Balmar alternators overheating

[neilbatcheler]

I have a twin engined sailing catamaran recently fitted with Balmar 100 amp alternators and ARS-5 regulators. They are working fine but if required to produce anything more than 60A or so heat up beyond the regulators pre-set temperature level of 108C which means the regulator reduces the field voltage, the current output drops until the alternator cools sufficiently whereupon the field voltage is increased, current output goes back up, until the alternator overheats, when the field voltage is dropped...and so on. This means that the alternator output cycles up and down as the alternator overheats and cools (relatively) so I'm not getting the full benefit of the high output alternators etc. All the cabling is within spec, the installation has been checked and is fine, ventillation is good. I've been in constant email contact with Balmar in the States (I'm in Grenada) who have been tremendously helpful but not really solved the problem. Their last suggestion was to reprogramme the regulator to a higher temperature cuttoff point (120C) which I've done but all that now happens is that the alternator produces for a little longer before overheating. Initially the Balmar tech dept offered lots of suggestions although said they hadn't come across this problem before, the latest suggests that the alternators do run very hot anyway and you have to live with the "cycling". Has anyone out there got any experience with this problem?

 

[Eygthene]

I would suggest that you need to provide forced cooling to the alternator. Try fitting up a large cooling fan with a duct to blow as much air as you can into the back end of the alternator. I suppose Grenada is a bit warmer than this summer in Cornwall?

 

[oldsaltoz]

G'day Maxim38Adonde,

You should be able to pick up a couple of very cheap fans that fit onto the front of the alternators from your local auto electrician, they throw out hundreds of them on old alternators from cars and trucks.

They fit onto the front shaft and draw from the back and out the front, designed to prevent water entering on road vehicles.

Hope this helps.

Avagoodweekend......

 

[William_H]

Gee what are you trying to power. With 120 amps total at 12volts?

I reckon you will find the alternators have been optimistically speced at 100 amps. Probably based on excellent cooling and for a short period only.

Usually any real power of this amount runs at 24 volts so only half the current.
So if forced air cooling doesn't help then just live with a limit of 60 amps. But if you need that sort of power 24 volt system is the way to go with a lot more real gutsy alternators available form aircraft or big trucks. good luck olewill

 

[charles_reed]

The 100 amp Magnetti Marelli alternator I've got fitted charges 3 batteries though splitting diodes and an Adverc smart regulator.

I get a similar cycling problem when charging with just one battery in duty.

Turning on all three gets rid of the problem.

Mine is not a question of the alternator, fitted with an integral fan, overheating, but rather the Adverc overcorrecting for increased circuit voltage.

 

[neilbatcheler]

Thanks everyone for your input - I think I'll try rigging up my engine room fans so that they blow directly onto the alternators (the fans suck cool(er) air from outside). It is a bit toasty here in Grenada - currently 32C...