B7100 hst charging system

[Rocketman.tractorbynet]

I have owned this 1984ish b7100hst for about 3yrs. I have never been concerned with the charging system, the PO said it does not work. I never used and lights, and it always started good. Now I am doing a power steering add on kit. I decided to go with a pump driven by the belt. I thought that I might as well dig into the charging system and find out what makes this thing charge. Well, it uses a "dynamo". a very simple belt driven two wire permanent magnet alternator. after disassembling it to clean everything, not an easy project btw, I was able to remount it and spin it with a drill (fixed a pulley to the drill) to test the output. I am sure I am getting plenty of rpm's, but only reading 13v A/C at max (it climbs steadily as rpm's go up. Before I put this back together I need to find out if that is good enough. This test is done by attaching the leads direct to wires coming out of dynamo. Other posts indicate it should put out around 30v. If that is the case, what would prevent it from putting out more (other than rpm). again, I am certain I am spinning it plenty fast. Once I get the dynamo figured out I will move on to the regulator for more testing.

 

[pedalstomper78]

Dynamos are basically weak generators. They use a commutator so they aren't exactly the most efficient beasts on the planet. They are small and they do provide power enough to recharge after starting though.....so that's why Kubota went with them. The big difference is that a dynamo generates dc current instead of ac current like an alternator. For a "free" repair, I'd go with it for now!

 

[RobertN]

That voltage is not surprising. Like the B8200 I used to have, a Mini-Maglight flashlight was far superior to the headlights on those things. Between the really weak lighting, and the minimal need for power with all mechanical diesel, there was little need for much of a charging system.

Unfortunately, it made it hard to add brighter lights and accessories.

If you're already adding a hydro pump, now might be the time to put a bigger alternator on(if you can squeeze it under the sheet metal). Maybe one off a GM, single wire.

This was a big topic from '98 when I joined the original version of this forum.

 

[pedalstomper78]

GM single wire alternators are wonderful things. You can add them to pretty much anything with a belt as long as you can make some mounts for it. I spent 10 years as a tech rep for Summit Racing Equipment and I've suggested those on anything from street rods to tractors to earthmoving equipment. It's really easy to get 60a out of one and most tractors in your size would only use a 15-20 amp alternator.

If you want to add lights to the tractor, something like the LED's from TractorHelp.com would be great. a 27watt light only needs 2.25amps to work. A battery can run that for a loooooooooonnnggggg time. I've got 3 of them on my tractor and they really make working at night comfortable......except for the whole cold outside thing. LOL