| Battery fault finding
OK. I am a battery/battery charger engineer and i'd like to weigh in with my 4p worth.... It's VERY unlikely that you will do any damage jump starting from a car engine provided the bike and car have the same battery voltage (12v), but some delicate electronics can be damaged if the cars engine is running - it's VERY rare though. I've known CAR electronics to be blown doing this due to a faulty BIKE regulator stuffing a voltage spike back up the jump leads! Best advice is to use the car battery to jump the bike WITH THE CAR IGNITION OFF.
BTW Car batteries have a signicantly higher capacity than bikes so can crank for longer - SO BE SENSIBLE. Don't hold the starter button in for ages and allow the cables to cool off if they start to get warm.
FAULT FINDING: If you measure a battery and it gives approx +12v but all you get is a click when you press the starter button, connect the voltmeter directly to the battery (not the connectors on the end of the leads but directly to the battery terminals themselves) THEN press the starter button. If the battery has a high impedence (ie it's knackered) the terminal voltage will collapse. Time for a new battery. If the battery voltage barely changes then no current is being drawn and the problem lies elsewhere.
This is a more accurate method than the old "see if your lights go out when you press the starter" method. Your lights will go out if the battery is duff OR if you have a bad connection.  |