Lister generator

[Deanforest]

Hi there. I have a lot of experience with SR and ST lister engines over the years and currently have an SR1 running a 3kw lister generator which is backup for our off grid solar battery bank. But currently needing to make an alteration to the generator itself. The current voltage output is about 222 volts, but at full load (10amps), there is a voltage drop of about 4 volts over the 100 metres between generator and house. There’s a good thick copper cable of around 20 mm sq installed. This has never been a problem till now we have another washing machine which goes into fault mode at less than 220 volts. I am trying to find out how to increase the voltage output on the generator. Washing machine runs fine on battery/inverter at 230 volts which is what I have set the inverter to. My immediate feeling is that I need to increase the field current, but I may be wrong. It’s a shunt wound generator by the look of it and the unit has a double slipping. The whole unit is from 1962, had been little used on emergency standby.
The actual generator is a Brush, model SCAF1, with the 12 volt starting coil integral in the generator, so the generator itself runs on 12 volts to start the engine. I have a quite comprehensive manual for it which states it is a 220/240 volt generator with 13 amp output, but it doesn’t give me the info I need. Can any lister expert out there help on this one?

[Oldgreybeard]

I used to have a similar generator some years ago and my recollection was that the output voltage was tied to the engine RPM, so if it was a bit low then the governor needed to be adjusted to increase it. Doing this also increased the frequency slightly, but these things were often not too precise at delivering 50Hz anyway, as they have very simplistic controls. I don't remember the one I had having any sort of AVR, everything was mechanical.

Probably worth having a go at increasing the engine RPM slightly, as I think that may well solve your problem. Unfortunately I gave away all the old manuals I had when I got rid of the generator, years ago, and I can't remember exactly how to adjust the governor, but do remember mine getting a bit sticky, resulting in the RPM slowing down a bit.

The other thing I remember fixing on mine was the selenium rectifier that drives the field windings. These have a habit of gradually failing, and may also be the cause of the lower voltage you're seeing. There used to be a replacement rectifier for the older selenium ones, made as an after market repair kit. Not sure if they are still available, but might also be worth looking at.

[openspaceman]

Why not run the generator into a charger and feed the battery directly when the washing machine is running? Okay there is a loss but much less fiddling than trying to get a vintage genset up to the job.

[Oldgreybeard]

I think there is a good argument to keep these older generators going, largely because the Lister/Petter engines are absolutely bomb proof and will run for decades, plus the fact that I think it's better to re-use/recycle than buy new and throw out something that can still be used.

I regret getting rid of mine, as the small petrol genset I replaced it with is a pile of crap in comparison. One big advantage with these older generators is that they are pretty much infinitely repairable, without the need for electronic parts that may cease to be available at some point.

[openspaceman]

That's a non sequitur young man; I wasn't suggesting not using the old genset, I have a rake of old machinery one of which which I have kept going for over 48 years and the other five are not far behind, indeed I even have the rusty hulk that was my wife's twenty first birthday present that I have just replaced the disintegrated distributor in.

Anyway my question was not entirely rhetorical. What would a simple charger cost to keep the battery topped up while the washing machine is running?

I wonder if I put a rectified 110V supply with a big capacitor bank across it whether my MPPT charger would work on a cloudy day.

[Marcus]

I'm confused - how does charging a battery keep the generator voltage above 220v?

[ALAN/ALAN D]

Post from. “ Mr Marcus “

“I'm confused - how does charging a battery keep the generator voltage above 220v?”


It does not keep the generator voltage above 220v.


But as “ Mr Openspacemann “ said.

“Why not run the generator into a charger and feed the battery directly when the washing machine is running? “

Mr “ Deanforest “

Said. “ Washing machine runs fine on battery/inverter at 230 volts which is what I have set the inverter to. “

If the generator cant be fixed. The washing can be done by charging the battery with the generator running a battery charger.

[Oldgreybeard]

I'm near-certain there is a fairly easy fix that will get this generator back up to voltage. These are really simple machines, they have no electronics or complex controls and rely on the engine running at the right speed to deliver the set output voltage, IIRC. They do this with a pretty simple RPM governor, that compensates for changes in load by changing the "throttle" setting (in reality it moves the fuel pump rack).

The other common cause of low voltage is when the selenium rectifier starts to fail. These fail gradually, over a period of years, but there used to be a replacement kit available, and in all probability it should be easy enough to swap a failing selenium rectifier for a modern silicon one. As the voltage is only a bit low, my money is on the governor needing adjustment or servicing.

[AGT]

Ken Boak/ power cubes used to run his lister and export the power to the house, he had underground insulted pipe work and connected the generator water tank to his central heating system.

Great days of watching that happen.

[Oldgreybeard]

Ken Boak/ power cubes used to run his lister and export the power to the house, he had underground insulted pipe work and connected the generator water tank to his central heating system.

Great days of watching that happen.

Always wanted to do something similar, even went so far as to try and import an Indian made "Listeroid" CS engine a few years ago. Got scuppered by SWMBO, who didn't like the idea of having something like this thumping away in a shed in the garden.