Ultra capacitor + LiFePo4 batteries

H

Hoskuldur

1 µW
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Sep 8, 2014
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Reykjavik 10th September 2014.

Has anyone tried the combination of 5 x 3,2V (16Volts) Headway 38120S LiFePo4 batteries(10 Ah) + 6 pieces Maxwell Ultra Capacitors -D-Cell size, 350 Farads, 2,7 Volts, a total 16,2 Volts? I.e. without any charge controllers (BMS) - just direct replacement of a normal 40 Ah lead acid car battery? (intended for a small japanese car)

If not, can anyone explain why it may - or may not work?

I also have a plan for electric bike, 24V system, to do similar: 8 x 3,2Volts LiFePO4 10Ah Headway 38120S =25,6V + 10 pieces Maxwell Ultra Capacitors -D-Cell size, 350 Farads, 2,7 Volts, a total 27 Volts. Have already a LiFePO4 29,2 Volts, 2 Ah charger.

I have seen on endless-sphere highly educated specialists, so it would be interesting to get some comment. I am totally new on "endless-sphere" so maybe this topic has been discussed before.

Thanks. Hoskuldur H. Dungal, Reykjavik, Iceland (e-mail: hdungal@internet.is)
 
Hoskuldur said:
I am totally new on "endless-sphere" so maybe this topic has been discussed before.
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In the upper right there is a search box, beneath it there is a tick box that is labeled 'using google search?', check that box and do some searching. I -highly- recommend doing this before posting, very often the same questions get asked endlessly.
 
Yes, do that for information on using ultra capacitors on an electric bike.

The situation with a starting battery is different as the battery capacity required and the duty cycle are very low. You might not need the lifepo4 cells at all - just use the ultra capacitors. Have a look on youtube for videos of people starting cars with just ultra capacitors...
 
Leakage on ultra capacitors big enough to start a car are typically in the 1mA range. That will effectively drain a 650F cap in about a week, not to mention other parasitic loads from your car (clock, keyless entry, etc). It may work in parallel to a smaller lead battery, but I suspect the youtube people doing this are doing it to make ad money.
 
Punx0r said:
Yes, do that for information on using ultra capacitors on an electric bike.

The situation with a starting battery is different as the battery capacity required and the duty cycle are very low. You might not need the lifepo4 cells at all - just use the ultra capacitors. Have a look on youtube for videos of people starting cars with just ultra capacitors...
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As dmwahl points out, the Ultra capacitors may lose their charge in approx. a week so I thought it would be necessary to have approx. 10 Ah LiFePO4 batteries as a kind of backup for the Ultra capacitors. But the original question is still unanswered: Has anyone tried this combination by replacing a car battery simply this way without any BMS?

Would highly appreciate more comments.
Thanks
 
Why not just use A123 LiFePO4 and forget about the ultra caps. You won't need them anymore. A123 charge acceptance is so good, they might as well be ultracaps, only with actual capacity. :eek:
 
That is a good point. A123 actually make lifepo4 car starter batteries.

You can also get ultracap starter batteries, but I don't know if they've actually sold any to OEMs.

Self-discharge on the caps is a good point and one I would solve using a small solar panel.

Either way, the energy (battery capacity) typically required to start a car is very small, it's just at a very high rate.
 
Punx0r said:
That is a good point. A123 actually make lifepo4 car starter batteries.

You can also get ultracap starter batteries, but I don't know if they've actually sold any to OEMs.

Self-discharge on the caps is a good point and one I would solve using a small solar panel.

Either way, the energy (battery capacity) typically required to start a car is very small, it's just at a very high rate.
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What is the appeal of using ultracaps to replace starter batteries? Lead acid starter batteries are really quite reliable and cost effective. Adding a solar panel would help the leakage issue, but what if you're sitting in your car with the radio on, dome light, etc? That will drain your ultracaps in little time. I could see the benefit of putting them in parallel with a smaller or weaker battery, but unless you're trying to cut weight at the expense of reliability I don't understand the goal here.
 
dmwahl said:
What is the appeal of using ultracaps to replace starter batteries? Lead acid starter batteries are really quite reliable and cost effective. Adding a solar panel would help the leakage issue, but what if you're sitting in your car with the radio on, dome light, etc? That will drain your ultracaps in little time. I could see the benefit of putting them in parallel with a smaller or weaker battery, but unless you're trying to cut weight at the expense of reliability I don't understand the goal here.
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I'm not sure what the OP is after....in new systems with start/stop, carmakers are looking at using a LA battery for most of the storage, and using a parallel bank of supercaps (or an A123 "aux battery" in some cases) to absorb big current spikes from the regen system. The LA battery cannot absorb that power spike well, but the other systems can, and then that energy can be buffered into the LA battery at a rate it can handle. This all enables the engine to shut off more often and regen ends up doing most of the auxiliary load carrying while the car is stopped. Cheaper than a big Li ion starter battery, but of course heavier too, so it's a game of hair-splitting tradeoffs.
 
Off topic but in usa AAA offers a great price on car batteries comes to your door and test your system with print out and 2 yr. replacement non-prorated. If problem on the road they come to you. Prefect for the wifie.
 
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