Battery Isolation for Parallel Batteries

[JohnV8r]

I was reading through the thread about UV's pink potion and came across this post from Bruce:

Postby Bruce » Mon Nov 28, 2011 3:04 pm

A word of advice when paralleling one or more batteries together for higher capacities.

Multiple batteries on the same bank of a charger will often charge at different rates due to plate inconsistencies. This often leads to batteries being over and under charged in the same parallel bank leading to shorter battery life.

Each battery should have its own isolation charge. One of the biggest issues I saw over the years was severely reduced battery life because of 12v paralleling or series connections for 24 and 32 volt systems.

Can someone please point me to a source for an appropriate battery isolator for the marine environment? Shambala has been running two battery banks of two Group 31 batteries in parallel for 10 years without an isolator between the batteries in each bank. I'd like to continue to use Group 31 batteries so I don't have to lift 130+ pound 8D batteries when they need to be replaced. Of course had I known about the need to isolate the batteries in the first place, I might not have been replacing batteries as frequently.

[Bruce]

John,
I believe that statement was for creating 24 or 32 volt systems series paralleling 12v batteries. Your not doing that.
If your putting two 31's together for each engine, go for it.

[JohnV8r]

Perfect.

Thanks Bruce!

[Tony Meola]

John

If you are turning over the Cummins one Group 31 per engine should do it. I hae two per engine and one for the house and I think the two per engine is over kill. But when we put it together, it was right after a local boat by us drifted the canyons for 3 days before the Coast Guard found them. Turned out they had one battery per engine and one house and for some reason, something went bad and when they shut the engines down all three batteries were dead. No EPIRB no life raft.

The mechanic said to me, there is no way these will not start. If needed you can bring all 5 online for one engine. I think a little over kill.

[JohnV8r]

Tony,

Thanks for that. The two Group 31's per side is how I started out with Shambala when my stewardship began. Whatever the reason, I've never had very good luck with wet cell batteries. I've always had a penchant for either drawing them down too far at anchor, or slow cooking them with my battery charger before I had it modified/updated. I finally got so paranoid that I rewired 90% of my house load to one bank so if I was going to damage the batteries by draining them down too far it would be contained to one bank. That served me fairly well.

AGM batteries and having my late '70's era Lewco battery charger rebuilt/updated by Lewco has helped tremendously. I haven't replaced a battery in 4+ years, which is a new record for me.

I'm seriously contemplating upgrading my batteries to the Mastervolt Slimline AGM batteries when I do the repower. Their dimensions are 22"L x 5"W x 11"H with 200 amp hours and 900 CCA's. An 8D is 20.6"L x 9.5"W x 9.4"H with 225 amp hours and 1300 CCA's. You essentially get a pinch more CCA's than a Group 31 battery, but 200 amp hours instead of 90ish on a Group 31. The real bonus is being able to fit two Slimline batteries in essentially the same footprint as one 8D. I could fall asleep with the flat screen in my v-berth on while my refrigerator and bait pump hummed all night long and not wake up paranoid about how much juice I had left. THAT would be nice!

[Bruce]

I could fall asleep with the flat screen in my v-berth on while my refrigerator and bait pump hummed all night long and not wake up paranoid about how much juice I had left.

That is as simple as having a dedicated house system and not combining it with engine functions and controlling any combining or paralleling thru battery switches.

The problem many older boats and their repowers have is that there was never a dedicated house system to begin with and upon install of new iron it remains the same. I'd say 80% of mechanics are electrical ignorant and don't grasp even the basics.

[Whaler1777]

Wait for these to go on sale... can usually get them closer to the $200. mark with some coupon codes.. Theyre basically the same as the oddessey batteries... Ive even heard that theyre made by the same parent company...
http://www.sears.com/diehard-platinum-m ... 850131000P

[JohnV8r]

$200 would be a phenomenal price for a Group 31 AGM battery. Thanks for that!

[John F.]

I'm doing just that--as soon as they go on sale this spring, I'm replacing my 8Ds with those. 1150 ccm for a G31 size is great. So is the price