12 replies to this topic

[mk=john]

Hi
My mini is an early 850cc with a dynamo.
I have a new voltage regulator (control box) for my mini. Does anyone have any guides to setting it up for initial engine start? I have never installed one or adjusted one before and my electrical expertise is not brilliant! I do t want to be sending too much charge to the battery on start up, and am wondering is this best left to an auto electrician?
Thanks
John

Edited by mk=john, 31 March 2012 - 02:39 PM.

[tiger99]

You don't need to do anything. They are correctly adjusted during manufacture.

The dynamo is what needs polarising if it is new, or fitting to a car of opposite polarity. All you do there is fit it in the car, and touch a lead from the battery live terminal (on a Mini you could pick that up at the starter solenoid) to the small dynamo terminal, marked F, for a second or two.

[mk=john]

Hi
So I do nothing at al as far as adjusting thr output voltage? I see there is some yellow paint on both of the adjustment screws. Is this when they mark it to show it's adjusted?
John

[tiger99]

Yes, they apply the paint after adjusting,in such a way that if it is damaged they know you have messed about with it. The paint may well also be locking the adjusting threads to prevent then loosening under vibration.

You may find other things like that too, elsewhere on the car, if so, do not disturb!

[mk=john]

Hi
I installed the regulator control box today, and I took some voltage measurements from the battery. With the engine running at normal idle, and the ignition light off, the voltage across the battery is approx 13 volts. At fast idle, it climbed to around 16 volts. At a higher rpm, it dropped to around 15 volts. Do the readings sound about correct?
Thanks
John

Edited by mk=john, 31 March 2012 - 07:08 PM.

[tiger99]

Yes, because regulation with these things is not as good as an alternator. The voltage is going a bit high initially (fine at idle), but dropping back at high revs, as dynamos do.

With an old-fashioned dynamo setup you will forever be topping up the battery with distilled water due to overcharging, and will find the system struggling when you have lights and everything else on,but that is how it always was.

[mk=john]

So does it sound like the readings are normal? The car will do approx 1000 miles per year, do won't be an everyday driver. I think this is a sealed battery. So I guess I woul be better off with a battery I can top up with distiller water?

[tiger99]

With such low mileage the battery may be ok. Sealed batteries may have arrangements to recombine the hydrogen and oxygen,usually a palladium catalyst.

[bmcecosse]

Voltages sound far too high to me - should only be 14 volts max. Check your voltmeter on another car in case it's reading high. If it really IS 16 volts - it will fry the battery and blow bulb filaments endlessly.........Adjust as per workshop manual.

[mk=john]

Hi
Isnt the control box set correctly from manufacture? I guess I should then proceed to adjust per the manual? The voltmeter is quite a new one, a digital one.

is it best to check the voltage on the regulator, or just the battery instead, so it shows 14V?

[mk=john]

Hi
I have read both the Haynes manual, and the original BMC Mini minor workshop manual on the issue of charging voltage and have two conflicting results as follows.

For the regulator voltage, the Haynes manual states the range should be between 16.0 and 16V at a temperature of 20 degrees C. That seems to be exactly what I am getting when I test the voltage across the battery terminals with the engine running. The highest voltage seems to be around 16.2 V. I have not adjusted the regulator in any way.
So, it seems the regulator Matches the values given in the Haynes manual.

However, the original BMC manual says the maximum voltage at the regulator should be 12.7 to 13.3 Volts, quite a bit lower than that shown in the Haynes Maual.

So the big question is, which is correct??

Am I right to assume the voltage at the regulator at any given time equals that across the battery terminals? I need to know this is right as I don't want to fry my battery and cause any damage.

Thanks
John

Edited by mk=john, 01 April 2012 - 07:02 AM.

[mk=john]

Hi
I think I have it all sorted out now! Instead if taking measurements across the regulator, all I did, keeping all wires connected, was to unscrew the regulator adjuster by half a turn so the dynamo wasn't charging, then, with the engine running, and the regulator cover removed, I set the rpm to fast idle. I tool voltage teadings across the battery, and slowly adjusted the screw to give about 14 volts. I them changed the revs ip and down slightly and soon found the rpm which gives highest dynamo output. I then set this on the regulator to 14.2 volts. When the rpm drops below this, or climbs above it, the voltage across the battery falls to around 13 volts, and at idle re voltage is the same as the battery voltage. I rechecked and the maximum voltage across the battery at all rpm is 14.2 volts. Too the car for a drive today, all seems fine, the battery is cold, not cooking!! I also read somewhere today that the manufacturer 16v setting on the regulator us fine for calcium batteries, but far too high for modern sealed lead acid batteries, and should not be set higher than 14.4 volts.
John

Edited by mk=john, 01 April 2012 - 02:19 PM.

[tiger99]

I have never seen any great accuracy in any dynamo systems, and my most recent certainly went well over 15 volts on occasion. I don't envisage ever having another, as I prefer reliability to originality, but I would agree that rare old models should be kept original, and should be well looked after. Just not for me, because I would want to do high mileage.

If you have set it to 14.2V maximum, you may find that it does not replenish the battery adequately when you have lights etc on. That is why they were usually set a bit high. Alternators are generally set at 14.4V. Battery chargers often go much higher, 17 to 18 volts is not uncommon. The difference is that the current tails off at high voltage with both dynamo and battery charger, while an alternator will deliver its rated current right up to the preset voltage, if there is any load to absorb it, so it has to be more tightly controlled.

Current compensated control, with three "relays" in the regulator box, instead of 2, was very much better, but not used on Minis as far as I can tell. My old Rover P4 had that, and the regulator was temperature compensated too. Sadly the regulator was under the bonnet and the battey under the back seat, so the temperature compensation was probably all but useless, but it did give somewhat higher voltage as the current demand rose, without going above 14V on light load. Not as good as an alternator, because you did need some revs to get a decent rate of charge, but I never did get a flat battery with that one.

But if you are happy with it, just run it and see what happens. If necessary, adjust slightly if the battery does start to get a bit low. It will probably droop at very high revs, especially when the dynamo is hot.

Oh, and I will bear in mind your point about calcium batteries. They might not reach full charge in an alternator system if that is correct, but 99% is good enough.

Edited by tiger99, 01 April 2012 - 04:22 PM.