2 6v's only or 2 6v's with the 12v

[ericsmith32]

Hate to bring up another battery question but this one is a bit different... Recently added the 232Ah 6v's from Sam's and combined it with a 29HM. That battery is about 3 years at this point. The converter in Jayco is a Iota 30amp with the 4 stage controller. The 29HM is in great shape and never had to add water.

A guy I work with, a electrical genius (yes it's hard to believe), was telling me that I really should just get rid of the 12v and let 6v's run. The 12v will reach it's charge limit way before the 6v's will and they may never get fully charged. Overall it does make sense. But in the big picture how much difference? In my mind they'd eventually even out, but the 29 is the weak link.

Technically could move the solenoid that switches the front charging to the back and tie the 29HM with the chassis battery. While driving it could recharge the 6v's faster. The other option is just selling the 29HM for other RV mods!

[wa8yxm]

HE does not understand batteires.

Fact: The battery with the LOWER VOLTAGE will accept the lion's share of the charge current. When the VOLTAGE in both batteries (the six volt pair is considered to be a single 12 volt battery) then charging will be shared in exact perpetrator to their size. IF EITHER battery should "Get ahead" (which is basically impossible assumign all connections are clean and tight) It will stop accepting power till the other one catches up.

Likewise when discharging the larger battery will provide, IN PERPURTION the lion's share. so once you go throug one charge/discharge cycle the batteries are in perfect lock step till one of them fails. It is IMPOSSIBLE for one of them to reach full first.. They both get there at exactly the same nano-second.

[liborko]

Of course they will charge and discharge differently because they have different Ah capacities. The 12V battery will reach full charge before 6V when charged and 12V battery will stop supplying current before 6V batteries will. That does not mean that they will not "play together". There is gazillion applications where batteries are paralleled without a problem. Paralleling 12V with 2x6V is not something that should be done by design but if you already have spare battery use it. There will not be any problems as long as none of the batteries is defective.

[Matt_Colie]

Eric,

I think you have it right, just always know where the baking soda is. Lead/Acid batteries do not play nice in parallel. If you think the older 12V has a problem, is loosing water or getting hot, get it out of there.

While your friend is largely correct, the reason is the total circuit's resistance and the internal resistance of the jars. They will never charge or deplete the same. There is nothing you can do about that.

If you have two 12Vs that came of the line in succession, and you strap them together they still will never charge or drain the same. That is just their nature.

Matt

[ericsmith32]

Yeah did a google search and over 20 posts came up on this very topic. And on this website, search on here is kinda iffy. You know I'm not going to worry about it. When the 12v hits 6-7 years I'll change it out for 6v's.. unless I hit the lottery sooner. I noticed with the 12v took a year to break in good also. I'll take a couple trips and see what happens. One trip next week and Florida with alot of dry camping the middle of March.

[liborko]

Perfectly OK as long as all batteries are same chemistry (wet, agm, or gel) and none of the batteries has shorted cell.

[prairie_camper]

I have 2-6 volt in series and 1 - 12 volt in our trailer. I also have a battery selector switch which allows me to select batt 1 (the 2 6 volt) or batt 2 (1 12 volt) or both or off. The 2 - 6's are my house batteries for boondocking, the 12 volt is used for extending/retracting landing legs, the breakaway switch for towing and when hooked up to shore power and other emergencies. This way I have 2 separate sources of power as long as I remember to make the right selections at the right time. The 6's are monitored by a trimetric! Works for me! 🙂

[Bumpyroad]

just get a marine switch to select which one/ones you want to be using to keep them separate.
bumpy

[MEXICOWANDERER]

Connected with no charging or floating, they'll play Hannibal Lectur, and eat each other. Mixing battery types means obeying a bunch of rules or suffer the consequences.

[time2roll]

As long as they are on float why would it matter which one arrives at 100% a day later? Not that they actually would.

Only time to separate would be for storage without float or for testing.

[red31]

ericsmith32 wrote:

The 12v will reach it's charge limit way before the 6v's will and they may never get fully charged.

Dis he say why? could ya share?