Home Made Auto and Truck Jump Starter

I have a few of the Anti-Gravity brand micro jump starters including the PS-1 and the XP-10 HD truck units. One of the PS-1's starter to swell the plastic case so I figured the Lipo had puffed. So nothing to lose by very carefully trying to open it up to see what's in there and if it could be replaced. There was no exterior cosmetic damage in opening the case but some of the glued mating edges broke so the case would not stay together very well. Before I knew the extent of the edge damage, I even went to the trouble of buying a quality Dinogy Graphene replacement Lipo and it all worked just fine but I can't live with a case that is marginally compromised.

So I made my own more powerful and reliable unit. I much prefer LiFeP04 batteries for their higher safety and almost zero self-discharge. I picked up one of HobbyKings 8400 4S2P bricks. It uses 8 AWG right off the tabs which is far better that other units that utilize only 10 AWG. I picked up a set of Anti-Gravitys new HD jumper cables which utilize 7 AWG cables and a heavier duty clamp. I soldered on some 175 Amp Anderson Power Poles to both cables and battery and I'm good to go now. I might end up wrapping some 1/8" hi-density foam around the battery and then shrink-wrapping it again for some protection. All of this fits nicely in the original Anti-Gravity pouch for keeping in the car. Another benefit with my system is that in the Anti-Gravity setups, there are 16 solder joints and contact points in the circuit, all adding up in resistance and Voltage loss. In my system, there are a total of 10. This will serve to keep loaded Voltage higher.

That's pretty neat. Never thought about using a pouch battery. I made one with 4s3p a123 32113 cells with studs and put them in an aluminium enclosure with batter cables and 6awg for 13500mah. Works like a charm and weighs almost nothing

Just some trivia regarding the jump starter. I had the first occasion to use my jump starter the other day. A neighbors Chrysler 300 SRT8 had a completely dead battery. Dim interior lights and would not budge the starter. I hooked up the unit and it started with the same gusto as the cars' battery normally provides. Maybe 1 to 1.5 seconds of cranking. From this 8400 mAh battery, I put back in only 352 mAh, or about 4% was used for one V-8 engine startup.

For anyone doing this: be careful since the alternator might be charging your pack overvoltage. Many off-the-shelf products include Schottky diode arrays in the cable to prevent this, e.g. see below are some photos I posted in a related thread.

For the couple seconds it's hooked I don't imagine it'll be a problem. Plus alternator output shouldn't be higher than full charge voltage. And if life they can handle a little extra easily

Whether or not it will be safe depends on many factors, the pack voltage, the chemistry, etc, and the cumulative damage that may be done to the pack after many jump start overcharges.

This setup specifically uses a 4S Lithium Iron Phosphate battery that is fully capable of handling 14.4+ Volts - nearly perfectly matched to the automotive system max charging Voltage. If using a 3S Lithium Ion battery - as many/most of the pocket starters do, then absolutely, you'll want to use cables with the above cited protection as they should not be seeing charging Voltage above 12.6V.