Anna,

I think you will find that your alternator can deliver a maximum output of 90 amps.

It would perhaps only deliver this when you have a lot of simultaneous electrical loads, such as headlights, blower, windscreen wipers, vehicle battery charging after starting, etc.

Dave

 

Hi,

We were told that the alternator on our 2.0 Fiat Ducato was about 100 Amps. What does this mean ?

Does this mean that it will deliver 100 Amps in 1 hours normal driving?

Is this just a maximum output, if so when will 100Amps be achieved?

Thanks, Anna

Hi Anna

You may be getting confused with the units, the Ampere is the unit of electric current and is the instantaneous value of current, time is not relevent. 100A delivered for an hour would be measured in AmperHours (Ah) and you could say that 100A alternator coud deliver 100Ah in 1 hour. ie it is the current times the time.

Battery capacity is measured in Ah as well. Don't run away with the idea that a 100Ah battery could be charged fully in an hour by a 100A alternator.

First of all 100A into a 100Ah battery is far too high a charge rate and would wreck it. A more realistic rate might be 25A max probably a lot lower

Secondly the 100A from the alternator at about 14V implies an external resistance of only 0.14 Ohms and the battery and its associated wiring will have a higher resistance than that. the higher the resistance the smaller the current that will flow.

Thirdly as Dave has said there are other loads that your alternator is supplying.

I apologise if your question wasn't going to be about battery charging I may have run away with myself.

Regards Frank

 

100 A Output

Hi Anna

The 100 amp alternator can give out around 90 amp with normal driving with the engine bay at working temp,

On slow running ie; tick over you may get around 30 amp output,

Having measured the output on a number of alternators in the past, and found the output to be from 15 amp, up to 40 amp on tick over, but the norm has been around 30 amp,

The design parameter when selecting the alternator, is for the optimum output to be at 56 MPH,

The 12 volt load (in amps) and battery condition will control the current output, but the voltage will be around 14.2 - 14.5

The 100 amp is the MAX output,

Head lights 10 amp
side lights 4 amp
wiper motor 4 - 8 amp
brake lights 7 amp
radio 3 amp
fridge 8.5 amp
engine controle 4 amp
engine heater 40 amp only on start up ( 2 mins )
starter motor 200 - 500 amp on starting

After starting the engine, due to the load of the starter motor & the engine heaters, the battery has to be charged up again, so this is when the alternator output will be high,

All figures above are approximate.

Good luck

 

THanks

Thankyou everybody the useful information.

Anna