Ok, let me start at the beginning. I really want to learn this all, but I find it impossible to learn from a book and only know what something can do and not how to implement it, so please be patient with me.

I have a moped engine w/ electric start that we have rigged up to 2 cadilac alternators to act as a generator. Now I want to make a circuit to control this engine so that it will start automaticly when voltage on the battery bank drops below say 11.2v and then shut down after a certain ammount of time and then restart when the battery gets low again. I am trying to do this myself but everytime I think I have one small fraction of the problem figured out, I find a huge flaw in it and Im back to square one.

Anyone have any suggestions?? Any help would be great.. Thanks..

 

hi

can you not use the regulator system of a car? check on books about electrical charging system for vehicles. i believe that would do the trick for stopping the charging and just build another system to monitor the battery voltage level by using a comparator ic.

 

The starting and stopping I already have done, just using two relays... Dosen't a comparator require a stable referance voltage to check the batteries voltage against?? Maybe you missunderstood me when I said start and stop charging. I mean physicaly stop the engine, to its no longer running, and then restarting the engine when needed...

 

Originally posted by kickit2@Aug 23 2004, 06:40 AM
The starting and stopping I already have done, just using two relays... Dosen't a comparator require a stable referance voltage to check the batteries voltage against?? Maybe you missunderstood me when I said start and stop charging. I mean physicaly stop the engine, to its no longer running, and then restarting the engine when needed...

[post=2291]Quoted post[/post]​

Try balancing the pullin and drop out current on a relay to turn the igntion on and off.

 

Remember the magic of Mosfets!

 

Battery monitor circuit
http://www.explorecircuits.com/circuit/cir_battery_monitor.htm
Battery charger circuit
http://www.explorecircuits.com/circuit/cir_6_V_battery_charger.htm

 

I'm doing the same thing with a Briggs motor and 2 GM alternators. Welcome to the club! If you use the search function the forum provides on my username, (pntrbl), you'll find a buncha threads where SgtWookie steered me through using an LM339 comparator and other mostly Radio Shack parts. Right now the circuit's about 75% checked out and I'm working on the mechanical aspects of the contraption.

A copy of the current schematic, which could change, is attached. The circuit basically has 4 functions.

1. Start the starter motor. (U1A)

2. Shut the starter motor off. (U1C)

3. Energize the alternator(s) when up to speed. (U1D)

4. Shut the whole thing down when the battery's charged to an acceptable level, (U1B), and that's the 25% that's not checked out yet.

11.2v is just about a wiped out battery BTW. You'll want to start charging before it gets below 12v from the fully charged 12.6v. R2 adjusts what battery level it starts on the attached circuit. My intent with R10 is to adjust what level of charging current it will shut off at.

Of particular interest is the tach signal the Sarge came up with ..... but you can read about it on the threads!

Also, I'm using 2 alternators in series because I need to charge a 24v bank of batteries. One will charge the high side and the other the low. Not knowing you're particular case the good Sgt advises against running the alternators in parallel due to phase issues between the two.

Hope that helps.

SP