Replace your car battery with capacitors!

[oldtamiyaphile]

Stop Start systems don't really work on battery voltage, they work on internal resistance. Change to a lower resistance chemistry and the system will always think the battery is low. I did a LiFe swap on my Fiat and that was the end of Stop Start. Switched back to Pb and S/S came back immediately. Same goes for adding a super cap across the terminals. Incidentally, the workshop manuals are very clear about not connecting any device directly across the battery terminals.

[teoman]

Well that sucks.

I wonder if it is the same for VW's.

Any ideas on how to fool it?

[oldtamiyaphile]

Same for Fiat and Renault, very unlikely to be different for VW.

My best idea would be to keep the Pb for running the car, and having the supercap wired just to power the starter itself. It would have to be 'trickle charged' to avoid upsetting the factory computers.

That or make friends with a really good hacker.

[freddyzdead]

My Greencaps have finally arrived. I found that out of the box they varied from 6 to 54 millivolts across them. Charging them one-by-one, starting at 3.3 amps, they took around 40 minutes to reach 2.5 volts. But 2 of them seemed to get to 2.5 volts while still drawing 1.4 amps. Not sure what's going on there. Or why they all had different charges on them initially. I'm leaving them overnight to see what they get to in the morning.

At one of my work places, I had a couple of 1uF 50,000 volt capacitors stored in a corner. Those things were lethal. They were used in a portable x-ray machine; They would be charged up and then discharged through the X-ray tube, producing a burst of X-rays. Fully discharged, and left to themselves, after a few days they would have several kV on them. Nasty bite. This would happen repeatedly, they would continually charge themselves up unless you fitted a shorting strap, which I certainly did after getting a few big surprises. I couldn't figure out where they were getting the electrons from. Must have been a bunch of loose ones lying around in the bottom.

[teoman]

Seems you can fiddle with the settings a little bit.

Volkswagen – Disable automatic start-stop system – VIDEGRO Consulting Blog

Wonder if doing an opposite change will enable caps.

[Enki]

Originally Posted by freddyzdead

My Greencaps have finally arrived. I found that out of the box they varied from 6 to 54 millivolts across them. Charging them one-by-one, starting at 3.3 amps, they took around 40 minutes to reach 2.5 volts. But 2 of them seemed to get to 2.5 volts while still drawing 1.4 amps. Not sure what's going on there. Or why they all had different charges on them initially. I'm leaving them overnight to see what they get to in the morning.

At one of my work places, I had a couple of 1uF 50,000 volt capacitors stored in a corner. Those things were lethal. They were used in a portable x-ray machine; They would be charged up and then discharged through the X-ray tube, producing a burst of X-rays. Fully discharged, and left to themselves, after a few days they would have several kV on them. Nasty bite. This would happen repeatedly, they would continually charge themselves up unless you fitted a shorting strap, which I certainly did after getting a few big surprises. I couldn't figure out where they were getting the electrons from. Must have been a bunch of loose ones lying around in the bottom.

I think it's better to think of batteries as a chemical reaction for creating (not storing) electrons, and capacitors are more of a high pressure storage of electrons directly (meaning you could potentially store a lightning strike or even static electricity in them). The closest analog for capacitors would be compressed air; the tank holds the charge, but must be filled by a compressor; the caps are like the air tank (without the compressor).

That said, there's still chemicals in them which could potentially generate a few stray electrons, not to mention the possibility of some electrons being jostled loose that were previously "stuck."

Hopefully that makes a bit of sense as to why you should always short-strap a cap.

[freddyzdead]

My Greencaps arrived a couple of days ago; I've been testing them ever since. The balance board arrived the next day, which was good timing.

I was having a bit of trouble making sense of what I had, but I now see that one of them is exhibiting excessive self-discharge. 2 hours after being charged to 2.5 volts, it has dropped to under 1 volt. This is obviously unacceptable, and I have requested a new one from the ebay seller.

The remaining ones appear ok; I was stupid for not ordering at least one extra to deal with this eventuality. The balance board has a LED for each cap; I'm not sure if the LED is used as voltage sensor, or just as an indicator. 3 of them tend to come on consistently more often than the others. The one at the location of the suspect cap never comes on. Not surprising.

I see on our local ebay, a Maxwell 165F 48V capacitor for AU $1,625.00. Admittedly, it's big and beefy, but still, it's over $90 per cell. Comes to about US$1200. Is that right? Or is it further proof of how overpriced everything is in this country?

@Enki I was only kidding about the electrons lying around on the bottom. The only place it could have gotten them was by plucking them out of the air.

[oldtamiyaphile]

I just fitted a pair of 7.6Ah Li-fe batteries to my Proton, backed up by the cap bank that I've had for years and has been through several cars.

In short, WOW. Best ~$100 I've spent in a long time.

Now I had a Li-fe in my Fiat before, but it seems that the smart alt meant that most of the difference between chemistries was masked (smart alt cars are designed to run at low voltages - around 11.5v- for one).

The Proton just runs a regular 'dumb' alternator.

In short I've got more power, a smoother idle, better throttle response, and less engine noise. All my electrical systems are much more snappy, the power windows wizz up and down, the headlights don't dim at all while cranking.

The alternator holds 14.2v, but even after the longest EOC I still have 12.8v vs the 11.8 odd that the Pb battery had. The Pb battery was fairly new, not one that was already dieing. I didn't see any gains in cranking power as I already had the supercap connected the day I bought the car.

My guess is that the alternator isn't anywhere near as taxed as before, and that the remaining improvement might be coming from the ECU, sensors, injectors, coils etc running more efficiently. Some racers run 16v Pb batteries for that reason.

The 1.5 SOHC now feels like a DOHC. At the very least it feels like the ECU's been remapped.

Too soon to judge economy, but it seems to be on the up. Very happy

[AlexanderB]

Originally Posted by oldtamiyaphile

Some racers run 16v Pb batteries for that reason.

To get almost twice the performance from the electric fuel pumps, mostly.

[freddyzdead]

@oldtamiyaphile That's a pretty impressive list of improvements. Apart from the engine cranking over at a faster clip than it used to, I'm not sure what effect I've got. But the fuel economy has noticeably increased as well. But I've switched from E10 to ULP91 at the same time, so it could be that.