Dynamo regulator setting.

[Diver300]

On my old car with a dynamo, the voltage setting is much higher than would be expected from an alternator system.

This guide:- https://www.trtriumph.com/Regulator adjustment.pdf has the voltages around 16 V. Another guide was a bit less at higher temperatures:-
10°C (50°F) 16.1 ‐ 16.7 V
20°C (68°F) 15.8 ‐ 16.4 V
30°C (86°F) 15.6 ‐ 16.2 V
40°C (104°F) 15.3 ‐ 15.9 V

Logging on the car showed 16.7 - 16.9 V when driving, without much in the way of electrical load. At first I thought that this showed that the regulator was not working at all well, but having seen the suggested settings, the voltage is maybe a bit higher than originally, but really a lot higher than on a modern car.

Obviously the battery is modern*. Should I be looking to reduce the voltage somewhat to avoid damaging the battery?

I know that I might get a lower rate of charge when running if the voltage is lower, but it's not as though the dynamo will keep up with the electrical loads in stop-start driving at night, just like the previous car I had with a dynamo. I leave a charger connected when the car isn't in use.

*Remarkably, the batteries and terminals haven't changed dimensions. I just needed to drill each battery terminal to take the screw that holds the connector to the terminal.

 

[JimB]

A long time since I have done this.
Thinking about it, it may have been a friends Triumph Herald that I tweeked.

These voltages in the table:

10°C (50°F) 16.1 ‐ 16.7 V
20°C (68°F) 15.8 ‐ 16.4 V
30°C (86°F) 15.6 ‐ 16.2 V
40°C (104°F) 15.3 ‐ 15.9 V

are open circuit voltages.

If you are seeing 16.7 - 16.9 V when driving, that suggests that the regulator setting is a bit on the high side, and would benefit from some adjustment.
Before diving in and adjusting the regulator, it may be a good idea to use an ammeter to check the charging current into the battery.

JimB

 

[Diver300]

The car has an ammeter, but that's not being logged. I don't remember what the ammeter was doing when the voltage was being logged as being around 16.8 V. However with the battery fully charged, the ammeter doesn't show more than an Amp or two of charging current. As the battery had been on a charger before being driven it would have been charged.

The voltage logging was in daylight, and generally at speed. The heater, wipers and lights weren't in use. The conventional coil and contact breaker ignition was of course on, and the Lucas fuel pump. The brake lights and indicators would have been used occasionally. I wouldn't have been using the stick-on screen heater.

(That's listed the entire electrical system, except the horn. It's not complicated)

 

[rjenkinsgb]

The voltage at the battery should not really exceed 15V, or not often; most lead-acid battery info I've seen say 14.8 as an ideal target voltage in cyclic systems, but a mechanical regulator is going to vary somewhere around the nominal voltage.

(13.8V with permanent float charge, for reference for anyone looking at other applications).

 

[Diver300]

The voltage at the battery should not really exceed 15V, or not often; most lead-acid battery info I've seen say 14.8 as an ideal target voltage in cyclic systems, but a mechanical regulator is going to vary somewhere around the nominal voltage.

Have you got any idea why the voltage was set around 2 V higher on the dynamo systems?