Battery advice: is it dead?

[Guest]

Hey, and thanks for reading.

The PO had not charged this battery in a year. I took it into AutoZone who said it was fine, just needed to be recharged. However, after 72 hours on the charger it is still only reading 10.3V on my multimeter. The charger is a cheap HF battery maintainer, not sure if that makes a difference.

Thoughts? Is it worth throwing on a better charger, or should I just replace it?

[Redman]

Even of the charger is 3/4th amp, at 72 hours would think it should have fully charged a 14AmpHour battery. So, yah, seems like the battery is bad.

Let it on charger overnight and see if still the same voltage, then you will know.

THe worst thing to do to a battery is to let it set uncharged for a long time, which is what happened to it. While it is uncharged it can build up stuff (I have forgotten what that stuff is) on the plates and short out that cell.

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[Steve]

While it is uncharged it can build up stuff (I have forgotten what that stuff is) on the plates and short out that cell.

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I <think> it's lead sulfate.

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[Brendan W]

Not trying to be smart here but....
Is the meter battery good?
They last soooooo long these days it's off the radar most of the time.

[thefoolofemmaus]

Dang it! Why is "read the manual" always the answer? Thanks for looking that up!

[Redman]

The HF Center manual says:
“The Battery MUST be fully charged to at least 12 Volts.”
“Note: This Float Charger is intended only to keep a fully charged battery from losing its charge.
It will not work to charge a battery that is discharged or damaged.”

https://manuals.harborfreight.com/manuals/69000-69999/69955.pdf

.....

I can understand the "will not charge a battery that is discharged...." portion of that statement, since I know many battery chargers have a circuit in them to detect that the battery is not connected in reverse polarity before it starts to charge, and if the battery is complelty discharged the charger will not pass the test and will not start charging. But in theOP situation he knows it is at 10 point something volts.

Also, these maintainer chargers also limit the current they put out, and if some of the battery the plates are sulfated (or whatever)(looks like corrosion) to were some plates are shorted together, then the maintainer charger isnt going to overcome that. Wereas an unregulated, say, 6 or 10 amp charger, might. (but dont leave it on for much more than 20 minutes).

I know that for large industrial battery banks, say, lead-acid for diesel generator starters or large UPS systems, they will occasionally raise up the charging voltage about half a volt for a while to reduce the sulfation (whatever).

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Thoughts? Is it worth throwing on a better charger, or should I just replace it?

So, maybe using a bigger, unregulated, battery charger, for just a while, might help situation.
Not a "better" charger, but a bigger dumber more brutish charger (just for a while).

But mostly, I think leaving the battery uncharged for a year has done it in.

If you dont really want to get another battery, and are desperate to try anything: Try connecting the battery and turning on headlight to drain the battery down quite a ways, till headlight is dim. Then charge back up (day or so on maintainer). See if any improvement.

[LAB3]

Started bringing some of the vintage bikes out of hibernation & ended up with a reasonably good test for the Optimate.


Have a small AGM in a kickstart two stroke with a 5.96V reading. Got an erratic flicker of the yellow charging light when I hooked up the Optimate. After two days got a solid green test light, which means it tested ok. (Don’t know how long it took because I didn’t check it often enough.) Unhooked the charger & let it sit for a few days, and still had over 12.4V. Battery looks to be OK.

12.4v after sitting awhile is already showing less than 50% of the batteries capacity, it'll work for now but suspect it won't for very long.