Farmall H charging system

About 10-15 years ago I restored my Farmall H. Rather than cleaning up my old regulator cover and repainting it I opted to replace it so I knew I had something good. That was a bad decision and stupidly, I tossed the old one in the trash back then. I've had lots of issues with the charging system ever since then. It dose charge now though. I had to haul it to someone to look at it. I was sorta "winterizing" it last weekend and decided to pull the battery out and put a battery tender charger on it. When I was having issues with the charging system I noticed that if a battery terminal was disconnected the tractor would quit. Being a young kid back then I really didn't know much about how charging systems work. So while I was fulling with it last weekend I decided to unhook the battery and see what happened. The tractor didn't quit. I figured that issue must have been fixed the when I had it looked at. I put the terminal back on and then I idled it down. I then decided to remove the battery while it was running and as soon as I pulled a wire off the terminal, the tractor quit. It then dawned on me that it must not be charging at lower rpms.


My question is,

Should or shouldn't it be charging at lower RPMS? I would think it should be and would want it to. It idles around at shows more than it ever gets to put the power down.

Details of the tractors charging system is 6 volt system wired as original with new harness. Original generator, starter and light switch. Generator and starter and test good.

I've put a multi meter on the battery and the charging isn't constant, its more erratic. I'm not sure that it should be on a generator charging system though. I'm more familiar with automotive charging systems.

I'm affraid to re-polarize the regulator since its working now, well sorta working.

Your charging system is behaving quite normally. Generators usually do not provide much, if any, charge with the engine idling. That is why the automotive industry made the switch to alternators back in the 60s.

Rusty is correct. the only way to assist the generator is to put a smaller pulley on the gen (or if yours is an adjustable pulley (split) thin a shorter belt, and opening it up to ride lower in the groove, will be about it. The generator will handle a pulley with smaller diameter, (about 2.5 diameter at the back of the belt) but the tendency to slip will be greater due to less belt length wrapping on the pulley faces. I would just use a 6 amp charger on it between uses when you are doing daily puttering around, and a maintainer between times. It was designed to make work, so it just was not important to charge at idle. Though many farmers were displeased with lights and charging when doing first cultivating at night. JimN

I agree with the other gents, A gennys output is increased EITHER by spinning it faster (smaller gen pulley or bigger crank pulley) or pumping more current through its field windings. However, on the old cutout relay systems that used the LHBD light switch for field current regulation, in the High charge position (and/or with lights on) shes already set up for max field current (max charge). Soooooo at real slow idle RPM's the gennys simply NOT charging the battery as once its voltage drops below that of the battery the cutout relay that connects the genny to the battery opens. i.e. the battery isnt seeing or connected to the genny anyway, and you dont want it to because then (gennys voltage less then battery) the genny becomes a LOAD sucking up battery current versus putting charging amps back into it.

Other then change the genny or the pulleys things that can help are a good tight belt and good grounds on the genny and especially a good light switch ground

Slow idle plus lights on just didnt get the battery charged much or none at all even when all was new on those type and age of tractors, it sorta goes with the territory

Ol John T (Ima gettin old my batteries dont stay up well either it seems)

The others’ comments summarize the situation pretty well: Those old 6 volt, 3-brush generators simply weren’t designed to charge at idle. So a modest discharge at idle (and at RPMs a bit above idle...) is perfectly normal.

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As JimN points out in his post, the situation can be helped by installing a smaller pulley on the generator to spin it faster. However it is not without potential problems:

1 – Driving the generator faster wears out the brushes/commutator proportionally faster.

2 – The 3-brush generator design is not very energy efficient. Ie. a significant fraction of the shaft energy going into the generator is wasted as heat in the windings. Spinning the generator faster creates more heat inside the generator. And a hotter generator = shorter generator life!

3 – Overspinning the generator increases the risk of destroying (“birdnesting”) the armature should the engine ever overspeed due to governor failure, rolling down a hill too fast, etc.

As mentioned, a Battery Butler would be a smart, and cheap, investment. I plan on getting one for my H so it has a full charge every time I pull it out.

Well If thats the way its supposed to be then I'm not gona change it. Its a wonder that when I first got it that the battery didin't go dead running it around. I normally idle around in a higher gear because it idled so quietly. People would always ask if its really running it was so quiet. I have no idea what happend because its not as quiet anymore, that also changed after I restored it. Oh well.

As for the battery tender, I havn't gotten one yet but I will soon. On the subject of that, has anyone ever hooked one battery tender to multiple batteries? I see on other forums that people have done it but the posts are misleading.


Thanks for the info