How many amps from my 350SD alternator? - PeachParts Mercedes-Benz Forum

Blevinsax · #1 11-17-2006, 02:21 AM

Simple question above - I need to do some math to make sure I'm not going to overload my alternator...

I'm installing a VegTherm Mega (draws a max 32amps - usually much less, but it CAN draw that much) so I can run on WVO almost all the time, but I also have a good friend (former ultra high-end auto electronics guy) who said he will help me install a new stereo with 2 or 3 amps and a really nice subwoofer (a recycled system pulled from his '72 Mercedes after it was totaled last year by a teenager in an SUV

) ... and no, I'm not into the thumping gangsta rap stuff - I listen to traditional jazz, so the subwoofer makes it possible to hear an acoustic bass solo over the engine and road noise!

I just want to make sure that I'm not going to be pulling more than my alternator/battery can handle, so where should my alternator be? (assuming that it is working as it should, and I've had no signs otherwise.)

pawoSD · #2 11-17-2006, 02:46 AM

It appears that the standard alternator on your car is 80 amps....depending on how many accessories you have on I doubt the car uses much more than 10-20 in normal operation of CCU/gauges/lights etc...maybe 30something with the headlights/wipers on etc....and 60 something with the rear defrost. The sound system probably wouldn't drain anything, especially since it won't be doing rap thumping.

32amps for the veg system will draw nearly 40% of the output, but I doubt it'd affect the rest of the system....it might only if the rear defrost is on....new sound system powered up and blasting jazz....and blower and headlights all on etc....in that case I'd install a 120+ amp alternator from one of the gasser models or something.

Blevinsax · #3 11-17-2006, 02:59 AM

Quote:

Originally Posted by pawoSD

...32amps for the veg system will draw nearly 40% of the output, but I doubt it'd affect the rest of the system....it might only if the rear defrost is on....new sound system powered up and blasting jazz....and blower and headlights all on etc....in that case I'd install a 120+ amp alternator from one of the gasser models or something.

Since I live in Las Vegas, the rear defrost will see zero use so I can mark that off the list. I have no other accesseries except the GreaseCar system and I don't think that is drawing very much - it's just the solenoid and the extra lift pump, but I'm not sure how much they draw. I'll see how things add up and I'll consider the new (or maybe a good used?) alternator if I end up pulling too much. Thanks for the help!

#4 11-17-2006, 03:10 AM

Be sure to install a good capacitor to dampen the amperage spikes that the amp will cause. Without one, the spikes can take out an otherwise good alternator really quick.

pmckechnie · #5 11-17-2006, 07:15 AM

What you really need to check is how much draw there is with every thing on and the engine idling. Remember the 80 amps is at 2000 RPM. If the alternator will supply most of what is needed at idle then you will be all right. If it won't than a traffic jam or such could leave you stranded. BTDT.