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Old 07-16-2007, 08:16 PM   #1
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Regenerative braking???

Has anyone had any thoughts about regenerative braking? I've heard talk of removing the alternator, and charging the battery off solar cells, but that sounds somewhat risky. What about a second alternator, with a clutch (similar to an a/c clutch activated by the brake pedal) to lighten the load on the primary alternator? In a manual transmission (like mine), I know engine braking is an option - which will spin the alternator - but most of that energy is wasted. Maybe a supplemental solar cell? I don't know where I'm going with this... I guess I'm looking for ideas. What would be the best way to supplement my electrical system? I just need that extra nudge to get over the 40mpg hump.
thanks to all, and remember, "let them go around".

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Old 07-16-2007, 08:35 PM   #2
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There are quite a few members on this site that have actually removed their alternators. I haven't seen mention of anyone using a solar charger, but they are all the rage over here in Japan now. My guess is that it would work, but only if you leave the car parked for a long time. It probably wouldn't help you much WHILE you are driving. I personally would not remove my alternator, as I just plain simply am not hardcore enough. If you do, some people have suggested that you keep two batteries in case one dies out. Again, I am not willing to sacrafice working electricity in my car for FE. I would rather take other routes. I am sure that many people would appreciate feedback on solar chargers though, if and when you decide to try them out.

While I do not have an engineering background, I do believe that adding more units to a system usually decreases efficiency. Rather than have two alternators, wouldn't it make more sense to just have one? If it were clutch-driven, then it could only be engaged when necessary, and the rest of the time it would be disengaged. You could rig up a system to monitor your batteries charge, and make the alternator kick in when the charge gets below a certain point. With some creativity, that should be totally possible. The parts are on the market, they just need a plan to be put to use.

I just barely understand the gist of how regenerative braking works, and not enough to comment on its usefulness outside of manufacturer-made systems.

As for the nudge you need, why not just stop using electrical parts? If no one is around, don't indicate. Avoid driving in the dark. Put rain-x on your windshield to limit wiper usage. Don't listen to music. Get a newer better battery. The list goes on.

Anyways, good luck on breaking 40. With a little persistence it should be easily attainable for you!

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Old 07-17-2007, 05:33 AM   #3
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Solar was discussed before but it would take at least 10-15 amps to run the car but it could be done and it would end up burning less fuel. If you could regen into another higher voltage battery and then regulate it down to the 14 volts needed to cut out the regular alternator then you could do the entire system passively and keep the engine stock. If you didn't have energy to add, the stock alternator would run normally - when the battery is supplied with more than 14 volts the stock alternator would shut down and lighten the load. Most alternators are connected via belt drive to the water pump so they have to be spinning all the time anyway. Return on investment is the part where it may not pay to go solar. Regen braking is going to be tough because of the needed connection to the wheels outside of the standard power train but if you can figure out a way to do it - it could work to charge the "higher" voltage pack to keep the 12 volt system powered up.
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Old 07-18-2007, 07:41 PM   #4
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I realize this whole thing sounds half-baked - but I just really wonder about all the power that's wasted braking down a hill.
Maybe someone with a Scangauge can answer this:
What is better for FE, braking down a hill (with the car idling, in neutral), or engine braking.
All I know is that vacuum is high at idle (good FE), but even higher when engine braking (better FE?).
Which would use less gas?
Am I splitting hairs here?
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Old 07-18-2007, 08:16 PM   #5
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80cvcc, you just gotta drive it as best you can.

I'd try and roll over the top of the hill just barely moving if possible and EOC down till I got worried then use the brakes (easier to replace than the clutch) unless I still had a long way to go, then engine off in gear coast (if the computer does it for me, fine, or just hold in the kill switch).
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Old 07-19-2007, 10:06 AM   #6
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If you want to try the alt delete, what you would need is a circuit to monitor voltage. GM currently uses this on their new trucks, and probably the cars. The circuit monitors battery voltage, and if it is above a predetermined threshold it cuts off the exiter voltage to the alternator and the car runs off battery only. Once the voltage goes below, it activates the exiter voltage and the alternator runs. With no voltage, the alternator is a free spinning pulley with almost no drag on it. Should not be a big deal to design a ckt that can monitor the battery and turn the alternator on and off depending on voltage, would probably run about 30 bucks in parts once you came up with how to build the circuit.

To make it more complicated, you could replace the battery with two deep cycle batteries. You could also add in an on-board charger that you could plug in wherever you go to top the batteries off. Two Optima deep cycles go for about 150 each, charger would run about 30 bucks, probably another 20 bucks in circuitry work. But, you could likely do all your daily driving on the two batteries without ever exiting the alternator.

Even more complicated, you could add in solar cells to help top off the batteries. This would be very costly, and make your car look weird since you'd have solar cells on the car. You'd need to mold them in to keep wind resistance down and prevent theft, and spring for the tough, flexible units for the occasional hail storm and rock throwing dump truck. Probably be looking at an additional 1500 bucks for this, but you might never run the alternator again.

Unfortunately, you'd likely only save 1-2MPG with this.

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