Possible issue with the charging system

I've had a few times the battery has been dead with the CBF500, if left
standing for over 4-5 days after a full charge. The battery was
probably 3-4 years old and I don't know if this is a standard shelf life
for a bike battery.

Anyway, I've swapped the battery but did a few additional tests at the
time. Leakage when the ignition was of, 10mA from the heated grips. At
2,000RPM I get 14.2V across the battery terminals, 5,000RPM 13.7V and it
drops a little more with more revs (red line at 10k, so I seldom get
about 7-8k anyway). 5,000RPM should be 14-15.5V according to Haynes.

Did a test on the three yellow cables from the alternator coil to the
rectifier, all came out at 0.7 ohms. Within spec according to Haynes.
So I swapped the rectifier, but got the same results at 5,000RPM.

Anything to do with the alternator isn't going to be cheap. Any other
suggestions as I've already spent £60 on a rectifier.

Is this going to cause any issues for the new battery i.e. significantly
shorter life span?

I've noticed my heated grips are great between 2,000-3,000 RPM and
almost off (through winter gloves) at 5,000 RPM. So I'm not sure how
much current is getting through. My guess is a battery needs 1-4A to
charge and the grips 2A.

Tim B

 

Figured the battery had seen better days and replaced it. But I'm still
a little concerned about only getting 13.8V across the battery at 5,000
RPM. The issue isn't the rectifier, so looking for another cheaper
suggestion than the alternator. Checking all the wiring is probably not
a bad idea.

Tim B

 

I wouldn't be. Sounds fine to me.

 

I would suggest that you've missed out "earth straps" inbetween reg/rec &
alternator.

some of it, at least, see above

 

Ah, there is a green cable going to the reg. This has continuity with
earth. I believe this is the wire to check.

Regards,

Tim B

 

Haynes states 5,000 RPM should be 14-15.5V. I'd probably expect to see
a steady 14.8V based upon another bike. 10,000 RPM is red line on this
bike. Unfortunately the voltage drops off as the RPM increases above
2K. Down to 13.6V at approx 7,000RPM.

I probably wouldn't have replaced the reg/rec if I hadn't started taking
measurements while changing the battery. So I would probably be £60 up
and none the wiser. I think 13.8V will probably be sufficient to charge
the battery for the time being. Maybe a future issue, I'll probably
mention it to the mechanic next service.

Fair enough. Do you know if it's possible/easy to check the voltage
coming out of the alternator? Nothing in Haynes about this, just three
yellow wires at the reg.

Tim B

 

That link is pretty comprehensive. A nice troubleshooting flowchart as
well.

Interesting to see Haynes state 14-15.5V at 5,000RPM, whereas this guide
states 13.5V to be the minimum. But also suggests 14.4V is to be
typically expected across the RPM range.

It's going to be a couple of weeks until I can play with this again
(bloody dark nights). I'll try a reading from between the three yellow
wires. After that I'll give the flow chart a try, even though I pass
step 1.

Looks like it's not currently a major issue. Though heated grips faster
than 55mph would be nice at this time of year.

Tim B

 

The falling voltage with rising revs seems a bit odd
but it wouldn't worry me much.

One possible explanation might be that the changing
waveform of the alternator output (frequency) with
increasing RPM migh be affecting the meter. Or the
regulator?

I would expect that a good meter should try to deal
with such issues but that one found inside a pack of
rice crispies would be a bit suspect.

Check that the battery is being kept fully charged.
13.2v

Regarding the heated grips vs RPM.
I would guess that this might be to do with airflow.
2000rpm - low airflow
5000rpm - higher airflow (over grips/hands/nose).
or maybe you did a dyno test?

 

Using the patented Mavis Beacon "Hunt&Peck" Technique, Tim B

They *tell* you that, but you should cut the blue wire. Trust me.

 

OK I'll give that a bash... hang on *Wicked*?!? With a name like that,
maybe this advice is not all it seems.

Tim B

 

It's a Halfrauds best, cost me £18 it did. Gunson's Pocketmeter 2.

Probably getting about 12.8V max. Which I think is the typical value
for this battery. Even if I strap it to a charger I only get 12.8V
after a full charge.

Yeah I thought this, but if I'm stuck in slow moving traffic at 2,500 -
3,000 RPM I have roasting hot hands. Do the same at 3,500 - 4000 RPM
and less heat.

I've no idea, just tested the resistance between the three yellows. But
I'm getting the impression that 13.8V will probably do, but is a tad low.


Tim B

 

In which case you guessed right. I was going to leave it attached to
the reg/rec and try and measure. I didn't think the battery would be
took keen on powering the bike by itself.

Tim B

 

12 - 15? It's a CBF500 has a mere 8.6Ah. I think my CG125 (sign of the
holy pushrods) is a tiddler at 4Ah. Stays charged even though it gets
used about once a month (if that). Before I got a charger I was going
to try and jump the CBF from the CG, but got talked out of it before
attempting.

Thanks for the tips all, probably going to just suck it and see. I've
been recommended to put the heated grips on a relay. As apparently Gel
Batteries are not keen on a constant drain.

Tim B

 

That's the badger that makes me trickle charge the bike if it hasn't
been used for a bit

 

I've worn out one Optimate be leaving it pretty much on for several
years. A decent battery doesn't need it.

 

In the days of points ignition it would be ~4A at idle, dropping to 1A
at anything over 2000rpm, as the points spent less time in contact with
each other.
With electronic ignition Iwt the 1A figure might be somewhere in the
ballpark, but I haven't bothered measuring it, since they've been so
reliable.