TheBackShed.com

Forum Index : Electronics : Backup Genset Fun

Author

Message

Bryan1

Guru

Joined: 22/02/2006
Location: Australia
Posts: 2096

Posted: 06:04am 20 Jun 2026

Copy link to clipboard

Print this post

G'Day Guy's,
Well this 80 amp Staff&Stanbury solid state battery charger has claimed a few gensets to date, now a few years ago bought a 7.7KVA genset from Paramount Browns where it did work for a couple of years then onday it just decided to stop outputting 240 volts AC. So went back in only to be told they don't sell spare parts so I bought a 4KA genset which did work fine with the charger.

Now after I put in that 1.9Kw solar array running the genset became a thing of the past where we didn't use the genset for well over a year. Now after several dull days the genset was needed and when I started that 4KVA genset found it wouldn't run with the 13 amp load so I had to drag down my 20 year old Honda genset from my shed where that has just worked ever since until recently.

So decided to have a look at this 7.7KVA genset and the first thing was getting rid of the old fuel. Now I did see this hack where if one drills a hole in the bottom of a 2 litre bottle of coke and put in a tube then seal it with hot melt glue, put the tube in the fuel tank squeeze the bottle and out comes the fuel

Got 99% out and put some fresh fuel in and got the engine running but silly me had the fuel turned off.

When I tried again with the pull start the cord broke so had to go in and buy some starter cord to reset the pull starter. Got it fired up and found with a new regulator I did manage to buy after talking with the boss the genset was only outputting 4volts AC, I put my DMM on DC volts and found the brush's were outputting 5 volts.

Rang the boss and asked him what else could be wrong and he said the brush's could be the problem, now if the are outputting 5 volts they are connected so it does look like the engine of this genset is going to be a donor for my 6" Jaw Crusher.

Now as the Honda genst kept cutting out this morning went and bought a new spark plug and the genset run until the house battery was fully charged

So it does seem the old stuff just continues to work where this newer stuff just lasts for the warranty period.

Regards Bryan

Godoh
Guru

Joined: 26/09/2020
Location: Australia
Posts: 661

Posted: 06:12am 20 Jun 2026

Copy link to clipboard

Print this post

Hi Bryan , it sounds like the genset may have lost its residual magnetism.
The ancient dunlite generators have the brush gear accessible so that one can take the insulating caps off, and put a 9 volt battery straight onto the brushes to excite the alternator. And away they went.
Different types of alternators will need a different system. But if you got a 12 volt battery and put some leads on it and put one on each rotor brush or on each slipring then it may just decide to work.
I don't have a 240 volt gen set any more. Once every few years we live inside the clouds and if that goes on for more than 3 days I need to charge the batteries as I don't like them going below 70% charge.
So I have a 5 hp petrol motor and a car alternator. I use a rheostat to control the field current. No regulator, just power straight to the field coils. And usually set the alternator current to around 50 amps. As I say it only gets used once ever 3 or 4 years for a couple of hours, so no need for anything flash, but it works great.

Godoh
Guru

Joined: 26/09/2020
Location: Australia
Posts: 661

Posted: 06:18am 20 Jun 2026

Copy link to clipboard

Print this post

I forgot to mention Bryan that you only need to connect the 12 volt power to the field coils for a very short time, just a few seconds is enough to remagnetise the fields
Pete

Bryan1

Guru

Joined: 22/02/2006
Location: Australia
Posts: 2096

Posted: 06:22am 20 Jun 2026

Copy link to clipboard

Print this post

Pete I did flash a 12 volt battery across the brush's and it made no difference and after I take the gen head off the engine I do think I will find the cause.

This Honda genset has eaten several run caps and replacing the cap with a new one got it working again so it can live on doing it's job

Now the engine for a 7.7KVA genset would be around 15HP so with that powering my Jaw Crusher will crush quartz nice and easy and the best part if I don't find any gold the very small rocks do make good road base

I do want to get this Jaw Crusher project finished as I reckon I can sell it for around 10K to some gold hunting freak that has more money than sense

Regards Bryan

phil99

Guru

Joined: 11/02/2018
Location: Australia
Posts: 3290

Posted: 08:41am 20 Jun 2026

Copy link to clipboard

Print this post

Re the Honda, I have a very old one (3.6kW side valve engine, 1980ish model) that had similar symptoms a few decades ago. The very low output voltage turned out to be due to a partial short between the main winding and regulator/field supply winding.
This messed up the feedback voltage sensing, which is taken from a tap on the main winding.
The cure was a small isolating transformer to provide the feedback voltage.

Post the model number and I will try to find a circuit diagram. Perhaps a similar trick will work with yours.

Revlac

Guru

Joined: 31/12/2016
Location: Australia
Posts: 1276

Posted: 09:02am 20 Jun 2026

Copy link to clipboard

Print this post

Quote The ancient dunlite generators have the brush gear accessible so that one can take the insulating caps off, and put a 9 volt battery straight onto the brushes to excite the alternator. And away they went.

Yep that reminds me of the old Dunlite (think its 4Kva) with 13Hp B&S motor,

We did replace the high speed diode on the Back of the Brush plate, last time I ran it on gas so no longer have issues with stale fuel....Haven't used it for years, for Honda there are LPG Carburettors around makes it very easy to start but was never impressed with the mixture when the governor opened up, regulator might have been too small.
Anyway we moved on to the old Lister genset....never fail.
Don't use it now the solar powers the house so well.

late to the post, never mind.

Edited 2026-06-20 19:03 by Revlac

Cheers Aaron
Off The Grid

Bryan1

Guru

Joined: 22/02/2006
Location: Australia
Posts: 2096

Posted: 09:21am 20 Jun 2026

Copy link to clipboard

Print this post

Phill the 7.7KVA genset is a Paramount Browns model now all that genset did was supply 13 amps to the S&S battery charger and oneday it decided to stop working, now I did buy a new regulator for it and it didn't cure the problem. So as the engine is still good it will be a good exercise to convert the output to a V-pulley for my 6" Jaw Crusher.

That Honda 5KVA genset was bought in '05 and with it using a genuine Honda motor there are 3 things that stop it working usually. Air, fuel and spark as the auto start failed years ago and I did buy enough starter cord to redo the pull starter.

A few years ago it stopped working so bought that 7.7KVA and dragged the honda upto my shed, replaced the run cap and reflashed the stator and it served as my shed charger for years.

Now as that 4KVA was no good did a swap of gensets so I have a spare supply for the shed, now since that madboard is working it does everything I ask inculding keeping my tobacco seedlings warm.

Regards Bryan

Print this page

To reply to this topic, you need to log in.