# and Type of house batteries

pnichols wrote:

BFL13 wrote:

ron.dittmer wrote:
My personal experience with motor home batteries......

Two smaller 12V batteries will not perform better over time compared to one larger battery. They will when new, but year number 2 will have noticeable degradation. Year number 3, they will be working against each other. Indication of battery mismatch will show up as acid boil-overs.

I do feel that two 6V batteries of a smaller size will perform better than a single 12V battery of a larger size.

To clarify the report, were those two 12v batteries "balanced" as in the loads and charging were "across" the two, or were the loads and charging on one of them with the second battery "downstream"?

BF - good point.

I don't see how a couple of 12 volt batteries connected in balanced parallel can ever have one working against the other. After all, with two in balanced parallel what it seems that you really have, electrically, is six (6) double plate size 2 volt cells stacked in series to produce 12 volts - of greater current capability than only one 12 volt battery with it's hence smaller plate size 2 volt cells stacked in series.

Two 12 volt batteries connected in unbalanced parallel is another situation altogether, since when supplying or receiving current the two 12 volt batteries do not have the same potential across their plus and minus terminals. Over time this will cause different age-related plate and/or electrolyte degradation between the two 12 volt batteries.

I would have not believed it myself so I understand why you both posted your comments.

Our rig has two batteries by design, wired in "perfect balance" fashion. The original batteries were two-12V. Year number 3 was a weak battery year with serious acid boil-overs. Year #4 was a very poor year with serious energy deficiencies. The same exact thing happened with the second pair of 12V batteries of a different brand, paired from a common production month. Each time I pulled the batteries, placed them on a work bench, and monitored their charging as a pair and then independently. I concluded this in each case.

For reasons I cannot explain, one battery would consistently drain much faster, rendering the other battery less utilized. When recharging, the battery with more energy would get fully charged quickly while the other battery never gets fully charged due to it's weakened state. Then comes serious acid boil-overs because one battery gets over-charged while the other never gets fully charged, hence working against each other.

With two 6V batteries hooked up in series, they drain in unison and recharge in unison, a perfect arrangement utilizing 100% of available energy. It is just like stacking batteries in a flashlight that drain in unison.

The last time I replaced my batteries, I switched to two-6V AGM Duracell brand batteries GC2AGM purchased at Sam's Club for a little less than double the cost of 12V lead acid. What a huge improvement in battery reserves on trips along with faster recharge times. I installed them 4 years ago and they are as good today as when I first installed them. With AGMs, the only maintenance is charging. And the battery terminals are always clean.