AGM battery Depth of Discharge myth busted

SamG340

rh5555 said:

I agree that Lithium batteries can be charged twice as fast as AGM, but they don't have twice the usable power.  That was the message in the original post.  You can safely discharge AGMs by 80% without compromising them.

If you discharge a Lithium battery of equivalent Ah rating to zero, you only get 25% more power.  If you're not concerned about weight, then AGM batteries are not as bad as people make out.  When my batteries get to end of life, I'll probably switch to lithium, but I'm in no hurry.

Does the maths work out the same for gel batteries 

bergger

Yes most believe you can only discharge AGMs to 50% which as @rh5555 mentioned is not true.  They can go down to that 80%.  NuCamp even says this on their website.  Maximum depth of discharge is 80%, but for best longevity try to keep discharge to 50%.  But no damage if discharged to 80%.  Our dual stock 6v batteries can give us a maximum of 176ah.  Not bad for half the cost of a battleborn.  Honestly I'll when time comes to replace the two batteries in our 2021 400 I'll probably just stick with the same Harris batteries or some Trojan equivalent.  We never come close to running out of power and in our cold climate they are pretty worry free over the winters.  If we ever get a new trailer I'll probably go with a big enough lithium set up to run the air conditioner.  If you can't do that I really don't see the big advantage of a 100ah or 200ah of lithium over dual 6v batteries. 

SLJ

Everybody talks about amp hours but It's not good for equipment to run at lower voltages. Current draw increases as the voltage drops. The 12 volt threshold most equipment is designed to run at is still around 50% of an AGM. Running the AGM down 55% puts you below that 12 volt threshold. That AGM battery will draw down even faster as the voltage drops and current draw increases. While you might have usable amp hours left, they will be used quicker and at the cost of shorter equipment life. Sorry but once a battery drops below 12 volts it's done. A Lithium will still be pumping out more than 12 volts when it's over 90% used. So yes, about double the usable power. Especially if you're counting actual usable time which is what it's all about when boondocking. Those charts don't show that.

AnOldUR

I got that the point of this thread is that draining an AGM to 10% to 20% doesn’t reduce the amp hours provided over the life of the battery very much as opposed to only using 50% before recharging.

Comparing usable amp hours over the life of an AGM to LiFePO4’s is a different matter.