I’ve seen some small car jumper booster battery packs on Amazon, are these just 18650’s?
How are they getting 200 to 400 amps out of such a small pack, maybe two 3x series batteries?
You don’t need that many amps to boost start, 10 A will do. I plan to build one with the 18V drill packs that I always have with me
They are super caps, not 18650 batteries
If you have a good battery in the car that is just discharged, then a few minutes at 10 amps may be enough to revive it for a quick crank. Most starters require 100s of amps cranking current and even more during inrush. One of the things commonly reported by people using the boosters is that the 10 gauge cables tend to get hot.
Interesting stuff on the super caps, unfortunately still too pricey for my ideas.
I doubt they are super/ultra-caps. The one’s I’ve seen have LiFePO4 cells, which can support significantly higher discharge currents, in both absolute and relative terms, than most LiIons. Spec sheet for an A123 cell I was looking at promised >25c continuous discharge, which is somewhat less impressive given the capacity is only ~1,100 mAh, but still works out to 30A.
I doubt that the packs can deliver full cranking current, but they can dump a bunch of energy into the existing battery quickly, and I expect the two together can usually get the job done.
On average today’s engines are probably about half the displacement they were 25 years ago. That and electronic controls/fuel injection have greatly reduced the ‘cranking time’, and the required amps to crank. Yes, it really did take 300+ amps to turn over that 400 Cubic Inch V8, but figure 200 cubic inches (about 3 liters) would only need 150 amps, and wouldn’t need it for very long either.
Several very different technologies “look” sort of the same.
Typical car booster pack is a AGM advanced glass mat lead acid battery, and some deliver a whopping amount of current, as in enough to start a diesel truck. These small packs appear to be super caps with a single serial bank rated at close to 100 amps for 1 sec. Some packs I get the impression are maybe hybrids, not really too clear.
http://www.garagejournal.com is where I hang for mechanic talk, and the guys there report starting totally dead cars even with a bad battery using some of the boosters.
Brush motors have about triple the full power run current at start up, and many cars have more than 10 amps of fuel pump and ignition etc related power requirements that are NOT happy with less than 10v or so. OTOH nobody is doing tests with hard numbers that I have seen.
That’s exactly what I have in mind. Sort of a portable mini car battery charger. If one is patient for a few minutes and all the battery needs is a boost (quick charge) then this works. I plan on using a couple of the LM2596 boards in parallel set to about 14.4V and connected to an 18V drill pack for the power. Connect it through the cigarette lighter for a few minutes to a battery that is not overly discharged and it will charge it up enough to start the car.
No way are a few Li-ion 18650’s gonna start a car all by themselves. Super Caps won’t either.
Oh yes they most definitely will. Original battery removed, only 6 series 350F supercaps in its place. Vroom!
It would help to have a link to a couple example products.
The things I’ve seen are positioned as multi-purpose portable powerbanks capable of charging USB devices, perhaps a laptop, and jumpstarting a car. At least some of them can start a car on their own, without the main battery connected. Accurately or not, they are positioned as something you can throw in the glovebox and use when you need. That doesn’t sound like something based on supercaps, which self-discharge and even if they didn’t, they aren’t going to hold ~100Wh in something the size of a hardback book.
I’m having some doubts on my own guess that LiFePO4 explains everything either. Power and energy density might pencil out, I’m not sure cost does.
Maybe some of both?
This all by itself will crank a Honda Civic: http://www.ebay.com/itm/301128832966
Has nearly zero reserve capacity though, you get about 3-4 seconds of cranking time then it's over.
LOL, I thought you said a car. 
Yeah, I know. But it's OK really, when I need to do 70MPH rolling burnouts I use the single turbo smallblock El Camino.
This one will start a diesel, but its $160, Amazon.com
18,000 mah, 600 peak amps, weighs about 2.5 lbs, one of the junk yard guys says its his daily use jump starter.
18,000mA (which is the one used in the description) and 18,000mAh (which is not mentioned) are not even remotely the same thing.
I’ve been reading reviews of these things. I’ve only found one review that seems at all informed and he pretty much rips it apart. One of the comments on the review seems to be from a shill. It reminds me a lot of the handwaving I read in an off-road forum by a representative of Antigravity, talking about about one of the smaller Antigravity packs.
I was thinking of buying one and doing a teardown and some tests, but now I worry that the chance of getting anything worth having is low. Clearly they work for some people, but I’m more than a little worried that it’ll won’t work beyond one or two test discharges, which would be a waste. And if I didn’t know it had died, it would be wasting storage space in my car on a false sense of security.
Use a LIPO pack, they give out more than 200 amps if you need them 
Yes you are right, that car in the YouTube video did start, no battery in place.
I don’t have such an easy starting car but rather a V8 Chevy Van that needs about 3 seconds of cranking at 300A. That is what I based my comment on. But I was wrong, it will start some cars.
1 Farad can deliver the equivalent of 1A for 1 second. 6 - 350 Farad capacitors in series is 350/6 or about 60F. So that setup could deliver 60A for a second, or 120A for 1/2 second. So yes they can start a smaller car that starts instantly. That explains it.
My van needs 300A for at least 3 seconds, yes it could use a tuneup, but that is 15 times what it took to start that car. 300A for 3 seconds is only 250mAh, easily attained if that 250mAh is feed into a partially discharged car battery already installed. That is why charging a battery at 6A for about 10 minutes can bring it up enough to start my van.
The lesson for me here is, never say never
I was so irritated by the fact I couldn’t find any teardowns that I ordered a little/never used PowerAll PBJS12000R from an ebay seller. I figure, at the very least, it has enough juice for my hybrid.
On more than one occasion I’ve been unable to start the car, despite the fact that the big NiMH traction battery was full of juice, because the dinky 12v battery had run down somehow and didn’t have enough to run the “ignition” and operate the safety relays.