Forum

[Brazilla]

Some background:

1997 350

For a few weeks Roy has seemed to charge more than usual on startup and the ammeter stayed in positive for a bit longer. A couple of days ago I accidentally left the ignition on overnight in the garage and in the morning the battery was totally discharged. I think I am right in saying this shouldn't run down overnight and made me suspect I had a short somewhere. I had to use the bike the next day so went and bought a new battery when the old one didn't seem to recharge. Rode on that for two days intending to investigate source of the problem. Ammeter staying in positive all the time which made me think something was sucking power from the battery and the alternator was doing its best to recharge it.

Anyway, suddenly conked out on way home, battery totally dead, no horn nothing. Checked it out and ground lead was badly melted and came away in my hands when I investigated. Left bike locked up and took battery home, no reading at all from multimeter and charger seemed to do nothing.

Pretty sure I have foolishly killed two batteries. Planning on testing the function of alternator before installing new battery and trying to track down the short.

Any advice on how to proceed, tips for hunting down the short or telling me I am barking up the wrong tree would be greatly appreciated.

Many thanks

[Les]

If it is a short and caused the earth lead to cook I would have thought there would be signs of burning were the short is perhaps a good look over the wiring looking fore damage, if not it will be down to testing with a meter I would suggest not fitting a new battery or running the bike without a good check out first

[Girish]

Same thing happened to me few weeks ago. My battery terminals were touching the frame!

[PeteF]

Interesting Girish, perhaps we should have a fuse on the earth strap.

[stainer]

hi all,when my ford fiesta alternator gave in it took the battery with it but that earth lead needs more investigation got to be a short cheers

[Frank]

If the ignition had been left on overnight and the points were closed, I would have thought the battery would discharge itself through the primary of the ignition coil. If the primary resistance of the coil was 4 ohm it would draw about 3 amp and so would drain in about 4 hours.

[Adam]

A pal of mine had discharge problems (ooh err matron) on a Bullet the age of which I cannot remember but it turned out to be a short to a chaffed rear light wire inside the rear number plate bracket, the harness was about 300mm too long and was stuffed into a very restricted space. Might be worth a look?

[AA maniac]

Even if the earth lead was just loose or corroded it would have got very hot and melted the insulation,repair/replace the damaged earth wiring before anything else, and if your lucky then that will be all you need to do.Make sure the earth wire is good ,and has good clean connections both ends.

[Brazilla]

Thanks for the advice guys, here's what has happened:

Visually inspected wiring loom on bike and looks ok.
New battery on with new wire from negative to earth, starts ok but throttle indicates charge going into battery with + reading on ammeter.
Multimeter shows good reading on battery but when I start the engine it goes too high 16v plus with a bit of throttle...tested on regulator and same result.
I think I am right in saying the first course of action is a new regulator, I have the one which is 2 separate units so I guess it is Boyer powerbox time?

Only other thing was: can anyone recommend a good way to check for an unwelcome draw on the electric system, how much charge should a battery lose after an hour of sitting? Is there another way to check?

Thanks

[papasmurf]

If the battery is a normal lead acid one it should charge at maximum 14.4 volts. (Assuming your meter is accurate.)
Gel filled batteries can charge at 16 volts.