dumbass battery question

[crump]

What can cause a battery to discharge voltage when there is no load upon it and the battery is in perfect condition?? I have a charging problem on a motor bike which I cant diagnose.Battery can sit on bench and loses bugger all charge, connect battery to bike leads and battery discharges.Ignition off, clock disconnected etc. Place battery in other bike with exact same system, battery remains charged.Swap battery with brand new one from other bike, battery discharges.:eek::eek:The bike in question has a brand new reg/rectifier and the alternator has been rewound.The only clue I have is that I recently had the points ignition replaced with an electronic module and from then on the bikes volt meter started reading incorrectly.The other bike has the same ignition system and its volt meter reads correctly.Should I be looking for some kind of short from the ignition module that is draining the stored charge even with the ignition off???

[PhilipA]

Diode in alternator?
Just because its new doesn't mean its good.
Have you placed an ammeter across the battery + or -, and seen the drain?
You then disconnect circuits one by one to see where the drain is.
Regard sPhilip A

[davros]

I guess you could connect a multimeter to the two battery leads with it set to beep if there is continuity. Then disconnect items one by one untill it stops beeping? Or if it's a very slow leak, use the ohms meter and follow the same procedure?

Dave

[waynep]

Diode in alternator?
Just because its new doesn't mean its good.
Have you placed an ammeter across the battery + or -, and seen the drain?
You then disconnect circuits one by one to see where the drain is.
Regard sPhilip A

That could be misread as placing an ammeter across the battery + and - which would not be a good idea - it's effectively putting a short circuit across there and it'll probably cook the meter for a start.
To use the ammeter to check residual current drain, disconnect the + lead from your + battery terminal and place the ammeter in between them. ( i.e. in series )
Once you have it hooked up you'll see the amount of current being drawn ( in Milliamps) then you can start disconnecting things until it goes down to zero miiliamps or close to it.
Most of those cheap multimeters have an ammeter setting that will do the job.

to get more clues on this technique watch the movie Apollo 13 ! ;):)

[klimb90]

I have heard of an issue like this before where the new ignition module was wired directly to the battery instead of through the ignition switch. This caused the module to be permanently powered, causing a slow leakage current that would eventually drain the battery.

Hope it helps.

[Psimpson7]

Over what period of time is it going flat? I take it it hasnt got an alarm...?

[crump]

Over what period of time is it going flat? I take it it hasnt got an alarm...?
drops from 13.2 volts across the terminals to 10.8v in about 72 hours, no alarm fitted.

[Psimpson7]

Thats quite a big drain......... Can you disconnect things and see if you can pinpoint it?

[camel_landy]

Well... There's obviously a short there somewhere (swapping to another bike proved that), from here on in, you're going to have to try & work out where on the bike the problem is.

Here's how I'd approach it:

Before kicking off, I'd stick an ammeter between the battery & battery lead, this way I can tell if there is any current being drawn and take a measurement (we should see something as that's what's causing the battery to discharge).

Once setup, pull all the fuses, relays, etc... and see if the load has gone.

If it has, replace the fuses & relays, one by one until you find the offending circuit. Even when you have found the circuit, continue to check your findings by having a look at any remaining circuits as there may be more than one!

If you still have a short with the fuses, etc... removed, one of the other modules there might be causing problems... Disconnect all of those (lights, ignition, etc... and then start re-connecting as described above.

However, if you find that the short is still there with everything removed... There's probably something wrong with the loom and that's where things get interesting!!!

Good luck!

M