Jump Start Packs? How do they work?

[Oakmaster]

I've always been intrigued by these compact Jump Start Packs?  they see to defy the laws of physics?  How do they work?

Some of them are advertised as being able to kick-out 4000 Amps, yet they have smaller diameter cables than the cheapest of Poundland jump leads?  

What is it that I'm missing?  Where is the catch?  I've been looking at the Ring RPPL300 Lithium Cobalt for my daughters VW Fox.

[PaulN]

Good question so I'm watching!  🙂

[monkie]

Interesting question. I don't know the exact answer so had a quick look at what was readily available in the UK. Halfords advertise as an example the GB70 from Noco. Details on the technical spec from Halfords were unsurprisingly sparse, so I looked the full spec up on Noco's own Web site. 

They say a peak output of 2000amps and upto 40 starts. But I'd say there are a few variables on that. Does that mean 40 attempts at starting a cold 8 litre diesel engine with a totally dead battery? I doubt it. 

The spec says the battery has a capacity of 56W hours. So I think they are just good at delivering a lot of amps quickly, which is what you want for an average vehicle in good health if the only issue is a flat battery just to get you on the move again. I doubt they'd cope with a large diesel engine with air in the fuel system that needs a bit of cranking, but that isn't their intended use. 

 

 

[SteveG]

It’s simply that they use lithium ion batteries. So they’re good at releasing large amounts of current quickly without much voltage drop unlike a typical lead acid battery. 
 

No idea on large diesels, but I’ve cranked a 4.6 rover v8 multiple times from a mid range unit with no issues. You can crank for longer with them, and they can certainly crank multiple times with no problems.

[Tanuki]

The good ones are surprisingly-good; the bad ones are predictably-bad.

They use Li-Ion batteries [as found powering Teslas etc] - and generally work on the principle that they can quickly shove some significant number of Joules into your dead battery, rather than attempting to directly crank the engine from the battery-pack itself.

I've got one [badged "RING"] that as well as doing the boost-thing also has a Hella-socket so I can use it to power my coolbox and HF radios when camping; I've only once had to use it to jump-start a car [an Audi A6 3.0 V6 Diesel] but it did the job surprisingly well.

[Stellaghost]

+1 for ring had mine over a decade and still working regards Stephen

[zardos]

4 hours ago, Oakmaster said:

Some of them are advertised as being able to kick-out 4000 Amps, yet they have smaller diameter cables than the cheapest of Poundland jump leads?

The current carrying capacity of a cable is mostly about heating effect caused by the resistance of the cable over time before the cable gets too hot for the insulation to melt and then the metal cable to melt.

So this is affected by many factors, e.g. resistance of the wire, insulation type and melting point, current ambient temperature, air flow around the cable, etc, etc.

But the big one in power packs is time the current is flowing for and it is expected that the current is flowing for a very short time to start a vehicle.
And they also tend to have a limited current generating capability (so what it does not say is that it can kick-out 4000 Amps for 0.01 of a second) before flat.

For example some electrical products have specifications like

"rated at 300 amps continuous, 600 amps for 20 seconds and 2400 amps for 1 seconds. "
Taken From https://www.durite.co.uk/ItemDetails/ItemDetails.aspx?ItemNumber=060533&SingleResultCriteria=&catid=75299

 

As you can see it can take 300Amps continuously but higher current for shorter period of times (before it would melt)

Edited November 30, 2020 by zardos

[zardos]

Also should have said there is also an interaction with length of cable which affects the voltage drop, etc
As cable resistance is measured per meter.

And these jumpstart packs tend to have very short leads (some not much more than the distance between battery terminals).

Standard jump leads are usually many times longer to reach from one vehicle battery to another and thus have to be bigger.

[FridgeFreezer]

Big Clive on Youtube has torn down, explained, examined, and indeed exploded quite a few jump start packs if you're curious.

[Romahomepete]

If you read the small print for the RAC badged one on Amazon it is only for petrol engines smaller than 1500cc, not  alot of use to us.

Peter

[Quagmire]

I've used a couple of my lipo RC car/boat packs in parallel recently to start my old Rover saloon car. I have an xt90 style connector wired to the battery terminals, this branches off to two xt60's with a lipo on each one. I was concerned that the connectors weren't rated anywhere near high enough, but so far no drama. They started the car when it would barely turn over on its own battery.

[Bowie69]

The XT60/XT90 are continuously rated at 60 or 90A, so to start a car for what, 5 seconds maybe, they should be more than up to it. Most cars cranking don't take much more than 200A.

All about the duty cycle

[FridgeFreezer]

^ As Bowie says, I measured the V8 at ~300A peak and less than 150 once it got turning, even a flat car battery is going to be able to contribute 100's of amps to cranking, just not much voltage, so I suspect the jump packs are enough extra to bring it up a bit and kick it over / fire.

[Ed Poore]

I also wouldn't be surprised if there's some careful selection of numbers for advertising / datasheets. You may well find that the batteries are capable of supplying 2000A so technically they can claim 2000A starting capacity - the fact that the rest of system can't handle it is a moot point .

You'll not uncommonly find in MOSFET datasheets (as an example) that they state they claim in big numbers they can handle 100A continuous current however when you read the datasheet you find that it's only one very specific package that can handle that and it's not available! They're not lying just advertising well 

[BogMonster]

I have a Noco GB70 and no, it doesn't fire out 2000A continuously for 40 starts but it does work and works well. I've only had to use it a couple of times for properly flat batteries (rurrrrclickclickclick flat) and it works well and is infinitely more convenient than jump leads.

Use it as a powerpack (e.g. running a 12v tyre compressor) and the battery life will deplete fairly quickly but it is still useful and the Noco will charge off a phone charger (slowly) or by plugging into a running vehicle's cig lighter socket.

 

This is a pretty good write-up 

 

[Anderzander]

That’s helpful @BogMonster  I’ve just borrowed my neighbours to jump start a 200tdi and it started instantly. Very impressive and I’m thinking they would be a great insurance product on solo trips.

[Oakmaster]

1 hour ago, Anderzander said:

That’s helpful @BogMonster  I’ve just borrowed my neighbours to jump start a 200tdi and it started instantly. Very impressive and I’m thinking they would be a great insurance product on solo trips.

Echoing that - very interesting Thanks @BogMonster and to all the other contributors - My Daughter bought one a NOCO Boost Sport GB20 500 Amp to start her VW Fox (she initially bought a lead Acid Jump starter from CarEuroParts - but it never turned-up, consulted me and bought the NOCO- for twice as much - but its been brilliant immediate start from a completely dead battery - less than 2 volts)

I will say that I used my CTEK MXS 5 battery charger to 'renovate' the Fox battery - which it did - going from going flat in 24 hours, to 5 starts in 3 hours with less than 10 total metres of travel, having been left out in the snow for 5 days.  That is the third out of 6 'lost cause' Batteries that the CTEK has rejuvenated - 50% isn't bad - across a range of batteries: Leisure, compact car,  Defender.  (I've ignored Lawnmower and literally dozens of Computer 'life expired' UPS 12V batteries) 

This performance is measured against about 8 Aldi or Lidl 'intelligent' chargers - that trickle charge the Land-Rovers, camper, and cars, at around £12 each they are cheaper than most/all the simple trickle chargers - but fail to rejuvenate, and more irritatingly if the mains fails they revert to standby.

This would indicate that you get (more or less) what you pay for, a hard lesson for someone as notoriously 'tight' as I am!

[simonr]

I was given a (blue box) one - which turned out to be, err, well, less good than advertised!

It claimed 2000A IIRC - but even with the leads shorted only managed 85A.  Inside was a 16V LiPo battery, a low quality voltage regulated charger & cheap (78 Series) linear voltage regulators for 12V and 5V USB out.

It had a thing you plug in to the side which connected to the jump leads (with 10 sqmm cable) but it was potted so hard to figure out what was inside.  It had a buzzer and detected short or open circuits.  It clearly also had a relay inside (which I doubt would have handled 4000A for more than a few uS).  The relay only closed if it thought it was connected to a battery & the voltage was higher than about 10V - presumably to stop you trying to see if it actually delivers 4000A in to a short circuit.
That bit went into the bin.  Without the magic box, it was a lot more useful.

It worked like that a couple of times, but more often let me down.  The rest of it followed the magic box into the bin!

Then I built my own with a much safer LiFePO4 20Ah Battery in an Ammo tin.

It has a small 300W Inverter, proper mains charger and a variety of useful outputs.  Everything, apart from the Anderson is switched by a 100A SSR via the key switch.

It only delivers 80A or so into a car battery - but I've used it again & again and it's not let me down yet.  You just connect it up and leave it for a couple of mins to charge the car battery.

[Oakmaster]

Greetings Battery booster people -  I have another question that is puzzling me:

My daughter has a NOCO Boost Sport GB20 500 Amp for her VW Fox It works very well to the point where I bought my self a much bigger one for my Landrovers.  The problem is the VW doesn't get used much and the battery is always drained flat when she wants to use it.  (the battery was new last spring)  Is there a way that she can use the NOCO Boost GB20 to charge her car battery without actually having to start the car?  She is worried that the car battery might get damaged by possible excess charging.  

thanks 

Bill

[Bowie69]

On 1/10/2021 at 5:57 PM, simonr said:

Then I built my own with a much safer LiFePO4 20Ah Battery in an Ammo tin.

How did I miss this, what an excellently useful looking piece of kit!

[L19MUD]

51 minutes ago, Oakmaster said:

Greetings Battery booster people -  I have another question that is puzzling me:

My daughter has a NOCO Boost Sport GB20 500 Amp for her VW Fox It works very well to the point where I bought my self a much bigger one for my Landrovers.  The problem is the VW doesn't get used much and the battery is always drained flat when she wants to use it.  (the battery was new last spring)  Is there a way that she can use the NOCO Boost GB20 to charge her car battery without actually having to start the car?  She is worried that the car battery might get damaged by possible excess charging.  

thanks 

Bill

Constantly running the battery down to nothing is not going to be doing it much good. A dedicated trickle charger would be the right thing to do here. The Noco will just flatten itself over time too. If you don't have access to power to trickle charge then a solar trickle charger might be enough? I fitted one to a 300tdi Defender that attaches to the sun visor and it has certainly reduced the number of times that truck needs a jump start

As an aside I have the GB150 NOCO and it is excellent. it amazes me how many jumps starts it will do on a charge. This weekend my old International forklift  - old 2.5 Diesel turned over about half a turn before the dreaded click. I hooked up the NOCO, gave it 30 seconds heat and then she fired up no problems. Ended up jumping the Forklift twice needing heat both times and a little Massey 135 twice without heat. Started with 3 out of 4 bars charge and still on two bars

 

Yes it won't replace the big mains booster if it is really cold/really flat but certainly more than enough so something like a TDI where they start almost instantly

[Oakmaster]

21 minutes ago, L19MUD said:

Constantly running the battery down to nothing is not going to be doing it much good. A dedicated trickle charger would be the right thing to do here. The Noco will just flatten itself over time too. If you don't have access to power to trickle charge then a solar trickle charger might be enough? I fitted one to a 300tdi Defender that attaches to the sun visor and it has certainly reduced the number of times that truck needs a jump start

I agree, and that is what I do with my Series One which is not near to any mains (and any extension lead would be constantly run over) My daughters car is in an underground car park with no powerpoints. no sun and no power.

As an aside Ive heard adverse comment about solar charging, but dont understand the technicalities? 

 

cheers 

 

Bill

[L19MUD]

3 minutes ago, Oakmaster said:

I agree, and that is what I do with my Series One which is not near to any mains (and any extension lead would be constantly run over) My daughters car is in an underground car park with no powerpoints. no sun and no power.

As an aside Ive heard adverse comment about solar charging, but dont understand the technicalities? 

That is a tricky solution to solve other than just driving it more often! Driving it every couple of weeks should be enough to keep it topped up?

I have not heard about that and can't see why a small trickle would be doing any harm? My main aim with that really was to offset the small draw from the stereo memory. 

[David Sparkes]

4 minutes ago, Oakmaster said:

... My daughter has a NOCO Boost Sport GB20 500 Amp for her VW Fox.
It works very well to the point where I bought my self a much bigger one for my Landrovers. 
The problem is the VW doesn't get used much and the battery is always drained flat when she wants to use it.  (the battery was new last spring)

... My daughters car is in an underground car park with no powerpoints. no sun and no power. ...

Now we have a clearer view of the circumstances, I suggest a battery isolation switch to leave the charged battery totally disconnected, but still take the NOCO Boost Sport GB20 500 Amp along when she does want to use the car, until she is confident the new regime works for her.

This does presume she remembers to open the bonnet and throw the switch everytime she leaves the car.

Regards.

[Oakmaster]

12 minutes ago, L19MUD said:

That is a tricky solution to solve other than just driving it more often! Driving it every couple of weeks should be enough to keep it topped up?

I have not heard about that and can't see why a small trickle would be doing any harm? My main aim with that really was to offset the small draw from the stereo memory. 

if they leave it for 2 weeks the battery is flat (which doesn't seem right)  if I leave my 110 Puma for more than 3 days it wont start (I thought that was the stereo - but is plainly more than that!) and my 89 110 V8 drains its battery in 6 to 7 days - Its making me paranoid!