Why would this little 6 amp hr battery need battery clamps as it would not start a model airplane. Perhaps to charge it? Oh, to give it the appearance of something awesome. My car battery is 500 amp hr.
Electrical engineer here.
Every time one of these jump starter packs is sold on WOOT, someone inevitably comments “That little battery can’t put out that much power! It can’t possibly work!” I shall try to clear up this matter once and for all (yes, this is a pet peeve of mine, so there).
The internal resistance of lithium batteries is very low - for a pack like this its somewhere in the 15 milliOhms (i.e 0.015 Ohms) range. Dividing the output voltage (about 12V) by the resistance (about 15 milliOhms) gives a peak current of about 800 Amps. Allowing for real-world batteries, a peak current of 700 Amps and a continuous starting current of 350 Amps is not unreasonable. Also, the battery is producing this current for a short amount if time - maybe 10 second per start. The battery is rated for 6000mAH. Dividing current by time, this means that, theoretically, it can provide 6000mA (i.e. 6A) of current for one hour. Or 12A for 1/2 of an hour. Or 24A for 1/4 of an hour. Or (remember I said “theoretically”) 2160A for 1/360 of an hour (which is what 10 seconds is). Back to the real world - obviously, the battery is not producing this much current; the point is that it CAN provide sufficient current for a short period of time and provide several engine starts.
Damn, payaz got schooled
Wow!!! That was a great tutorial and as I always say, "knowledge is power.
I have a similar device that has started my dead car battery. Apparently, Florida’s heat takes a greater toll on car batteries than the cold in the North East. I made the mistake of leaving my charger in the glove compartment where high temps destroyed the lithium battery. In for another.
This does NOT include the white split charging cable that’s pictured. It only includes a USB—micro USB cable. So, if you want to charge your iPhone, you’ve got to plug that cord into the charger as well.
I bought another brand that looks very similar to this. I religiously kept it charged every 3 months. When I needed to start a dead 1995 Corvette, it indeed started. However, the battery pack swelled to 2X the size - breaking its plastic shell. I freaked out and kicked it 20 feet away as I thought it would explode. It was useless after 1 start. While this unit may not do this, I’d recommend testing within the warranty period to see if it works without self-destructing. You don’t want to find out in an emergency that it doesn’t work or destroys itself.
Did the battery get hot?
The only thing I can think of is that metal expands if it’s heating up and if it’s coiled around itself to step down the voltage, it could potentially have broken out of the case because of a higher resistance conductor than probably should have been used.