JUMPR by Junopower

[liquibyte]

This would be a great product if it works.  How can they get 300A out of something the size of a cellphone would be my question.  Seems more like April 1st to me but then again, I know very little.

[Jon86]

Nah it's possible with very high rated current li-po's, but it's going to last for such an incredibly short amount of time that I can't see it being practical for any kind of cold start.

[liquibyte]

Given that whenever our cars battery was drained enough to require a jump, it usually takes at least 3 seconds of turning over to start.  I just can't see that this will work except for maybe a motorcycle.  I think I'll bookmark the site and await the reviews one way or another.  I know the big portable ones you carry in your car don't seem to have very good reviews either so I'm kind of curious as to how quickly this will fail as a product.

[janoc]

Well, to me it looks like a good way to jump start something else - you hook the thing up, turn the ignition key and then jump and run once the LiPo catches on fire along with your car ...

[AG6QR]

Is anyone else bothered by the publicity photo showing it lying in a toolbox with a bunch of loose metal tools, pliers and wrenches?  I don't see a literal crowbar in there, but one of those wrenches would serve the function of a power supply crowbar quite effectively if it touches the metal parts of both clamps.

It says it has a 6 amp-hour battery.  But due to Peukert's law, it won't have anything near that capacity when discharging at 300 amps.

[echen1024]

Number one, the math proves it can't reach 300amps. Number 2, if it could, it would blow up in your hand.

[mux]

Why does the math prove it can't reach 300 amps? If they're not lying about the 1/20C capacity (which they say is 6000mAh), it's only a 50C (burst)/25C(sustained) battery pack. There's lots of 50-75C lipo's on the market, this is totally doable.

The big question is indeed: can it sustain sufficient current for long enough? I highly doubt it; those tiny little wires as well as the cells themselves definitely have in the order of milliohms resistance, so at 300A you're dropping a couple volts just over ohmic resistance. That's not even counting recombination speed internal to the battery, which has time  constants in the order of seconds usually. Most very high discharge rate batteries can indeed provide pulse discharges for a couple tens or hundreds of milliseconds, but their sustained rate is 1/2 or 1/3rd of rated discharge. So I'd bet money that internally this is really just a 20 or 25C lipo.

http://rightbattery.com/483-1s-3-7v-160-mah-turnigy-nano-tech-25-40c-lipo-battery-tests/

[G7PSK]

It's the connectors on the box that will give trouble at 300 amps.

[nitro2k01]

Who even says it will jumpstart the car? Forgive me if I'm missing something on that page, but all I'm seeing is claims that it will keep phones and mobile devices charged on the go. 

Edit: Didn't scroll down.

Nevertheless, those 300 A won't necessarily have to come from the battery directly. They could for example have two modes, trickle charge, which will charge the lead acid battery, and a crank mode that will precharge a super cap to follow the car battery's residual voltage, which would then have low enough resistance to enable you to crank the engine. Then again, those wires are troubling me, just like everyone else in this thread.

[amyk]

A 50C lipo is definitely not something to be handled casually... and I doubt it will have much protection. If it can output 300A to start a car, it's just as happy to put 300A through any other bits of metal that happen to land across the terminals. The equivalent of carrying a small incendiary device in your pocket.

It's also not a constant 12V, a 3S pack varies between ~9 to 12.6V and a 4S between 12 and 16.8V empty to full. The other downside to a high-discharge design is that self-discharge is going to be extremely high as well.

[peter.mitchell]

[Jon86]

Who even says it will jumpstart the car? Forgive me if I'm missing something on that page, but all I'm seeing is claims that it will keep phones and mobile devices charged on the go. 

Edit: Didn't scroll down.

Nevertheless, those 300 A won't necessarily have to come from the battery directly. They could for example have two modes, trickle charge, which will charge the lead acid battery, and a crank mode that will precharge a super cap to follow the car battery's residual voltage, which would then have low enough resistance to enable you to crank the engine. Then again, those wires are troubling me, just like everyone else in this thread.

I don't see how they're going to fit a decent size supercap in there...

[miguelvp]

I don't see how they're going to fit a decent size supercap in there...

Graphene and Graphite Oxide? 

Actually... Maybe... Eventually

[daveshah]

How are they going to handle reverse current protection - 300A MOSFETs are pretty beefy, plus only 1mOhm would dissipate 90W at 300A

[janoc]

Strictly speaking, you don't need 300A to start a car. A small car, with lights and other electronics off will draw around 80-100A when cranking the engine. The 300A (and more) cranking power ratings of car batteries are there mainly to be able to start in cold weather, when it is both harder to turn the engine and the batteries have less capacity.

That said, using a LiPo for this really doesn't sound like a good idea - extreme fire hazard if the battery fails, with the engine full of gasoline right next to it.

[NiHaoMike]

How are they going to handle reverse current protection - 300A MOSFETs are pretty beefy, plus only 1mOhm would dissipate 90W at 300A

Reverse polarity would basically cause a short circuit, blowing the fuse. There's a chance the alternator diodes would fail first, but at least good quality automotive electronics are designed to survive reverse polarity.

[Danw33]

I received mine today (in the UK), the jump leads each have an inline "box" which I presume contain some sort of protection circuitry (this isn't shown in any of the demo videos I had watched, although not really an issue).

The instructions that came with the device mentioned something about the lights on the front reading like a charge level for the car battery, and the device shouldn't be used if less that three lights show - Again I presume that this is to protect the device.

The sticker on the back says the device is rated for 150A starting current with a 300A peak current, and the device should be used with engines smaller than 2.5L "for best performance".

The good news is it charges my phone pretty quickly and shuts off automatically after a few minutes of the phone being fully charged  , although interestingly there is a small "explosive" sign on the back of the device

I'd quite like to try this thing out properly , but for now it shall sit in my glove box and probably not see much use! If anyone is interested in pictures of the device or the instructions that came with it I'd be more than happy to post a few.

[Monkeh]

I received mine today (in the UK), the jump leads each have an inline "box" which I presume contain some sort of protection circuitry (this isn't shown in any of the demo videos I had watched, although not really an issue).

That's a fuse.

[SirNick]

Not necessarily.  My gadget-loving significant other picked up a set of jumper cables that don't have polarity markings on them.  (Both clamps have blue boots.)  You're supposed to hook either side up just any which way and the cables figure out the rest.  (You know how hard it is to trust instructions like that when you're looking at two lead-acid batteries in the proximity of flammable liquids, and don't have the luxury of casual consumer ignorance?)

Turns out, the lump in the middle of the cable has diode-operated relays.  No MOSFETs, so just contact resistance when engaged.  When you hook up the clamps, there are a few clicks and a diagnostic LED shows you it's ready to go.  My little Ghia managed to jump-start a Forester through those crazy things.  I'll still take normal jumper cables over that unnecessarily complicated contraption, but it does actually work.

[cimmo]

Not necessarily.  My gadget-loving significant other picked up a set of jumper cables that don't have polarity markings on them.  (Both clamps have blue boots.)  You're supposed to hook either side up just any which way and the cables figure out the rest.

Wow. What a lot of complication for people who can't work out "Red to Red" and "Black to Black".
They'd need to be big-arsed relays as well!
I wonder what happens when a set of contacts get welded together and the thing is used again but in the opposite polarity.
It go bang?

[Monkeh]

Turns out, the lump in the middle of the cable has diode-operated relays.  No MOSFETs, so just contact resistance when engaged.  When you hook up the clamps, there are a few clicks and a diagnostic LED shows you it's ready to go.  My little Ghia managed to jump-start a Forester through those crazy things.  I'll still take normal jumper cables over that unnecessarily complicated contraption, but it does actually work.

Huh, interesting. Looks just like a fuseholder.

[amyk]

I received mine today (in the UK), the jump leads each have an inline "box" which I presume contain some sort of protection circuitry (this isn't shown in any of the demo videos I had watched, although not really an issue).

The instructions that came with the device mentioned something about the lights on the front reading like a charge level for the car battery, and the device shouldn't be used if less that three lights show - Again I presume that this is to protect the device.

The sticker on the back says the device is rated for 150A starting current with a 300A peak current, and the device should be used with engines smaller than 2.5L "for best performance".

The good news is it charges my phone pretty quickly and shuts off automatically after a few minutes of the phone being fully charged  , although interestingly there is a small "explosive" sign on the back of the device

I'd quite like to try this thing out properly , but for now it shall sit in my glove box and probably not see much use! If anyone is interested in pictures of the device or the instructions that came with it I'd be more than happy to post a few.

Teardown please!

Do be careful though, a 300A lipo is definitely something you don't want to damage or short.

[dannyf]

Seems more like April 1st

It is OK for someone to try to pull a con like that.

It is not OK to believe in such a con.