gpz 500 battery going flat

[nigel_robbins]

Hi,
My battery is about 1 year old.
After riding for 30 miles I stopped for petrol.
My bike wouldn't start due to a flat battery.
After charging the battery I measured the voltage with a multimeter as follows:
12.39 when not started
11.2 on power up
13.8 at 5000 rpm
13.2 when ticking over (less than 1000 rpm)
After 3 days riding (30 miles each way per day) the battery has gone flat again.
Any idea what the problem may be ?
Thanks in advance.
Nigel

[stinkwheel]

Do you have any accessories running like a phone charger, gps or heated grips?

Check your battery terminals are on tight as a first stop.

If it's a conventional battery, check the electrolyte levels.

Your voltages sound good so statically at least, your charging system is working.

Could still land up being the battery.
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[Nemo]

Time for a new battery I reckon.

The charging system is working ok so process of elimination, unless you have something draining the battery when the bike is off.

You could take it to a garage and get them to test it for you.
____________________
Previously owned: Kawasaki KH125, Suzuki GP125, Suzuki GX 125, Honda CB125 TDC '83, Honda ntv 600, Kawasaki ER5, Kawasaki ZZR600, Aprilia RSV 1000 Mille
Now own: Ducati 848 evo

[stinkwheel]

Can be interesting to rig a voltmeter to the dash to keep an eye on things on the fly. You might find the voltage takes a major drop after a certain period (thermal breakdown) or when you use a certain accessory.

You can get cheapo LED digital ones off ebay for a couple of quid. If it's for pure diagnostics, you could just hook it directly to the battery terminals, tape it to the handlebar/dash then go out for a run and see what's happening.

I've fitted one to my VFR permanantly (attached to a switched live) because I've had an odd intermittant fault. As others will confirm, the "background" voltage will vary slightly depending on where you attach it but it should be consistant. Not the silliest mod in the world.

https://i48.photobucket.com/albums/f216/stinkwheel/drumbrake/CIMG1686_zps2e9b0a95.jpg
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[Snowdonia Rider]

Time for a new battery. Sounds identical to the problem I had only my battery was just 3 months old. I was getting good voltages etc and even after long runs the battery would be dead the next day. I too stopped for fuel and then bike wouldn't start
____________________
I want your clothes, your boots and your motorcycle.
Suzuki GP125 Suzuki GSX600F Suzuki SV650S KTM EXC250F SkyTeam Bongo 125
My YouTube channel: https://www.youtube.com/c/SnowdoniaRider

[unitynotsocri...]

As Stinkwheel but also check your starter motor is nt crudding up and causing current leakage .

plus dont buy the cheapest battery.
____________________
nearly a normal tax paying tosser.......with ferrileness suzi100,cg125,cb125scb100n,cb175,cd100,cj250t,kh250,c15,125 bantam,super 6,rickman gs750,xt500,250rs,dt175,lifan125,dolomite1850,metro,Morris220ld,morrisfg,leyland princess,range rover,corsa,vw camper .now struggling with legs. MORE ORDER = MORE CHAOS

[monkeybiker]

The battery should not die after a year if the bike is used regularly. Has the bike been sat unused for any long period of time?

Did you not get a warranty with the battery?

[Taught2BCauti...]

You need to test current drain before you buy a new battery.

If the Reg/Rec is playing up, it can cause the battery to leak back through the alternator windings and drain the battery.

Test it by disconnecting the earth lead from the battery, and connecting an ammeter between the earth lead and the battery terminal. With everything turned off, there should be nothing reading on the ammeter, unless you have an alarm/immobiliser fitted.

If you are getting a reading on the ammeter, try disconnecting the Reg/Rec and test again.
____________________
Honda Varadero XL125(V8)
www.TheFutureIsHere.eu

[nigel_robbins]

Thanks for all the replies.
I tested the resistance in the rectifier and on one pair I was getting a reading both ways.
When this happens my Haynes manual states a faulty rectifier.
I bought a replacement which fixed the problem.