Automated alternator delete
 

I ordered a shifter knob from Daox, very excited for that, and got to thinking, what should I do with the toggle switch. Daox recommended I use if for an alternator delete.

Unfortunately, I drive so much highway, and my stops would not be enough to keep the battery charged. But, I had an idea.

Tap into the power for the fuel injectors. When the deceleration fuel cut off activates, power stop, it also could activate the relay for the alternator delete.

Are you suggesting that you turn off the alternator when dfco'ing? I would think that would be the best time to have it ON, since that is the only form of 'regenerative braking' a gas car can do.

I am suggesting that when the current stops to the injectors, it also stops to a relay that would turn off the alternator delete.

Or you could just use the switch. YOU can account for daytime and projected usage pattern for the trip which if automated may not.

So I saw your post title and thought, "Damn, that's a great idea", then I opened up the thread and it went a totally different direction than I was thinking.

Why not just have a Raspberry Pi or arduino or other micro-controller/micro-computer monitor a few inputs (Battery voltage, draw, throttle position) and have it throw a relay to cut your alternator in and out when it meets the prescribed variables?

Wouldn't the goal be to arrive home- or at a place to charge up- needing a wall-power charge? Otherwise the existing voltage regulator more or less does the job, unless you have a car with a "smart" regulator which does a bit of regen charging.

I think better than an alternator "delete" would be an alternator cutout switch attached to the throttle that activates when you press the pedal past some point. The higher the load, the less efficiency you gain from adding load. If the engine happens to be idling or DFCOing, you might as well charge the battery. This is how the new BMWs and Mazdas work. You probably want a manual switch anyways to charge the battery if you haven't charged it in a while and don't want to be stranded.

I like the idea of using an arduino, but then I asked myself, when else do I want to charge the battery? Almost never. Possibly a manual override would be nice, but the DFCO thing handles almost all the regen situations you would want.

I think a switch that triggers on throttle-off is the best way to do it, that way you don't need to detect if the injectors are off, just screw a 1 dollar switch near the gas pedal and it's good to go. Foot off the throttle = either DFCO, slowing down in gear at low speed, or idle, which are all good times to charge.

How does one determine if they already have a smart alternator?

Monitor the voltage from the cigarette lighter?

This is how all new cars work. Problem is at hypermiling speeds/ revs, I found my smart alt is basically reluctant to keep the battery charged. You have to downshift during DFCO to get any decent charge, and then it's only for a few seconds.

They actually essentially have three modes:

Idle: No charging at all - battery voltage around 11.7-11.9. This happens on a full battery or when accelerating. I drive about the first 5 miles in this mode each morning (still goes into regen when it can).

Normal charging: Maintaining roughly 12.8v

Regen: 14.5V on overrun - you might not get as much regen as you think especially if you have eco friendly tall gearing. My Fiat has two regen modes, ~14v on overrun, 14.8 on overrun +brake.

Also if you EOC, you'll probably find you want the alt on all the time that the engine is running.

Personally, I mostly see value in an alt cut out at high loads, especially in a small car, but even that would be a problem during EOC.