question

insequent avatar image

Supercycle battery life used in deep cycle mode

I have 170Ah supercycle batteries in a house bank on a boat. I believe performance is deteriorating after just 15 months use. Can any body share experience of longer life? I was expecting something in the range of 7-10 years as operating life based on other premium AGM deep cycle batteries.

AGM Battery
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Extra info. Overnight drawdown is typically between 300-400Ah. Only short high discharge rates eg microwave via inverter. Bank is 1700Ah. With mains power at dock, alternators when using engines, and 2730W of solar capacity the bank is recharged to "float" condition almost every day. Previous premium brand AGM lasted 8 years, but that life was reduced bu a couple of full discharges. Interest in Supercycle type is to mitigate consequences of rare full discharges. But are there trade-offs, such as longevity, that come with such benefits?
4 Answers
klim8skeptic avatar image
klim8skeptic answered ·

Saying that you are deep cycling your batteries is kinda vague. Quantify your remarks.

How many Ah are you drawing from your batteries overnight?

How large of a current do your loads peak at?

Are your batteries being properly charged?

Is charger temp compensation set up correctly?

How hot do your batteries get?

Victron Supercycle battery specs.

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cheyenne7 avatar image
cheyenne7 answered ·

The standard and most widely accepted rating period for deep cycle batteries is 20 hours. This means that the battery was discharged down to 10.5 volts over 20 hours while measuring the total amp hours it supplies.


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Matthias Lange - DE avatar image
Matthias Lange - DE answered ·

7-10 years? With a lead battery? Under deep cycle conditions? Never!
Maybe 1-2 years, with luck 3 years.
You will reach 7-10 or even more with lithium.

Our experience with different brands of lead batteries (all types - wet, GEL, AGM, Carbon ...) over more than 15 years is that the quality is going down over the last few years.
We had many problems with new batteries (defective after a few months - one year) so we decided to stop selling them and since 2 year we only sell lithium.

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JohnC avatar image
JohnC answered ·

Hi @Insequent

It seems you have 10x of those batteries in parallel? If so, that's an expensive mistake.

What happens is that they develop differing resistances, some get lazy, then others do all the work. And they deteriorate and die early, one-by-one. (Lithiums do this too, but they usually have a bms to control it.)

Run a 'touch test' after a decent Absorb session to find the hot ones. If detectable, remove the offenders. Doesn't mean they're no good, just that they can't be paralleled in with the others. Maybe assess, then repurpose them in a separate system.

And given you seem to have plenty charge options, maybe go less aggressive on the charge V's. (I have 680Ah of old batts surviving from such a parallel system, charged at a flat 13.5V with an Orion converter, not heavily loaded, and they've lasted some 4 years longer than I expected.)

I changed to a 48V system to help avoid this issue. With a separate 12V system for legacy loads.



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Thanks for your comment. I previously ran 6 in parallel without issues. This time, with 10 in parallel, I made sure that cable lengths to each battery were the same, just for that "different resistance" issue. Although I suspect you were referring to internal resistance in the battery which of course is beyond control.

@Insequent

Yeh, the internal resistance is the unseen concern. But you're not really 'deep' cycling the batts, so they may still be fine.

I'd back off the Absorb V a little, and maybe invest in a temp scanner to do regular checks (that T is a real giveaway).

A batt monitor like a BMV or Smartshunt would be a great asset too. Can teach you a great deal, even seasonal differences in performance due to the ambient temp will show to the observant.

Staying aware is the key with a setup like yours. Good data helps with that, and you could still get long life if you're careful. A little luck too.. :)