testing a motorbike battery
Miks15 - 9/8/10 at 12:36 PM
Im having a few problems with the battery on my motorbike. Is there a DIY way of testing the battery to see if its still any good?
Basically it seems really weak, if i do a short journey (2-3 miles) it doesnt regain enough charge to start the bike again sometimes. And you can tell
after a long stint, that theres only just enough to start it. i want to do a check on the battery to see if its this, rather than the charging circuit
on the bike. Anyone got any ideas?
02GF74 - 9/8/10 at 12:51 PM
measuring the voltage across the terminals is a good start.
also do the same when engine is running at about 2,000 rpm - you will see if the charging circuit is working.
how old is the battery?
2-3 miles isn't a long way but assuming the bsattery is the corect size for the bike, it shouldn't struggle to turn the engine over.
interestedparty - 9/8/10 at 01:01 PM
quote:
Originally posted by 02GF74
measuring the voltage across the terminals is a good start.
Yep. Look for around 12.5 before starting, and around 14 when the engine is running.
Miks15 - 9/8/10 at 01:08 PM
A few weeks ago i started the engine about 10 times in a few minutes absolutly no problem, no signs of the battery weakening. (I left the side stand
down and it kept cutting the fuel pump as i put it in to gear, and i didnt realise it was the side stand doing it! Wasnt my cleverest day ill admit 
)
But then i had to go out to birmingham last week, i left my house there (student in birmingham) to go to sainsbury a couple minutes away, went home,
then went to tesco for petol on my way back to grantham, and it would start again after filling up! luckily there was someone else broken down in the
petrol station and had an AA man there so his starter pack sorted me out!
Then no problem again since, until yesterday. I went to watch my dad do the newark half marathon, and i went to a few points to see him go past. So it
was about 15 minute journey there, stopped, moved a mile, stopped moved a mile, etc for a while, after a few of these it wouldnt start again, and i
had to bump start it. then i drove around for a bit following him on the road, parkedup near the finish to see him finish, after that it started up
again no problem. So the problem is a bit intermittant.
carpmart - 9/8/10 at 01:16 PM
Check voltages as described above then get the battery off the bike and on a charger for a few hours and see how you get on from there!
Bike batteries are not that expensive so the belt a braces approach, assuming that you have 14v plus when running, is to get a new battery! For the
price, its better than being broken down somewhere without a friendly AA man!
Miks15 - 9/8/10 at 01:23 PM
yeh my other bike has a brand new battery actually, assuming there the same size i might swap it in after doing some voltage checks, and then see if i
get any problems
interestedparty - 9/8/10 at 02:45 PM
I thought motorbikes had kickstarts?
bmseven - 9/8/10 at 02:57 PM
If you have another battery then great just swap it over and if eliminates the problem then job done.
If not then check the charging output as above.
As your problem seems a bit intermittent if its not the battery on it's way out then check for a drain after checking you first have a good earth
?
With a multimeter set to amps and connected between the negative battery post and the negative lead(s} expect to see a reading of no more than
0.2-0.4amp (allowing time for an alarm to stabilise if fitted)
quote:
Originally posted by interestedparty
I thought motorbikes had kickstarts?
What's a kickstart 
[Edited on 9/8/10 by bmseven]
Miks15 - 9/8/10 at 03:19 PM
quote:
Originally posted by interestedparty
I thought motorbikes had kickstarts?
Hmm dont fancy kick starting my 600 tbh!
Miks15 - 9/8/10 at 03:20 PM
quote:
Originally posted by interestedparty
I thought motorbikes had kickstarts?
Hmm dont fancy kick starting my 600 tbh!
britishtrident - 9/8/10 at 06:50 PM
It takes 20 minutes driving to replace the energy lost in a single cold start.
Only way to test a battery is to trickle charge it for 24 hrs or longer if not fully charged then leave it to rest for 24 hrs, check the voltage with
nothing connected then use a high current discharge to check the voltage drop under simulated starting conditions.
interestedparty - 9/8/10 at 07:10 PM
quote:
Originally posted by Miks15
quote:
Originally posted by interestedparty
I thought motorbikes had kickstarts?
Hmm dont fancy kick starting my 600 tbh!
Wimp
ReMan - 9/8/10 at 08:30 PM
Bike batt life varies considerably
As little as 12 mths is not uncommon 5 years about max
RAYLEE29 - 9/8/10 at 08:36 PM
Hi, if its a gell battery the helpful AA mans booster pack could have fried the battery
you need to be very carefull with modern bike batteries overcharging boils the gell away from the plates and thats the end
also do a voltage check before fitting a new battery over charging ie 16v will kill the new battery quicker than under charging
Ray
ps did you say what bike it was blades and 80s suzukis are known for regulator faults
RAYLEE29 - 9/8/10 at 08:40 PM
oh and bike alarms kill batteries too so get an optimate and always use it if you have an alarm
Ray