Topic: Did I kill my battery?

[Jayelwin]

So I have a newly restored '75 750 that runs great. Started in an instant. On Sunday I accidentally left the key on and the headlight and stuff completely drained my 3 month old eBay Chinese battery. Oh crap. Threw it on a tender and now Monday night I thought it should be charged. Nope. It has enough juice to make the neutral light barely visible when the headlight is off. So I grabbed another battery and with jumper cables I was able to fire the bike up. But then the instant I took the jumper cables off it would stall even from a high rev. I got it running goosing it and had it going with the jumper cables off then I turned on the headlight and it stalled.

Could I have killed the battery and created some sort of internal short? Can you kill a battery by leaving the ignition on in the summertime?

[Jayelwin]

Ok. I have two chargers. It was on the 0.5 amp one. I have a 2 amp one.

[TwoTired]

Check the electrolyte level.  Add distilled water if necessary.
Charge the battery and check the voltage after 2hours rest off the charger.  S/B 12.6-8V.  If less than that, the battery is probably damaged.

[Jayelwin]

Fluid level good. I took the battery out and let's see what 12 hours on the 2 amp charger does.

[jdubb1977]

did the same thing to mine a few weeks ago.  refilled w/ distilled water and left on the charger for about 24hrs.  it's good now.  i've checked it every couple of days w/ the multi-meter and its still keeping a good charge.  you should be fine.

[scottly]

Fluid level good. I took the battery out and let's see what 12 hours on the 2 amp charger does.

A "battery tender" is not necessarily a charger, regardless of the amp rating. Monitor the voltage while the battery is on the charger; it will need to get to at least 14.5V to recharge. "tenders" limit the voltage to about 13.5V, which is the float voltage of the battery, where it is neither charging or discharging.   

[Jayelwin]

The 0.5 amp one doesn't have the voltage. The 2 amp one was more than 14 volts on. The dead battery was at 11 volts when I removed it. So not totally dead. Fingers crossed I didn't kill it. It was cheap.


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[dave500]

11 volts is cactus!use a normal car charger for half an hour on it then try the tender?a better quality battery might take that abuse better?you can be lucky and it might come back,main thing is not to leave discharged batteries stand for any time,recharge them straight away.

[Vinhead1957]

Never charge a motorcycle battery on the car setting.  Good chargers have a low setting.  If you do at the high setting it will warp the plates and they may short. 

[TwoTired]

11 volts can be a poor battery charge level, or it can be a good charge level with a dead cell.  That's why you give it a charge that should make all cells provide full voltage, wait 2 hours to let the electrolyte equalize/stabilize its charge saturation, and then take a voltage reading. 2.1 volts per cell x 6 cells = 12.6V.  2.1 volts per cell x 5 cells = 10.5V.

There are many failure modes of batteries.  But, a good one will respond predictably with a proper charge procedure.  For example, my Cb700SC battery receives a charge and shows good voltage after wards.  But, it fails a load test, dropping the voltage down to 9-ish volts (and then lower) when the starter load is placed on it.  Battery is old and tired (~5 years).  New battery holds voltage, allowing the bike to start and run as it should.

I've had other batteries that had just one cell fail.

A good battery that is simply drained can take a far higher amperage for a short time to do a bulk charge (50-80%).  But the electrolyte needs a much slower charge rate to saturate fully without heat damage.  The danger from fast charge (which is no worse for the battery than starter current drain load rates), is doing it when the battery is already near or closer to full capacity.  When the charge rate exceeds the chemical saturation rate of the battery, damage can occur.