that Amps and AH add in parallel, but not in series)

Actually, if you have 2 12v batteries in parallel now, you would be using 4 6v batteries in a series/parallel configuration. They will likely take up a bit more room as well, so measure before you buy.

6V are made for deep cycling unlike most 12V batteries that RVers purchase. Also, you'll get more amp hours than most single 12V batteries. There are exceptions but are more expensive and heavy.

Thanks to everyone for the advice. The TT has been on shore power for over a week. I will take a reading tomorrow; disconnect the battery then after letting it sit for 24 hours or more. It was supposed to be a new battery and certainly looked new, but functionally it does sound like a several years old battery. Why is two 6 volt batteries in series better than two 12 volt in parallel? I would assume each 6 volt cost more than a 12?? Thanks again.

The good thing -- you have a good excuse to get a good pair of six volt batteries that will last a long time.

Good advice on the first reply.

Your battery is about 4 years old. If you have been camping with shore-power for your last trip or two, a good battery should have held full charge between trips if left plugged in at home, or if placed on "disconnect".

Checking while plugged in with a good battery (reading voltage across the battery-terminals with a multi-meter) should be holding 13.2 volts (full charge) or 13.6 volts (slight discharge) and needing some charging.

If your voltage reading is less 12.6 volts after 24 hours (as suggested in 1st reply) I would let it sit another 24 hours (unplugged) and check reading again. If it is lower than last reading, your battery is no longer capable of charging anywhere near new capacity due to sulfation and age.

The awning motor can have heavy draw causing a bad battery to not be able to retract it. Turning on one 12v light should not cause a 0.1 volt drop. The battery is essentially dead.

Your "new" battery is pretty discharged. 12.2 volts with little load is about 60% of charge (and you shouldn't go below 50% charged or about 12.1 volts). Also since your converter when powered is running at 14.4volts it sounds like it is trying to charge the battery as 14.4volts is boost voltage.

Assuming there is nothing really wrong do the simple things first:
- check the water in the battery to ensure it is just over the plates
- plug into shore power and let the converter charge the battery for at least 24 hours. Around 3 hours or so you should see converter voltage&battery voltage drop down to the 13.6 range
- After the 24 hour charge unplug and unhook the battery, let it sit for 24 hours. Measure voltage, should be 12.6+

If all of that works as described then your problem was only a pretty discharged battery.