Lithium Jump Starters…. A word of advice.

Standard jump packs and nearly all battery chargers are the same so you don't connect the leads backward and damage the vehicle electronics. Battery chargers are usually 5-6 volts trigger so you have to jump start the charger to get it to start.

From memory my unit indicates it will not work with a dead flat battery and has a led to indicate
voltage to low or something along those lines though I think I have seen other types start car without a battery but I may be wrong.

I assume you are supposed to connect it to the battery and wait till the battery has enough charge to activate the boost feature. All sounds good but...

I recently found my hybrids 12V battery died when I pushed the start button after leaving the car idle for about 3 weeks. No problem I will use the jumper starter, wrong! I connected the jump starter and pressed boost, straight away all the automation kicked in the car, head lights, wipers and everthing esle trying to fire up and the boost disengaging. Tried a few times then thought ok I'll let the battery charge a bit and try again but again no joy. I suspect all the electronics, ie voice commands are still active even when everything appears off and that with whatever else is running expecting the car to be started prevents the battery charging to a point where the boost can be used. In the end I gave up and connected my battery charger to it, waited a few minutes then it started. For me the jump starter was not a success with a hybrid vehicle. I also found with my Prado many moons back the same, I had a high resistance develope in the battery isolator switch and couldn't start the car. I thought flat battery and connected the jump starter pack,. All seemed well pushed the boost and tried to start and immediately the boost dropped out.

When I realised what the issue was I was surprised as I thought the jump starter would provided the cranking current if the starter loads the jump pack to much and pulls the voltage down the boost drops out. It appears it is more of a hit the boost and wait some time for the cranker to charge before trying to start. I'll have to do some more testing in the future. This might also expalin the 70A relay.

My Lithium jump starter, GooLoo, has a button to press if no voltage detected. I had successfully started my V8 Landcruiser diesel, in the middle of NE Vic winter, with the starter battery disconnected.

Kevin

Wow, from the responses so far, it would seem that not all Jump Starter Packs are the same.

Macca.

I have found after having a few of the little jump packs that if not used regularly they eventually die.
A better solution is one of the supercapacitor jump packs as they don't have a battery that must be kept charged so nothing to die. Like most jump packs they need the battery being jumped to have at least some voltage and the one I've got will charge off the flat battery and once it has charged after a few minutes will then do the job. It can also be charged off mains and a good batttery in a few minutes.
I've started trucks bulldozers, tractors and of course 4wd's and cars from it over the years.
It's often been over 12 months between uses and it still works fine after many years.
As others have found keep an old transformer based charger for those really flat batteries that the so called smart chargers won't charge from dead flat.

The Gooloo GP4000 looks to be an impressive unit and will provide an impressive, 800 cranking amps.

I just watched a video where a guy did 3 consecutive 6 second start attempts on a diesel engine without any issues.

Real world test on a carbon plie produced 708A@9.54V.

Good post with some interesting info.
I have the Noco brand and they apparently can start a car with a dead flat battery which I didn't know about or even think of when buying it. I have only used it on a car with a flat battery that still had some power but not enough to start the engine by itself. So I won't no till or if the situation arises.

Good idea tbh the low voltage sends battery to sleep as a protection feature

Somehow old man deep discharged auxiliary batteries on their camper he couldn't recharge them on bms in camper

I used a 9 volt battery across terminals to wake up batteries charged up normally