charging rpm

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Radcap
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Posts: 133
Joined: Wed Oct 12, 2005 10:45 pm
Location: MANCHESTER UK

charging rpm

Post by Radcap »

My 18c 1950 6 volt system charges ok at 8 volts but i need to be doing 70mph.
One manual say 2000 rpm
Ive got a modern regulator fitted and a new battery . I dont what to run tbe engine so high
Groily
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Posts: 2151
Joined: Thu Jul 04, 2002 1:00 am
Location: NORMANDIE FRANCE

Re: charging rpm

Post by Groily »

'Correct' charging voltage for your system would be 7.2v or near enough, and the ammeter should be in balance at around 35mph in top gear with a normal 35W-ish headlight on. It should show a very small charge when running along if the battery is well charged (more if it's a bit flat), dipping to 0 amps (or a discharge with the lights on) at tickover. (Some regulators allow a discharge of about 2 amps at tickover even with the lights off though.)
Normally, 2000rpm engine should be plenty for the dynamo to be charging the battery properly as well as supporting whatever is switched on. A decent dynamo will normally cut in at about 1000-1200 rpm engine and be working fully regulated by about the 2000 mentioned.
If it isn't, then either the dynamo could be tired, or the regulator is an inferior one - they sadly exist - or there's a wiring fault. Some regulators don't ever really get to proper charging voltage.
Suggest you do some simple dynamo output tests to see whether the problem is at the generator or upstream. You could start by noting whether the lights get brighter with revs as you move from tickover up the range? Then you could bridge the F and D terminals on the dynamo (with the usual leads removed), start the engine and put a battery and bulb or meter actross the bridge to an earth, and see whether the bulb lights or the volts flow. It/they should. Testing like that you'd expect to see up to 20v without loads on (so a bulb can blow quite easily). If that works, then you could measure the voltage from the wire from the regulator to ammeter/switch/battery, or simply measure across the battery terminals with the engine running. You should see a charging voltage there according to revs and load. If the dynamo is chucking the volts out but the battery isn't receiving anything worthwhile, then there is a regulator problem or a wiring fault. I'd check first all bullet connectors, the earths, the wiring at the ammeter and switch, and go from there.
Radcap
Member
Posts: 133
Joined: Wed Oct 12, 2005 10:45 pm
Location: MANCHESTER UK

Re: charging rpm

Post by Radcap »

Ive linked the dynamo wires and tested the output its does rise to 18v but it needs a lot if revs . think its time for a dynamo repair .
Thank you for the reply
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