My
google research found that automotive alternators are built for hot engine bays thus around 120°c. As an industrial electrician I tried to run
electric motors at about 40°c with the knowledge that every 10°c would halve the life expectancy. At 40°c you may get 40 years, at 50°c 20 years, at 60°c 10 years etc. This really can’t be right as motors/alternators are all different.
What I also read was there are things you can do to help your alternator run cooler and still produce the amps (power) you need.
1. Make sure your engine room
exhaust fan is working. Many of these blowers are only
bilge blowers that are designed to be used to ventilate the
bilge before starting a petrol engine. Get one that has a continuous rating.
2. I installed an inline blower, no ducting, just points at the alternator to blow the hot air away from the alternator so it’s not sucked back in by the internal
cooling fans.
3. As I had enough room I put a longer serpentine belt on so I could rotate the alternator on its pivot point further away from the
exhaust manifold.
4. I used a hole saw to put some holes in the belt guard. I’m not prepared to run the engine without it. Many motors don’t have guards over rotating
parts but this is dangerous cowboy behaviour.
I’m currently getting 104 amps out of my Valeo 125 amp alternator and it runs at about 87°c. I have fitted a Balmar regulator. This gives me about 80 amps charge to my batteries continuously till they are charged or I stop motoring.
Further things I intend to do are.
Install a switch to turn the alternator off before I stop the
motor so the alternator cools while it is still rotating.
The engine room exhaust fan is only drawing half its rated
current which indictates to me that there it is blockage, maybe the duct is too long or too many bends.
I may also use an external rectifier to remove more heat from the alternator.