Author Topic: alternator  (Read 740 times)

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Offline sidevalve

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alternator
« on: January 29, 2019, 05:49:47 pm »
Just curious - what is the alternator output of the C12 unregulated unrectified and unloaded ? Just wondering if it would be possible to upgrade to 12v by simply fitting a modern reg/rec unit across the output. Units cost under a £5 so might be worth an experiment

Offline hampshirebiker

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Re: alternator
« Reply #1 on: January 29, 2019, 05:59:14 pm »
They can give well over 12v. Many have converted to twelve.
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Offline Owen

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Re: alternator
« Reply #2 on: January 29, 2019, 06:08:55 pm »
There are many articles on converting to 12v with both dynamo and alternator.
See this thread https://bsac10c11c12.co.uk/smf/technical/convert-to-12v/msg291/#msg291
1940 C12 (350cc)
1945 C10 & C11
1953 C10 & C11
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Offline George B Walke

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Re: alternator
« Reply #3 on: January 29, 2019, 06:29:54 pm »
MyC12, and all the previous ones have run 12v; its best to use an encapsulated   2 wire alternator. I use standard 12v Lucas parts, coil etc and have never had any problems; the black rectifiers are quite adequate but you will need to add a zener diode and heatsink.  You can  utilise a condenser attached to the coil, a la Triumph twin circa late 1960s.
Good earths are paramount, you can even start with a flat battery just off the k/s spin.

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Offline sidevalve

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Re: alternator
« Reply #4 on: January 29, 2019, 06:39:14 pm »
interesting all. If the reg/rec unit is in circuit can't see any need for a zener [or obviously a rectifier] and if the original alternator gives enough volts can't see much need to upgrade it - after all double the volts = half amps. Should simplify the wiring and reduce chances of a wire 'diss' causing problems. Batteries bulbs etc are all easier to get and the switches carry less current - Think I might give it a try

Offline hampshirebiker

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Re: alternator
« Reply #5 on: January 29, 2019, 07:05:55 pm »
I put a zenner diode in a fined heat sink (ala Triumph) on my C12, but that was more out of ignorance. I did fit a small 4 pin rectifier to give me D C. Also my alternator was three wire. Someone on the site told me which pair to twist together to give two wire output. I can't remember the colours though. These days I would go to Rex Caunt for a suitable regulator/rectifier as he supplies units to suit most applications. They're not cheap, but very well made.
Postal - Liphook Hants - But just into West Sussex.

Offline sidevalve

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Re: alternator
« Reply #6 on: January 29, 2019, 07:47:38 pm »
I was thinking something along those lines. I think it's dark green / green yellow wires to link. I have used Rex Caunt before but for an simple experiment I'll just use a cheap one, [for £3.60 it's not much of a risk]  if the plan works out ok I'll try a better one.
Have to wait until the weather warms up a bit though

Offline Tman

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Re: alternator
« Reply #7 on: January 29, 2019, 08:13:21 pm »
You'll need a rectifier to be able to charge the battery and a Zener to make sure you don't boil it, but I agree with the above in that a Rex Caunt unit would be easier and simpler to install.

Offline Donald

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Re: alternator
« Reply #8 on: January 29, 2019, 09:08:00 pm »
Hi there, I have used the 'cheap' reg/ rectifier' on a few of my bikes in the past, At the moment I am making a wiring loom for my C11g, and using  one on that. It makes for simple wiring and for the price it's cheap. No Lucas rectifier or zenor diode reguired

Offline Ginge

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Re: alternator
« Reply #9 on: January 30, 2019, 05:10:54 am »
I’ be done the same as Donald on my Triumph 500.  I rode the headlight on all the time to dump a bit of current.  I boiled three batteries though.

That bike spins a bit faster though.  I’d recommend a zener or something else to bleed of current.  The system needs to be regulated somehow.
Ginge.

Offline timsdad

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Re: alternator
« Reply #10 on: January 30, 2019, 07:09:52 am »
Some folk seem to be confusing a rectifier with a rectifier/regulator, which are obviously more expensive and do the two jobs in one. A rectifier will need a zenor diode to prevent the battery overloading  if converting to twelve volts.

My '66 Triumph 650 still uses its original system of rectifier/zenor diode but several years ago I replaced the plate rectifier with a little solid-state five quid rectifier and then, a couple of years later, fitted a new zenor diode when the original fell to bits. This system still works perfectly, day and night, and, as has been said, starts normally with a completely flat battery.

A new electronic rectifier/regulator costs much more and is more efficient at getting every ounce of voltage through to the battery. It's also something more expensive to replace if anything goes wrong with the electrics, like an accidental short circuit or battery fitted the wrong way round. The basic system like BSA and Triumph fitted when they uprated to 12 volts in the '60s, with just the old plate rectifier replaced, works very well for me.

As has been said many times, all wiring, connectors and earths need to be good to let all the volts through to where they need to go. Old wiring is like furred up pipes restricting the hot water flow in a heating system - it will always struggle to do its job.


Ray
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Offline Vreagh

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Re: alternator
« Reply #11 on: January 30, 2019, 10:01:36 am »
I've used the cheap (under £5 from China) rec/reg unit, and no problems. Most of them to use the same alloy heat sink casting as the £35 units, are these just rebranded ?

Offline Donald

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Re: alternator
« Reply #12 on: January 30, 2019, 10:48:18 am »
Hi there, When I fit the cheap rec/ reg I have used a 12 v battery, I test the unit by running the engine and check the voltage  output . Need about 14 v to keep battery charged, any more than that will damage battery.

Offline sidevalve

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Re: alternator
« Reply #13 on: January 30, 2019, 07:13:02 pm »
agree with above re confusion - a reg/rec unit does both jobs and since the influx of chinese scooters the price has dropped way down. The electronics world moves fast. Plus there are only so many suppliers so I suspect many even now are just re-badged chinese units. The one I've ordered is rated at 100w so I reckon it should hold a headlight and tail light bulb and the whole thing will easily fit behind the side panel out of sight

Offline Ginge

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Re: alternator
« Reply #14 on: January 31, 2019, 04:47:03 am »
My reading says that a C12 has the RM13/15 alternator.  Six volt, 10 amp, 60 watts.

If power equals volts multiplied by amps then at 12 volts you get 5 amps to run ignition, lights and charge battery.

Probably okay for daytime running.

Presume the cheap £5 units you are all referring to are negative earth?
Ginge.