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Originally Posted by Stubby79
Seems like a good idea.
I'd assume it would register deceleration the same as a downward slope. You know what assumptions are worth, though.
Not sure why you wouldn't want it charging at a light. Yes, it would use a bit more gas...but at that point, 100% of your gas is going to waste. At least you'd be getting a bit of something back for it. Killing the engine would kill the alternator - and everything else - from wasting gas. Coasting with the engine on would amount to the same thing.
You could get creative and use the throttle position sensor as part of the information the Arduino is looking at. Could take it farther and figure out how to make the alternator pout out lower voltage (12.6-13) when at a light or engine-on coasting, go full ham when braking.
Personally don't see "regen braking" worth the effort with a regular alternator and a 12v lead battery...they just don't accept a quick, high-current charge easily. The right kind of lithium might. Bigger lead would accept a charge faster, but then you're carrying more weight.
YMMV.
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Thanks for your input. you got me thinking.
I think there will be a pay off for smart charging. The purpose of letting the battery go down to 12.4 is because at the lower voltage it can accept more current. I would consider a lithium battery after the lead acid battery dies. A .3-.7 mpg gain would be worth the sub $60 cost to me. Truthfully, at current gas prices few mods make financial sense. There is also the benefit of reduced pollution from saving a few gallons.
I agree lithium offers more benefits, at a greater cost.
My main reason for not charging at lights is most cars made in last thirty years automatically control the throttle to handle loads at idle and a alternator charging a heavily discharged battery would be a noticeable load and burn more fuel.
But now you have made it really simple if don't mind charging at red lights. just hook a relay to brake switch to cut the field current except when braking. edit- or the accelerator switch idea.
That would be super simple. add in the tilt sensor in parallel with the brake light switch( diode to keep tilt sensor from turning on brake lights) so when one or both is activated, the relay gets power to energize the field windings.