my battery keeps going flat!

veze · Trackday Trickster Joined: 20 Jun 2007 Karma :

my battery kept going flat, so i bought a new one, but that goes flat after a day! is it the regulator?
beacaus i know the alternator is working because even though there wont be enough power to make that flasher unit work, it will when i rev the engine.
so regulator maybe?
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tlm50,mt5,sr50. rs125 extrema, cbr 400rr nc29 suzuki gs500e.Honda cbx250 rs . FJ1200 .fz6,fjr1300

loply · World Chat Champion Joined: 24 Mar 2004 Karma :

Do you have a multimeter?
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Yamaha SZR660 Caution to the wind, the throttle pinned!

veze · Trackday Trickster Joined: 20 Jun 2007 Karma :

yeah i got one at my dads house
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tlm50,mt5,sr50. rs125 extrema, cbr 400rr nc29 suzuki gs500e.Honda cbx250 rs . FJ1200 .fz6,fjr1300

loply · World Chat Champion Joined: 24 Mar 2004 Karma :

Alright, set it to 20vdc and put the two prongs on the terminals of your battery. Probably get 12.8v or thereabouts.

Turn the engine on, and measure it again. If it's normal you should get 13.5v or therabouts.

Rev it up to 4k or thereabouts, it should rise now to something like 14v.

If the voltage doesnt go up when you turn on the engine and/or rev it, then your charging system isnt working probably. Either the alternator or reg isn't doing its job. You can test those by following the procedure in your workshop manual.

If the voltage DOES work as described above, then it appears to be charging. Perhaps it's running out when you arent using it...

To test this, disconnect the positive red cable from your battery. Set your multimeter to ADC and put one prong on the positive terminal of the battery, and the other end on the cable you just disconnected. With the engine OFF this is.
It'll tell you how much current is being drawn by the bike. Ideally 0! Sometimes 5-10ma if you have clocks or alarms. Any higher might indicate a shortcircuit or faulty handlebar grips or suchlike.
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Yamaha SZR660 Caution to the wind, the throttle pinned!

NSR Mick · World Chat Champion Joined: 26 Jun 2005 Karma :

Does the bike have a cheap alarm?
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chris-red · Have you considered a TDM? Joined: 21 Sep 2005 Karma :

veze · Trackday Trickster Joined: 20 Jun 2007 Karma :

no alarms or heated grips, ive tried that test on the batt, the voltage doesnt improve that much, alwost reaches 13 but not quite. if the regulator/ rectifier is but should it run hot? someone told me that. i havent had a chance to test it just yet?
if its that thats but im goin up newark autojumble on the weekend hopefully i could pick one up.
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tlm50,mt5,sr50. rs125 extrema, cbr 400rr nc29 suzuki gs500e.Honda cbx250 rs . FJ1200 .fz6,fjr1300

hopoffbaby · Spanner Monkey Joined: 16 Mar 2002 Karma :

Hi all, im having a similar problem with my bike.
It doesnt seem to hold its charge for more than a few days without use. I have just brought a new battery but want to check the old one while its still on the bike because i want to know if my heated grips are causing the problem.
I understand the bit about the VDC test.
What i don't understand is how to set up on my multimeter to do the ADC test.
My multimeter has 3 sockets on it. I have the black lead plugged into the one that says COM. The red lead is plugged into the one that says "V<ohms>mA" (the other socket says 10ADC) is this right? I dont wanna blow up my bike lol.
Neil.

el_oso · World Chat Champion Joined: 17 May 2008 Karma :

the multimeter will not do any damage to your bike no matter what weird and wonderful way you may set it up it will just give you an incorrect reading or no reading at all.

a good garage will check whether you have a dead battery or not for free. take it into them if your not sure. batterys do tend to die this time of year especially if they havent been run for a while or used for short journeys

Sir Black Pig · World Chat Champion Joined: 22 Oct 2007 Karma :

For the Amps DC Put the black lead into the COM (-) and the red lead into the ADC (+) and measure, setting you multimeter dial to DC Amps.

The reason ADC has a seperate socket is that is individually fused so if you have a massive surge it will protect the muttimeter and (of course) you!

Hope this helps.
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Sportugal 2010

loply · World Chat Champion Joined: 24 Mar 2004 Karma :

If the voltage doesnt reach 13v even wen revving the engine, then definately its not charging.

Either the reg/rec is shot or the alternator is, or any of the wiring/connectors that they rely on.

To test the alternator is pretty easy, just find the plug going into the reg/rec that leads back to the alternator. Itll probably have 2-4 wires in it. Run the engine, disconnect the reg/rec and test the AC voltage between those... I dunno what you would expect, maybe 60v or 45v or something.

If it's 0v or 5v or something daft then it's your alternator. If it seems normal (check the right amount in a manual) then it's presumeably the reg/rec and not the alternator.
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Yamaha SZR660 Caution to the wind, the throttle pinned!

loply · World Chat Champion Joined: 24 Mar 2004 Karma :

Incidentally if you ride without your lights on and charge the battery nightly you can probably ride it like this for quite a while.

Obviouslly though just bear in mind you are using up battery charge like fuel, so always make sure you are able to charge it, and try not to turn the engine off till you get home (else it might not restart)!
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Yamaha SZR660 Caution to the wind, the throttle pinned!

Sir Black Pig · World Chat Champion Joined: 22 Oct 2007 Karma :

Pete. · Super Spammer Joined: 22 Aug 2006 Karma :

Well not really as you generally get warnings if your battery runs flat when riding. The bike will start to mis-fire when you use the brakes etc. They don't usually just cut out dead.
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veze · Trackday Trickster Joined: 20 Jun 2007 Karma :

ran out of battery earlier, took to hours and 4 long hills to get home. i tried bumping it but the back wheel locked in all gears even with me jumping on it. it was a farce. i will test hat in the morning then and hopefully i can see what the problem is.
cheers folks.
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tlm50,mt5,sr50. rs125 extrema, cbr 400rr nc29 suzuki gs500e.Honda cbx250 rs . FJ1200 .fz6,fjr1300

Phoenix · Twisted Firestarter Joined: 01 Aug 2002 Karma :

Regulators are a pain in the arse to check with a multimeter, the readings never come out right. It sounds like it's your regulator anyway, they do run hot and heat kills them over time. You should be charging at over 13volts and if the bike is dying while you're riding it's not a current drain or short somewhere that's causing your flat battery it's the charging circuit, and i'd bet on regulator rather than alternator.