I just got a emergency jump start kit off of Amazon for about $50 and gave it a test by removing one battery cable and using this to start my car. Well it did crank a bit slower then normal but did start and run entirely off of this battery pack. The slower cranking could be because of the clip connection, IDK.
Looking at the wire for the jump starter it have on it 10 AWG, so I assume 10 gauge.
My Q is how it can do this? I’ve heard that for jumper cables you want 6 gauge or better and have experience trying to start a car off of a jumper cable, yet this thing, with smaller wires and small connectors seems to do it alone. Second question is if this 10 gauge wire works fine, why do jumper cables need a lower gauge? And for that matter the battery cables themselves?
Also it does appear that this terminal is 12V, it does not try to boost voltage to compensate AFAIK.
Also what is going on behind the scenes here. Is this raw battery voltage, or through some converter to provide the 12V for jump starting. Other outputs on this is 12V, USB power and 18V.
I dunno, but don’t do that! Modern cars aren’t meant to run without the battery connected and you could fry all kinds of different things by doing it. I saw someone blow every airbag in the car by doing that once.
Well there was a battery connected at all times, in the form of this emergency battery jump starter. Never did I run the car solely off the alternator.
After having my first flat battery in probably 12 years, I bought a “power pack” that has 1000 amps of jump-start power, 200W AC inverter, two 12V power sockets and two USB power ports. Part of this was to avoid buying a very expensive battery for my summer car (with a battery tender and this thing in the trunk, I can probably get two more years from the existing one) and part of it is that the box can do things like power trade show tents for most of a day.
I didn’t know such things had reached porta/power combo until the AAA guy started my big-big block with a unit not much bigger than a lunch pail. Cool.
That’s what was used in the story I told, except it was a larger, more robust jumper. Unless the battery pack was rated to perform voltage regulation for a running vehicle, and I doubt $50 Amazon Li-Ion jump starter is, you’re asking for trouble.
Actually considering it I do agree, it was not worth the potential risk as though this thing was providing 12V, it most likely could not accept what ever the alternator was putting out as it was not designed to which could result in a floating voltage. Lucky that the car still starts/drives fine, and I know that battery pack really can start the car.
I used to have one that used a internal lead acid battery, it also had a tire inflator and I could plug a small inverter into it for a/c power - the battery died on it and instead of replacing that battery I decided it better to buy a newer one as that old one never really had a place it fit in the car. Even that old one had some heavier gauge jumpers, this one uses much smaller gauge. It’s just hard to believe that one can use such wire to start a car. It doesn’t heat up, well I didn’t notice any hot spots and I did check.
As for the specs it list starting current at 200A and peak at 400A.
Simple answer is that it can do this because the wires are only about 6" long. Your main enemy in being able to turn the engine over is resistance in the cables. Conventional jumper leads need to be quite long in order to bridge the distance from car to car, and do it safely. 6 foot long cables will have 12 times the resistance as 6 inch cables. Or put another way, you can get away with 1/12 the area of wire in the 6 inch cable as in the 6 foot cable for the same resistance. 6 gauge versus 10 gauge is a bit less than 3 times, so you are actually well ahead.
The other problem is heat. Jumper cable manufactures will try to get away with as little copper as they can for the price you pay. There is a balancing act here, as when the engine is turned there is a lot of current flowing, and cheaper jumper cables will start to heat up. Astoundingly, for the time it takes to start an engine, the thermal mass of quite thick insulation, and the additional surface area it exposes, may be enough to compensate. So you see dirt cheap jumper cables that are very thick looking, but are actually mostly plastic. (Don’t buy them. If you need to turn over a large engine nothing beats low resistance.)
The internal resistance of a Li ion is remarkably low, which is the other reason the whole thing works.
I looked up and down the line at various price/quality points and settled on the Schumacher XP2260 (which Lowe’s has the best price on, even over Amazon, at $110).
On the one hand, it’s as cheesy and plasticky and sort of Go, Transformers, Go as all the rest, but OTOH it has a great feature set and great ratings. Also better reviews than most under the $200 mark.
Starting current is listed as a whopping 1200A, which may be a little overstated but is more than the 300A or so ones, which have reviews of choking a little on anything bigger than small V6’s. My most immediate need for emergency jumps is, uh, 446 cubic inches, and this unit had good reports from people starting SUVs and trucks.
One thing to remember about high-current cables is that current ratings for them are often for continuous use - if you try to run 100A through a cable rated for less than that, it will slowly heat up, possibly to the damage point and certainly with some efficiency loss. For short-duration uses like jumping, it’s certainly nice to have 2-4 gauge cables, but smaller ones will deliver just as much current for 10 seconds at a time on a 50-50 duty cycle. Unless they’re really flimsy, you’re more likely to be limited by the unit’s battery than the cables, which are only two feet long anyway.
Thank you this answered most of my questions and makes plenty of sense.
The remaining one is really how the 12VDC is produced (as well as the 18 and the USB voltage). Li-ion typically runs in the 3.7 volt range or so. Are there multiple Li-ion cells that make up a higher voltage battery? The unit charges off of 12V from either a wall adapter or car lighter plug.
The reason I ask, well I am curious, but besides that I would also like to know what happen in the case I attempted, running a car off of it, what happens to the power that the alternator adds to the system, can this battery accept it coming through the jumper cables? The old lead acid battery jump starter did have a direct connection between the battery and the booster cables, so in a pinch could be used to run the car, though I don’t think it’s the case here.
My guess is that it is made of a battery of 4 Li-Ion cells connected in series, perhaps multiple cells connected in parallel. Four of the 3.7 Volt cells would make for 14.8 volts when fully charged, which would explain why it can use smaller wires (higher voltage means lower current for the same power). Your car’s charging system runs at nearly 14V, so while it would not fully charge it, it would not run a risk of over charging. One way to find out would be to check the voltage of your fully charged Jump Start Kit across the cables with a volt meter.
The lack of response to you question on your second question suggests to me that nobody really has a factual answer. My guess is that a lot would depend on how the “jump start kit” is designed. The auto’s electrical system does not know whether the battery in the system is lead-acid or Li-Ion, nor does it care. There are Li-Ion batteries sold for automotive applications, but they are expensive and the only real benefit is weight, so there is nothing intrinsic about a Li-Ion battery that would make it unsuitable to be used as you describe. I was not aware that auto batteries were rated for “voltage regulation” and I am not able to find any such ratings for either car batteries or jump start kits. I am doubtful they exist.
Yes, the nominal 12V jump voltage is created by combining Li-Ion cells in series. Sorry, that’s pretty basic tech info and I think those of us who knew it failed to recognize the question. All “batteries” consist of one or more cells - that’s why they’re called “batteries” even though the term has come to mean single-cell things like AA, AAA and D cells. Cells are more or less fixed in their voltage depending on the chemistry used internally, so to get more voltage you stack them in series. (To get more current, you stack them in parallel.)
No conversion is needed, and I think that trying to convert 3-4V up to 12V at jump-starting current levels would probably require a box about 50 pounds heavier…
There are roughly three categories of jump-start boxes as well. The beefiest have enough capacity to actually jump larger engines directly - anything from about 500A to 1000A or more should be able to jump V-8 engines without any workarounds. The smaller units, 300-500A or so, can directly jump most 4’s and 6’s, but might choke on bigger engines, diesels and situations where more than average current is needed to get things going. (But wait! There’s more! Keep reading!)
Then there is the very small emergency unit, which is not used to jump an engine but to “top up” a battery - you connect it, usually through the 12V power port, and let it drain its power into the vehicle battery for a few minutes. That’s often enough to overcome a battery run down by leaving the lights on, etc. but not enough if the battery is really dead or failing. The advantage to these small packs is that they’re relatively cheap, easy to keep in a car, work a lot of the time and require almost no technical knowledge to use. The disadvantage is that they do have limits.
The mid-size units can also be used in this “drain and go” mode when they don’t have enough oomph to start an engine directly. Connect, wait 5 minutes (or until the unit’s display, if it has one, says voltage has stabilized, meaning all the power that can be transferred has been), and then try starting. This One Small Trick can get more out of a modest-sized jump pack when needed.
That’s within range of normal. I’d guess there might be some small internal load on the battery, enough to knock down that peak voltage. If you connect it to a modest load - an old headlight is a good 12V test load - it should not drop very much from the current reading within a minute or two.
(Testing batteries completely open-circuit tells you almost nothing - completely “dead” batteries can produce their rated voltage with no load. Even a small load, like those household battery testers use, is enough to pull the voltage down to a more realistic level.)
OK here’s more details, I connected a 1000W inverter to it and plugged in a 63W lamp, So perhaps with the inverter itself 70W total draw.
I ran it for 1 minute under load:
Loaded voltage started at 11.65 and went down to 11.50
Then I turned off the inverter and let it rest for 8 minutes:
Voltage went from 12.27 to 12.40
Second test
1 minute under load:
11.70 to 11.42
Rest for 8 minutes
12.20 to 12.27
3rd test:
1 minute load:
11.57 to 11.34
Rest 8m
12.00 to 12.18
4th test:
1 minute load:
11.50 to 11.24
added 30s: 11:20
added 30s: 11.16V
Rest 3m:
11.82 to 11.97
Note it appears that the inverter even when ‘off’ does have a capacitor as it holds the voltage if the jump starter is disconnected, for all except the 1st test I left it connected.
Good testing! It’s hard to say exactly why the output voltage is so much lower than the nominal battery voltage of 4x3.7… unless it’s actually 3x3.7 and reading just a tad high under light load. (Is there a technical spec for how many individual cells are actually in there?)
But many factors go into measuring battery capacity and the unit could be designed to limit the output voltage, or internal circuitry could be tapping off that faint phantom volt. It does sound like the unit is capable of delivering ~12V for a considerable time, though, which is what it’s all really about.
No technical specs that hint at multiple cells, they treat it as a black box (even though it is white).
Li-ion can get as high as 4.2V fully charged, so perhaps 3 at 4.2V, which would give the open voltage fully charged of 12.6 which is pretty much spot on. Though I would expect them to drop to the 3.6 under load, which only gets 10.2V
But yes it does what it says it does and is pretty darn impressive given its size and weight.