Need some help verifying something about my battery. I charged up my battery overnight and then went over to the bike to try to turn it over today but the bike would not turn over. My DVM showed 12.5 volts, when I tried to crank it over the voltage dropped to 0 and the engine was trying to turn over but didn't have the extram OOMPH! It looks like the battery doesn't have enough cranking amps and my battery is toast. I don't know the age of the battery. Can someone confirm that this sounds like a defective battery?

I charged up the battery to 14.2 volts and after the first crank it dropped to 12.5 then to 12.0, then to 11.58v.

 

Charge your battery until it measures 12.4 volts. Let it sit an hour or two and then turn on all your lights - high beam, passing lights, what ever you have. If your battery is serviceable it will hold near 12 volts for quite a while and then slowly start to go down. If it all of a sudden drops from 12 volts to 10 volts that is a good indication that one cell is defective and the battery is junk. Your battery is actually six 2 volt cells connected in series. If you loose one cell, the whole thing is scrap.

When you see something like 14 volts on your battery it is because it has just been charged and there is a "surface charge" on it. Its sort of like overfilling a cup a little. Doesn't really mean much and goes away quickly. Typical lead acid battery cells charge up to a shade over 2 volts each. When your engine is running it will show around 14 volts because the charging system has to develope a difference in potential for current to flow to the battery and charge it. Water won't flow across a flat area to another body of water! It has to be raised up higher to cause a difference of potential for it to flow. Electrons work like that too.

The best way to check a battery is to charge it to 12.4 volts and then use a load tester on it. A load tester draws a lot of current out of the battery while measuring the voltage. It must not drop below 10 volts while delivering that flow of current for a certain period of time. Auto stores usually have load testers they use to test customer's batteries. Placing a load like your lights on your battery for a while is not as good a test as a load tester but it will often reveal a bad cell.

Your voltmeter shouldn't show "0" volts while cranking. If I understand your post, you stated it read "0" volts while cranking. If you think about it, this is impossible. Your starter needs at least 10 volts to even try to spin the motor over. Perhaps you have a modestly priced meter. On the other hand, if it actually reads "0" volts when you hit the starter button maybe you have a bad battery connection. The starter won't even try to spin with this condition. You'll probably just hear a "click".

If the battery is more than a couple of seasons old it is probably toast. If it has not been used in a while it may be sulfated. A run down battery sitting for a few days or more will get a coating on the plates and electrons won't flow. A sulfated battery might drop to "0" but it won't even attempt to crank the engine.

 

Thanks Square Dude. I took it over to Autozone and tested it under a load. Sure enough the voltage dropped to 0.13 volts. The battery as the guy at Auto Zone said was "Boned". The meter I use is a Fluke 87. I also thought my meter was bad, and that was why I took it to Auto zone. Thanks for the help.

 

I'm glad you figured it out. That sounds like a sulfated battery to me. Here in Houston we ride all year and that keeps the battery pretty much charged. I still have a trickle charger I use it if I only start it to put it back into the shop (uphill). I don't leave the trickle on it cause it doesn't cut off although it only puts out about a 1/8 amp. If you don't ride regularly I would get a battery maintainer.

You have a great meter. There are cheap units out there that may lie to you. I use a Fluke 77.

 

Bought a new battery, charged it up and the bike turned over with no problems.