12v and 6v hookup

RussellBerge wrote:
Hi all,

My trailer is equipped to install 4 batteries. I did intend to put in four 6v Trojans. But now after examining my two 12 v deep cycles, I think they may have a couple more years in them. Keeping them would save me $300 for the time being. I know how to wire batteries together but my question is : If I hook up my 2 old 12v batteries together with 2 new 6v Trojans, will this arrangement decrease the life or performance of the Trojans ?

Russell

I'm a bit confused here. First off, are you wiring your batteries in series or parallel? Large trucks still often use 2 6 volt batteries in series to replace one 12 volt. The voltage is the same but the amperage available is quite a bit more. Look at a pre-1955 car and you'll see the cable are much heavier than late model cars as the amperage draw is much more.

If you're going to mount the btteries in parallel, you're going to have three battery sets. If you're going to use 2 12 volt batteries, there's no need for any 6 volt units. I'd either use 2 12 volts units that you have or 4, 6 volt units new. This will make charging more reliable. Unbalanced battery charging can boil a weaker battery and make it go boom. Then you have to clean acid off everything. With the hydrogen gasses given off, you have a fire risk too.

RussellBerge wrote:
If you do a quick internet search you'll find huge banks of batteries in homes storing solar and wind power. Seems to be common practice. You'd think if explosions were commonplace then there'd be some warnings or at least some mention of them.

Not to contredict anyone, but is it really COMMON ?

Solar/wind battery recharging systems rarely have a charging rate equal to that of the alternator in my Ford E350 V-10.

Those that do have battery recharge cycle rate control and/or a battery temperature sensor.

Do you need the extra batteries? Batteries are heavy, smelly, short lived, expensive things. I would rather spend the money putting solar panel or two on the roof and switching to LEDs than try to store a bunch of electricity.
I'm not saying you don't need the batteries, but in my situation I decided I'd rather make electricity than store it. With one 136 watt panel I do fine on one group 31 battery.

What about an "A, B, A/B, full off" battery bank switch. If I had two sets of batteries that were radically different, I'd separate them and use a switch. This way, they are less likely to decorate the surroundings with acid.

I have a fifth wheel that I have always used four Trojans in. I do alot of dry camping and find they come in useful. When I bought my current trailer I moved two of the Trojans from my old trailer that were already about three years old. When they finally wore out and needed replacement the oldest two were shot and the newer ones were reduced in output, but not entirely shot. I just replaced all of them at once. The older batteries made it 11 years and the newer over 8 years.

In theory, the combination of the two 6 volts and the two 12 volts could work and be done, but considering the limited life left in the 12 volts batteries I would just bite the bullet and go with all 6volt. I should say this. Based on having used both 12 volt and 6 volt batteries in the same (previous) trailer, I found that the 6 volt batteries seemed to charge faster and last longer. When using the 12 volt batteries, despite having approximately the same total amp storage as the six volt batteries, the 12 volt always seemed to run down faster.