Author Topic: C15 Charging Problem  (Read 388 times)

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gusmagicbus

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C15 Charging Problem
« on: 15 December, 2018, 21:17:48 »
Hello,

I have a 1964 SS80 C15, with a charging problem. It's converted to 12volts by joining the green/yellow & dark green (or the 1 wire and 2 wire connections at the alternator stator) together and then into a rectifier.

When I run the bike and test the voltage at the battery terminals (with a cheapy multimeter set to 20v DC range), it is wild and ranges from 0 to about 20 volts and sometime goes into minus. My headlamp brightness increases with revs too. I first assumped it was a rectifier issue so I got a new one from podtronics but it has made not difference. It has also got a new battery because I think the charging fault cooked the last one.

Any advice on what to check next would be appreciated.
« Last Edit: 15 December, 2018, 21:33:21 by gusmagicbus »

JulianS

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Re: C15 Charging Problem
« Reply #1 on: 15 December, 2018, 22:45:52 »
Do you have a voltage regulator/rectifier unit or just a rectifier?

A rectifier just converts the ac voltage from the alternator to dc volts for the battery it does not control the voltage, which can go to 20 volts if not regulated.


AdrianS

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Re: C15 Charging Problem
« Reply #3 on: 16 December, 2018, 10:41:50 »
You cannot measure the output with a cheap multimeter! You will get readings all over the place with spurious figures.
An old damped analogue meter is needed - I am not sure if a load resistance needs to be put across the leads as well.
If your battery is not going flat when the bike is not used, and the headlights brighten when revved, I would assume the alternator is charging.
I think the reason for not being able to use a digital multimeter is that ignition interference causes the fluctuations at the meter.

gusmagicbus

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Re: C15 Charging Problem
« Reply #4 on: 16 December, 2018, 18:59:52 »

Funny you should mention the battery going flat. I've had my opti-mate switched off for a few weeks and it's as flat as a pancake - guess I should figure that out first before looking for other problems. Any hints?

I assumed that because I was measuring DC across the battery terminals and after the regulator/rectifier it would be fairly smooth. It has been on any other vehicle I have worked on....but never worked on electrics on a 60s m/c before mind!

Thanks

DerekAnderson8

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Re: C15 Charging Problem
« Reply #5 on: 16 December, 2018, 20:20:54 »

Funny you should mention the battery going flat. I've had my opti-mate switched off for a few weeks and it's as flat as a pancake - guess I should figure that out first before looking for other problems. Any hints?

I assumed that because I was measuring DC across the battery terminals and after the regulator/rectifier it would be fairly smooth. It has been on any other vehicle I have worked on....but never worked on electrics on a 60s m/c before mind!

Thanks

the digital multi meter should be fine for measuring dc across the battery terminals, no matter how much you paid for it!

 ;)

OVERTHEHILL

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Re: C15 Charging Problem
« Reply #6 on: 16 December, 2018, 21:54:34 »
On my C15 a digital meter works ok when the engine is not running but gives erratic readings when the engine is running.  The ignition upsets it.

gusmagicbus

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Re: C15 Charging Problem
« Reply #7 on: 27 December, 2018, 20:34:06 »
Hi all,

I thought I'd give you an update. Following your comments that you can't measure charging circuit voltage with the bike running, I connected the output of my C15 rectifier/regulator to a battery on another bike and started up the C15, it held a fairly steady 14 and a bit volts. Then when I reran this test on my old C15 battery (which is still hanging around the garage), the voltage actually dipped sharply when I revved the bike. Which all worked to confirm that the charging circuit on the C15 is working ok, and the old battery I had was done in. I took the bike for a little spin today with a new battery and it seems to be charging fine. Yay!

Looks like it was just an old battery I had which was causing the problems, but because I didn't know the charging circuit voltage normally looks bonkers on a digital multi-meter while the bikes running I went out and bought a new reg/rectifier for no reason at all!!

Anyways, thanks for your advice.