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I got this unit to explore it as an option for providing a high current 12V power supply for short term use. It's a car jump starter and USB power bank. The 12V output is direct from the lithium battery pack with no protection, so care would need to be taken not to over discharge the pack when using it as a 12V supply.
The connector is a standard EC5 high current battery connector, which is handy. The USB connector has floating data pins, so it may not be recognised by some devices.
It's a very modular design. A microcontroller that displays charge level and controls the buck regulator for the 5V output that is also used for the LED, and a current regulator for charging the lithium pack that has a three cell protection chip and matching charge/discharge control MOSFETs. One oddity is the use of the microcontroller to directly drive the charging buck regulator's MOSFET.
The Battery pack has a four pin connector for charging and monitoring individual cell voltage. There's no balancing, just a shut-off when one of the cells reaches about 4.25V. It also has the high current connector tapped directly across the pack that then feeds a plug-in jump start module that contains the anti-reverse charging diodes and the MOSFETs used to switch the output to the beefy alligator clips when a separate microcontroller detects that suitable conditions have been met.
The lithium cells used in these are usually the high current type that have a different internal construction from normal cells. Instead of the electrode foils being long spiral-wound strips, the high current cells often have a stack of alternate layers of electrode foils and dielectric separators with a cluster of parallel tabs brought out the end of the cell. This allows discharge at very high currents, in brief bursts of hundreds of amps.
It looks a fairly sensible design, but as with most of these jump starters it's only really suited to an occasional quick jump start as opposed to endless cranking of an engine with issues that caused the car's battery to go flat in the first place.
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11 thoughts on “Inside a combined power bank and jump starter”
  1. Avataaar/Circle Created with python_avatars Sundog says:

    Unmatched parallel diodes is not such a big deal as each will have some dynamic resistance (of a few mil ohms) thus donating some current to the next one.

  2. Avataaar/Circle Created with python_avatars Anchevauls Walker says:

    Can I send you pictures of a circuit board that won't work from a side by side RC car?

  3. Avataaar/Circle Created with python_avatars Jacob Petersen says:

    Not sure I'm keen on the 15V input. It might be able to charge the cells quickly, but is it worth not using a balancer? My Roav pack (Anker brand) charges with USB-C, so it definitely has balancing. Unfortunately they quit making them. It's sad when such a high quality manufacturer simply can't compete with all the cheap stuff.

  4. Avataaar/Circle Created with python_avatars Who Kares says:

    Clive when you were talking about the input connector you were pointing to the light not the usb c connector

  5. Avataaar/Circle Created with python_avatars pontymike56 says:

    I dont quite understand how this starts a car, given the crank amps needed with a lead acid battery

  6. Avataaar/Circle Created with python_avatars Phonotical says:


  7. Avataaar/Circle Created with python_avatars Brad Meek aka SilverTopFlyer says:

    You mentioned there is no balancing, will the cells become unbalanced and end up swelling and becoming unusable?

  8. Avataaar/Circle Created with python_avatars Callum Mitchell says:

    Hi there clive, just seen your video on reusing disposable vape batteries. Me and my room mates tend to take them to recycling centres, but we currently have a couple hundred sitting in our living room. I thought id ask to see if youd be interested in me sending them to you so you can put them to better use?

  9. Avataaar/Circle Created with python_avatars MD4564 says:

    Wouldn't use these things for cars.

    You can buy decent Portable Starters for a couple of hundred, why risk the safety ?

    Good for parts though.

  10. Avataaar/Circle Created with python_avatars fla playa says:

    Another great choice of tear down and reverse engineering. I own a Schumacher V8 1200 amp one $100 at Walmart. Thing is really good, zero polarity or short protection as I found out being ultra distracted by a woman hooking it to her broken car backwards… It did go into some protect after a huge amount of sparks being thrown and thankfully was no worse for wear. Be careful with these I'd say it could be a stick of dynamite easily. Cheers Happy 4th of July.

  11. Avataaar/Circle Created with python_avatars immrnoidall says:

    Have you looked at the jump packs that are just capacitors and can charge to jump ,from a dead car battery? I don't hear about them lately, although it sounds great.

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