New RB106 15v at the battery

[Michiel]

Dear all,

At the restoration of my '67 1000 Convertible I had to renew the dead RB106 and the battery, now 60AH. After a test drive I noticed some dried-up electrolyte near the battery vent hole. The new battery is fully charged showing 13v after a long rest but with the engine running it shows a steady 15 v at higher revs. I checked the regulator side of the RB106 as per the WSM and it reads a steady 15.6 volts between D and E at higher revs.

Is it wise to adjust the regulator to deliver 14.5 volts at the battery at 3000 rpm to avoid the battery boiling if it is fully charged.

Also, has anybody done the A and A1 wires swap as advised by H. Holden.

Michiel

[geoberni]

Well there's a lot of 'New tech' out there these days regarding what the battery actually contains, but I would say 15+v is definitely too high for any 12 battery, especially if it's already fully charged.

I seem to recall the max charging voltage for a 12v battery should be 14.7v, otherwise it's going to eventually boil.
I would see if you can adjust it as per the manual. There's also plenty of videos on youtube about adjusting the RB106.

As to

the A and A1 wires swap as advised by H. Holden

I've no idea what you're referring to.... so I looked it up. I found it here if anyone else is interested/curious:
www.mgexp.com/phile/3/191288/REPAIRING_ ... _RB106.pdf
See page 10

The inescapable conclusion is that theC40/RB106 system would be improved by reversing the A and A1 terminals.This results in better voltage stability with external loading and less battery over or undercharging with variability of the external load currents in the car, provided the voltage setting is reduced to a lower value than Lucas recommended.


I actually found Section 4 about adding the Diode most informative....

The life and reliability of the contact can be greatly increased by adding a snubber diode across the field coil connection and earth. This clamps the -100V voltage transient to -0.7V and controls the field coil current when the contacts are open. This significantly reduces contact arcing and burning, not to zero, but to a very low level. A 6A10 diode is a robust option and a 1N5404 is also a suitable diode. Note that if the regulator is fitted to a positive ground car, this diode must be reversed.

[JOWETTJAVELIN]

As the voltage and current regulators are analogue, it is normal to see a variation which depends on the state of the battery and electrical loads. To measure it accurately you would have to monitor the voltage whilst driving with a calibrated meter. 15 volts is on the high side, 14 is the ideal figure and the adjustment should be made after the car has been running on the road for some time, to avoid false readings as the battery is given a high boost charge after using the starter motor. The workshop manual should be followed when making any adjustment. First of all, check all the dynamo, regulator and battery connections are clean and making good contact.

In one of my cars with a 3-bobbin RB.310 each unit I tried was so inconsistent that I was relieved to come across a solid-state conversion which fits inside the regulator case, replacing the bobbins and does not require any alteration to the exisitng vehicle wiring. This has been a 'fit and forget' component and I have been very pleased with the stability and reliability it brought.

[Michiel]

As mentioned in the beginning, I allready checked with the manual the output of the regulator side and measured 15.6v between D and E. If I crank that up to the required 16v as per the manual the battery voltage won't come down...
As for the solid state conversion, yes I can do that or go for an alternator, but I prefer finding the fault or solve it by lowering the output. And avoid introducing electronics to the old girl
If I lower the output to give 14.7v at a fully charged battery at higher revs I guess the charging capacity of the generator will not be affected?

[oliver90owner]

Adjust the maximum voltage to that required by the battery. VRLA batteries will not tolerate charging voltages above the listed maximums.

These systems were designed with FLA batteries fitted with vented, removable caps - and the cells were expected to be checked and topped up, as necessary, with distilled water at regular service intervals.

[geoberni]

Sorry, I'm not following you with the 15.6v, I thought you were referring to the actual voltage you were getting delivered to the battery, when all back together and engine running.

The new battery is fully charged showing 13v after a long rest but with the engine running it shows a steady 15 v at higher revs.

As I understand the system:
The D to Earth measurement is done with A/A1 disconnected and shorted together, thus disconnecting the Dynamo from the battery.... that's when you get the 16v ish reading.
D to E with around 13v is checking the Cut Out with the A/A1 correctly connected.

With it all set correctly and charging, you should only be getting about 14v max at the battery.

[Michiel]

As I understand the system:
The D to Earth measurement is done with A/A1 disconnected and shorted together, thus disconnecting the Dynamo from the battery.... that's when you get the 16v ish reading.
D to E with around 13v is checking the Cut Out with the A/A1 correctly connected.

Yes, that's what I did. I get 15.6v instead of 16v.

With it all set correctly and charging, you should only be getting about 14v max at the battery.

Now comes the crazy part: 15v at my battery.

oliver90owner

These systems were designed with FLA batteries fitted with vented, removable caps - and the cells were expected to be checked and topped up, as necessary, with distilled water at regular service intervals.

Yes absolutely true. I have to keep that in mind. I think I still can get to the cells at my battery by prising a part of the top off. So I'll leave it for a while and see if it realy keeps boiling and in the meantime fill it up with dest.water if necessary.

I am probably over concerned as usual. Thanks all for your support!

[geoberni]

Well I've just been reading this:
https://www.mg-cars.org.uk/imgytr/pdf/lucas.pdf

'Lucas Generator and Control Box Tests' and it's a lot easier to understand than the BMC manual for checking a system.
If you read all the tests in Part Two, particularly Tests 6 and 8, it would appear what you have is correct.

So perhaps the settings need adjusting down for modern batteries that don't like to be over charged.

I'm downloading this useful little booklet.

[Michiel]

I'll certainly read it. And it is a beautifull period booklet. Thanks!