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Motorcycle Repair/charge battery


I have a 2005 Yamaha classic v-star 650.  It has a new battery that I bought 2 months ago.  my bike started after I put it in on a full charge.  I have started the bike every 3-4 days,( but not driven it) to keep the battery charged.  Now I am having trouble starting the bike almost doesnt turnover.  Also ive been told the bike needs a tuneup, carberator cleaned and spark plugs.  
I have disconnected the battery, put it on a charger on a piece of wood. the charger is a 12 volt charger and I am charging on a medium charge 12v at 6 amps.
My question is how long to charge the battery on 12v 6 amp, medium charge?

Hi Lisa,

Motorcycle batteries can be rather fragile things.
When you buy a new battery it should be charged
a bit before use if possible. Motorcycles are also
bad for having very little charge a low engine speeds.

If you did not actually drive the bike at higher engine speeds
then it probably did not give the battery much charging.
They charge very little until they reach 2000 rpm or more.

Motorcycle batteries are better charged on a very low
amp charger like one or two amps. These are called
trickle or battery tender maintenance chargers.

The higher amp auto chargers are okay but can overheat a
motorcycle battery if left on too long.
Too long can be as little as an hour of charging.

If your battery was very low it might be okay for an hour
and then check how warm it is. If it starts to get warm
then turn the charger off to let it cool down.

If your battery gets too hot it can be damaged.
Also if the battery was low for too long it may not
recover.  If you charge it for an hour and it still will
not start the bike then it may already be faulty.

There are also some cases where the battery is okay and
the starter motor is weak so having the battery load
tested at an auto zone or some battery shop
might be a good idea too.

The battery tender type chargers can also be used to
maintain a battery when the bike is not ridden often.
It keeps the battery at a "float" level where it charges
just enough to keep the battery healthy.

If you get it running I would also suggest putting
a multimeter on the battery terminals and
checking the charging voltage at different engine
speeds. It should read about 13.5 - 14.5 volts
at higher engine rpms.


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Wayne S.


Licensed Motorcycle Mechanic, Knowledge of motorcycles from 1960 up, Japanese, British and most other brand motorcycle repairs.


Worked for Yamaha, Honda, Suzuki, Kawasaki British: Triumph, Norton, BSA Other: Most Scooters and Mo-Peds

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