How to Lighten alternator load

[giamar339]

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

[big-all]

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

[kellys_eye]

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.

[ericmark]

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.