New battery but slowly loosing charge

Hi, I have replaced my battery but over a period of about 2-3 weeks it gradually looses charge, eventually getting to the point where it will only just manage to start. I replaced the rectifier about 18 months ago because of the cutting out issue, I think I may need to replace it now because of undercharging? My Fi had done 60k, what about the magneto? Are there any common issues with undercharging?

 

You need to systematically identify why the battery is being drained. If the battery is disconnected and it continues to loose the charge at the same rate then it probably needs replacing. If the battery holds its charge when its disconnected from the bike, but looses its charge when connected, then it is probably due to some sort of electrical drain. Using a mutimeter check to see the drain on the battery. Progressively pull fuses until the drain stops and you should have a pointer to which circuit to examine.

Not sure what VFR you have, but early models have a history of charging system issues. Basically all four bits of the charging system (Loom, Stator, Battery, RR) need to be in good condition. A fault in one can damage some or all of the others. If the battery is not being recharged enough whilst you ride, then a dead or dying stator is a possibility especially if you have had issues with the RR.

If you do end up needing to buy parts - then try to stick to OEM as there are quite a few on here who have had issues with aftermarket RR's/stators failing soon after being installed. In the UK try David Silver Spares but don't just visit their website - I found their telephone people really know their stuff and can also advise if a part has been uprated or superceded. On occasions their telephone staff have even managed to undercut their own online web-price.

Anyway rather than repeat stuff, the following thread should tell you what to look out for and how to check...

http://vfrworld.com/forums/5th-gene...how-fix-common-regulator-stator-failures.html

Good luck, and let us know how you get on.


SkiMad

PS you may want to update your forum profile to include whatever VFR model you own in the section marked "My Ride".

 

I'm returning to this again as over the summer the issue has been less apparent. Now the cold weather is making it worse again. I have just tested the voltage across the battery this morning from cold and I'm getting 13.70 volts. Shouldn't this be enough? I will test again when back after a ride to see what it is when the bike has warmed up. Can I test the voltage directly from the stator, disconnected from the rr? At least this will tell me if any voltage drop is coming directly from the stator. As I mentioned before the battery and rr are both new items

 

If the battery is healthy then at rest it should read between 12.7-13.2 volts.

If you tests for volts across the battery terminals, normally a healthy stator and RR should be delivering 13 - 14 volts+ at idle and between 14 and 15 volts above 2,000 rpm. It should never exceed 15.5 volts or things like headlight bulbs will blow. (Lights on/lights off should make no more than about 0.5V difference to those numbers.)

So 13.70 volts at idle looks, OK. It would be good to see what you find at 5,000rpm. Also repeat those tests as soon as possible after returning from a 30 minute plus ride. Battery on its own (engine and ignition off) = ?volts then bike at idle and bike at 5,000rpm.

We need to test when the bike is hot because the insulation on the stator windings can fail when really hot and instead of charging OK when cold can start to discharge the battery.

If the battery volts remain low or fall but the other results are as above then it looks like the stator and RR are working fine and you have some sort of continuing drain on the bike. Pull fuses to look for the drain.

If you have an alarm/immobiliser check the manual to see what drain they impose. If you don't ride often or do loads of short trips then you may just need to routinely hook the bike up to a decent digital battery charger like an Optimate to to offset the drain.

Let us know what you find.



SkiMad

 

Tested battery after returning home, only 13.09 V volts and actually dropped slightly at 5k revs to 12.6 I know there's no drain on the battery because I've left it for 2 weeks at a time and she started fine. I think I'm going to replace the stator and hope for the best.

 

Yep, RR was at fault again even though it was a uprated unit replaced only 2 1/2 years before. This time I have a SUN uprated model, who knows how long this one will last...?

 

Use this to test all the components before throwing any more money at it.

https://www.electrosport.com/media/pdf/fault-finding-diagram.pdf

In the winter especially, I keep the bike on a trickle charger to keep the battery topped off.

 

It's a big mistake to simply drop in a new battery without testing the charging system output at the same time and also inspecting the red plug on starter relay as well as plug between r/r and stator for poor condition. Undercharging might have killed the previous battery.