Replace your car battery with capacitors!

[redpoint5]

I'll be running the same setup very soon on the Camry once I get a day off, which might be another 3 weeks. I have some Anderson power pole connectors that I'm going to connect everything with.

I've seen the video above and posted some questions to Rob, but it appears I need to answer my own questions. That's why I've purchased 2 amp loggers; to track all energy going into, and out of the LiFePO4.

[Cobb]

Back in the day caps are used to lessen the load of the starting of an electric motor. Most electric motors start much faster than a gas or diesel engine. Thats what makes it hard for me to wrap my head around and say with any reliability one can safely and a frequent bases use a set of caps to start a car.

Typically caps dry out or have a dead short from the dielectric material breaking down and no longer hold a charge. Not sure if load plays a big of role or not as when caps die, the load is just greater on the power supply. Of course in this case with a car, the cap IS THE POWER SUPPLY.

[ecomodded]

My car stereo's amp uses a Big cap , I wonder if they could work for a battery..

http://www.youtube.com/watch?v=HwvrqFIc_xA

[redpoint5]

Originally Posted by ecomodded

My car stereo's amp uses a Big cap , I wonder if they could work for a battery..

It's not the size that matter, but the farads. Caps in audio applications tend to be big, flashy, expensive, and lower in capacity than the Maxwell units we are looking at.

As already discussed, a capacitor is not a replacement for a battery. It simply doesn't have the storage density of a chemical battery. If a vehicle had a very low parasitic drain when parked, or if supplemented with a solar charger, a capacitor could "replace" the battery.

I've been running on only capacitors since January on the motorcycle. I connect to the battery tender when I don't expect to ride in the next couple days. It cuts charging completely when it hits 14.15v, and will begin charging when volts drops to 13.5v.

[ecomodded]

The stereo amplifier capacitor are also heavier than a brick , literally and many of them are only 1.5 to 2 Farad.
They must be building car stereo caps using a cheaper poorer quality material that is bulkier/heavier.

Your bike capacitors do prove the concept works, I am curious if a solar panel would keep the caps charged ? and if so if having a flexible solar panel strapped down or attached with Velcro around the gas tank or fairing would provide enough energy?

[Daox]

A123 has some small B-grade cells that would work great as a starting battery.

http://ecomodder.com/forum/showthrea...tml#post430806

Oil Pan used a few of these in a series/parallel pack for his diesel truck for a while. Later on he added another AMP20 pack in parallel for winter starting. I just asked him for updates on how its working out here:

http://ecomodder.com/forum/showthrea...tml#post430814

[Cobb]

My cap is 10 farad and Ive seen them up to 30 for audio use. A cap just helps to firm up a weak power supply for short bursts. A cap will only help for audio systems that have a beat, drum or burping. If you want to win a bass contest you need a strong enough power supply for a sustained beat to get the better SPL ratings.

So, even if you got caps, they need to get the power from somewhere.

[Enki]

Hey folks.

Came across this thread while checking to see if there had been developments on other projects I'm following and decided I'd throw my $0.02 in.

I have a project car (1965 Ford Falcon Wagon) that I'm seriously considering running with a cap bank instead of batteries primarily for space and draw constraint requirements; cap banks are nice because they can take a whole bunch of different/odd shapes. I'm building my existing cap bank into a triangular log shape and will be using that as a jump pack for my pop's racecar on track days (it doesn't have an alternator and our current battery charger takes a long time to top off the battery) as an example.

I'm currently using what amounts to a motorcycle battery in my 2009 Mazdaspeed 3; unfortunately, the Mazda draws about a quarter amp under full shutdown (measured through voltmeter), so a single 500 farad bank (6x3000 farad caps in series) won't cut it for my usage of the vehicle (sometimes 5+ days without driving it). As it is, if I don't drive the car for more than a week, it may not start as a result of the passive drain.

Here's the video of my slowly dying battery kicking over my Mazda on a cold start:

http://www.youtube.com/watch?v=p-Ud0yf1YAI

That said, I have done testing with capacitor banks, and they are viable if you daily drive the car and/or have a solar cell for trickle charging to counteract any low amount of drawdown and/or have an older vehicle which has very little key off draw, like in the following video.

Here's a vid of my bank starting an older V8:
NSFW language (I was excited) https://vimeo.com/86949274

Also, if anyone is interested, I've included a screenshot of my capacitor math Google Sheet and I can provide any formulae requested.

[Enki]

Actually it seems to me that when the cells are charged and maintained, they don't leak down as bad. The first time I charged them, leakdown was pretty bad. They got down to 12.62 volts in 19 hours, but then I recharged them; see the attached image for stats before and after the recharge. Note that my bank has *no* cell balancing, which would likely improve leakdown further.


The following numbers are for *post* screenshot data:
2-22 (morning):
Bank: 13.245 v

2-23 (afternoon):
Bank: 13.08v
1: 2.23v
2: 2.22v
3: 2.145v
4: 2.19v
5: 2.14v
6: 2.125v

3-03 (morning):
Bank: 12.5v

[redpoint5]

Originally Posted by Enki

Actually it seems to me that when the cells are charged and maintained, they don't leak down as bad. The first time I charged them, leakdown was pretty bad. They got down to 12.62 volts in 19 hours, but then I recharged them; see the attached image for stats before and after the recharge. Note that my bank has *no* cell balancing, which would likely improve leakdown further.

Excellent post!

I've been charting the leakage of my 350F series of capacitors over the course of the past few days and will put it into an Excel sheet soon. Mine are balanced by the LED/diode method, so most of the initial "leakage" is just driving those lights. Do you find balancing to be unnecessary? I've wondered if higher charged cells would also have a higher leak rate, effectively balancing themselves. This would be a worthwhile experiment since eliminating the balance circuit simplifies things and lowers the parasitic drain.

Your parked parasitic draw of 250mA is extreme. I'd only expect that draw on a cheap aftermarket alarm system install, or a failing electrical component. Have you measured the drain after letting the car sit for a longtime without opening the door or messing with the door locks? I ask because my TSX has a higher draw just after parking, and whenever the door has recently been opened. It eventually settles to 40mA.

The 14v-10v 560mA figure in your spreadsheet is very helpful because I found conflicting methods of how to calculate it (please PM me your spreadsheet or the formula). It looks like my truck, with a 20mA parasitic drain, can only sit for 28hrs before your 3000F caps would fail to start it. I believe I can get the drain down much further after disabling a thermometer with constant LED back-light. I'll try that tomorrow.

Can you explain the V+W -> A and the V+A -> W table a little further? I know how they are calculated, but I'm just wondering what the figures have to do with replacing a car battery with capacitors. I'm also curious what you are planning with those resistor calculations.

I bought 2 amp loggers to measure the amps going into, and out of a capacitor or battery so that I can determine the charge/discharge efficiency between capacitors, LiFePO4, and lead-acid. When I start getting more than 1 day off per week, I'll start experimenting and share my methodology and results.