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Old 03-10-2015, 10:10 PM   #1
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Onan MDJE 12 Volt Voltage Regulation

Hi Folks, Rob here and I'm new to this forum. Anyone have any experience with after market voltage regulators for an Onan MDJE 7.5KW Diesel Genset. I'm tired of mine toasting my genset battery and am looking for alternatives. Any suggestions appreciated. Thanks, Rob
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Old 03-10-2015, 10:58 PM   #2
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There is a variable resistor in the air discharge from the gen end. Set resistor to get enough amps to keep batt topped up, but no more. Crude stupid system, no regulation what so ever. It's just a rectifier, resistor and zero regulation.

Best thing is to disable the charge circuit and let the boat charger handle the gennie batt charging. Charger has power if gennie is running, so why not.
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Old 03-11-2015, 01:00 AM   #3
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Quote:
Originally Posted by Ski in NC View Post
There is a variable resistor in the air discharge from the gen end. Set resistor to get enough amps to keep batt topped up, but no more. Crude stupid system, no regulation what so ever. It's just a rectifier, resistor and zero regulation.

Best thing is to disable the charge circuit and let the boat charger handle the gennie batt charging. Charger has power if gennie is running, so why not.
Thanks for the info Ski. That's been suggested before. Care to elaborate on the Charge disable trick? I take it you've done this to yours? Thanks, Rob
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Old 03-13-2015, 08:57 PM   #4
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That is correct no charge regulator, constant charge rate of 2 - 5 amps, depending on what you have it set for.

The disable switch (either a switch or a jumper depending on your board) to turn off the battery charging circuit is on the regulator board inside the electronics box. You can access it by removing the lid on the electronics box. I don't have my personal Onan manual here at home to tell you which switch. Maybe someone else has their book at hand and can give you the switch/jumper number. As others have said, your boats smart charger will do a better job of keeping your Genset battery charged and not over charged.

PS: I have the Flight Systems aftermarket electronics board in my unit. Yes, it's better quality and moisture proof, but doesn't solve the charging issue you are having.

Here is a link to an online Onan MDJE manual, but I don't think it covers the electronics box. Check it out though.


http://www.cumminsonan.com/www/pdf/manuals/974-0750.pdf
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