Battery: AGM vs. Flooded Cell

BFL13 wrote:
You can't charge any faster than your charger's max amps.

There is a slight time saving once you get to the Absorption Stage where the AGM has a little more acceptance rate per SOC, but Bulk Stage timing is about the same.

Some figures from past examples on this topic, noting the %SOC when Bulk ends using various charging rates. (The lower the charging rate, the higher the %SOC when Bulk ends after a time at constant max charger amps)

Wets- 32% and 65%SOC
AGM- 40% and 63%SOC

Wets-19% and 72.5%SOC
AGM- 15% and 75% SOC

So if you are off-grid doing 50-80s you are going to shut off the gen not long after Absorption starts anyway, and you will not realize much of any theoretical time saving by having AGMs.

Solar usually has a very low charging rate, so a high SOC when amps start to taper. This is true with Wets and AGMs. Hard to say if you are any more likely to get to 100% before dark with either type.

Li batts do shine in this regard. At 100% charging rate, they reach 65% SOC when Bulk ends, and at a less stressful (and recommended rate with Battle Borns) 50% charging rate, Bulk ends nearer 80% SOC. Solar with Li means you won't see much of that faster charge with them either due to the low charging rate, unless you have a very large solar array.

We were looking at all this a while back when discussing the wild claim seen in advertising, that AGMs charged "five times faster" :)

Your numbers sure don't match my experience. I used to work for GM on the EV1 back in the day. AGM, although never made it into the car for the public, were experimented with and were going to be the next battery after the FLAs that were used. The reason they were going to be used was their higher charge rate. It wasn't 5 times but it was closer to 2 times faster. I have seen the tests the guy did on the marine how to site. He used old batteries that he even admitted were likely sulfated.

As far as lithium are concerned, My 2 100A lithiums are pretty much in bulk charge with a lithium specific charger until they are 98% SOC. My charger is 60A. The absorption phase is very short and you can see the charge rate taper down to 0 within a few minutes.