Replace your car battery with capacitors!

[Enki]

There's a video of a guy with "enough" capacitors that the entire car runs off them only...He uses the big 3k farad Maxwells and says the only real advantage is saving fuel driving to and from audio competitions.

[quagss]

Originally Posted by RiceCake

Capacitors have self-discharge.

Couple that with the fact that the caps don't have a lot of amp-hour capacity, and your car will undoubtedly pull a tiny trickle of current to keep your clocks and settings in order...

So unless you plan to charge the car after it sits a few hours (which will undoubtedly result in a totally dead capacitor bank), you'll need a battery.

And then you've defeated everything.

Neat idea though as a boost option. If you could get 6 seconds of cranking out of a bank of them, it would be nice to have in winter.

2000+ cranking amps for the win

Edit: Also without inter-cell balancing, a single cell could (theoretically) be overcharged by the cars alternator, resulting in a nasty explosion (or just the cap venting, YMMV).

Thankfully you payed attention in Physics!

[Enki]

Originally Posted by quagss

Thankfully you payed attention in Physics!

Congratulations on quoting the first page of a thread from literally over two years ago on a subject that's already been heavily covered by multiple people and found to be not that big a deal depending on the vehicle.

Kudos.

[redpoint5]

Originally Posted by Isaac Zackary

First, why not hook the caps directly to the starter, but put some resistance between it and the alternator (and any battery). That way you get full power to your starter, but the caps don't put a strain on your alternator.

I put a power resistor in series with a LiFePO4 battery and my supercap to prevent the cap from trying to charge it too quickly when the battery voltage drops relative to the cap. Essentially I was preventing the alternator from trying to charge it too quickly. I figured the small battery could drop as low as 10v after supplying a parasitic load for some time, and I didn't want the alternator exceeding the charging limits.

I'm still not convinced the alternator needs to be protected from the demands put on it by a supercap. I'll take some measurements and report back here, but it'll be a couple weeks since I'm working 12hr shifts the next 8 days.

In other news, the Acura sat for several weeks and the battery was dead when my wife went to start it. I'm kinda hoping it won't recover so I can replace it with supercaps! However, even with 5x 3400 Farad caps in series, my spreadsheet is telling me that the 21.5 mA parasitic draw will only allow me to park for 1.5 days before I risk no longer being able to start. That means I'll have to get a small battery of some sort. I'm certainly not buying another Pb battery.

[cts_casemod]

Originally Posted by redpoint5

Is that the single capacitor impedance, or the total impedance of 6 capacitors added in series?

Nice catch. Yes for 6, it would be 6 times less or 95Amps. But this works both ways, if the impedance is too high the capacitor wont be able to deliver the rated current to the starter with an acceptable voltage drop.

My lithium pack has 24mOhm (12mOhm/cell in 4S2P) and turns the starter a bit slower than the 70Ah battery it replaced. At 10C discharge rate, the CCA would be about 200A with a terminal voltage of 10V.

Originally Posted by redpoint5

I believe you, but I'm going to verify this sometime when I am messing around with caps and starting again. The alternator in my TSX varies output modes depending on electrical demands including the state of battery charge.

Those receive the signal from the ECU, having the aim to unload the alternator during acceleration/heavy engine loading and the opposite during braking. I'm guessing it makes it easy that something set to 14.4 all the time.

Normally the issue is during high rpm (2500+). The easiest way to try is to get a clamp meter and start the car with a bit of throttle. Current should drop fast on a capacitor, however. A lithium pack is probably more of a problem as current is sustained for a few seconds/minutes. When I have some time Ill try to log this on mine.

Originally Posted by redpoint5

The cheapie panels I see on Amazon for $20 don't have any regulation, but balance circuits are fairly cheap for the common supercap sizes on the market and can easily handle a few watts of extra juice.

A simple 5W zener (or two) such as a 1N5352 across the solar panel should work fairly well.

Originally Posted by redpoint5

I had wondered how much of an issue freezing was considering that the battery will quickly heat up with use. I'd still be hesitant to run it during the coldest days in the Portland area, which might be 15 F. I'd have no concern if with the battery in the passenger compartment.

Well, one could always use the capacitor and use a removable lithium battery to top it up if required. This could be a small pack, charged at home rather than in the vehicle.

The lowest I've run mine was -8C (18F), on engine bay, covered with some cardboard. CCA capacity goes down a bit (still enough to start).

[Enki]

More discharge numbers:

10-15-2015 (posted near top of prior page): 13.64v
11-23-2015 (today): 13.375v

Self discharge has minimized to a hefty degree.

[werefree]

how about two of these sets in parallel for a ford F250? ebay.com/itm/6-pcs-Farad-Capacitor-2-7V-500F-35-60MM-Super-Capacitor-Black-/301834868305 6 Pcs Farad Capacitor 2 7V 500F 35 60mm Super Capacitor Black | eBay

my need comes from:
1)being a super cheap person who does not want to replace the dead battery
2)I moved the truck 2 times last year to go less than 10 miles to home depot and back.

My set up will be basically finding the right amount of cheap caps to start the engine. figuring out how many times I can start it by trying it out. And finally in case something eats up the power while I pick stuff up from the store, I will carry a cheap lipo battery.

what I want to accomplish is to be able to drive the truck the few times I need with:
1) no battery/ucaps blowing up
2) remove the ucap and leave it in the garage when not in use.

so do you guys think two of these ucap (sets of 6, total 12) will start my truck? should I get 3 sets?

regards

[jray3]

1000 Farad seems marginal- I use six of the 3000 Farad ultracaps to crank my F250 with the 6.9 diesel, and if leaps to life better than it ever did on a battery alone.
Good thing is, with an Anderson connector on the box o caps, it can live daily life unloading the battery of your daily driver, and also be fully charged any time you want to crank up the truck.

[werefree]

OK, I calculate that I can fit 12 of the 6 cap sets inside the volume of an F250 battery.. 2Lx2Wx3H. So I'll start low with just 2 sets for 166F, then if it seems wimpy or needs more power I'll get another 2 or 4 sets. At that point I'll CAD up a wooden box to hold the final set. It will be awesome to have a car battery that never really dies. I used to work for a company called ISEcorp. We used these ultracaps from Maxwell to power transit buses for different transit agencies. Company got sold to Blueways. Now I still see some of our connectors, reject ucaps and balancing resistor assemblies on Ebay. I find it cool that even the trash made it self this lasting. I think the buses are still running around (chicago, edmonton, longbeach, SanDiego and las vegas). Anyhoo, I would just like to mention that the oil inside the capacitors, however small a quantity, is a carcinogen. Never handle one of these things bare skin. We did many tests with overloading using very large electrical test machines. At worst the sides burst, but mostly they just puff out. That puff contains the carcinogen oil and so that would be the bigger concern for me, knowing what I know.

[jray3]

Thx Werefree- I should've mentioned that I do have a large number of the 3000F Maxwell ultracaps complete with 6-pack interlocking frames. They were used in hybrid bus research by Azure Dynamics. I'm not actively marketing them, but PM if you're interested. The six I'm using have been propping up dead lead for four years now. I haven't gotten around to building any balancing boards to use this large lot.