alternator? rectifier? battery?

hello
i have a 2000 sv560s and i am having problems with it
it has an alarm fitted and some days it will start and others it wont because the battery hasnt got enough. i test the battery when its running, sometimes it will run and 13.7 volts with the lights on and revving it and other days it will run after a bump start at only 12 volts with the lights on and revving it
i stated it one day drove 20 miles left it for about 6-7, hours tried starting it again and the battery didnt have enough
i know its not the battery because its only about 2 months old
any ideas people? or is it just a temperamental sod?
thanks

Can you provide some voltage figures for:

idle, no lights
5000 rpm, no lights

idle, lights
5000 rpm, lights

generally, the voltage should stay between 13 and 14.5 volts if the reg/rec is doing its job correctly. How old is the battery, may I ask? you can get that tested for efficiency aswell to see if its ok you may have a dud battery (it happens) but chances are its not

sorry i wrote in wrong idle with lights is roughly 12 volts without is about 13. and when it was revving only goes up a little bit i cant remember exactly because the it was the break down recovery mans meter
but yesterday it started fine but at most was reading 13.7 lights on and revving and today no start
the battery i got on the 5th of december 2009
i reckon its the regulator but im not to sure, i hope i make sense

Originally Posted by Alpinestarhero

Can you provide some voltage figures for:

idle, no lights
5000 rpm, no lights

idle, lights
5000 rpm, lights

generally, the voltage should stay between 13 and 14.5 volts if the reg/rec is doing its job correctly. How old is the battery, may I ask? you can get that tested for efficiency aswell to see if its ok you may have a dud battery (it happens) but chances are its not

Ah, to me then it sounds like a bit of a pooped regulator / rectifier - however, I can't be completly certain of this (I'm no expert!) since it is more usual for a faulty reg/rec to give higher voltage readings. You could PM either Spannerman, Yorkie Chris or Sid Squid for a more well-informed opinon

[Biker Biggles]

If you are getting 13.7 volts with lights on at 5000 rpm this suggests the charging system is OK.What battery did you buy and how much did you pay?It may be a dud.

i got it from my local garage and it cost me £80

Originally Posted by Biker Biggles

If you are getting 13.7 volts with lights on at 5000 rpm this suggests the charging system is OK.What battery did you buy and how much did you pay?It may be a dud.

[Biker Biggles]

For future reference you can get a good new battery from Batteryman on this forum(based in Enfield)for under £50.
As for your current situation do you have a Optimate charger or can you borrow one?
Try charging your battery and see if it takes a full charge and holds it.If it doesnt take it back to where you got it and get it replaced or a refund.Other checks to do are that all the connections are tight,especially the battery terminals and the block connectors to and from the regulator.And the earth strap.
As your bike has an alarm I would advise you to get a charger anyway,and make a point of ensuring it gets charged every week or two.

i charged the battery not long ago and it held its charge and i only have a halfords motorbike charger
i have also checked all the connections but i will go over it again tomorrow
i have got a feeling its going to be something a bit more serious than the connections though
and cheers for the heads up on batteryman

Originally Posted by Biker Biggles

For future reference you can get a good new battery from Batteryman on this forum(based in Enfield)for under £50.
As for your current situation do you have a Optimate charger or can you borrow one?
Try charging your battery and see if it takes a full charge and holds it.If it doesnt take it back to where you got it and get it replaced or a refund.Other checks to do are that all the connections are tight,especially the battery terminals and the block connectors to and from the regulator.And the earth strap.
As your bike has an alarm I would advise you to get a charger anyway,and make a point of ensuring it gets charged every week or two.

[Biker Biggles]

OK if you do have a charging problem it looks like undercharging or it would probably have cooked the battery by now.One further check you can do is alternator output.With the meter on AC check the three yellow wires that come from the engine (alternator)to the regulator.Disconnect these at the block connector at the reg,start the engine and measure the output across each of the wires,That is---1 and 2,then 2 and 3,then 1 and 3.You should get a similar reading for each and somewhere round about 70 volts.If one result is significantly lower then the alternator is duff.

[Spanner Man]

Good afternoon all.


It sounds as if you have a little charging going on. It may be that there's a bad connection between the reg/rec & the battery. Check your lights on/off voltages again, & write them down for reference.
If you're a little mechanically minded, remove the red output terminal from the reg/reg plug, (on the reg/rec side) & run a lead from it directly to the positive battery termianal. keep the connector away from the frame etc. If your accross battery voltage increases over what you had before, then it's likely that there's a dodgy contact somewhere.
A quick battery test is to see what voltage it drops to on starting. With your battery fully charged, clip a meter across the terminals, & whilst watching the meter start your bike. If the voltage drops below 10.5 volts it's a good indication that the battery is lacking in capacity. It's not infallible, but gives a reasonable indication.


Cheers.