PLEASE HELP - Bike's voltage drops low (more info inside)

[JBL]

so i'm a new rider with little experience on how the electrics work so apologies about that.

here's my problem, with a fully charged battery everything works great but it seems to drop a lot of voltage when riding with the lights on.

here's some results from testing:
-nothing on - 11.98v
-just engine on with revs - voltage rises to over 13v
-after engine is turned off from rising to over 13 it drops to about 12.2
(this makes me think that it isn't a problem with the battery charging)

-JUST LIGHT ON - drops immediately to a pathetic 8.9v
-engine and lights on with revs - very slowly rises from 8.9v to only 9.2v (lights too dim to drive safely at night)

I would really really appreciate if someone could tell me what to do from here, thanks.

[Turkish]

Should be in the workshop really

What bike is it?
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ZX-6R G2
CBR125R RW6

[JBL]

[J.M.]

Not an expert by any means of the word, not sure even, but couldn't this be caused by a short/bad earth on the lights wiring somewhere?
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2004 R1 & 2018 XSR900

[BigGeeking]

Hello and welcome to the forum mate
1st should be posted in the work shop for things like this but never mind.

With the volts dropping that low the battery is shit, is it a MF battery or a serviceable battery you can top up with electrolyte.

If it is the latter top it up and recharge.

The charging of the battery on the bike when running sounds good 13V

What are the volts across the battery when cranking it?

But with the info you have give us the battery is fooked new battery time.
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Bendy "Flip front. I can filter down the M4 while shoving a Twix in my face."
honda CG 125 2001 SOLD-- current Bandit 400--SOLD. current SV650s 2000
MOD 1 ON 20/7/2011**passed** MOD 2 ON 17/10/2011***passed***,,

[Vincent]

To do a proper voltage test, you need to rev the engine up to 3000 - 4000rpm. It should be just over 12V at tickover and up to 14V when you rev the engine. Test with the lights off first then try again with the lights on.
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Space Is Deep

[Stalk]

Just had exactly the same problem with w 125 Sanya, turned out to be a short circuit to earth on the rear light. Unplug all the lighting connectors. See if battery voltage is ok with lightswich on. Leave lightswich on and start to plug things back together. Voltage will drop sharply and dashboard will dim dramatically when affected light plugged in.. that should point you in the right direction. Than its a case of visual inspection and measureing for continity on that part. Where are you?

[Kickstart]