Replace your car battery with capacitors!

[Daox]

I really doubt thats enough capacity. A quick google search gave me this: Amp hours to Farads conversion

1 Farad is 1 Ampere second per Volt. 1 F = 1 As/V.
1 Ah = 3600 As
3600 As / 12V = 300 As/V = 300F
But you need more then that because the voltage will drop as the capacitor discharges. Half the charge means half the voltage.
With a lead acid battery that's different. A battery that is half empty still has nearly the same voltage as it had at the start.
Maybe 600F and some electronics to automatically step up the voltage so it stays at 12V.
So you'd need to buy 160 capacitors with 3V and 60F each.

So, it looks like you have a 10Ah of capacity, but it will not maintain the voltage you need to start the vehicle. So, you more realistically have maybe... 2Ah of usable capacity.

Putting them in parallel with a small lead acid battery might be a nice combo though.

[California98Civic]

Originally Posted by Daox

Putting them in parallel with a small lead acid battery might be a nice combo though.

Yes, and that's kinda what the guy who started this thread ended up doing, IIRC, eventually. Another thought is that some of the new Mazda's use capacitors for brake regen, I think because they can absorb the power generated more efficiently, more quickly, more completely, than batteries. So a combo lead acid and capacitor set up might also do a better job of storing DFCO energy too, no?

[redpoint5]

Originally Posted by Daox

I really doubt thats enough capacity.

So, it looks like you have a 10Ah of capacity, but it will not maintain the voltage you need to start the vehicle. So, you more realistically have maybe... 2Ah of usable capacity.

Putting them in parallel with a small lead acid battery might be a nice combo though.

If I did have 2Ah, that would give me 2Ah x 60 minutes x 60 seconds = 7200 amp seconds.

Air intake heater calculation: 7200As - (180A x 8s) = 5760As
Fuel pump calculation: 5760As - (10A x 30s) = 5460As
Starter calculation: 5460As - (400A x 3s) = 4260As

Based on this worst case scenario (very cold), the supercap would have 4260 amp seconds in reserve after starting the truck. Even if it only had half that capacity, or 1Ah, it would still be capable of starting the truck with 660As to spare.

I might have more confidence in doing this now that I've run some numbers.

Originally Posted by California98Civic

the new Mazda's use capacitors for brake regen, I think because they can absorb the power generated more efficiently, more quickly, more completely, than batteries. So a combo lead acid and capacitor set up might also do a better job of storing DFCO energy too, no?

To get the most out of this, you would also need the associated circuitry that Mazda uses to step up or down the voltage to the caps.

It would still help with capturing energy from DFCO assuming the cap wasn't already charged to 14.4v; the cutoff voltage for the alternator. The driver would have had to already be drawing down the voltage by either running with the alternator disabled, or by engine off coasting. In this case, the cap might draw down to the voltage of the battery, 12.5v. When engaging DFCO and re-instating the alternator, the capacitors would have about 2v to gain before hitting 14.4v. Based on the numbers from the calculations above, a 3000F capacitor-series could accept about 1.5Ah of charge before hitting 14.4v. That is 5400As, and at an alternator charge rate of 100A, it could accept that charge for 54 seconds until it is full.

Seems like a good idea if someone is running an alternator kill or does EOC.

[jray3]

Originally Posted by redpoint5

My truck batteries (2x group 27) have finally degraded so much that they cannot start the truck after sitting for a day. I can replace them for about $200, or I can eliminate the batteries entirely and run a supercapacitor.

Someone talk me out of spending $319 on this! The auction is for 6 used 3000 F capacitors with balance circuits.
.

I've used six 3000F capacitors to boost the 9 year-old AGM batteries on my 6.9l diesel truck for over four years now. They keep the voltage up nicely during glow plug operation and starting is typically much faster due to the stiff voltage. With low batteries, if the truck does not start, then voltage recovery is longer before the next cranking attempt, but the capacitors help get the engine turning better even on low voltage. I call 'em a win-win, but spent about half that price on a fully-assembled set with balancers from seller cusdn on EBay.. (I'm due to replace those batteries now, but got 4 more years out of them than I otherwise would have!)

IMHO- you could run the six caps without balancing circuitry just fine if you periodically switch them out of parallel with the house battery and do a bottom balance (bleed 'em down to zero). However, I do not see ultracaps as a practical stand-alone battery replacement.

[redpoint5]

Originally Posted by jray3

I've used six 3000F capacitors to boost the 9 year-old AGM batteries on my 6.9l diesel truck for over four years now. They keep the voltage up nicely during glow plug operation and starting is typically much faster due to the stiff voltage. With low batteries, if the truck does not start, then voltage recovery is longer before the next cranking attempt, but the capacitors help get the engine turning better even on low voltage. I call 'em a win-win, but spent about half that price on a fully-assembled set with balancers from seller cusdn on EBay.. (I'm due to replace those batteries now, but got 4 more years out of them than I otherwise would have!)

IMHO- you could run the six caps without balancing circuitry just fine if you periodically switch them out of parallel with the house battery and do a bottom balance (bleed 'em down to zero). However, I do not see ultracaps as a practical stand-alone battery replacement.

I bought a 350F kit from cusdn, so that was the first place I looked for the 3000F kit, but it looks like prices have gone up since then and cusdn doesn't supply that kit currently.

Have you ever tried starting the truck with just the supercaps?

If I could get the caps for half the price I would have jumped on it already. I'm assuming yours were new, also.

[Cobb]

Sounds like a lot for a set of caps. Have you checked the starter to see if its shorted? I know many of those big trucks need the 2 bats just because the windings in the starter are shorting to the grounded areas causing a short and such a high current draw.

[redpoint5]

Originally Posted by Cobb

Sounds like a lot for a set of caps. Have you checked the starter to see if its shorted? I know many of those big trucks need the 2 bats just because the windings in the starter are shorting to the grounded areas causing a short and such a high current draw.

Looking at past ebay auctions, it looks like used 3000F caps sold for $25/ea back in 2011, and a group of 12 used could be had for $250. I emailed Cusdn to see what the prospects were for buying 6 from him. His response:

Only have what is listed. Have several hundred of the 1500 and thousands of the 350. Waiting for new product. Not sure when or what is coming.

So, I'll hold off because $319 for used product is too high. Strange that supercaps have become more expensive over time. Usually technology falls in price over time.

I believe my starter is functioning as it should. It has 2 batteries because of the high draw from the air intake heaters and the starter, which has to overcome 5.9L of high compression.

[dirtydave]

I want to know how many times can it start a warm engine back to back.

[Cobb]

Cusdn has told me the same Id like to buy some of his cis solar cells, but I think his prices with shipping are still on the high side.

Yeah, caps for audio seem to go down in price and go up in capacity. For the super caps that can be used to start a car, they seem to go up in price and are hard to find or find enough to make a 12 or 14 volt pack.

If I did do this, Id get the balancer circuit and use a solar panels to make up for the electrical losses in the newer cars. Mines is like 60ma an hour.

[Cobb]

Originally Posted by dirtydave

I want to know how many times can it start a warm engine back to back.

https://www.youtube.com/watch?v=0KT_...ature=youtu.be