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Old 01-10-2014, 02:06 PM   #1
squish OP
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Battery voltage question 93 R100GS

Ok
I've got a R100GS with a wet cell style stock battery
I've got my DMM
I don't have any of my manual's or notes handy.

What is good voltage for the battery that's been charged with no load and with load, (Bike on not running, headlight on Led tail light)

I'm 90% sure my battery is dead, but I just want to confirm.
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Old 01-10-2014, 02:24 PM   #2
190e
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No load voltage for a fully charged wet cell should be 12.65 volts but this must be measured after an overnight period of rest. 12.45 Volts is 75% charged, 12.25 volts 50%, 12.05 volts 25% and 11.8 volts flat. Measuring voltage after charging or running the engine is largely meaningless as the battery retains what is called a surface charge which will give a false high reading.

The voltage will drop under load but with headlight only not much say to approx. 12.0 volts.

Voltage when cranking is a good load test and should not drop below 9.5 -10 volts.


The voltage drops under load increase as the battery ages due to the batteries internal resistance increasing and in the absence of other faults this is what eventually kills off a battery. For the same reason another good indicator of battery health is the self discharge rate. You can have a rested fully charged battery at 12.65 volts but if due to a high internal resistance and self discharge rate it falls to say 12.45 volts after a day or two then it's on it's last legs.

190e screwed with this post 01-10-2014 at 02:39 PM
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Old 01-10-2014, 03:12 PM   #3
Warin
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What you do not know about batteries -

www.batteryfaq.org

No connection, it is just a good site.
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Old 01-10-2014, 08:55 PM   #4
squish OP
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Thanks.
To both of you.

I spaced on the surface charge and kept checking the battery shortly after charging. I'm now even more sure it's dead. Not bad for a 5 year old battery of a lightly ridden bike.
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