Dynamo questions

[Greybeard]

Hi fellas,

My dynamo shows up to 14 volts when measured at the dynamo sockets with the wires removed. I have a new 13 amphour 6v battery that has been fully charged on the bench. With the engine running and headlights on if I raise the revs the ammeter changes from showing a discharge to 0 amps; ie. no positive charge value. Am I correct in thinking that as the battery is full I should not see a positive value at the ammeter?

Neil Ives UK

[a10 gf]

That seems correct. One way to test it out, with engine not running drain the battery for a while (put the lights on), then start up and see if the meter goes into positive then slowly goes back to 0.

[bsa-bill]

That's the assumption I would make Neil, if you have an old battery a bit down put it on and look for a + deflection on the ammeter

[duTch]

 G'day Neil, (and All), What the other guys say, but as I'm no expert on this either, think it's worth also checking the actual 'OUTPUT VOLTAGE' at wherever you need to check it. Something I have to do too, and read up on it last week, but other things to tend to for the next couple of days, but I put a meter on mine the other day, had a 'high reading' as am blowing fuses (the Amp meter does the stuff t should do, (-lights only, + @road speed/~0ish @ road speed w lights on), so think I may have an 'Over-charging on a BSA-you better believe it' kind of issue(remember that post?-I'll be looking it up), probably just need to tweek the reg., but have to check it out.
 hope  I got that right....! good luck, cheers

[iansoady]

I'm not quite sure what you mean about 14 volts with the wires removed. Is this between the two (F & D) terminals or between them bridged and earth? If the former, it's a bit meaningless - if the latter I would expect more.

Otherwise agree with what else has been said - if the battery is fully charged you shouldn't see any great reading. But if you put the lights on it should show 5 amps or so discharge at idle but come up to mid point at 2,000 rpm or so - which is what you see. And if you put a voltmeter across the battery you should get around 7 volts or a little over at fast idle with the lights off.

[bsa-bill]

I would expect more.

if it's any help I tested mine some time ago and saw 18 but not constant, jumped around a bit but there again holding meter leads - one on a wire the other against the frame is not too scientific, didn't need to know any more then it was charging so was happy

[Greybeard]

I'm not quite sure what you mean about 14 volts with the wires removed. Is this between the two (F & D) terminals or between them bridged and earth? If the former, it's a bit meaningless - if the latter I would expect more.

With F & D bridged measured to earth: 9 ish volts at tickover but increasing with engine revs:  I saw 14 ish volts but didn't over-rev the engine.

Otherwise agree with what else has been said - if the battery is fully charged you shouldn't see any great reading.

Thanks:  reassuring.

[A10Boy]

I swear by the DVR2 regulator from Dynamo Regulators Ltd. [No connection]. I usually swore AT the old mech ones.

[bsa-bill]

I was a bit suspicious of my Vreg after hearing all your glowing reports about the DVR2, however after disconnecting everything it turns out the battery just leaks it's charge, runs down over three or four days.
Hey Ho  Cyclone here I come - funds willing

[warmshed]

You say your battery runs down after a few days. By "disconnecting everything" do you mean the wiring from the battery? if not you could have a drain by the wiring.  Regulators are not unknown to do this under a fault condition.

[bsa-bill]

do you mean the wiring from the battery?

Yes, precisely because I read here that regulators could drain (and suspected mine) I disconnected all wires from the battery apart from the two leads to the insulated charger plug (it's on to simplify charging and sited just under the edge of the seat, I've charged the battery up thrice and the charge lasts about three days by which time it's down to around 7 - 8 volts (12 volt system).

I've had duff batteries on my Flash also (6 volt) a Lucas glass mat type spent two years on a shelf in my shed and in that time I was pleased with it not seeming to go down, once I put it on the bike though it worked for a year or so then would not accept charge, bought a replacement (Chinese but looked identical in too many ways)
it failed within months, my MOT guy got me a "Varta" it's been on two years now and still good.

yes I know, after nearly 70 years you'd think I should know when cheap is not a bargain, but I am half Scot

[muskrat]

Most people kill new batteries by putting them straight to service. I try to always charge them overnight. The last time I didn't I killed a new Motobatt AGM in my Rhonda Whore in a month it would not accept a charge.
Also for the big companies to keep making more and more profit they make their products less robust. Seems nothing these days last like they used to.
Cheers

[BSA_54A10]

Most people kill new batteries by putting them straight to service. I try to always charge them overnight. The last time I didn't I killed a new Motobatt AGM in my Rhonda Whore in a month it would not accept a charge.
Also for the big companies to keep making more and more profit they make their products less robust. Seems nothing these days last like they used to.
Cheers

Musky you are really showing your age here.
that has not been necessary for the last 40 years ( oops am I showing my age ).

The biggest battery / regulator / generator killer is dirty, corroded terminals.
Best trick is to clean them , bolt up the wires, paint them with liquid electrical tape and fit a plug to the ends of the battery wires.
the results will be a glorious 6 V every where that it needs to be.

[morris]

The biggest battery / regulator / generator killer is dirty, corroded terminals.
Best trick is to clean them , bolt up the wires, paint them with liquid electrical tape and fit a plug to the ends of the battery wires.
the results will be a glorious 6 V every where that it needs to be.

I get good results by protecting the terminals with copper grease

[BSA_54A10]

I used to use grease as well but it ends up getting in between the contacts and over every thing every time you disconnect the battery.
The Liquid Electrcal Tape was basically an accident as we were putting an order in to Electus and needed to make up the minimum wholesale order and the bottles of goop were on special.
The stuff is really thick & plastic like the coatings on the ends of new chisels.
It will not wick in between the contacts .
Ever since the B50 self ignited due to the battery earthing out onto the metal side cover ( leaking fuel tap did not help the situation ) I have fused both side of the battery.
The battery terminals were never undone because I disconnected the fuses to remove the battery.
However when we changed to using blade fuses this was no longer possible so we started using a " T " type 2 pronged spade plug.
When I did this suddenly the bikes electrics started to work perfectly due to the fact that there was no corrosion or resistance at the battery terminals ansd like bullets spade are self cleaning every time you connect & disconnect them