How many amps can I pull from a marine battery (for charging)

[ryanha]

Short version of the question: How can I figure out the C rating of a marine deep deep cycle battery (e.g. how many amps I can draw continuously)? The "cranking" ratings are only for 30 sec, so I want to know the continuous rating but could not find it.

Here are the specs on the battery:

Duralast 29DP-DL:

• 675 Cold cranking amps (840 @32F)
• 106 Amp hours
• 210 reserve capacity

Long version of the question:

My buddy and I use 2 marine deep cycle batteries at the field in series to power our two iCharger 306Duos at 24V.

Yesterday, one of the marine batteries was not fully charged and it caused the voltage to drop significantly, presumably because we were pulling too much amps for the battery that was low to handle.

This was due to the low voltage on the second battery, but that got me thinking about what the actual maximum amps that we can draw. I looked at the spec sheet for the battery but it did not say anything about continuous current ratings.

Where would I find this info? What is the typical C rating for a marine deep cycle battery?

--Ryan

[Slyster]

I run two in series (24v out) and routinely charge pulling 30A and often 45A (30A on one charger channel and 15A on the other). Works great. My cheap lead/acid deeps typically last 3 seasons or so. These I bought this spring so very little voltage sag at all yet. They 'might' last a 4th season if I limited the current... but at $90 each no big deal.

Be careful that both deep cycles are matched.. same size, age and CHARGED. If one goes way down you are killing it.. especially in series because the charger might not sense this and won't shut off. And they like to be FULL at all times (storage)

[ryanha]

So can I go 80 amps? That would be parallel charging 4x 700 stick packs at 2C.

[Slyster]

80A? I'd say no. I was saying 30A is working well and at times I will pull 45A but I'd never go over that.

[jhamel]

Originally Posted by Slyster

80A? I'd say no. I was saying 30A is working well and at times I will pull 45A but I'd never go over that.

How do you determine the maximum safe current you can pull from those batteries?

The OP stated:

Duralast 29DP-DL:

• 675 Cold cranking amps (840 @32F)
• 106 Amp hours
• 210 reserve capacity

and he asked, "Where would I find this info? What is the typical C rating for a marine deep cycle battery?"

Can that information be determined from the the marine battery label?

[Slyster]

Well I do know charging is 1/10th C. Far far less.. 30x less... than a lipo. So discharging is going to the same.

Go here..this page may help.

http://www.solar-electric.com/deep-c...ajor%20Battery