Alternator relaxer

[Frank Lee]

"Brake". I'm anal about that sort of thing.

I'm kind of scared of batteries as it seems far too easy for a simple caveman like me to mess them up via over- or under-charging, or charging at too fast a rate. It would be nice to engage the alternator only or mainly when braking but a battery can only take so much at a time.. I see the appeal of "smart" loading strategies and in fact there are plenty of them on new vehicles so if you are succeeding with this great!

For the serious modder a strategy that depends on recharging with wall power has the most fuel efficiency potential. Requires more baby sitting though.

I went with reducing the rpms of all the driven accessories, most of all the alternator. I never did come up with a figure for how much it improved fuel efficiency, if any.

[DieselJan]

Originally Posted by gumby79

Nice write up

How would you do this as a window ?? Charge on at 10v and off at say 14.7 to cycle a deep cycle

Hi Gumby79
Thanks, I haven't thought about a automatic cycle window. But here is a suggestion.
Lets say your alternator charges at 14V. You put in about 8 diodes in the pink area. That will keep the minimum charge level at 10V. Just make sure your deep cycle battery will have a decent life with 10V discharge level.

Also put in a switch on the left of the green diodes to keep circuit from getting any high charge command. Meaning it will not charge battery if it's level is above 10V. You control this switch from inside. If you feel the battery is at 10V for long enough, switch on the regenerative charge circuits, and let it charge again.

Hope this is useful.
Jan

[teoman]

Great work. I am curious how the newer cars like 2010+ VW's would react to this.

I think my 2003 mb would benefit from this.

Ps: i was asking for a picture of your implementation and what gauge wires you have used.

[Stubby79]

Originally Posted by gumby79

Nice write up

How would you do this as a window ?? Charge on at 10v and off at say 14.7 to cycle a deep cycle

I'd not recommend that, unless you have a separate battery for starting the engine. You might shut off the car with just over 10v in the battery, and not have nearly enough juice left in the battery to get it to start again. So, either a separate starting battery, or a supercap and some circuitry to charge it higher than the 10v it would get from the deep cycle battery.

DJ: Nice, well-thought through mod you have done. I was considering something a bit more simplistic to do a similar job, but with a proper schematic in front of me to follow, I could more easily just duplicate your work and tune it to my needs. Love the idea of tricking the alternator to put out less than full charging voltage. Thanks!

[DieselJan]

Originally Posted by teoman

Great work. I am curious how the newer cars like 2010+ VW's would react to this.

I think my 2003 mb would benefit from this.

Ps: i was asking for a picture of your implementation and what gauge wires you have used.

Hi Teoman
I usually use the same gauge wires as the ones I tap into. For if there is an accidental short circuit, the wires doesn't burn before the fuse will blow.

I think I forgot to mention before that the sense input wire running from the battery or voltage monitor point into the alternator is cut and HER508 diode is added in between.
Actually all the components is on PCB inside above driver feet and wires is run from the cut sense wire in engine compartment. I also used a wire with ignition voltage that was close to circuit. The break pedal voltage is also close by.

I see a lot of alternators doesn't have a sense input, but have a D+ output going to the battery charge indicator light on display panel.

If yours is like that do exactly the same as if alternator had a sense input. Just connect it to D+ instead of Sense input. The circuit will generate a voltage higher than battery voltage and "fool" the regulator on the D+ line to switch off the alternator. The alternator will charge at normal charging voltage during "regenerative breaking" and not a higher voltage like alternator with Sense input. This is due to internal alternator circuits.

I haven't tested it on an alternator without Sense input, but from what I can see from circuit diagrams of alternators with D+, it should work perfectly.

Jan

[freebeard]

This doesn't make a lot of differnce to me because my car has a generator; but two questions:

• Others on Ecomodder have experimented with totally replacing the battery with supercapacitors. Could you suggest a way to have a supercapacitor buffering a battery? Because if you could I could see dual alternators on a serpentine-belt pulley system with big, fat wires.
• There exist sites like https://www.instructables.com/ where you can get greater exposure for your idea. Have you thought about posting it on a maker website?

[DieselJan]

Originally Posted by Stubby79

I'd not recommend that, unless you have a separate battery for starting the engine. You might shut off the car with just over 10v in the battery, and not have nearly enough juice left in the battery to get it to start again. So, either a separate starting battery, or a supercap and some circuitry to charge it higher than the 10v it would get from the deep cycle battery.

DJ: Nice, well-thought through mod you have done. I was considering something a bit more simplistic to do a similar job, but with a proper schematic in front of me to follow, I could more easily just duplicate your work and tune it to my needs. Love the idea of tricking the alternator to put out less than full charging voltage. Thanks!

Hi Stubby 79
Yes I also wouldn't recommend discharging to 10V, but that is what I thought you asked from your question. I don't think going lower than 13V or so will have any significant gains anyway.

You asked for something more simplistic, see attached. It is essentially the same circuit. This is the first concept I thought of, but realized that I would have to change the Penlight battery periodically.

In this circuit you add more diodes in pink area to increase the voltage you want the battery to normally run at. Not decrease as in more complex circuit.
The regenerative input from break light doesn't have any delay to stay on. You can add a capacitor in parallel with relay coil to get some delay. The capacitor size will depend on your relay, so you will have to experiment with that.

I can't really quickly think of something simpler for you.
The only downside would be periodic battery changes, so I would recommend the more complex circuit for long term hassle free driving.

[Stubby79]

Originally Posted by DieselJan

Hi Stubby 79
Yes I also wouldn't recommend discharging to 10V, but that is what I thought you asked from your question. I don't think going lower than 13V or so will have any significant gains anyway.

You asked for something more simplistic, see attached. It is essentially the same circuit. This is the first concept I thought of, but realized that I would have to change the Penlight battery periodically.

In this circuit you add more diodes in pink area to increase the voltage you want the battery to normally run at. Not decrease as in more complex circuit.
The regenerative input from break light doesn't have any delay to stay on. You can add a capacitor in parallel with relay coil to get some delay. The capacitor size will depend on your relay, so you will have to experiment with that.

I can't really quickly think of something simpler for you.
The only downside would be periodic battery changes, so I would recommend the more complex circuit for long term hassle free driving.

Thanks. I didn't mean I needed it simpler. I meant if you hadn't posted this, I would have made something more simplistic myself. But with you having done all the hard work, all I need to do now is copy it.

And that was Gumby79's question involving 10v, not mine. He's got a pretty good nickname though.

[DieselJan]

Originally Posted by freebeard

This doesn't make a lot of differnce to me because my car has a generator; but two questions:

• Others on Ecomodder have experimented with totally replacing the battery with supercapacitors. Could you suggest a way to have a supercapacitor buffering a battery? Because if you could I could see dual alternators on a serpentine-belt pulley system with big, fat wires.
• There exist sites like https://www.instructables.com/ where you can get greater exposure for your idea. Have you thought about posting it on a maker website?

Hi Freebeard
I see instructables is ranked much higher than ecomodder, so they have many more visitors. But no I haven't thought of it. I like ecomodder as people have helped me, so I would like to help them if I can. It is also more interactive like your question, so we can solve problems easier.

I am not 100% clear with your question. From what I understand you want to put supercapacitors that is fast charged during breaking, for better regenerative breaking. Then they will discharge to charge the normal battery. Is this what you are asking.

I have some idea that can work, but want to make sure it is what you mean before drawing. I see that most supercapacitors is of a low voltage level, but that's not a big problem. A buffer system could also be build with high voltage caps. As I understand an alternator can also generate high voltage, but I think probably at higher RPM.

Also why would you want to put in 2 alternators, 1 should be enough. Can you please explain your question differently so that I am clear with exactly what you would like to get.

Thanks
Jan

[Stubby79]

I get the idea of a second alternator, but if you're going to the effort of adding a second alternator, you might as well put a compact motor (think etek/mars/motenergy) on it instead, with a small 48v lithium pack (a123 20ah, for example) and do some actual regen as a small hybrid. You could then just bleed off the 48v pack to top up the 12v battery, and have a few "free" KW of extra power on-tap.