Automatic alternator cut out/regen braking - Fuel Economy, Hypermiling, EcoModding News and Forum

AXMonster · 03-13-2008, 01:21 PM

If the alternator produces parasitic drag when the field windings are powered up, but its not really needed to charge the battery, how about this for an idea?

A smart controller that cuts the power to the alternator's field windings in normal cruise or accel conditions, thus removing the electrical load on the engine caused by the alternator.
When decelerating (0% pedal and no fuel injected so 0% duty cycle) the alternator is switched back on and charges the battery at a high current, thus providing more braking effect.

If the battery voltage gets too low the controller can switch the alternator back in until its within a reasonable range again.

Any thoughts?

tjts1 · 03-13-2008, 01:24 PM

All new BMWs have this.
http://www.greencarcongress.com/2006...troduces_.html
Pair it with a deep cycle battery and you have yourself a winner.

Daox · 03-13-2008, 01:25 PM

This would be a real problem for us P&Gers haha.

AXMonster · 03-13-2008, 01:37 PM

Quote:

Originally Posted by Daox

This would be a real problem for us P&Gers haha.

Shouldn't be as the charging wouldn't occur without the engine turning

I'm sure even the most hardcore P&Ger has to brake sometime??? LOL

Daox · 03-13-2008, 01:43 PM

I read the whole thing now. It seems the system monitors battery charge, so if you get low enough it should just kick in no matter what. But, normally its not charging during acceleration. When your P&Ging, your engine is only on when your accelerating.

H4MM3R · 03-13-2008, 01:55 PM

http://www.msdignition.com/2006/06-18.htm

http://www.msdignition.com/rpm_6.htm

http://www.msdignition.com/new_products/8940.html

These are links for switches that might work for you.

AXMonster · 03-13-2008, 01:57 PM

It would have to charge during accel if the battery got too low, well that's what I'd set my system to do

H4MM3R · 03-13-2008, 02:12 PM

On board battery charger. Keeps the battery fully charged. Link>>> http://batterytender.com/default.php...855899dc011c2c

Use only one deep cycle "AMG" battery for everything including starting.

I used this set up in 2003 Suburban worked great.

AXMonster · 03-13-2008, 02:19 PM

Ok, I have it sorted. Two systems required. First is the duty cycle switch system which will switch an output if a duty cycle goes above a set value. This would be set to 1% and then the output reversed (so 1 is 0 and 0 is 1). Therefore when the duty cycle drops below 1% then the alternator is energised. The reversing of the output could be simply done with a small relay.

Secondly there would be a voltage controller switch that cuts the alternator back in at a set voltage (say 11.5v) and then switches it off again at another value (say 12.5v).

These circuits are available here http://www.autospeed.com/shop/category_579/browse.html

Item numbers KC5375 & KC5377

H4MM3R · 03-13-2008, 02:24 PM

Nice link. Can't wait to hear how it works for you.

tjts1 · 03-13-2008, 05:09 PM

I still think you are better off just running a deep cycle battery charged at home every night and completely eliminate the alternator. 100 miles range is good enough for me 99% of the time.

extragoode · 03-13-2008, 08:32 PM

I've posted this in another thread, but it's the same idea. If you MUST recharge the battery on the go instead of like tjts1 suggests doing, belt the alternator to a driveshaft and only energize the coils with the brake lights. That's REAL regen braking. You'd only be charging when you're trying to stop when you're trying to bleed off energy anyway and you could still put in a switch to kick it in full time if the battery got too low. The only problem I see is possiby the speed the driveshafts turning could be a lot different than the engine, but that just requires a different sized pulley on the alternator.

LostCause · 03-14-2008, 07:45 PM

I'd love a write up if anyone has success.

I figure the easiest way would be to switch the alternator fuse on/off with a microswitch attached to the brake. Every time the brake is depressed, the fuse contact is closed and the alternator starts functioning again.

Low battery voltage can be solved by monitoring and using a switch to permanently engage the fuse.

- LostCause

AXMonster · 03-15-2008, 07:01 AM

Quote:

Originally Posted by extragoode

I've posted this in another thread, but it's the same idea. If you MUST recharge the battery on the go instead of like tjts1 suggests doing, belt the alternator to a driveshaft and only energize the coils with the brake lights. That's REAL regen braking. You'd only be charging when you're trying to stop when you're trying to bleed off energy anyway and you could still put in a switch to kick it in full time if the battery got too low. The only problem I see is possiby the speed the driveshafts turning could be a lot different than the engine, but that just requires a different sized pulley on the alternator.

Quote:

Originally Posted by LostCause

I'd love a write up if anyone has success.

I figure the easiest way would be to switch the alternator fuse on/off with a microswitch attached to the brake. Every time the brake is depressed, the fuse contact is closed and the alternator starts functioning again.

Low battery voltage can be solved by monitoring and using a switch to permanently engage the fuse.

- LostCause

Some good ideas, but I want a system that I DON'T have to plug into the domestic power supply after each journey. If I had that then I may as well have an EV

I don't think there would be enough braking time during a normal drive cycle to keep the battery fully charged..... unless each wheel had an alternator that was energised during the first stage of braking, and a second stage actuated the hydraulic brakes (two stage brake pedal)?

And why only regen when braking? I tend to use over-run deceleration more than braking. As the engine is already slowing the vehicle then why not regen during this phase? Of course this will also work when braking

s2man · 03-15-2008, 04:51 PM

Quote:

Originally Posted by AXMonster

And why only regen when braking? I tend to use over-run deceleration more than braking. As the engine is already slowing the vehicle then why not regen during this phase? Of course this will also work when braking

My thinking too. I'd put the microswitch on the throttle. 0 throttle = charge. Besides charging while decelerating, that would also charge during my neutral coasts on the hills where the stupid a/t is pushing the rpm's up around 1100. I'd also add a parallel switch so you can energize at will (eg the battery is low, headlights or fan on, etc)

I've bought the parts for a manual version (wires, switch and ammeter). I'll have to remember to switch it on when I'm coasting. I've already tested to verify the engine runs ok on 12V (some ECU's prefer the 14.5V from the alternator). I intended to do a highway test to verify it also likes 12V when under load. But my daughter (she used to own the car) said she drove it 60 miles at night without the alternator, and she had no issues with the engine running poorly.

AXMonster · 03-15-2008, 06:35 PM

Sounds like a plan S2man

I've ordered the parts I need for my automatic system. I'm too lazy to flick switches

Let us know how it goes.

bennelson · 03-21-2008, 01:11 PM

I love the idea of being able to "turn off" the alternator.

Simple question - how does one do that?

When I took the Metro engine out, it looks like it's just one big power cable that goes from the battery to the alternator.

Are we talking about disconnecting that cable, or something internal to the alternator?

If I just wanted to test the effect of the alternator on fuel economy, could I just disconnect that big alternator cable?

RH77 · 03-21-2008, 02:04 PM

Quote:

Originally Posted by s2man

My thinking too. I'd put the microswitch on the throttle. 0 throttle = charge. Besides charging while decelerating, that would also charge during my neutral coasts on the hills where the stupid a/t is pushing the rpm's up around 1100. I'd also add a parallel switch so you can energize at will (eg the battery is low, headlights or fan on, etc)

I've bought the parts for a manual version (wires, switch and ammeter). I'll have to remember to switch it on when I'm coasting. I've already tested to verify the engine runs ok on 12V (some ECU's prefer the 14.5V from the alternator). I intended to do a highway test to verify it also likes 12V when under load. But my daughter (she used to own the car) said she drove it 60 miles at night without the alternator, and she had no issues with the engine running poorly.

I really like this idea

-- I'm looking forward to see if it yields some positive results (may try it myself). I have an ancient batt, though... It just may do it in (it's overdue, best I can tell is 6-years).

RH77

AndrewJ · 03-21-2008, 10:18 PM

Quote:

Originally Posted by bennelson

Simple question - how does one do that?

When I took the Metro engine out, it looks like it's just one big power cable that goes from the battery to the alternator.

Are we talking about disconnecting that cable, or something internal to the alternator?

If I just wanted to test the effect of the alternator on fuel economy, could I just disconnect that big alternator cable?

you're alternator should have some smaller wires plugged into it somewhere. Those wires comprise the field circuit. The field circuit is what "powers up" the alternator. If you break the field circuit, you turn the alternator off. When you complete the circuit, the alternator resumes its normal functioning.

psmithrt · 03-23-2008, 12:42 AM

Would simply interupting this field coil wire actually turn alt off and on. I think one of the small wires is for the dash light correct? How much juice goes through this field wire? My thought is to just interupt during acceleration like some do with a/c. I know it would only save a little, but would like to use this switch for both if current not too high.