When my old fire truck was in service it had two batteries, one solely for the Briggs V-twin powering the water pump. I just today ran a cable from the Briggs in back to the main battery, to eliminate keeping two batteries in it (but still be able to run the pump). I just realized the Briggs has it's own alternator, so if both the truck and pump are running they both will be charging. Could this be a problem with one alternator backfeeding into the other? I suppose it's no different than two cars running with jumper cables connected.
Competition stereo guys run multiple alternators. I have seen as many as six. All of the large lugs led to the same large terminal.
I suspect the reason for the separate alt is largely due to the amount of power draw the pump requires. When you are at a fire, the last thing you would want is for the battery to run dead and the pump to stop running because one alternator can't keep up with the power demand. Modern alternators can put out a lot more power then the early versions, but still the more the load on the alternator, the better the chance for the belt to slip, or for a single alternator to fail. With a lot of fire equipment, like aircraft, redundancy is pretty common, a second system reduces the chance of total failure.
I don't think the Briggs has battery Ign, should then have magneto so bat. is only used for starting. However it will charge the firetruck battery when running, so yes leave you can leave alt [behind flywheel 20a tops] hooked up just be sure pump engine is grounded good to the F'truck.
The pump he's talking about is powered by a Briggs & Stratton V-twin gasoline engine, not the electrical system of the fire truck. The two alternators are the one on the fire truck engine, and the one on the Briggs powered pump.
Hmm, OK thanks. I think one of those stereo competitions guys must live somewhere behind my master bedroom window. That is correct. Battery is only for starting.
The Briggs engine doesn't need a battery to run, just to start. You should check to make sure there are no other things drawing on that battery. Personally, I would keep using two batteries. A pair of jumper cables would be all you need in case one fails.
You could stick a Ford (or continuous duty) Solenoid in the positive cable to the pump and avoid feedback from the generator. just rig a wire and switch to energize the solenoid when you need it to start the pump and the alternator spins with no load.
I came across that pic, and the accompanying article, in the course of the line shaft daydreams which led to my discovery of link belts.
Seems to me I’d just eliminate the one on the pump engine, disconnected it since it’s not needed anyways.
In this application there should be no issues with the two alternators being its an older vehicle. I have similar setups on work vehicles but they are computer controlled and I didn’t want any feedback so I disabled the alternator on the small engine. As said the briggs only needs power to spin it over. And if it runs well doesn’t use much power to start.
Dosn't that happen when you jump start? Alternators see voltage if one is putting out more voltage than the other the one with less output will back off.
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