Amps jumping around on AGM finishing charge

[HiTech]

At a battery temp of 81 degrees and a float charge of 13.33v, the charge was settling in toward .1 A when it started jumping around more and more. Still settling, but jumping from .02a to .15a. The pseudo random motion in the amps is very different from normal charging, and intuitively similar in rythm to dropletts condensing and dripping across say 6 cells. Any chance that is what it is? No outgassing at all.

I have never seen amps act like this, but I never had such precise control over manual charger generated float voltage until I got the buck converter.

Jim

[HiTech]

True! Once I learn.

Jim

[pnichols]

My AGM battereis come up against a "hard Stop" when they're fully charged. In other words, the ammeter in series with the AGM batteries reads a solid zero after so many hours of charging. Nothing I can do makes the ammeter show any more current flow into the batteries at that point. Even increasing the charge voltage back up to boost value will not make the ammeter show any charge flow once the AGM batteries are fully charged.

I've never seen any jumping around in current flow rates with my AGMs. That does sound strange ... I wonder if your ammeter or charger could have some instability somewhere in their cicuits ... IAW nothing to do with the AGM battery(ies)?

[BFL13]

Worth checking it all out when you know how for sure. At the end of the day, you have to kick them out of the nest and see if they can fly--fingers crossed.

[HiTech]

I have not been quite ready to leave these AGMs under unattended solar care yet. For one thing the spec rating float voltage bubbles occasionally which may be ok but I need to understand that before I just leave the bank there drying out. For another I am just curious about real float so I'm dabbling with it.

I am thinking if mild gassing happens under float but below the release pressure of the valve, that could be the ideal state of the universe for minimizing plate corrosion and also reversing/avoiding sulphation. If that's true my LandStar won't quite achieve it since the temperature compensation factor is not quite right and is not programmable. But I could probably pick a voltage that is correct on the high temp side, and rely on the daily overcharge to get close.

Jim

[BFL13]

Not a clue 🙂 But I do note my LandStar plays with the amps to maintain the rating voltages when it gets past Bulk stage.