Charging system or battery?

[Bill_Walker]

This is only sort of motorcycle talk, so feel free to move it. I've got a question regarding my Kawasaki Mule 550.

 

It's used by my guys at my stable. The battery keeps going dead. I charge the battery, it starts fine. My DVOM says the battery is 12.6 volts when charged, and shows 13.8 at the battery terminals when the engine is running. So it seems to me the charging system is OK. And the battery takes a charge from my Battery Tender. So what's the issue? The battery is about 8 years old, so it seems reasonable to me that it could be time for a new battery. But then, why does it take a charge and work OK at first after charging?

 

 

[ShovelStrokeEd]

Voltage and current are two different, albeit interrelated things.

 

Hook your VOM to the battery and monitor cranking voltage. Starting at 12.6 volts, a healthy battery should stay well above 10 volts while cranking the engine to start. If it is dropping below 9.6 or so, it is an indicator that the battery is about done.

 

Basically, current is a function of plate area. As a battery ages, sulfation and erosion take their toll on plate area and, while the battery can still produce the desired voltage, it can no longer maintain that voltage during high load conditions.

[Survived-til-now]

Bill - over how long a period does it go dead?

 

Have you eliminated a drain on the battery caused by a short somewhere - by hooking up the meter between the battery + terminal and the positive lead and reading amps (do't crank the starter when doing this or you'll fry the meter). If current is flowing then pull out the fuses and re-insert one by one to find the circuit with the short..... (sorry if this is teaching Granny to suck eggs). Then you have to track down the faulty wiring but it could be frayed wiring on an always live circuit (i.e. one that is not switched off by the ignition switch).

[boatzo]

Bill,

 

I would guess that the battery needs to be replaced. After a lot of charging and discharging the plates get coated and do not function efficiently. There is a de-sulfication process that can be tried by disconnecting the battery and applying approx 15 volts for several hours. Then reinstall the battery and see how long it will hold a charge.

[Bill_Walker]

Thanks, gents. I'll try those tests.

[racer7]

???? Except in unusual cases, 8 yrs is certainly the life expectancy of typical lead/acid batteries. If it ain't dead yet, its about to be - just get a new one.

 

The only common tool of any real utility for testing a battery is a load tester. If its got a charge voltage and you want to know if its any good, this is the required tool. I replace my batteries when the ability to deliver load slides about a third because once that happens, they go downhill quickly. Ideally, this gets done before winter (if its a 4 season vehicle) because lead/acid batteries lose ability to generate current when its cold - so combining "old" and "cold" can leave one stuck on an early winter morning. The check is also the time to clean battery connections, another common problem.

There are load testers available for smaller batteries used in bikes and ATVs- they typically draw around 50-100 A. Most car units draw too much current to be useful for assessing bike-size batteries.

 

Newer maintenance chargers re better than older ones and have cycles that help prevent and even remove sulfation. Will extend battery life, especially for things that get laid up periodically...

[Bill_Walker]

Well, I misspoke, the battery was only 6 years old, not 8. (*#$%@# CRS). Anyway, rather than recharge the battery AGAIN so I could run those tests, I figured it was time and ordered up a new battery, betting the odds that that's my problem. If the problem returns with the new batt., I'll do the tests. Thanks!