Replace your car battery with capacitors!

[Enki]

Originally Posted by teoman

Enki, why do you need to have the pump and fans running?

More passes at the dragstrip, faster cooldown at other times (in case the cooling system can't keep up with summertime temps and low airflow due to traffic). I figure being able to circulate the water with the fan running (and engine off) will help with potential overheating issues.

Largely, just hedging my bets as it were.

[redpoint5]

Originally Posted by teoman

They have a 3v 3000f version now if i do not remember wrong.

Indeed they do!



A 5-series of these would start most anything, and has a healthy headroom at 15v (5x 3 volts). It will comfortably take the 14.4v output from an alternator.

At $65/ea, they are the same price as the 2.85v 3400 farad caps.

[freddyzdead]

In Aussie dollars, those would be around a hundred bucks each. Probably a lot more. Things are very expensive here, because, well, everybody knows things are expensive in Australia. Kind of a self-fulfilling prophecy, I think. Anyway, I don't think we'll see them here.

[teoman]

What would be the requirement for a newer car with start stop feature, like a passat.

I wonder if 2*5 of the 3v ones would suffice?

I do not mind carrying the initial charge of the day with me,

A lithium ion battery and a boost coverter to charge the capacitors up to 15V or to charge charge each one individually to 3V.

[Enki]

Well the caps would charge up in just a few seconds, but in city traffic your alternator might get a bit on the hot side as a result. The 5s2P arrangement would be 1200 farad and more than enough for a few starts/stops, but the cost and the footprint would be large compared to a regular lead acid.

[AlexanderB]

Originally Posted by redpoint5

At $65/ea

Times 5, is 3 whole new lead acid batteries or 10 of the lithium packs I use to start my track car.. Caps are really cool, but thats probably beyond not cost effective.

The big downside to any small capacity battery is that you have to make sure you don't leave your lights on, or it'll kill the battery and thats no bueno. For that I installed a big red switch, but I might re-wire some stuff so all the big consumers get turned off if the engine is not actively spinning, just to be sure. If its just caps, its only annoying, they're not immediately worthless.

I might also get a small solar panel and a little (custom) charge controller to keep the battery topped up, so I can keep my clock and central locking and what else connected if the car sits for more than a week or two.

For $325 I could also install a pile of lipo's that 3x the stock battery capacity, but that wasn't the point, the point (for me anyway) was saving an additional 2% off of the total vehicle weight by deleting the lead.

[oldtamiyaphile]

Originally Posted by teoman

What would be the requirement for a newer car with start stop feature, like a passat.

Supercaps and lithium batteries will kill factory stop start unless you know how to hack the system.

[redpoint5]

Originally Posted by teoman

What would be the requirement for a newer car with start stop feature, like a passat.

I wonder if 2*5 of the 3v ones would suffice?

I do not mind carrying the initial charge of the day with me,

A lithium ion battery and a boost coverter to charge the capacitors up to 15V or to charge charge each one individually to 3V.

You wouldn't need 2x to accomplish this. A single series cap bank would give you a few starts without charging.

The downside is you would often lose remote lock/unlock, radio presets, etc from the caps draining down.

I'd keep a small battery connected to eliminate the hassle of charging the cap bank up each time, and losing presets.

Don't charge the bank to 15v. That doesn't leave enough headroom and you are bound to overcharge one of the caps. I'd charge to 14v and then let the alternator decide what voltage to maintain once the vehicle is started.

Originally Posted by AlexanderB

I might also get a small solar panel and a little (custom) charge controller to keep the battery topped up, so I can keep my clock and central locking and what else connected if the car sits for more than a week or two.

For $325 I could also install a pile of lipo's that 3x the stock battery capacity, but that wasn't the point, the point (for me anyway) was saving an additional 2% off of the total vehicle weight by deleting the lead.

The battery in my Acura has died, so I'm considering a series string of 350 farad caps to start the car, and a small LiFePO4 battery in the passenger compartment to keep the caps topped off.

LiFePO4 doesn't tolerate charging below freezing, so I wouldn't consider putting them in the engine bay in climates where freezing is likely.

Rather than mess with a charge controller or subjecting LiFePO4 to cold/hot temps, the best solution is likely to get a very small lead acid battery and pair it with caps.

[AlexanderB]

I put my lipo brick in the center console for exactly the opposite reason. Its a race car, its gonna get quite toasty under the bonnet, and batteries don't like the heat either. It doesn't freeze much where I live, but thanks for the heads up, I'll bring it inside when it does freeze.

[teoman]

My concern was that with the start stop systems (and by that, i mean a modern car which also has a bunch of gizmos) and i would not want the caps to drain in the minute or two that i am stuck at the stoplights. (Also having the radio and the ac blower on min or headlights would be nice).

Some vehicles consume batteries rather quickly. My motorbike usually kills a battery in 2 years.


How does the autostart stop system need to be hacked for lithium or caps? What makes it unhappy? Lower voltage so it does not stop to engine because it believes a weak battery condition?