dead battery ??

[wishbone]

Would there be a warning light if the alternator wasnt working properly
Ive had a few problems over the last couple of weeks starting the bike , last week it wouldnt start at all and had to jump it off the car , i charged it back up and it stated 'strong' on the optimiser ,
this weekend i got to the petrol station at the bottom of the road , it started ok but i left the bloody side stand down it wouldnt start after that , I looked a pathetic figure stood with a pair of jumpleads looking for assistance , anyway Im thinking the battery f**ked but my mate says it could be the alternator
the bikes been away all winter , I have an 05 gs1200 i bought it last june and is still under warranty ,
any ideas chaps

 

[Stahlgewittern]

deed battery

My battery shows 13.5 volts at full charge. but will not start the bike twice in quick succession when cold.
Its got the volts but not the Amps, so new battery for me.
ps
I can let the bike stand for two weeks and it will start on the button but not twice.

 

[Pukmeister]

It's not your alternator, it's the CAPACITY of your battery that is the problem (the ability to chemically store electrical energy and then release it again).

The batteries internal chemistry degrades with age and use. It will continue to show the correct voltage until it is almost totally knackered, but will gradually hold less and less, especially if it is short-cycle charged by an optimate etc. Think of it in terms of pressure and volume. The pressure (volts) are the same but the volume of stored power (amps) gets less and less with age and use. Your battery is like an electrical sponge that gradually shrinks as it ages.

An optimate does NOT measure the amount of stored charge, only the batteries ability to lower the voltage from the optimate itself when on charge. It gives you a ballpark indication of the batteries health, and is so very often wrong.

The only way of testing a batteries true capacity is to put it across a drop tester, which is a 'load bank' that rapidly discharges the batteries energy to prove it can handle the task at hand.

Your alternator will deliver Amps up to its maximum rated capacity, and volts at a constant rate. The Amps provided are 'drawn' by the battery being charged, the volts are forced (electrical pressure, remember). If the batteries capacity has decreased, it cannot draw the Amps from the alternator, so your battery power goes down.

 

[wishbone]

Sounds like a new battery then , Ive been quoted £50 for a varta ytx 14bs seems a good price