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Delco and other Low Voltage DC Light Plants Antique Generators, Light Plants, Typically 24, 32 or 48 volt although some are 110 volt. DC Lamps, Motors and appliances.

Delco and other Low Voltage DC Light Plants

Calculate the correct resistor to use?

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Old 10-14-2018, 03:21:47 PM
Mike Schweikert's Avatar
Mike Schweikert Mike Schweikert is offline
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Default Calculate the correct resistor to use?

My brain hurts....

This is the wirewound resistor off of Western Electric light plant #2 that I have. It is still intact, where the one on #1 light plant is a mess of broken magnet wire ( cannot save it period).

The purpose of it is in the charging circuit, when in battery charge mode, the current is limited through this to the battery. When in overcharge mode, the small portion of the resistor is used via a knife switch to go from one to the other. I get it changes the resistance to either charge at a reasonable rate or overcharge to equalize the battery set.

I need to figure out what wirewound power resistor to use. So far I have tried to meter it from lead to lead on both sections. Perhaps 175 milliohm for the large side and 50 milliamps for the small one. That does not make sense to me..

Ok, then tried to figure out amps. Hooked a 12 volt battery on one lead and a meter lead on the other and one on the battery. Large section dropped from 12 volts to just under one. Small section dropped to 1.5.

Then I put a 12 volt bulb in series with it and measured at battery. About half an amp for both. I am going to use 3 12v garden tractor batteries.

The specs for the plant are 1500 watts at 40 amps at 40 volts. It uses a charging relay in series with this resistor. The literature suggests to adjust it so the relay opens when the current drops to about 14 amps, stopping the charge. The literature says the batteries are fully charged. It supposedly takes 7 hours to charge the 180 amp batteries.

I've been on those sites with the calculators for watts and power resistors The literature does not specify the ohm or watt rating for this resistor. I am not coming up with a plausible replacement.

Could someone hurt their brain too and let me know what you think??

Thank you
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Mike Schweikert
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