Alternator Information

Modification of your existing alternator to accept an external regulator is a requirement and can be done by yourself or a reputable auto electrical shop. Depending on your alternator type, an external brush block is available from most auto electrical shops.We also offer a service to modify your alternator.

Alternator size

I always recommend a Bosch 80-90 amp alternator, which is about the highest rating without going into high priced alternators.

No matter how good any smart regulator is, if the alternator is not spinning fast enough then you will not get a good charge current into your battery bank.

You need to calculate what your lowest cruising rpm is and arrange your pulley size to ensure your alternator is producing the best possible output.

Remember, for every 25 amps you will draw 1hp power of engine energy.

 A rule of thumb for alternator belt size is a follows;

Alternator size

Battery size

Belt requirements


0 -75 amp

200 to 400 AH

single 10mm belt


75-100 amp

400 to 600 AH

single 12mm belt


100-150 amp

800 to 1000 AH

dual belts