Battery max amp draw.

[Deano]

Question for those of you who grasp all of the ratings for batteries.
I have a pair of GC2 batteries in my 05 210 Pop. They each are rated at 122 minutes at 75 amps and 20 amp hour capacity of 232.
I need to know the maximum amp draw over several minutes that will not damage the batteries. The expected draw would be approximately 100 amps or slightly less.

[booster]

Originally Posted by Deano

Question for those of you who grasp all of the ratings for batteries.
I have a pair of GC2 batteries in my 05 210 Pop. They each are rated at 122 minutes at 75 amps and 20 amp hour capacity of 232.
I need to know the maximum amp draw over several minutes that will not damage the batteries. The expected draw would be approximately 100 amps or slightly less.

I assume you mean the 20 hour rating is 232ah, which is actually very good for GC2 batteries. 100 amps would be an easy thing for AGM batteries, probably OK for most wet cells. The fact that you batteries carry a reserve minutes rating is somewhat a worrisome as that would often indicate an non true deep cycle battery.

It is probably best to just give it a try and see how much the voltage drops at the 100 amp load. If you start dropping into the low 10 volt range, you are pushing things pretty hard.

It is likely you will find that the 100 amp load will be fine when the batteries are at 50% full or more, but shakey at less than that. When we had 260ah of wet cells (Trojan GC2 batteries) that is how it worked out for us. AGMs will do better than wet cells.

[Deano]

Booster, thanks for the quick reply. I appreciate your input and will test keeping an eye on the voltage.
Mine are wet cells made by Johnson Controls.
The spec sheet I have just says "20 amp hour capacity: 232"
They are labeled Deep Cycle.

[Sehc]

I have not seen a GC2 battery that was not deep cycle. What the 20 hour rate means; 232 amp divided by 20 hours. 12 amps steady draw for 20 hours drained the battery dead. That would imply 100 amps for 2.3 hours. However higher draws kill batteries faster than slower draws. Add this; as lead acid chemistry will not survive being discharged below 50%, you are toast at less than one hour. For such draws as 100 amp, you should plan for more battery.

[booster]

Originally Posted by Sehc

I have not seen a GC2 battery that was not deep cycle. What the 20 hour rate means; 232 amp divided by 20 hours. 12 amps steady draw for 20 hours drained the battery dead. That would imply 100 amps for 2.3 hours. However higher draws kill batteries faster than slower draws. Add this; as lead acid chemistry will not survive being discharged below 50%, you are toast at less than one hour. For such draws as 100 amp, you should plan for more battery.

The question of if they are true deep cycle is based the fact that they carry a reserve minutes rating, which makes any battery suspect.

As to the high draws kills a battery faster, you might be interested in this thread.

http://www.classbforum.com/forums/f5...tood-3770.html

Concerning the 50% drawdown rule, take a look at this one.

http://www.classbforum.com/forums/f2...imit-5595.html

I think you will find them interesting.

[Sehc]

Yes, interesting. Thank you for the links. Myself only wants to make coffee and toast in the am, and heat my neck wrap in the evening using the microwave. That requires a 2000 watt inverter, up to 150 amp draw, and that leads to battery bank size. I went after 4 GC2, at 460 amp hour. I ended with 6 GC2 and 690 AH as the deal was too good. I would rather not experiment with my money, and thus rely on accepted wisdom from the battery manufactures. But I do agree that lead acid chemistry will recover capacity after a rest.

[booster]

Wow, 6 GC2 batteries, we were hesitant on putting in the 4 we did. What are you hauling them around in?

[Sehc]

Dodge, B250. I built a custom battery box to hold them. I originally planned on using 4 and having 460 amp hours. But at the store there were 6 matched batteries only 2 months old. So. It is probably over-built for my needs, but I believe they allow me higher discharges, such as brewing coffee while making toast. All while the 12 volt refrigerator purrs on.