Some questions we have been asked and the answers...
"Does the DVR2 suit both Lucas E3L and E3LM dynamos?"
Yes, it also works fine with the lower power E3H and E3HM versions.
"How do I polarise ('flash') a dynamo for NEGATIVE earth?"
Your battery's NEGATIVE terminal should be connected to the chassis or frame.
Disconnect the D & F wires from the dynamo. Take a wire from the unearthed (POSITIVE) terminal on the battery and 'flash' it onto the F terminal of the dynamo. That is touch the 'live' wire onto the F terminal briefly, for a second will do it. A small blue spark should be seen.
Your dynamo is now polarised NEGATIVE earth, simple as that.
(Swap POSITIVE and NEGATIVE in the above to polarise for POSITIVE earth)
This procedure may be used to 'wake up' an old dynamo which has not been used for a long period or to confirm polarity in case of any doubt, as well as to deliberately reverse the polarity.
It is a good idea to stick a prominent reminder near to the battery when the vehicle's earth polarity has been swapped, to avoid future polarity sensitive connection problems.
"Will your DVR2 suit:
a. The Lucas MC45L dynamo fitted to my Sunbeam / Scott?
b. A Lucas C35SD dynamo on my Ariel Square Four?"
Yes, in both cases.
"Is the DVR2 suited to the Miller dynamo fitted to my Vincent / Velocette (etcetera)?"
Yes, as long as field is wired to earth and original cut-out
removed.
(view Miller DVR modification for use with DVR2)
"Is DVR3 suitable for use with the 3-Brush dynamo on my pre-war car?"
Not without simple modification to 2 brush.
(view instructions to connect a DVR3 for use with modified 3-Brush dynamo)
"Will the DVR2 suit the dynamo fitted to my MZ?"
Yes, as long as field is wired to earth (shunt connected, and resistor (if fitted) is removed. Similar for Jawa / CZ.
"What is the maximum power output of the DVR2?"
Maximum output is not really limited by the regulator. 75W for 6V system and 100W for 12V system is safe for the regulator.
"Will I benefit from fitting a larger capacity battery?"
No, not really helpful. Unless you must have a 12V 60W headlight in a lot of slow traffic. A discharged large capacity battery loads the dynamo more and for longer. If a large battery is fitted as with an retrofitted electric start a current limited regulator is recommended to protect the dynamo and prevent nuisance fuse blowing.
"Will I benefit from fitting a voltmeter or voltage monitoring device?"
Spend your cash on an ammeter that works well instead. They do not all flicker wildly all the time. A voltmeter can show a good reading for a shot battery. Monitoring charging current is a better option in a dynamo system.
"What voltage can I expect at the battery using the DVR2?"
Nominally 7.2 V in a six volt set-up and 14.2 V for twelve volts. More is definitely not better here. For example 14.5 V as commonly stated as 'correct' will mean higher trickle charge leading to more topping up and shorter life for your battery.
"Will the dynamo start up with a completely flat battery?"
Yes, the DVR2 will start with a very low battery. If fully discharged it will wake up with battery disconnected (magneto ignition assumed!). Regulation will not be as good as in normal use, but a useful get you home measure after dark.
"Wouldn't I be better off installing a modern (expensive) alternator alternative?"
A matter of taste perhaps. But the Lucas dynamo (for example) in reality is a rugged & reliable unit, and requires minimal maintenance. It is evident that modern a.c. generating replacements do have significant reliability issues, and that low speed output may not be that much better than with the d.c. technology.
In addition click Lucas dynamos and charging system for a good practical help resource for fettling your electrics.
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