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+--- Thread: Anyone else got these? Ultracapacitors for car starting (/showthread.php?tid=7379)
Anyone else got these? Ultracapacitors for car starting - NZScott - 08-28-2016
Hello
One of my many other distractions from my Mercs...
I got inspired from this video and the others that followed it
https://www.youtube.com/watch?v=GPJao1xLe7w
https://www.youtube.com/watch?v=OvbuJwYnbvE
Basically ultracapacitors are "canned lightning" being able to charge and discharge current quicker than just about anything.
Pros:
The caps are rated for a million charge/discharge cycles. They'll outlast any vehicle you put them in
Each cell has a 9300A short circuit current (yikes)
Unaffected by temperature
Charge as quick as you can get current into them
Charge up to the voltage across them
Give high current until the voltage is way down (my 617 will keep cranking down to about 5V!)
Cons:
Capacity is far less than a battery. 18 of them worked out to be like 1/20th the capacity of a 88Ah 850CCA battery. With my 6, if you leave the headlights on for 5 mins you'll need a jump. At least it'll only take a few seconds to charge up
Self discharge - the pack voltage drops by itself a little bit, and every parasitic load will drop it even more. Was a problem in my corona but not in the merc at the moment with only a clock to run.
Overcharging - the only way to kill these is high voltage. Basically going over the rated voltage breaks down the materials inside. They would last just about forever if you were charging them to a silly low voltage though
Balancing - every cell in theory is slightly different so will charge to a different voltage, possibly meaning you could be overcharging a cell and killing it without a resistor or circuitry to bleed current around it. I'm looking into 2.5V zener diodes for this.
Voltage drops linearly with charge. So for anything needing a constant voltage you'll want a dc/dc converter or something.
Also a note, when putting capacitors in series, the capacitance is divided by the number of caps in series. So 3000F/6 = 500F
I bought a used Maxwell 48V module from ebay. 18x 2.7V 3000 farad caps. About $800 odd NZD - yup not cheap! Best $/cap though unless you buy a literal bus load (some buses and trams etc are ultracap powered, they charge at each stop). Maxwell make 2.85V ones and 3400F ones now.
Taking it apart
I made a box to put 6 in, 6*2.7 gives 16.2V so fine for a car. I cut the terminal posts off an old battery and bolted them on to the caps. Used it for about a month in my toymota, was rather annoying however as the pack would self discharge below 9V and the starter wouldn't crank. I got a solar panel (being a sunny place here) but never hooked it up.
Made a video too
https://www.youtube.com/watch?v=sSP8yfdBRx0
My dad's vectra had trouble starting recently so gave him the battery out of my '78, being euro and all, it was 480CCA and never had any trouble starting a 617 in winter. The genuine MB 850CCA that I got from the wagon I briefly had is a bit past it to crank but it good enough to keep the ultracaps topped up whiel the car sits on the driveway being worked on.
I have plans to install all 18 caps under the backseat -got the cable etc. 3 strings of 6. 3x500F=1500F. 18,900A short circuit current!!! I have a fuse + safety switch for disconnecting when working on the car wiring....
Ideally, you'd be best to use a hybrid battery/capacitor setup. The battery would keep voltage topped up as normal so you could run the radio etc, and the caps would be there just for cranking. Around here, the smallest 12V batteries (~12Ah) are still $50, so I'm going to keep with the 18 cap pack idea as I shouldn't have any issues, with the 5W solar panel especially.
Will I get my money back from them? Doubt it, but a fun experiment. I've never bought a car battery yet
RE: Anyone else got these? Ultracapacitors for car starting - NZScott - 09-10-2016
Nobody? I might be a pioneer of sorts with these for diesels
RE: Anyone else got these? Ultracapacitors for car starting - Greazzer - 09-10-2016
How big? Weight?
RE: Anyone else got these? Ultracapacitors for car starting - NZScott - 09-10-2016
http://www.maxwell.com/images/documents/hq_48v_ds10162013.pdf
So about 30lb for the whole module. That's with the case etc, but they're not light
6 of them take up about the same volume as the battery I had in there.
RE: Anyone else got these? Ultracapacitors for car starting - Petar - 09-11-2016
They seem to be a great solution, especially for cold starts to boost the cranking amps. If I were you I would have a normal battery in parallel. So the battery charges the caps slowly and they boost cranking power. But they are just too expensive in my opionion... I would just buy a high quality battery with lots of CCA, maybe even two in parallel, and have money to spare for a superpump
