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Bigger alternator or bigger battery?



Hi all,

I've fitted a larger electric fan for my intercooler project, it works well but the problem is that it draws around 20 amps at max load. This seems to place some load on my car's charging system, with lights dimming momentarily when the fan kicks in.

I measured across the batt terminals with the car engine idling at 800 rpm. Without the fan turning things are healthy at 14.5 V. When the fan kicks in, the voltage drops to 13.2 V, which is still in the charging range, then climbs back up to 14.5 V after a while.

Should I be looking at a bigger battery with more capacity, or an aftermarket alternator (for which I really don't know of any for the S15...)?

Thanks! :)