Topic: Is my battery toast?

[Laminar]

Well, it turns out that I accidentally left the ignition on on my '76 CB550K project a while back. I checked it a couple days later and the battery was totally dead. I threw it on the charger but it wouldn't go about 11 volts or so, even if left on overnight, and if left to sit, it would drop down to about 6V.

I brought it inside where it was warmer and it would still only charge up to 11.8V or so. I bought some distilled water and refilled all of the cells to the top line last night, but this morning it wouldn't charge more than 12.0V.

This battery was brand new in September of '09, and it worked great up until I left the key on. Since this bike is a project, the battery was rarely used, but it never failed to hold at least 12.0V after sitting for a few weeks, and I periodically put the charger on it to keep it up.

So is it toast? Or is there some magic recipe for getting it back?

[cookindaddy]

A lead acid battery should not go bad by being discharged flat.

If you only got it last September, is there a warranty?

[bistromath]

Hit it with a specific gravity meter and determine how much acid is in there. Another way would be to drain the battery and refill it with acid.

Generally, if you over-discharge lead-acid batteries, the plates will sulfate and it won't hold a charge. But that process usually takes some weeks, not just a couple of days.

[scottly]

What is the voltage with the charger on? How much current is the battery drawing from the charger? Be aware that the battery may overflow, when and if it does take a charge; only add enough water to cover the top of the plates until you can get it to take a charge. Sorry, kind of late now...

[Laminar]

Right around 12.0V with the charger on it. When I put the charger on another battery that's been on the maintainer all winter I see over 13V.

I put the bad battery on the maintainer to see if it would make a difference.

I don't know if there would be a warranty, I've moved since buying it so there's no chance of me finding the receipt.

[scottly]

I take it you are using a small charger with no ammeter?

[Deltarider]

Right around 12.0V with the charger on it. When I put the charger on another battery that's been on the maintainer all winter I see over 13V.

What kind of a charger is that?! Those values are too low.
Can't judge from here if your battery is toast though.

[Laminar]

Wal-Mart $20 1.5amp 6/12V battery charger. It's worked great for me.

[scottly]

Do you have a way of measuring the current the battery is drawing? If It is drawing say, 1.5A, and reading 12V, I would say it's sucking as much as the charger can supply, pulling the voltage down. That is a good sign, and means the battery will probably charge eventually. If the battery is only drawing minimal current, and the voltage is, say 13.8V or higher, that indicates sulfation. If the current is minimal, and the voltage is only 12V, I would suspect your charger.

[TwoTired]

Make some sacrificial leads for your voltmeter.  Simple nails using alligator clips works.

If you dip the nail into the electrolyte, you can measure the voltage produced at each cell. (at one end of the battery you use the post for the connection).

Anyway with this method you can find out which cell is dead.

Then you can probe adjecent cell electrolyte to the plate material in the dead cell to determine if the cell is shorted, or has a corroded/open interconnect bar.

If the interconnect bar is corroded away, that's it for the battery.

If the cell is shorted, you can turn the battery upside down and see if vibration will dislodge the shorting material.  If not, then it is new battery time.

If the plates have sulfated, then you might try EDTA to remove it.

Wal-Mart $20 1.5amp 6/12V battery charger. It's worked great for me.

Is this an automatic type charger with a float level?  If not, did you leave it charging the battery after the battery was fully charged?

[scottly]

OK, here is my magic recipe for resurrecting batteries that have suffered from prolonged discharge. It has worked for me many times...

Put the battery on a charge. If the voltage goes way up, but draws no current, shut off the charger, and while monitoring the voltage, connect a load across the battery. (I use ballast resistors, or headlights, or a combination, depending on the size of the battery.) Note how fast the voltage drops. Let it get down to, say 6V (in extreme cases it may be necessary to go almost to zero).  Put it back on the charger, and note if the current is higher, and the voltage lower. If it is, keep cycling the battery from charge to discharge until it draws a healthy, for the battery's size, current.

[scottly]

Duh, is it possible that your dual voltage charger was accidentally set to 6V? (the duh is for me, I did it before, and couldn't figure out why both my current and voltage were low)

[Laminar]

Do you have a way of measuring the current the battery is drawing? If It is drawing say, 1.5A, and reading 12V, I would say it's sucking as much as the charger can supply, pulling the voltage down. That is a good sign, and means the battery will probably charge eventually. If the battery is only drawing minimal current, and the voltage is, say 13.8V or higher, that indicates sulfation. If the current is minimal, and the voltage is only 12V, I would suspect your charger.

At last check, the battery connected to the charger showed 11.96 V and was drawing 1.6amps. Disconnected from the charger it showed 11.0V.

Duh, is it possible that your dual voltage charger was accidentally set to 6V? (the duh is for me, I did it before, and couldn't figure out why both my current and voltage were low)

Checked and double checked already. 

[Laminar]

Make some sacrificial leads for your voltmeter.  Simple nails using alligator clips works.

If you dip the nail into the electrolyte, you can measure the voltage produced at each cell. (at one end of the battery you use the post for the connection).

Anyway with this method you can find out which cell is dead.

Then you can probe adjecent cell electrolyte to the plate material in the dead cell to determine if the cell is shorted, or has a corroded/open interconnect bar.

If the interconnect bar is corroded away, that's it for the battery.

If the cell is shorted, you can turn the battery upside down and see if vibration will dislodge the shorting material.  If not, then it is new battery time.

If the plates have sulfated, then you might try EDTA to remove it.

From the negative post through a drywall screw into cell#:
1: 2.05V
2: 2.20V
3: 3.94V
4: 6.09V
5: 8.25V
6: 8.26V

Across the leads: 10.20V

It would appear that I have a couple of cells that aren't adding anything.

[scottly]

Ok, it sounds like your battery has a shorted cell (don't bother trying to find out which one; it wouldn't do any good if you did know). This is usually age related, though.... Hmmm, at this point, I'm thinking toast.. Sorry

[Laminar]

Well maybe this is just a good excuse to pick up a sealed battery like I actually want.