Test: Alternator vs. no alternator = 10% MPG gain @ 70 km/h

[Crashy]

Originally Posted by Stubby79

In a Geo Metro with it's tiny 1.0L engine

Do you have evidence of vastly lower improvements in every other vehicle?

Do you have your own mods with similar improvements?

[Crashy]

Originally Posted by redpoint5

The highest self-discharge is near the voltage limits of the supercap

I've had them on my solar setup and gave them the boot. The problem is high ESR and high self discharge. At 2.7v per cap, it's quite difficult to reach the voltage level you are working at. They must be connected in series which divides the capacitance and multiplies the ESR. They must be balanced. Using your argument, to avoid high self discharge, stay away from the voltage limits.....that would require even more caps in series, thus decreasing overall capacitance and increasing ESR (losses). Once again, more losses cannot possibly improve efficiency.

I found that my 6S pack did not charge quickly at all. From zero to 6v it was quite decent current over 2 minutes (too long!), but quickly dropped off and took 20 minutes total to reach 14v. And as soon as it was disconnected from the charger voltage dropped like a stone. And capacity out vs in was only 20%. 80% loss...no thanks

I know several people who have huge banks of them in 48v systems and they often comment on how warm they are. These are connected 24/7. Any time an electrical component is warm that's losses. A huge bank of them getting warm = huge losses. Doing this 24/7 = idiotic

I've been following Robert Murray Smith for years. Eventually we will perfect caps and they will replace batteries but we are not even close

[redpoint5]

Originally Posted by Crashy

I've had them on my solar setup and gave them the boot. The problem is high ESR and high self discharge. At 2.7v per cap, it's quite difficult to reach the voltage level you are working at. They must be connected in series which divides the capacitance and multiplies the ESR. They must be balanced. Using your argument, to avoid high self discharge, stay away from the voltage limits.....that would require even more caps in series, thus decreasing overall capacitance and increasing ESR (losses). Once again, more losses cannot possibly improve efficiency.

I found that my 6S pack did not charge quickly at all. From zero to 6v it was quite decent current over 2 minutes (too long!), but quickly dropped off and took 20 minutes total to reach 14v. And as soon as it was disconnected from the charger voltage dropped like a stone. And capacity out vs in was only 20%. 80% loss...no thanks

I know several people who have huge banks of them in 48v systems and they often comment on how warm they are. These are connected 24/7. Any time an electrical component is warm that's losses. A huge bank of them getting warm = huge losses. Doing this 24/7 = idiotic

I've been following Robert Murray Smith for years. Eventually we will perfect caps and they will replace batteries but we are not even close

You had defective caps, which I have heard is common. My 6s bank charges up quickly and takes months to drop a volt. Never any heat, and minuscule charge / discharge losses due to the extremely low resistance. Maxwell's BCAP series are rated at 0.29 mOhms. My 6s never needs balancing as they naturally find balance and are closely matched.

There's nothing more efficient than capacitors for accepting a charge and then discharging. There are serious drawbacks as you say, such as greatly diminished capacity when connected in series, inability to hold voltage during discharge, and inability to accept an overcharge.

[RedDevil]

Originally Posted by redpoint5

The ICE is only 25% efficient itself, so the actual efficiency of converting gasoline energy into electrical must be much less than 21%. I'm assuming the 21% is the efficiency of converting the mechanical energy of the motor into electricity?

I took the % from the PDF linked in my post.
It assumes a typical engine efficiency of 40%, which is indeed high for gasoline engines. Even so, Toyota is already beyond that in the new Prius.

There is another way of looking at this efficiency number.
Assuming the engine is running anyway on partial load (as most of the time) then it is wasting energy on pumping loss and such.
Adding the load from the alternator will make it work harder, but because of it it will have a better relative efficiency. In that case the 10% extra load would require less than 10% extra fuel; if it raises the overall ICE efficiency from say 20% to 21%, then the 10% alternator load would take just 5% more fuel, so the extra power produced to run it would be 40% efficient.

What we have then is 20% absolute engine efficiency for that typical load, 40% efficiency for the addition of the alternator.
I don't know if it would work out like this in reality, it is just my theory.

[oldtamiyaphile]

Originally Posted by redpoint5

You had defective caps, which I have heard is common. My 6s bank charges up quickly and takes months to drop a volt

This. My bank only took 90mah to charge. Six months later, I used them to test a power window install. Multiple window operations and they weren't flat. Extremely low self discharge. They've been working great for three years now.

[redpoint5]

Originally Posted by oldtamiyaphile

This. My bank only took 90mah to charge. Six months later, I used them to test a power window install. Multiple window operations and they weren't flat. Extremely low self discharge. They've been working great for three years now.

Yes, as I've mentioned elsewhere, I eliminated the battery altogether from my motorcycle. I'm only running 6s supercaps to start the bike. Been running it that way for years.

[teoman]

I found this to be a good read regarding alternator efficiency.
http://www.delcoremy.com/documents/h...ite-paper.aspx

[enator]

Why not use a relay that connects the alternator everytime the brake lights come on? You would waste a little at a stop light but be able to recycle a tiny bit of Kinetic energy when you slow down?

[redpoint5]

That solution has been discussed before. I don't know that anyone has actually implemented it yet, but the theory is sound.

I had bought a used 4-wire alternator harness to test killing my alternator in the TSX, but never got around to testing. From what I have read, simply disconnecting the 4 wires may not kill the alternator.

[oldtamiyaphile]

Originally Posted by enator

Why not use a relay that connects the alternator everytime the brake lights come on? You would waste a little at a stop light but be able to recycle a tiny bit of Kinetic energy when you slow down?

Most new cars do this factory. On a full charge, my Renault will go about 6 miles before engaging the alternator, other than under deceleration.