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Hello to all
I would like to know how can I lighten a car alternator load.
I am trying to charge 3 car battery of 12 volt 45 amps with an alternator of 12 volt 45 amp in my garage.
The alternator run with a small petrol motor but it became "heavy" if I connect more battery to it.
I know there is a cheap way to make it lighter but I don't remember where I have read it.
Thank you very much

heeelllooo and welcome giamar339
not sure what you mean
if you are trying to charge batteries then the mains with a sutable charger will be far cheaper and more efficient than running a car to do it

an alternator will have a maximum output so perhaps charge 2 then one

The load on the alternator will depend on the state of the batteries (their discharge state).

You problem(s) start with connecting multiple batteries in parallel - the one with the largest discharge state will dictate how long the system 'tries' to charge the other batteries and, as a result, will OVERCHARGE the others.

If you connect multiple batteries you MUST separate them using diodes (a blocking diode). Google 'split charge diode' and get one suitably rated.

Depends on alternator, but you need to reduce field current so remove a wire going to brushes and fit a bulb holder between wire and brushes then try will different size bulbs until you find one which reduced max charge by required amount.