Batteries don't last in my bike - causes?

[yorkie_chris]

If your reg rec is toast then you will likely see it on multimeter just from voltage test. Not seen any SVs feeding AC, but it can happen. Generally they just go kaka and under or overcharge.

Hello hopefully helpful people!

I have done some testing and the resilts are not what I expected them to be:

I charged my new battery and it read at least 13.6v before I put it in the bike, but I had to go to work today and when I got back the reading was 12.83v with the whole bike off and 12.66v with the ignition on and nothing else.

Then:
Idling engine (1,000rpm), no lights: 13.6v
Idling engine (1,000rpm), with lights: 13.25v

Engine revving (5,000rpm), no lights: 13.4v
Engine revving (5,000rpm), with lights: 12.72v

Now correct me if I'm wrong but this looks like there is little or no charging going on at all!?

I can't expect my battery to last a week like this but it has been going about 6 months each time before just not cutting it - so it must be charging a bit??

Does this look like a reg/rec fault or an I going to have to dig for my alternator, or shall I just burn the thing and be done with it!!??!

[yorkie_chris]

Next step is to check the voltage output from the alternator, remove the tail plastics and find the connector with 3 yellow wires.

You should have 70V (AC!!!) at least between each of these pairs (i.e between wire 1-2, 2-3 and 3-1) at 5k rpm.

You should also make a careful check after the reg-rec too, corroded wiring could also make the volts "go missing". You can check this by putting the volt meter on DC between the ends of the red wires, i.e between red on the reg rec and red on the battery. If there is significant voltage here, there is significant resistance.

[embee]

Originally Posted by MoggyW

Then:
Idling engine (1,000rpm), no lights: 13.6v
Idling engine (1,000rpm), with lights: 13.25v

Idle speed should be more like 1300rpm, some people prefer slightly higher. 1000rpm is too low.

As well as the other things to check, make sure all the fuse blades are clean and shiny and check all the electrical connectors you can get to. Use some lube on them, dielectric grease is perfect, vaseline works fine. You'd be surprised how much volt-drop you can get from poor contacts.

Lead-acid batteries don't like being kept undercharged for prolonged periods, that might well be the cause for the short service life you've experienced.

I'd still put money on the reg-rec if I had to..............

Hello! I am very chuffed to say - I'm fairly certain my reg/rec is knackered lol!! Funny to be happy about this but it feels satisfying to have tested absolutely everything I can and decide that the problem must, most certainly, be there, and if I change it I don't have to get rid of my unreliable bike!

Hurrah! I've seen a pattern part for £70 and don't want second hand, I'm guessing this is a good price...

A huge thankyou to all who gave very useful advice - without the forum my bike would have been sold by now!

[embee]

http://www.electrexworld.co.uk/home-1-0.html are pretty well respected quality parts if you want to go with a known source.