13-08-13, 06:38 PM
You may think you have a charged battery, but if it has suffered sulphation (very likely if it has spent much time discharged) it may not be absorbing very much power, so the charger comes upto voltage very quick then goes into float mode (or whatever it does), but no real amount of energy has actually been put into the bettery. And what you see after you take the charger off is just a surface voltage and does not represent the charge in it.
Go wit a load test as mentioned by Paul
Start with a "charged" battery" The meter here is not crucial, but it will give a bit more info.
If your meter has a 10 or 20A current range, make sure you have your probes in the right holes on it and connect it in series with your negative terminal ie one attached (black) to the battery neg post and the other (red) attached to the bikes negative lead.
Now lets add up headlight 50Watts 2x tail lights 10W thats 60W or 5amps at 12v allow a bit for dash lights, guages and ignition and I would guess 5.5 amp
Turn it on dip lights see what it draws, a 10amp-hour battery even at HALF it's capacity should be able to keap this up for approx 50 mins, so if yours can't for even 15 mins I would say it is pretty shot
How old is battery and how long has it spent flat in it's life ?
Or you might find some strange readings
Alternately/and/or on lines with Andy, From a charged battery, measure the voltage ( DONT FORGET TO MOVE THE LEAD ON YOUR METER if you moved it before and reselect voltage ) across the battery directly on the terminal posts and then turn dip lights on and see if and how fast the voltage dips/dies and to what voltage
Post up results, Ill keep an eye on this as I can but it is sounding typically a sulphated battery not holding much energy
Go wit a load test as mentioned by Paul
Start with a "charged" battery" The meter here is not crucial, but it will give a bit more info.
If your meter has a 10 or 20A current range, make sure you have your probes in the right holes on it and connect it in series with your negative terminal ie one attached (black) to the battery neg post and the other (red) attached to the bikes negative lead.
Now lets add up headlight 50Watts 2x tail lights 10W thats 60W or 5amps at 12v allow a bit for dash lights, guages and ignition and I would guess 5.5 amp
Turn it on dip lights see what it draws, a 10amp-hour battery even at HALF it's capacity should be able to keap this up for approx 50 mins, so if yours can't for even 15 mins I would say it is pretty shot
How old is battery and how long has it spent flat in it's life ?
Or you might find some strange readings
Alternately/and/or on lines with Andy, From a charged battery, measure the voltage ( DONT FORGET TO MOVE THE LEAD ON YOUR METER if you moved it before and reselect voltage ) across the battery directly on the terminal posts and then turn dip lights on and see if and how fast the voltage dips/dies and to what voltage
Post up results, Ill keep an eye on this as I can but it is sounding typically a sulphated battery not holding much energy