curious issue with my SLA battery - not charging

[acecafe1000]

I have a 1975 xs650 with a slight electrical issue. The bike has been torn down to the frame and rebuilt bratstyle...including the wiring harness. Kick only, head/tail light...that's it. Built new wiring harness from scratch following one of the many "chopper" diagrams floating around.
Last sunday gave it's first kick in who knows how long (bike has 4600 original miles). As i was sorting out sparking issues, noticed that the SLA 12v battery (.8amp) was pretty warm from the few kicks i'd given it. Didn't think anything of it...fast forward 4 hours and a couple battery re-charges, finally got the engine running...noticed the battery no longer was warm/hot. Went on my first run around the block and she died out within the first mile. Flipped the light switch, no juice...dead battery. Tonight i was planning on attacking the rotor/stator/regulator/rectifier tests to see where the problem might be.

But then it hit me...those first few kicks, the battery was obviously getting juice from the alternator due to the heat it was picking up. After those few hours of kicking it over, and the battery no longer hot, does that point me in a more obvious direction?

I know this is a pretty open ended question but was hoping an obvious one to the experts...

Alex in austin.

 

[pamcopete]

ace...,

You probably fried the battery. A .8 Amp battery should only be charged with a .08 Amp charger. The stock alternator puts out about 15 Amps with maybe 2 or 3 Amps left over to charge the battery after servicing the headlight, ignition and regulator.

This is if the battery is discharged (10.5 Volts) If you start out with a fully charged battery, then it will draw zero current, so no harm done. The trick with these tiny batteries is to keep them charged up on a trickle charger so they will not draw excessive current from the alternator.

The fact that the battery was getting warm (hot?) is your clue. If you charge any battery with more current than it can handle, then the excess current is converted into heat.

 

[acecafe1000]

thanks for the response pamcopete (i'm new to the xs650 but man your name is all over the place)...so a little more to the story.

After that first run and the first dead battery, i got the bike home and recharged using the duracell motorcycle charger i've used on my KZ1000 (stock battery) for years. This one will charge the sla in about 15 minutes..then shuts off. Spent the next few hours buttoning up a few loose ends...then set out for another ride (i assumed my first dead battery was due to me getting the bike started the first time)...making a turn down my street, i let the clutch out like a newbie and killed the bike. Went to kick start and nothing, flipped the lights on, dead. But there was evidently enough juice left in the battery to pop the clutch and it got me back to my garage.

I assume I didnt kill the battery because i can still put a charge to the thing...and the charge will hold sitting in my garage. Since that initial kick when the battery got hot, i've probably charged the thing 3-4 times. Honestly though...i havn't checked the volts at the battery as my multimeter is hiding somewhere in my 6 year old's room. Just been going off "brightness" of my head/tail lights as a judge.

 

[DogBunny]

pamcopete, I just thought I would give you a little update.
I helped cafeace1000 on Saturday. His rotor was open (infinity ohms). We put a good rotor on, and then his stock regulator seemed squirrely. He got an AutoZone reg, but I haven't talked to him since then.

It looks like he did not fry his battery, because his alternator was putting out zero amps. He just killed the battery on his test runs, and then re-charged it each time with a trickle charger.

 

[pamcopete]

DogBunny,

OK. Thanks for the update. He should keep that battery charged up every night on a very low output trickle charger to reduce the overheating from the bikes alternator which puts out way too much current for that tiny battery, but if the battery is charged up there is no charging current initially on the bike. I would also suggest that he increase the idle revs a bit to put more of the load on the alternator.