Brand New SLA Generator battery will not reach 14.4v

[ThermallyFrigid]

Hello wonderful person,

Today I have a new Expert Power YTX7A SLA battery for use in my 3500watt inverter generator.

As I always do with new batteries, I first do an absorption charge to bring the battery to full charge and check the IR with a SMB124A.  The IR was 10milliohms.    Good.

I then set my charger to 14.4v and over the next 15 hours it rose very slowly from 12.85 to 14.39 but would not go over that.  Maybe that's ok ?

It hovered there for several hours drawing 0.039Amps (39 milliamps) but after the current didn't drop anymore after 2 hours I disconnected it.
Should I have left it on the charger longer?


So it appears this new battery won't ever reach full absorption charge of 14.4v and I don't want to leave it connected any longer for fear of damage to the plates.

I'm concerned that this battery will have a short life.  For all I know someone had it before me and over charged it or over heated it etc.
Or maybe I'm overly goobulated on this and the battery is just fine?

Any comments would be appreciated.

[bdunham7]

If you are concerned enough to be measuring things that precisely, you can't omit temperature from the discussion.  What were the ambient and battery temperatures?

If the answer is 23C/73F, then I'd say that you probably just need a bit more current to get your 14.4 volts.  On a 7AH AGM battery, 70mA should be OK for a float charge for a little while.  For any float current there's always going to be a point of equilibrium where the battery will simply absorb the power through a recombination process (or outgassing which is less desirable).  It just sounds like 14.39V @ 39mA @ whatever your temp was, is just an equilibrium point.

[ThermallyFrigid]

If you are concerned enough to be measuring things that precisely, you can't omit temperature from the discussion.  What were the ambient and battery temperatures?

If the answer is 23C/73F, then I'd say that you probably just need a bit more current to get your 14.4 volts.  On a 7AH AGM battery, 70mA should be OK for a float charge for a little while.  For any float current there's always going to be a point of equilibrium where the battery will simply absorb the power through a recombination process (or outgassing which is less desirable).  It just sounds like 14.39V @ 39mA @ whatever your temp was, is just an equilibrium point.

Ambient temp in the room was 75F

[BrokenYugo]

I don't mean this as put down or anything, but this is the most precisely I've ever heard of anyone handling a lead acid battery, you're seriously worried about 10 millivolts?

Sounds full and balanced to me, I'd stick it in the genset, give it a test start, and park it on a good float charger. If you really want to see higher voltage, push higher voltage/current to it, though I'm wary of overcharging anything I can't easily pull the caps on.

[bdunham7]

Ambient temp in the room was 75F

Close enough.  Give it a little more juice if you like, but it is probably just fine.

[james_s]

It's a lead acid battery, not a precision voltage standard. Install it and use it, it'll be fine. If you keep trying to get the voltage to the level you think it should be you'll just boil away the electrolyte and cause it to have a short life.