Battery running down? Testing?

[tri650]

78 XS11 - put in a new battery not long ago after other one crapped out. This one ran fine until the other day - then it was dead. I could bump start the bike and it was OK. Charged it back up and everything is OK. Wondering if my alternator is bad and I am draining the battery without recharging. Could this be an alternator problem? If so, how do I test?

[CatatonicBug]

Start the bike, with the front end pointing at a dimly-lit wall (like a garage). Rev the engine, and see if the headlight gets brighter. Of course, you could also use a multimeter and check that your battery has 12v when it's not running, and 14v when revving the engine.

[fredintoon]

78 XS11 - put in a new battery not long ago after other one crapped out. This one ran fine until the other day - then it was dead. I could bump start the bike and it was OK. Charged it back up and everything is OK. Wondering if my alternator is bad and I am draining the battery without recharging. Could this be an alternator problem? If so, how do I test?

Hi tri,
if your tach still works the alternator wire it's hooked to is still sending current.
Alas, there's 3 of them.
The first Q&D test is to point the headlight at a wall and rev up.
If the light gets brighter, it's charging. If it don't, it ain't.
Next comes checking all the wiring connections and applying the multimeter.
The usual suspect is the big white plug under the fuse panel with the 3 white wires in it. That plug has been known to melt into a blob.

[tri650]

Funny you mention the tach. It started to bounce around right before the battery went dead. Thought it was broken. Since the battery was charged it is working fine. When I checked the battery it was at a little over 12V. I will try it running. Thanks for the input.

[jjwaller]

Funny you mention the tach. It started to bounce around right before the battery went dead. Thought it was broken. Since the battery was charged it is working fine. When I checked the battery it was at a little over 12V. I will try it running. Thanks for the input.

How much a little over? A fully charged 12 Volt battery is in reality a 12.6 VDC
battery. When a 12 volt battery actually reads 12 volts, it is in fact 100% discharged.
So yes check it with a voltmeter. When running, minimum charging voltage is
around 13.6 VDC. A good check on a battery is to fully charge it with a plug in
charger. and then let it sit for approx. 12 hours. After that time it should be a minimum of 12.6 VDC. If lower, then it is on the way out.

[3Phase]

Tri, my bike did pretty much the same thing as yours last month and I discovered that the positive battery cable terminal was loose. Since you just put in a new battery, double-check the battery cables and terminals.

While you're at it, check and clean the ground cable connection to the frame below the battery box and the Black wires on ring terminals that are bolted to the regulator/rectifier under the gas tank.

Unless you like to ride your XS through the surf at the beach to impress the ladies and kick sand in squids' faces or you follow a lot of salt trucks around in the winter, a small amount of copper-based anti-seize spark plug grease on the connections will help prevent corrosion. Be careful with it. The stuff gets everywhere, it conducts electricity and it clings tenaciously to almost everything it touches!