Originally Posted by
LarrBeard
Let's try ito readjust the regulator for an 8-volt battery.
Now, before I start – a word of warning. I’ve not done this procedure – I’ve just read about it. That’s kind of like that guy who isn’t a pilot or doctor, but he did stay in a whatever hotel last night.
Second of all, there is nothing I can find about 8-volt regulators, so we’ll have to do some mad science here. Where do we want to set the regulator charge cut-out voltage? Specs for 6-volt regulators say that at about normal temperatures (70 – 80 degrees), the voltage regulator should cut out at about 7.32 – 7.35 volts. I’ll call that 7.3 for our purposes. A six- volt battery has three cells, so that is 2.43 volts per cell. An 8-volt battery has four cells, so I want to charge it to about 9.72 volts, call it 9.7. Now, this is not going to be critical since we are using that battery to spin over a 6-volt starter and if we get it up to 9.3 or 9.5 volts, it is still an improvement over the original 6-volt battery. But, we’ll do all we can to get it to 9.7.
Let’s talk about how the voltage regulator actually does its thing in regard to charge voltage. There are three relays in a voltage regulator. One of them has three or four turns of really big wire and a lot of turns of little wire. That is the reverse current cutout relay. We won’t work on that one.
The middle one has several turns of really big wire. That is the circuit breaker. We’ll leave it alone too. The last one has a lot of turns of little wire. That is the relay that performs the voltage regulation function and that’s the one we will work with.
How does it work?
This is a bit simplified, but if battery voltage is low, the voltage regulator relay contacts are closed, current flows into the field of the generator and the generator puts out a charge current (and raises battery voltage). The relay contacts are held closed by a spring and lever arrangement. As battery voltage comes up, more current flows through the relay coil and the magnetic force on the contact lever gets stronger – just like that wire and nail magnet you made in middle school. When the voltage gets high enough, the contacts open, no field current flows into the generator, the current/voltage drops, the contacts close again …. and so on. The contacts will open and close maybe a 100 times a second – more like a buzzer than a clunk-clack relay.
What we are going to try to do is hold the contacts closed with more force from the spring and that will take more force from the magnet/solenoid to open the contacts. Generating that force will take more current through the coil and that can only come from a higher voltage across the coil – our 9.7 volts from the battery.
I would start by seeing just where the regulator is already set. And, to do that, you need the engine running and the generator hooked up. Fire things up with the 8-volt battery and see where the battery tops off. I’d guess around 7.3 or 7.4 volts. (It may not drop off all that much unless you draw it down). Once you find a starting point – here we go.
Pull the voltage regulator – tag the three wires. Take the unit to a clean bench and take off the top. Find the relay with all of the turns of little wire – it will be on the end. The picture shows what a typical unit looks like. See the tabs on the spring? Bend the tabs to spread the spring a bit to increase the spring pressure. How much? Dern if I know! Don’t get too enthusiastic though.
Put it back together. Fire it up. You should see a charge on the ammeter. Watch the voltage on the battery terminals with a meter. If we did good – it should top off higher than it did originally. If it’s not up to our 9.7 volts, spread the tabs a bit more. I don’t know just how much spring pressure we can get by spreading tabs – but we should be able to get a higher charge cutout voltage that the original 7.3 volts.
The good news is that unless you break off a tab (!!!@#$$%%#), you can put it back where it was if you want to go back to a 6-volt system. And – now you’re an expert.
Let us know how this works…..
(And, after I wrote all of that - there is a redneck way to do it. Disconnect the lead from the field terminal of the generator, take a clip lead and ground the field terminal and let the generator charge at full current for a few minutes. Watch the battery voltage and don't let it run for more than a few minutes at wide open charge...)
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