Mercedes Sprinter Alternator is a Champ: Real Data on What it Can Actually Output for Amperage at Low Idle

Mercedes Sprinter alternator: 133 amps @ ~960 rpm idle

There is a lot of invalid and context-dropping information out there about how many DC amps the Sprinter alternator can deliver at idle.

I am pretty darn thrilled with what the Mercedes Sprinter Alternator can do under load, such as providing about 1500 watts (DC) at 960 rpm idle, almost enough to run a 1440 watt space heater*, at least under cool/cold conditions.

The bad news? It’s a smart alternator and won’t output that kind of power for charging. It ups its game for a space heater but not for charging. Must be some kind of sensing thing that differs between the two types of loads.

The really impressive thing is that these figures showing the high output were taken at an elevation of 10,600' and confirmed all the way to 11,800' elevation. That turbo is apparently doing its job.

See all the data I measured:

Mercedes Sprinter Alternator

* 1440 watts AC requires about 1670 watts DC, due to conversion losses. But in the case of a space heater, it is not an issue because that waste heat heats up the cabin also.

Mercedes Sprinter alternator can produce up to 133 amps @ ~960 rpm idle
at 10600' elevation (and higher)

Sprinter at 11,800' elevation (before upfitting of any kind)

f2.8 @ 1/1500 sec, ISO 20; 2017-08-09 15:20:20
iPhone 7 Plus + iPhone 7 Plus back camera 6.6mm f/2.8 @ 57mm equiv (6.6mm)

[low-res image for bot]