Battery Jump Starter

[Roker]

I am looking into purchasing a jump starter,  as we know there is no cranking current so a small one will do . I want to charge it from my car from the cigarette power socket in the boot. What I cannot understand is that most of power pack come with USB lead only. Where do they charge from? they don't even have a mains charger

I can get an adapter to go from power plug to USB but isn't the USB 5v to charge a 12v Battery pack

 

[Cyker]

Hard to say without knowing which pack you mean, as a lot of them do charge from barrel plug AC adaptors, but since lithium cells are only 3-and-a-bit volts it'd be pretty trivial to design the pack to be charged from a 5v USB plug, it'll just take longer to charge!

Some of them might use USB-C PD, which allows higher voltages too.

I suspect most of them use a lot of internal DC-DC conversion or cell-switching between series and parallel, esp. to get from lithium cell voltage to the 12v required for jump starting.

[tfc]

I plug mine into a usb adapter to cigarette socket  

[Derek.w]

I use a 5 volt usb adaptor to charge a 3 cell Li-ion Battery pack each cell rated at 3.7 volts.

So it electronicly steps up the voltage to 12.32 volts so most likely a 4 cell pack for starting a car.

Note some of these packs employ flat cell technology rather than the 18650 more common round type cell.

[Roker]

2 hours ago, tfc said:

I plug mine into a usb adapter to cigarette socket  

That's what I want to do,  do you use a USB lead to cigarette converter plug or does the lead have the plug already installed on the cable

[tfc]

Mine is just a cable , USB c end goes into the pack and a standard USB socket at the other end you can  either plug into the USB port in the car which is I think is slower than using a USB to mains plug adapter but either way I can charge it while driving along.

On my old car it had 2 USB sockets so didn't need a adapter but when I first got this car I used  a USB cig converter plug with only having 1 usb socket in the car but since then have bought a 2 into 1 USB plug for the car so can do away with the cig converter.