boiled battery

[edboy]

hi chaps,
my a10 was running fine with a jg regulator 12 volt conversion until i realised it was not charging anymore. the battery settles around 5 or 6 volts even when charged up to the nominal 12volts so i guess the acid has boiled away. i ve ordered a new battery.
however i ve read on some forums that jg regulators are well known for overcharging but i m unable to find an explaination why that happens. there is only one measurement across the wires ; .286ohms between d and battery connection which i think is normal. can anyone enlighten me?

[edboy]

well no replies yet so i phoned the prince of darkness himself and the conversation went similar to my favourite film bladerunner.
"ah roy what can i do for you?"
"my charge system wants more life f++++++r !"
" well roy the candle that burns twice as bright burns twice the time. but what sights youve seen in that short space of time with 12 volts burning the highway"
then he puts the phone down.
seriously though he did give some information{ not a lot} to ponder.
1.trickle charge the battery when new over 20-30hours.
2.send off the regulator to test on expensive diagnostic equipment.

[groily]

Hard to know what to say edboy! If a 12v battery charges up and then 'settles down' to 5 or 6 volts, it has to be very dead I'd have thought. A 12v battery is pretty flat at 10 or 11 volts usually!

I'm not sure whether that would  be due to death by overcharging, but it's one possibility I guess. Were bulbs blowing, and was the ammeter saying anything useful?
Good quick check is to stuff a meter across the battery terminals - another one! - with the engine running and see what the voltage is at a fast tickover and above. You'd expect to see about 14v, staying steady-ish with increasing revs. If the voltmeter acts like a rev counter and the thing starts to show shedloads of volts then there is no regulating going on, so switch off to avoid damaging the battery or any bulbs you might be tempted to switch on.

I don't know about JGs overcharging, or its being well-known. I ran one for 20 years on one beast and it worked OK and still would if I hadn't put a DVR2 on instead.

If there is overcharging going on, first thing I'd do is check the dynamo to be sure that the D and F tags aren't touching behind the end cover, as that would bypass the regulator completely.
Having done that, I'd check the voltage straight off the A wire from the regulator to earth with the engine running to see what's coming through. Steady-ish 14v-ish would be right (and should be what you'd see at the battery too if there aren't any heavy loads, like the headlight, on).

If you suspect undercharging or no charge  . . . If the bike is new to you, or the regulator is, I'd check the JG has been wired up correctly. JG regulators need the field coil wired from D to F, not from F to earth, being designed originally for what some people call 'series' wound dynamos like Millers rather than for 'shunt' wound ones like Lucas. I think JGs were first used by Vincent people back in the day on their Miller systems, so they were built 'that way round'.

The 'standard' Lucas dynamo connections are one brush and one field wire to earth, other brush to D terminal and other field wire to F terminal. With a JG it has to be field wires to D and F, one brush to earth, other brush to D.  The basic difference is between regulating on the live side or the earth side of the field.  In both cases, which wires/which brushes to which connection points will determine the rotation, so it matters. (The field coil wires are the two that come through from inside the dynamo, through holes in the brushplate.)

Don't know whether that helps or just confuses, but at least you have a reply apart from from yourself!

[a10 gf]

What can be done in-house if you have a multimeter with Ampere function (at least 10A).

Get a known good battery, charge it offbike with a known good charger.
Connect it back on bike, + in series with amperemeter (or use clamp meter), there should be next to no A (charge) going to battery (or at least A readout should fall very rapidly).

Also check voltage with engine running at different rpms, should not reach (much) over 14v.

[edboy]

thanks for replys to my problem. there is a lot there to consider but i can enlarge on a couple of points.
the dynamo has been good for a number of years and the wiring is correct.
i may be guilty of bad soldering as my connections were a little poor at the regulator. possibly due to heat also.
i ve been told d to earth dynamo casing open circuit is correct stationary by the expert, which goes against common sense. so the other brush [connected to earth]and d have a circuit through the comm.
he also said the field works regardless of voltage.
the battery is 6months old and could be the issue. i need to charge my new one over the weekend.
the system is now only charging 6volts and if the new battery does not rectify the fault i will go back to basic wiring and testing at the dynamo and try another reg.
there seems to be very little system information about the jd regulator and this is my second regulator of him.if i send it off for testing i will be on my third . or i may jump ship.

[groily]

It's good to hear the dynamo has been working - so you can probably rule it out then.

Yes, there is connectivity between the brushes across the commutator as you say.

The field gets fed its current from D, via the regulator, to create the magnetism required to generate anything beyond half a volt or so. How much the field gets determines how much comes out from D - some of which is snaffled back by the field to keep the thing going, the rest of which supports lights and battery. That's the regulator's (and cut-out's) job. If D and F were permanently connected, the regulator wouldn't be able to function and F would get everything D can produce - hence my comment about checking there isn't a short between the D and F terminals at the dynamo.

A standard Lucas field coil and armature will support a 12v system easily enough when a 12v regulator (and cut-out) is used - it just takes a few more revs to get things going fast enough to cut in at 12v compared to 6v. Belt drive helps here as it gears up the dynamo to reduce the engine revs required for cut-in.

I'm not quite sure about your "the system is now only charging 6v". If the dynamo and regulator are working, you should see the 14v odd mentioned on the wire off the regulator to ammeter/switch/batttery. I don't know if JG make a 6v regulator - but if they do, and if you have one  . . . and you also have a 12v battery etc  . . . Problem!

If you find you are struggling, many of us would recommend fitting a DVR2 instead, as it's a proven winner. But it would require reconfiguring the dynamo wiring  . .  hence my mentioning that side of things.

[edboy]

thanks for your explaination about the way the regulator controls grolly. that is what i was after. i m now suspecting my poor connections are the source and possible a duff battery.i m slowly charging the new one now and will post more info when i have connected and tested etc.

[edboy]

well i put a new , fully charged battery on and nil output. i did change a brush on the d side so may need to bed in. tomorrow i will run an earth to the dynamo case then go for a good run. the d and one field wire are permanently connected groily and the other field wire completes the circuit to the f terminal at the regulator. i wonder if the dynamo has reversed its polarity?

[groily]

To test to see if the dynamo is working as it should with the field from D to F, disconnect the regulator, connect the F terminal to earth and then put a bulb/meter between  D and earth and start the engine. It should light the bulb  / show plenty of volts.
(It's exactly the same test as bridging F and D and putting a bulb / meter across the bridge to earth on a standard Lucas arrangement.)

Or, if you have disconnected the drive from the dynamo, you could do a motoring test with a battery which would be indicative of the condition of the dynamo but not conclusive, and also ensure correct polarity (bridge F to earth as above, connect battery live to D, chosen battery earth to the dynamo body). The dynamo should spin in the direction it is driven on the machine, and the polarity will automatically be set.
Sometimes a dynamo will need a handful of revs to cut in and start working if it has been idle for a long time and the residual magnetism which kicks off the charging process is weak. The motoring test should also address that.

[duTch]

 About a year or so ago, I cooked a couple of batteries before I found one of the 'D/F' wires had earthed out on the inside of the alloy dynamo end cover. I made an insulator from a heavy-duty plastic drink bottle.
  Might be worth also adding an extra earth wire to/from the field/brush earth if not already done...?

[edboy]

well, it wasnt a boiled battery at all but a duff one instead i hope. as now its charging as before. turned out to be [ i suspect]the idler cog which was tight until the dynamo was on load and then span on the shaft. locktite and a tab washer seems to have done the trick for now but i may drill and peg the sprocket later. i think i ll keep the lights on this time, just in case.