combine 12v marine deep cycle and 6v golf cart deep cycle batteries?

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sprinterlivingkc

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Aug 19, 2015
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Recently came across a newer 12v marine deep cycle batt and would like to add it to my existing house battery bank which consists of a pair of 6v golf cart deep cycle batteries I just purchased from Les Schwab.  I know, I know.  It was kind of an emergency. 

Anyway, would there be any issue doing this?  Some additional info - two sources of charging; Ive got a solenoid/isolater connected to the van's starter battery, which charges as I drive, and a simple 100watt windy nation pv panel which will also be charging the batteries.  If I can safely combine the one 12v and the two 6v batts, how do I go about it?  Ive got the 6v batts connected in series, currently. 

Are there further issues?  thanks folks....
 
Not a good idea!  Mixing battery types is simply asking for problems.
 
Can it be done...? Yes, but I wouldn't recommend it. The differences in each battery type's charge capacity will make it problematic. Assuming all three batteries are healthy, the 12 volt marine battery will sap power from the higher AH capacity 6 volt batteries (which are wired in series to make one 12 volt battery) drawing them down until there's a balance in voltage. The 12 volt battery will also charge and discharge faster than the two 6 volt batteries, so the two 6 volt batteries may never get fully charged. Like I said, I wouldn't recommend it, but if you were inclined to do it, you'd wire the 12 volt battery to the other two batteries in parallel.

Kev 
 
OK, Im not going to bother with it then.  I figured it wouldnt be so easy to double my battery power...thanks guys. 
 
I've done it, but I keep a good eye on my batteries and have the knowledge to identify if the mix is causing a problem. For those who lack solid battery knowledge, I always recommend that they stay with the general "rule of thumb", i.e. "don't mix battery types, sizes or ages".  I notice you said "newer", not "new", so right away you would need to worry that the marine deep cycle is not in as good condition as the new 6v pair and won't charge or discharge at the same rate. A marine type battery is not one that has a long life or good resistance to abuse anyway, so a used one is immediately suspect.

You could still carry this extra marine battery with you and hook it in (jumper cables are fine) if you run low or need extra power. It won't hurt if the other batteries are already getting low and no charger is active.  Charge the marine battery separately at home, using a small automotive charger or even a battery maintainer.
 
sprinterlivingkc said:
Recently came across a newer 12v marine deep cycle batt and would like to add it to my existing house battery bank which consists of a pair of 6v golf cart deep cycle batteries I just purchased from Les Schwab.  I know, I know.  It was kind of an emergency. 
Click to expand...

not to hijack the thread.. but is there an issue with the 6v batteries from Les Schwab? I was planning to buy a couple of these as soon as I get home in a couple weeks.
 
Not at all. Most all 6v GC2 golf cart batteries come from the same couple of suppliers, regardless of whose label is on the outside. Just take notice of the amp-hour rating vs the price, because 6V's come with a couple different ratings. The standard is 230 AH @ 6v using the 20 Hour rate. Some models of battery may be slightly less (typically 210 AH) because they reduced the amount of lead inside but kept the case the same. These will be a bit cheaper. There is also a "tall" size (called a GC2H) that is 1" taller and has more lead plates and a higher AH rating, typically 260 AH instead of 230 AH. These justifiably cost a bit more. So, when comparing battery capacity and price, look at AH per dollar rather than case size alone.
 
Id vaguely heard the Les Schwab batteries werent the best, but gary is probably right.  Not sure why those brand rumors get started, or why I feed into them...

My only complaint about these batteries is they wont seem to charge over 12.70-80 or so.  I was under the impression other pairs of 6v batts got into 13-14 range, but was corrected in another thread. 
 
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