volts drop on 12v battery

[Jai466]

Hey,

On my CBR 125 the bike would not start...

I've removed the battery and placed is on chage with one of these battery changed that auto detects the amp... the battery been left on charge for an hour.

When I test the current it read 12.90 and then slowly drop to 12.89, 12.88, 12.87 etc...

Is this normal? or would you say the battery is dead?

Many Thanks

[Pete.]

You tested the Voltage, not the current. Let the battery stand for a while and see how much it has dropped. It will drop slightly right after being charged.
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a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[Jai466]

[carvell]

You're testing the voltage, not the current.

There's not really any point in testing the voltage of a battery. If it doesn't start the bike once it's been charged then it needs replacing. If it can start the bike, it doesn't need replacing.
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Yamaha TDM 850

[Pete.]

He hasn't posted the symptoms except that it won't start. The battery could well be perfectly fine, a drop-test would reveal that.

Jai: put the battery on the bike and put the meter on the battery then watch the voltage as you crank the engine.
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a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[Jai466]

[Blue_SV650S]

[bootsbiker]

I would leave the battery charging longer then 1 hour.. over night would be better.. At the end of the charge with the charger still charging it should read about 13.5.. Switch of the charger and leave it to stand for a while it should drop to about 12.7..

Re-fit the battery and do the drop-test it shouldn't drop below 10v(a guess).. When he bike is running on idle then it should be over 13volts at least.. With high revs over this..

If it doesn't start then try to jump it or bump it and then see if it starts..

What does happen when u crank it over,, noise etc..

Have u check the water level? btw
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https://justfuckinggoogleit.com/

[Blue_SV650S]

Oh and with the bike running, from tickover, I'd expect to see the voltage pick up a bit as you revv, then get to a point and then start dropping off, thats just the regulator doing its job. You will find the point where the voltage starts dropping off again is probably not that far off idle!!


My bike looks like this .... LIGHTS ON 13.5v idle ... goes up to 14.8v just off idle, then progressively gets LESS with additional extra revvs. With it just off the readline, it reads 14.1v

I consider this a perfectly healthy charging system!!
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The purpose of life is to fight maturity.

[Finglonga]

Also if it's one of the old non sealed lead acid type, make sure you check the electrolyte level (before charging ideally) and top up if necessary.
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Andy Sez....
F.Y.Y.F.F.