Pre war over charging

[AlanBartlett]

Has anyone had any experience with over charging of the battery?

The car has been doing local runs quite well, having just passed the 10,000 mile mark since the engine rebuild back in 2012. And a nice run over Exmoor, covering a short drive of 130 miles round trip just yesterday. Though recently there has seems to be a smell coming from the battery. Googling the symptoms it appears to be an over charging battery

I've had an auto electrican look at it today, though I'm fairly ok with general wiring, they dynamo is something I haven't investigated, as its always been charging.
He dug out an old Auto manual about old vehicles wiring, which we found the dynamo to be charging at a slightly higher rate, we set upon adjusting the dynamo brush to bring it down to a lower charge rate. But it still seems to be charging higher than what it should, with all the lights on it brings it down, but off it still seems to be charging considerably more.

This is all new to me as it isn't something I've looked at, so any pointers would be greatly received. Many thanks in advance.

[Tony Fearn]

Hello Alan.
I'm sorry, but I have no knowledge on what you should do. From what you write, it seems that you've already played with the moveable brush.
Tony.

[k. rogers]

Hi Alan, from what I remember the ammeter should read no more than 8 - 10 amps without lights on.

[BarryCambs]

Hi Alan

I'm about to set mine up (I hope!) this weekend and as above, I was told 8 amps max to avoid overheating the dynamo. My dad remembers them spitting the molten solder out they got so hot.

I can't think of anything that would suddenly start it overcharging if it was ok before. Could it be the battery failing that's putting an extra load on it or causing it to gas?
I'd recommend Paul at Smart Power if you need advice or do have a dynamo sorted.
Barry

[Tony Fearn]

Hi Alan, from what I remember the ammeter should read no more than 8 - 10 amps without lights on.

There's a summer and winter charge (F1 and F2 on the wiring diagram) controlled by the plc ignition switch.
Could something have gone wrong with the F1 side thereby only giving the maximum charging option of the F2 which is what the switch does if the lights are on.
Tony.

[AlanBartlett]

Now then, it was reading around 8-10 amps before, we then adjusted it down to about 4-5. Which came down to just above zero with all the lights on. Though when you stick the volt meter on battery going along a steady 30 it reads about 17 almost 18 volts going in. Which he (electrician) said is far too much for a battery these days as they have little tolerance. Which too my mind also seems too much, I would imagine around 12 - 14 maybe max. An interesting dilema. We also chatted about how the cut cuts in at certain revs, but appears there is no cut out the other end? Is this correct? Another one of those learning curves!

[BarryCambs]

Assuming your dynamo is the same as mine (1934 - pictures on my thread from a couple of weeks ago) , there is just a simple cut out under the terminal box on to of the dynamo. It is just an on/off to stop current flowing back to the dynamo if its output is below the battery voltage, so doesn't control the charge rate at all.

The summer/winter switch on the dash (could be built into the light switch on your later car?) bypasses the resister on the field coils that gives the high and low charging rates. What I do know, having talked to Paul who overhauled mine, is that on these dynamos the resister is actually wound into the field coils, rather than external as on some systems. I wonder if the insulation is breaking down in your field coils, causing them to short and bypass the resistance?? Or the resister has broken down? I remember putting a multimeter across the terminals on mine which did show two different resistances, though I can't remember the values. I think you should be able to test the resistance between earth and each of the smaller terminals on the cut out box to see if they are different. You might have to drop the wires off first.

Hope that makes some sort of sense! Barry

[Forumadmin]

http://www.austin7.org/Technical%20Arti ... refresher/

[Tony Fearn]

http://www.austin7.org/Technical%20Arti ... refresher/

Thanks for that link Keith, it makes interesting reading.
Tony.

[AlanBartlett]

Following on with this topic. The dynamo has now stopped charging. So I do believe something inside has broken down,

A few observations I have looked at.

Checking the connections from the dynamo to the cut out. I did find one of the wires had come off from the dynamo to the field terminal, reconnected this which made no difference.

Along with inspecting the brushes all having a fair amount of distance "meat" from their carriers.

Multimeter tests on the dynamo terminals with the wires disconnected showing readings of 0.40 climbing up to 0.70 which is basically not alot.

The cut out fails to "engage" when the engine picks up revs, you can coax it into action after the revs have picked up with your finger, but doesn't do it on its own.

As it is not an easy job to dismantle from the engine. I'm not going to take it out until I really have to. I do have a spare, but needs a total rebuild. Does anyone have any recommendations for rebuild companies. I did read in Barry's post about Smart Power. They are on the list to try.

Does anyone know the mileage limit without a charging battery?

I shall have to invest in a wind sail and solar panels

[Keith Clements]

We went many miles overnight on the Monte Carlo Rally in the Javelin without charging. We followed other competitors with our lights off until we fell off the road and overturned. We were dragged out and continued to the leg halt at 3 in the morning where I swapped the dynamo out for an alternator borrowed from a fellow competitor.

[BarryCambs]

HI Alan

I think mine draws about an amp once running, so with my modern 40ah battery, you should get 30 hours, ignoring what the starter draws. I used mine last summer without a charging system and it was still showing 13 volts after a couple of weekends and about 100 miles with plenty of stop stops and restarts. At some stage, someone fitted an voltage meter to the car which is quite handy!

The expensive part of rebuilding the dynamos is if the Armature needs rewinding. However, I think these are pretty robust and if you're lucky you might get away with having the insulation renewed on your spare . I don't know if other companies use the same technique of replacing the insulation as Paul. I used him as he was recommended by Daniel and I was more than happy. The cut out had gone on mine and these are apparently a right pain to rewind as the have the very fine wire inside. I think it was going to be about £170 to rewind it, of 50 quid to replace it with the electronic module, so you might want to think about that while you are doing a refurb?

[k. rogers]

Hi Alan,
I used the Weasel for a whole season, when I first had it, without any charge from the dynamo - I just charged the battery after each outing, but to be honest it didn't need it. As long as your battery is good you don't need to worry unless you are planning long distances, then you can get it done in the off season. Don't club spares provide an exchange service? I think they might do!

[BarryCambs]

I know JCS had some reconditioned dynamos in stock when I was looking, but they were all 6V and I needed 12. It would be worth double checking with them though.

[David Morris]

Hi All,

I know I am straying away from pre-war discussions, but it might be helpful to say that I am pretty certain Javelin dynamos are the same as those fitted to Morris 1000's. I know my Javelin has one fitted. About £60 on eBay, brand new. You may need to polarise it before you fit it. It's dead easy, just connect the body of the dynamo to the chassis of your car at some convenient point, take a feed from the 'live' side of the battery and 'flash' it onto the field connection on the dynamo, ( that's the smaller of the two connections on the back of the dynamo ). I have deliberately avoided saying 'positive' or 'negative', as your car might be set-up for either. Job done!

When fitting a different dynamo to your car, it's well worth going through the quick polarisation process above, just to make sure it's set-up for your vehicle.

David