M alternator conversion charging issues

Bill in IL · Jan 1, 2012

I just converted my M to 12volt with a hitachi alternator. Was pretty easy to do with searching the archives and using their advice. Tractor stars great and can actually clear a flood on its own.

I question though the ammeter indication. The ampmeter shows a good solid 20 amp plus charge like one could expect but it does not go down. I ran the tractor about 15 minutes yesterday thinking the charge level would back off after 5 minutes or so but it did not. I am worried I will "cook" the battery if this keeps up. I started with a fully charged battery and voltage levels out of the alternator are normal in the 14 volt range.

Jon Hagen · Jan 1, 2012

If voltage at the battery posts are not above 14.8V, everything is fine. The charge rate should drop back to just a few amps when the battery is full. Let it run a while longer and keep checking the voltage at the battery.

I am curious where the little Hitachi regulator kicks out. !4.2 is ideal, but many Delco SI series alternators have the regulator set at 14.6-14.8 which is higher than necessary.

mkirsch · Jan 1, 2012

Your battery likely wasn't fully charged to begin with, and needs some charging. It takes more than 15 minutes.

As long as the voltage to the battery looks correct, it can't overcharge.

Bob M · Jan 1, 2012

Bill - If the battery is partially down, it could take 2 or 3 hours of charging at 20 amps to fill it up and for the charge rate to then taper off.

Try sticking a battery charger on it overnight. Then start the tractor and watch the ammeter. If the battery is good the ammeter should drop to +5 amps after only a minute or two of running.

However as Jon suggests taking a voltage reading across the battery is the best indication whether the battery is being overcharged.

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Jon - The regulator on the Delco 10SI is temperature compensated. Depending on the ambient temperature output voltage at speed can range from about 14.2 (hot weather) to as high as 14.8 - 15.0 (temps below 0F). Thus you may see an apparent overvoltage condition in cooler weather when the alternator is actually performing as it should.

Janicholson · Jan 1, 2012

I will add that an old amp meter can have its shunt reduced by corrosion and read high. I would look to battery charging voltage at the battery for solid indication of control, as Bob points out. A second amp gauge might also test the output. Jim

David G · Jan 1, 2012

My dad always told me to take care of the volts and the amps will take care of themselves. You should be fine as long as the voltage at the battery stays 14.5 or lower.

M alternator conversion charging issues

Bill in IL

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Jon Hagen

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mkirsch

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Bob M

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Janicholson

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David G

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