Deceleration Alternator

[busypaws]

I put a switch on the field wire. That way when accelerating I switch off the alternator and when decelerating I turn it back on. The only issue is to make sure the switch is on when my wife drives the truck. Otherwise I get the dead battery call. I like the idea of making it automatic. I also agree you don't need any relay on the output leave it alone.

[Christ]

Dave -

I do this with the mountain truck... every light, accessory, etc. when coming back down the mountain with a load of wood on the back, usually in 1st (granny) and 4wd Low. (It's a '79 F150 w/ 300 6 cyl and 4 speed)

Frankly, I'd rather get diff axles with lockers in them, though.

[asimmons04]

why not just wire the relay to your brake lights so that when they get power, it throws the relay and kicks the alternator in. have it run to a manual switch on the dash that bypasses the brake light wire, so that if your cruising alot and arent doing much braking, you can always cut it on manually (or when stuck in traffic idling alot anyhow).

Or do like he said (or everyone said) having it come on at idle speeds (low duty cycle) AND run a wire to the relay from a brake light bulb wire so it also kicks in when stopping.

Use a cigarette lighter volt meter. Takes up no space, is digital. Buy deep cycle battery. Regular batteries, no matter how BIG or how many CRANKING AMPS do not stay running long. They are made to charge all the time, and work for about enough to either start your car, or to run radio/lights for an hour. LOL... deep cycle are made to run 12v power full blast for hours on end. Take longer to charge, but they LAST for longer cycles without recharging. Thats why he is talking about deep cycle batteries. Also, if your car once had a stereo amp, you can dual battery setup, second one in the trunk. Works great

[zonker]

another thought would be to use a comparator type circuit that can measure the TPS voltage, which then would trigger the relay at a given voltage. This would eliminate a micro switch under the hood, being subject to heat, moisture, and dirt.

[Varn]

Perhaps a micro switch in the throttle linkage or one activated by a vacuum dashpot and you could set it to trip a relay and only run when the engine is at light throttle or high intake vacuum. A simple mechanical adjustment could set the threshold. One problem with trying to charge a fairly discharged battery with the alternator is that the windings can get very hot reducing it's service life.

Personally it sounds like a lot of work for little benefit.

[bikepilot]

IIRC the civic VX does this to some extent - the alternator shuts down in low current draw situations and charges as needed based on voltage and load. It also kicks in during engine braking IIRC.

[Joenavy85]

Originally Posted by asimmons04

why not just wire the relay to your brake lights so that when they get power, it throws the relay and kicks the alternator in. have it run to a manual switch on the dash that bypasses the brake light wire, so that if your cruising alot and arent doing much braking, you can always cut it on manually (or when stuck in traffic idling alot anyhow).

that setup, combined with a deep cycle battery (or 2) and an Ultragauge would work great. set the high and low alarms for battery voltage (hi=~14.7, lo=~12.5) when it beeps, acknowledge it and flip the switch to turn on the alternator.

[usergone]

I did something similar in my jeep until I sold it. I had a fuel cutoff button and an alternator field switch, an a third switch.

I had it so that when the fuel cutoff switch was depressed and the third switch was engaged, the A/C would kick in. I used it with engine braking and it worked marvelously. The 2.5 litre 4 banger didn't have all TOO much engine braking, so you could feel it if you engaged/disengaged the A/C while engine braking.

I also had a diode so that when the A/C came on, the electric fan came on. Another diode so that if the electric fan came on, the alternator would come on. The diodes made it so that I could turn on one with its dependencies and not the higher-ups.

You could do the exact same thing with just the alternator, but I would recommend adding a diode between the electric fan and alternator field relay. That way you won't be as likely to drain your battery when your engine gets hot. But you probably don't see too much electric fan use because as an eco-driver you probably are either moving or have your engine off Unfortunately, with the cool down time of my turbo, I am EOC impaired

[Sularus]

Good info thecheese429. I wouldn't have thought to diode the circuits to turn each other on. It would really come in handy in the summer months when the temps can get crazy.

[usergone]

Just make sure you put the diodes to the relays controlling the loads... Or just use big diodes. Go for the fan relay for sure, they have a pretty big amp load and you could burn up a few diodes easily.

I find that PC power supplies tend to have anywhere from 4 to 8 big diodes on them (4 mm diameter)