overcharge spike

[Bsareg]

Surely an electronic regulator has a current limiter? I build my own and always build in a max current limit to protect the dynamo.

[JulianS]

I would avoid upping the fuse rating above the recommendation of the reg maker. If the rating of wire in your harness is less than the fuse rating the wiring could fail before the fuse, which could set the bike on fire.

The thinwall cable used by some of us is rated at 16.6 amps.

My 12 volt A10, using a 6 volt armature, has a 16 amp fuse which is good for a 60/55 watt H4 bulb. Never thought the 12 volt armature offered any advantage given the wiring on it must be thinner than that of the 6 volt type.

As the problem with the electrics has persisted for some time there must be a fundamental electrical problem and if it was my bike, I would completely rewire it and clean and service or replace all the switches. I would also look carefully at the dynamo.

[BSA500]

Dynamo is a 12 volt recent rebuild(last year) reg is new as of a couple of months ago. I shall check each switch and work from there. Surely if the reg was faulty it would always over charge lights on or not???

[mikeb]

Surely if the reg was faulty it would always over charge lights on

who knows how things die? maybe Manor Mike if he's watching.
Intermittent faults are physics reminding us we don't really know much

[BSA500]

Forgot to say without engine running the lights behave normally(for a BSA  )

[Bsareg]

There seems to be some new dodgy headlight bulbs about at the moment. If it only happens when the headlamp is on, might be worth checking the fillaments are not vibrating together when the engines running. Does the headlight get brighter before the fuse blows?

[BSA500]

Fixed it. The main light switch some where. It got to the point where just switching it to headlight tripped the fuse, so disconnected the wires cleaned up the contacts rewired and hey presto it all works. Thanks for all the pointers 

[BSA500]

I suspect some wires were touching off around the switch

[mikeb]

glad you got this fixed. interesting how the 'overcharge' fault showed a short due to the wiring. it may be worth checking if the lights should, for your bike, be wired as they are

good persistence!

[BSA500]

The wiring looks as per diagrams so who knows 

[Dynamo Regulators Mike]

Back from our holiday trip on Friday, so I have not commented until now.

Glad to hear that all now seems well on the BSA500 machine. This story emphasises the importance of fitting a fuse in the system, and 15 Amp for 6 Volt is what I recommend, and is very unlikely to 'nuisance' blow if all is working correctly.

None of the commercially available electronic regulators aimed at fitting to our kind of bikes incorporate current limiting (as far as I am aware). It is a feature which would rarely come into play with our simple electrical systems. That said we do recommend considering fitting a regulator with current limiting for electric start machines, or if a particularly large battery is fitted. Our DVR3 is then suitable, and costs around half as much again as a DVR2. A small price premium compared to the value of the machines we ride, but for many (perhaps most!) of our customers initial purchase price is a prime consideration, and often electrical details are not really appreciated.

Looking forward to a busy week starting Monday 9 p.m. 

Cheers, Mike

[duTch]

 Congrats also from me on your perseverance to find the issue- I think mine had similar but was the wire to the speedo where it goes through the headlight shell. Being an afterthought running LED's is just thin wire poked through and didn't have a fuse on, but now does....
 My wiring is out of ordinary due to bits stuck anywhere, so I have a fuse on each circuit as well as a main one at the battery, so if one pops I know which to look at, but they are various ratings (7.5A - 15A) depending on the load (or what I had at hand- working on that).
  I'm still sussing my positive ammeter reading, suspecting the meter or battery, but if it persists and I need ideas will probably find/start a different thread

[Bsareg]

Re current limiting regulator. I think it is good idea as even the Lucas mechanical regulator limited the current via the bimetallic spring connected to the regulator adjusting screw. If it's good enough for the Prince of Darkness etc......

[duTch]

 Thanks for mentioning that B-reg, I was wondering if there's any kind of current adjustment on the mechanical regs. (Mine is a aftermarket B107).

 Pulled the battery out overnight to give it a bench charge, and give it a bit of a shake-up to free up the air bubbles (did that with a spare one the other week and seems to have succeeded) , and the amp meter behaved itself on the way to work, so will see what happens.

[Dynamo Regulators Mike]

Re current limiting regulator. I think it is good idea as even the Lucas mechanical regulator limited the current via the bimetallic spring connected to the regulator adjusting screw. If it's good enough for the Prince of Darkness etc......

The bimetallic spring was there to vary the regulator voltage setting with temperature. Trouble is it responds to the local temperature of regulator (subject to load variation), not to the battery temp which might be useful, especially  if the voltage control were more precise in general.

The CVC (Compensated Voltage Control) 2 bobbin units did have crude current control by rolling off the voltage when the load current increased. Arguably not the ideal thing to do (as the voltage is reduced just when the maximum voltage is needed, that is with headlight on), but a low cost approach. The 3 bobbin controllers with separate current limit adjustment were used on systems where higher performance was necessary.

The Prince of Darkness stuff comes about due to poor maintenance of the electrical items over a long period, and not in my opinion due to the implementation of the design and technology of the time. But of course decent electronics can do a much more accurate job. The real key to successful regulator design has proved to be to make them robust against all the stresses they will encounter over a long period of use. It is fairly easy to design a basic regulator which functions adequately. There are plenty of DIY circuits available on the www, but I would not want to go far with some of them without breakdown recovery and time on my hands.