Performance Output Measurements of Stock 60A Alternator

Brought home a DC load bank and clamp on DC ammeter this weekend to measure the output of a stock military 60A alternator. Ambient air was 47F, and the measurements were done with the engine and alternator cold. Output will be lower as alternator warms. Measurements were done with calibrated equipment which was zeroed, on an M925A2 (Cummins 8.3), at engine speeds of 600rpm and 1500rpm. I used an external load bank to load the alternator until output saturated and would not increase any further. As reference, alternator output just after engine cold start was 4.6A, which is made up of both the current to hold the shut off solenoid open, and battery recharge. The 8.3L typically starts with just a mere bump of the starter switch, much less than 1 second of cranking. I am running twin group 31's for batteries.

Idle (max): 69.6 amps
1500rpm (max): 91.3 amps

Thanks!!

Good info, thanks!


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Is your voltage a little low, or was it just off at the time the camera shutter snapped?

Engine off while calibrating current probe to zero. Voltage shown on DVOM is surface charge on batteries. That would quickly dissolve if you turned the lights on for 45 seconds. Mind you, this is of course when this alternator works, which is not one thing they are known for. You all know my feelings about this alternator. I can't keep my 130A units in stock, every time I try to shelf one for my own upgrade, along comes a purchase request.

This well working stock alternator is now listed for sale in the classifieds.

74M35A2 said:

Brought home a DC load bank and clamp on DC ammeter this weekend to measure the output of a stock military 60A alternator. .....

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Thanks for this info.

Do you perchance still have access to an external load bank; better yet two of them? If so what can we do to twist your arm to run a similar test on a dual voltage Alt. on an LMTV. There are several in MI. Hopefully one near you. Reason asking is there is several considering using 12v or 24v Cab AC systems. Knowing typical "real" amp output when not in adverse conditions, are being put out, will tell them if it is a necessity to add the very spendy 200amp alt. or not. The 200amp Alt. Kit is near about same cost as a whole DC powered AC system.

Sorry I'm late on this. Yes, we could do it.

Do you know the curret draw of the A/C system? Condenser fan will likely be the largest part if electric.

From my experience, I would not put a heavy continuous load on an older technology single fan alternator. Not only from a cooling airflow perspective, but also the electronics (diodes, regulator) are likely not rated at as high of a temperature as the modern stuff.