24v automotive alternator control

[chainsaw]

I am attempting to use a 24v 70amp one wire alternator direct coupled(2500rpm) to a one cylinder diesel for a backup generator to my solar system. When the generator is started with the battery bank(12 T105 trojans) is at 24 volts, the alternator puts out 125+ amps  which far exceeds its capacity. I'm afraid that this output will "smoke" the alternator if allowed to run very long. My intent is to only use the alternator for one hour or less early in the morning to carry my battery bank through until the sun comes up these short days. Not to attempt any type of full charge.

When the battery bank is up to 26 volts or more the alternator puts out a more reasonable 50 amps and continues to taper until the bank reaches 27.4v. But if the bank is at 26 volts that means the solar is starting its daily charge and the alternator is not needed.

How can this excess charge current be regulated when the bank is at low voltage? Can the alternator be tricked to believe the battery bank is at a higher state of charge? All comments welcome.

[Flux]

The internal regulator is not really suitable for this duty. Probably the charge will fall quickly enough not to bother the alternator but you may prefer a lower charge for the battery.

If you can drop the speed that would fool it, depends on how you are driving it whether you can do this. Another way is to get into the field circuit and add some resistance in the circuit to the rotor. You need to go in series with one of the brushes.

This will reduce the maximum charge and still let the regulator take charge when you reach regulating volts.

You may just find it easier to remove the regulator and excite the field via a series resistor or some lamps.

There have been a lot of posts about using these alternators without the regulator if you google the site.

Flux

[Norm]

You may just find it easier to remove the regulator and excite the field via a series resistor or some lamps.

 I think hiker does this on his ped-generators.

          ( :>) Norm.

[chainsaw]

Thanks Flux for your suggestion on regulation of the field current. What exactly would I need to add for some some resistance that would decrease the amperage output?

[Dozzer7]

I'm also using a 6.5 HP Kubota, single cylinder, direct driving a 70 amp prestolite 24 volt alternator. I clipped out the factory regulator and went with the Balmar 624 regulator. It's quite nice in I can adjust it to bulk at 29.6 volts. It charges the batteries (2 sets of 4 L16s) at about 60 amps when the alternator is hot. It also has alternator temp protection and battery temp sensing. Fairly expensive but feel that it takes good care of my batteries. I'm lucky to recieve free throw away fuel from a test cell.

I have several BRS 2-24 Balmar regulators also that are spare to my needs. You can look them up at Balmar.net.

If you want one, send your address to s64f AT msn.com. All I ask is when you recieve it send me the postage and a small donation if you think its worth it.

Hope to be flying my 17 ft DanB soon, the wind is blowing.

[Flux]

Dozzer's offer is so tempting that I assume you will go that way but if you want to try with the original regulator you could experiment with resistors in the 5 to 10 ohm range, capable of about 3A. A nice variable 10 ohm rheostat would let you set the current to what you want but not everyone has one.

24v bulbs in parallel would do for the resistor, just add more bulbs to increase current.

Flux