Generator Test Stand Question

[Jerry VanOoteghem]

I have a generator test stand that my dad made years ago. Not fancy, but works great. However, for the "load", I need to have a 6V battery handy. Problem is, I don't often have one laying around to spare. My current one is a 6V Optima that belongs in my Sedan. It's at full charge right now and frankly, I don't like putting more charge into it with my tester, although it's only for a few minutes.

So, the question is, is there a resistance load that I can build into my test stand to replicate the load of a battery? Ohms? Watts? I guess having a "dummy" load, and not a battery, won't allow me to test the motoring capability of a generator however...

Thanks!

[Moxie26]

Get some headlight sockets, larger wattage incandescent headlight bulbs, hook in parallel, use as a load, so the generator will start gennin' after bulbs have been on for say 5 minutes or so. Using a standard cut out or voltage regulator to measure generator output ??

[speedytinc]

I have the same issue. You can use a 12V battery. Setting the null is a bit pickey. I find setting the null by reading the amp output, per Ron P. works best anyway even with 6V motoring.
To set the output use 1/2 the amp reading. In other words set the output to 3 amps. When you put it in your T with a 6V battery it will read 6 amps. Recent experimentation confirmed.

I Dont use a mechanical 6V cutout on the test machine. Its a diode unit that works on 6 or 12V.

[JohnH]

So, the question is, is there a resistance load that I can build into my test stand to replicate the load of a battery? Ohms? Watts?

It's not as easy as that because a resistive load is very different to a battery. There's nothing to actually clamp the generator voltage as the output voltage rises - unless the load current is greater than the third brush setting. For the purposes of just running the generator you could use as many headlamp bulbs in parallel as required, to keep the voltage under control. The load would be connected after the cutout so the generator can get itself started on the residual magnetism in the usual way.
A more elegant way would be to load the generator with a very high power zener diode of 7 to 7.5V rated at about 100W. Such devices would be hideously expensive, assuming you could even get one, but a lower power zener with a power transistor is much cheaper and works the same.

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