Super Capacitor Jump Starter

Thread Starter

Zalos

Joined Nov 12, 2019
5
i need your opinions if the pack on the foto can start a car without battery. and please your opinions for any upgrade i can do to this pack

maxwell 2.7V800F Super Farah Capacitor Battery Module 16V133Fimage_123650291.JPG
 

Papabravo

Joined Feb 24, 2006
21,225
Exponential decay is a fearsome impediment in this application. I am extremely dubious of claims that this might be a good idea. I actually think it could be dangerous.
 

LowQCab

Joined Nov 6, 2012
4,053
So what is proposed to happen if the Engine doesn't start within 1 rotation ?????
Walk home I guess ?, or maybe call an Uber to pick You up ?
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Ya’akov

Joined Jan 27, 2019
9,117
Exponential decay is a fearsome impediment in this application. I am extremely dubious of claims that this might be a good idea. I actually think it could be dangerous.
There are commercial capacitor-based jump starters that work very well. But they aren’t just a bunch of caps and a fuse.
 

Thread Starter

Zalos

Joined Nov 12, 2019
5
I don't want to replace the lead acid with this one just I need it for an emergency
But if it's to be one rotation only i don't think so
 

MisterBill2

Joined Jan 23, 2018
18,442
If that device in line is either a fuse or a diode, NO, it will not deliver any useful current in the range that a starter motor requires long enough to spin the starter more than a fraction of a revolution. A starter motor must drive at least one cylinder thru a compression stroke while providing enough voltage to the ignition system to produce at least one spark. If the cranking current is 20 amps (probably more) and the cranking time is ten seconds, and the applied voltage is 12 volts, then the required power is 240 watt seconds. That is not likely either from that capacitor pack or through that small glass device, which looks like a ten amp diode.
 

geekoftheweek

Joined Oct 6, 2013
1,204
I looks a lot like something I found on aliexpress. The google link I tried to copy was very long and I couldn't get aliexpress's search function to find the page to get a better link.

It doesn't list using it as a jump starter, but more or less a bunch of gibberish relating to making your battery last longer and sound quality issues with radios and such. I'll believe the sound quality part, but everything else it claims is more or less not going to be solved by adding capacitors.

A diode doesn't make much sense to me unless I'm not seeing something.... power is going to need to flow both directions. I would be more willing to say the device is a fuse of some variety... it's not listed on the site either.

Edit... in case anyone wants it
https://www.aliexpress.us/item/3256...6661bf&afSmartRedirect=y&gatewayAdapt=glo2usa
 

WBahn

Joined Mar 31, 2012
30,034
A car without a battery? Even if it could, that might not be a smart thing to do. The electrical system in many cars can be damaged if run for a prolonged amount of time without a battery.

But let's assume that's not the case. The capacitors in that device are not on Maxwell's current list of products. The closest I could find was this one:

https://maxwell.com/wp-content/uploads/2022/07/3003329.2_2.7V-600F-Final-DS_20220121.pdf

The peak current is 290 A, but that is not an actual performance spec, but rather is just there for reference and it's simply the peak initial current that would result in the capacitor being brought from the rated voltage to half the rated voltage in one second.

So it may or may not be able to deliver that current -- could deliver more, for that matter. But that gives you and idea of the numbers available. Some small cars might be able to start with that. My truck definitely wouldn't. It requires several hundred amps for two to four seconds to light off (if everything goes well).

But the next question is how are you going to charge this thing up so that you can use it to start your car in an emergency? The leakage current on this cell is about 1 mA (and that's after it has been held at the rated voltage for 72 hours, The initial leakage current when it is first charged is usually quite a bit higher. But let's assume that it is charged and allowed to sit on the charger for three days before being disconnected and thrown in the truck. At 1 mA, that will pull 3.6 C of charge off the cell in one hour. The total charge stored at 800 F and 2.7 V would be 2160 C, but if you pull off 1000 C you are down near half voltage and that would only take about 12 days. It would be down to the point where you wouldn't stand a chance of starting the car much sooner than that.

Oh, and that's just the leakage current of the cell. The modules (such as you show) all include resistive balancing circuits which effectively add to the leakage current. In order to work effectively, the balancing current generally needs to be an order of magnitude greater than the leakage current and if you look at Maxwell's data sheets for their 16 V modules, they specify a leakage current of 25 mA. So now that 12 days is more like 12 hours.

Then there's the question of the size of the fuse on that module you show. If it blows under the cranking load, then it's a moot point whether the module can deliver the power to start the battery.

But let's assume that everything is in your favor -- the fuse is adequate and the module can actually deliver enough current for long enough to start your car. There's still the issue of how to charge the module. I see a couple of plausible scenarios. One, you could charge it from another car instead of jumpstarting with a set of cables (which perhaps you don't have, or perhaps the owner of the other car is unwilling to jump start, but willing to let you plug in your module in order to charge it up). A more practical scenario might be to couple this with a solar powered charger so that you can use sunlight to charge up the module in order to try to start he car. If it doesn't start, you wait until the module is charged. Wouldn't help you at night, but with a suitable solar cell array, it might be practical during the day.

The total energy stored in the module would be about 17 kJ. Sunlight is nominally about 1 kW/m² and I think most panels are about 25% efficient (very roughly). So about 250 W/m². So a one-meter square panel could ideally charge this thing in about a minute. So if your panel was a tenth that size (roughly a foot on a side) you would be looking at ten minutes to recharge. Of course, you have to overcome that 25 mA of leakage current along the way, but 25 mA at 16 V is only 4 W, so if you have something that is putting out 25 W, you would probably be looking at 15 minutes.

These are all back-of-the-envelope calculations, but assuming I didn't make any mental math errors or overlook something major, it looks like something like this COULD be useful in an emergency situation, if it were coupled with a solar charger.
 

MisterBill2

Joined Jan 23, 2018
18,442
Here is a bit of really bad news: If that six capacitor assembly is able to work at 12 volts, then those capacitors are in series, and so the effective capacitance is 800/6 farads.
And if you have ever seen the super-cap assembly that replaced a regular battery, it is a bit larger than that regular lead/acid battery. The module shown would be good to put across the supply terminals of a big booster amplifier to offset the resistance of the undersized power supply leads. THAT is a valid application.
 

k1ng 1337

Joined Sep 11, 2020
960
I boosted my car a few times with 18V drill batteries so this could work in a pinch if you have some way to charge each capacitor to 2.7V or some multiple. I don't know how to model a starter motor but there appears to be sufficient energy in this bank to turn over my car once or twice on a warm day. Paired with a solar panel, this could be handy if the details are worked out.

Untitled.png
 

MisterBill2

Joined Jan 23, 2018
18,442
I boosted my car a few times with 18V drill batteries so this could work in a pinch if you have some way to charge each capacitor to 2.7V or some multiple. I don't know how to model a starter motor but there appears to be sufficient energy in this bank to turn over my car once or twice on a warm day. Paired with a solar panel, this could be handy if the details are worked out.

View attachment 311943
"Boosted"????? Does that mean that the battery was not able to turn the engine over at all??? Or does it mean something different from that?? It has become very clear to me that some folks attach entirely different meanings to words, and so I am asking for a clarification. Some of those differences are quite a lot.

A few years back I had a winter incident with my car at an airport parking lot, after a five day trip away. the weather while I was gone had stayed well below freezing the whole time.
I tried to start it, and there was not enough to turn over the engine on a 5 second try.
So I abandoned the effort and spent many minutes digging the snow away from the front so I would be able to get a jump start. Then, before walking the long trip to get the battery cart for the jump start, I tried once again. The battery had warmed up just a bit and it had enough to do a feeble crank, which was all it needed.
So the difference between a start and a no-start may be a small amount
 

k1ng 1337

Joined Sep 11, 2020
960
"Boosted"????? Does that mean that the battery was not able to turn the engine over at all??? Or does it mean something different from that?? It has become very clear to me that some folks attach entirely different meanings to words, and so I am asking for a clarification. Some of those differences are quite a lot.

A few years back I had a winter incident with my car at an airport parking lot, after a five day trip away. the weather while I was gone had stayed well below freezing the whole time.
I tried to start it, and there was not enough to turn over the engine on a 5 second try.
So I abandoned the effort and spent many minutes digging the snow away from the front so I would be able to get a jump start. Then, before walking the long trip to get the battery cart for the jump start, I tried once again. The battery had warmed up just a bit and it had enough to do a feeble crank, which was all it needed.
So the difference between a start and a no-start may be a small amount
My 05 Civic has a parasitic load which randomly appears. I think it is has to do with the subwoofer wiring routed by the previous owner. Anyway, I would come out to find the battery discharged to 11.5-12V and the car would not start on that.

I got stranded one day and all I had was a Ryobi PBP006 18V 2Ah 36Wh battery and a pair of jumper cables. I did some rough math and figured the current would be close to what the power tools draw. There were sparks but it took about 2 minutes before the car would start. I wasn't willing to push the battery more than that in fear of a fire. There was no heat and the battery appears to be ok.

Not surely if I did any damage to the battery or vehicle but it was worth more to me to get home. I wouldn't use this as my primary backup but it does work.
 

WBahn

Joined Mar 31, 2012
30,034
"Boosted"????? Does that mean that the battery was not able to turn the engine over at all??? Or does it mean something different from that?? It has become very clear to me that some folks attach entirely different meanings to words, and so I am asking for a clarification. Some of those differences are quite a lot.

A few years back I had a winter incident with my car at an airport parking lot, after a five day trip away. the weather while I was gone had stayed well below freezing the whole time.
I tried to start it, and there was not enough to turn over the engine on a 5 second try.
So I abandoned the effort and spent many minutes digging the snow away from the front so I would be able to get a jump start. Then, before walking the long trip to get the battery cart for the jump start, I tried once again. The battery had warmed up just a bit and it had enough to do a feeble crank, which was all it needed.
So the difference between a start and a no-start may be a small amount
One thing I learned, on sub-zero days, was that if the thing didn't want to start, turn on the headlights for a couple of minutes to warm up the battery. That worked on a number of occasions. The battery had the necessary energy stored, but the internal resistance was too high at the temperature to deliver the needed current.
 

WBahn

Joined Mar 31, 2012
30,034
My 05 Civic has a parasitic load which randomly appears. I think it is has to do with the subwoofer wiring routed by the previous owner. Anyway, I would come out to find the battery discharged to 11.5-12V and the car would not start on that.

I got stranded one day and all I had was a Ryobi PBP006 18V 2Ah 36Wh battery and a pair of jumper cables. I did some rough math and figured the current would be close to what the power tools draw. There were sparks but it took about 2 minutes before the car would start. I wasn't willing to push the battery more than that in fear of a fire. There was no heat and the battery appears to be ok.

Not surely if I did any damage to the battery or vehicle but it was worth more to me to get home. I wouldn't use this as my primary backup but it does work.
Sometimes ya gotta do what ya gotta do.
 

k1ng 1337

Joined Sep 11, 2020
960
One thing I learned, on sub-zero days, was that if the thing didn't want to start, turn on the headlights for a couple of minutes to warm up the battery. That worked on a number of occasions. The battery had the necessary energy stored, but the internal resistance was too high at the temperature to deliver the needed current.
My friend asked me to boost him yesterday but before I got around to doing it, his truck started up after resting for 10 minutes.

I didn't think headlights alone would be enough current to heat up the battery.
 

WBahn

Joined Mar 31, 2012
30,034
My friend asked me to boost him yesterday but before I got around to doing it, his truck started up after resting for 10 minutes.

I didn't think headlights alone would be enough current to heat up the battery.
I don't know if it would on today's cars with modern headlamps. This was on a '75 Bronco with the old-fashioned sealed beam headlights, which took about 15 A to 20 A, IIRC. It was enough to do the trick several times. Of course, in addition to the headlamps, all of the running and parking lights were on, too. I don't recall if I turned on the high beams or not -- way too long ago, but I might have.
 
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