Battery jump start packs ....how is it working..magic?

ltcom

Well-known member
Joined
27 Mar 2017
Messages
1,202
Visit site
I bought one yesterday thinking it would be handy on the boat. Could jump start the engine if needed ever (I have seen my friend jump a few cars with the identical pack) and it has two usb outlets and a 12v 10A cigar socket outlet. Nice and portable.
But I cant work the science out.
It says battery capacity 16500mAh (16.5Amp hours) and 61wh. Fully charged it is 12.4 Volts
jump start current 300A or 600A peak

The thing lost a lot of juice charging up 2 kindles and a mobile phone. So if think P=IV
61/12.4 = 4.9 Amps...........pretty low capacity and doesnt match the 16.5 Amp hours

So HOW does this thing jump start cars successfully? I have seen it do it Is there a big voltage booster in there or what magic?

Bought it from Amazon.........on a lightening sale deal £50 instead of £59
https://www.amazon.co.uk/TACKLIFE-C...1766360&sr=8-4&keywords=tacklife+jump+starter

So 2 questions? How does the magic work?
Will it have much capacity to drive things on the boat at 11.8 volts to 12.4 volts? (The voltage drops off as the pack is used). Or does it really only have 4.9 Amps in there? Though the cigar outlet says 12volts, 10 Amps? But for how long?
And I just spent £77 on a brilliant Lucas car battery of 650 cold cranking amps, so wondering if this £50 was a waste (even though the two things are not doing the same job)
cheers
 

TopBanana

Member
Joined
14 Aug 2017
Messages
152
Location
Poole, Dorset
Visit site
Starters need plenty of current, not voltage. Lithium batteries happen to be very good at delivering large currents.

One day we'll all be using them on our boats, but the charging tech isn't really there yet.
 

neil1967

Well-known member
Joined
28 Nov 2007
Messages
1,134
Location
Tavira, Portugal
Visit site
OP appears to be confusing Amp-Hours with Amps. So if it is 16.5AH and you were to run it at max rate of 10A, then it would theoretically last approximately 1.6 hours until dead - not sure how low you can actually take this sort of battery without damage. Same battery can produce large current (100's Amps) but only for very short periods.
 

Daydream believer

Well-known member
Joined
6 Oct 2012
Messages
20,065
Location
Southminster, essex
Visit site
First thing I suggest that you do, is disconnect your battery & see if you can start your engine using the jump start.
I bought a jump start from Halfords & when i went to use it a year later (charged regularly) i realised I had been sold a dud. If I had tested it I could have taken it back straight away.
being out of warranty & no receipt they did not want to know.
 

oldharry

Well-known member
Joined
30 May 2001
Messages
9,881
Location
North from the Nab about 10 miles
Visit site
These things are a bit of a delusion. Yes they will give enough power to start a good engine, but only for a matter of seconds. Your 16 ah battery has an effective discharge rate of around 10ah under heavy load. That gives around 5 seconds cranking at 500 amp starter load.. Small engines need less so you might get 10 - 15 seconds. Ok just for a good engine but a waste of time otherwise.
 

davidej

Well-known member
Joined
17 Nov 2004
Messages
6,579
Location
West Mersea. north Essex
Visit site
These things are a bit of a delusion. Yes they will give enough power to start a good engine, but only for a matter of seconds. Your 16 ah battery has an effective discharge rate of around 10ah under heavy load. That gives around 5 seconds cranking at 500 amp starter load.. Small engines need less so you might get 10 - 15 seconds. Ok just for a good engine but a waste of time otherwise.

Sorry but your arithmetic is wrong here. 500 amps for a minute is less than 10ah
 

ghostlymoron

Well-known member
Joined
9 Apr 2005
Messages
9,889
Location
Shropshire
Visit site
If they are up to starting a car engine, they should be able to start a small boat engine. Average car engine - 1.5l, average boat engine 0.7l. You need to keep it charged up though. I was once helped by one of the old type briefcase sized ones.
 

Daydream believer

Well-known member
Joined
6 Oct 2012
Messages
20,065
Location
Southminster, essex
Visit site
I was at our model flying club one day when a lipo battery must have developed a short.
It smoked for a few seconds then exploded into flames. It burnt a hole through a table & went right through. We warn member never to carry them in their pockets.
Not sure that I really want them on a boat, as the crocodile clips could short out in a locker.

Here is an example of some exploding ones, but I would doubt that you would want to drive a nail through it or bash it with a rock--- unless the d..d thing did not start that engine after you had lugged it about for 6 months depending on it to get you out of trouble:ambivalence:

https://www.youtube.com/watch?v=m_8QGBv4v7E
 
Last edited:

scottie

Well-known member
Joined
14 Nov 2001
Messages
5,401
Location
scotland
Visit site
If they are up to starting a car engine, they should be able to start a small boat engine. Average car engine - 1.5l, average boat engine 0.7l. You need to keep it charged up though. I was once helped by one of the old type briefcase sized ones.
Selective statistics? Based on ?
 

lw395

Well-known member
Joined
16 May 2007
Messages
41,951
Visit site
Assuming your engine starts reasonably easily, you should only need to run the starter for, say, 10 seconds. If it draws 300 amps, that is less than 1 amp hr used.

Exactly so.
I have seen one of these starter packs in use, about the size of a paperback book. Car dealers have them, because they work.
I looked at some cars last year with SWMBO, I was more impressed by the jump pack than the cars. The dealer said it would easily start several cars one after the other. It's very common for cars at a dealership to get flat batteries, becuase they leave the doors open to air them after cleaning, and the cars sit around for weeks.
Of course they put them back on the proper charger every night.
 

oldharry

Well-known member
Joined
30 May 2001
Messages
9,881
Location
North from the Nab about 10 miles
Visit site
Sorry but your arithmetic is wrong here. 500 amps for a minute is less than 10ah

Maybe, but thats all they do. A few seconds cranking and thats it, unlike a proper starter battery which will give several minutes effective cold cranking. More likely my guesstimate of 10AH available at CCA is too high! Amps provide the power, but few starter motors operate properly much below 9v or so on cranking. Often the solenoid starts to drop out when voltage drops that low anyway.
 

penberth3

Well-known member
Joined
9 Jun 2017
Messages
3,461
Visit site
And the other thing to bear in mind is that your seemingly flat battery might be about to supply some current too.

Good point. These portable packs are for use in parallel with an existing battery -same as the conventional "jump start".

My concern with these things is the stored energy in a box that might not be handled with the greatest of care i.e. chucked into a car boot and so on.
 

lw395

Well-known member
Joined
16 May 2007
Messages
41,951
Visit site
Maybe, but thats all they do. A few seconds cranking and thats it, unlike a proper starter battery which will give several minutes effective cold cranking. More likely my guesstimate of 10AH available at CCA is too high! Amps provide the power, but few starter motors operate properly much below 9v or so on cranking. Often the solenoid starts to drop out when voltage drops that low anyway.

A 2kW starter motor is on the large side. that's 200A at 10V.
200A for 20s is 1.1 Ah.

If your only problem is that the battery is flat, these jump packs work. I have seen it with my own eyes and been impressed.
Not sure we need them on yachts, we generally have house batteries sat there begging to be used.
 

greeny

Well-known member
Joined
15 Jun 2004
Messages
2,205
Location
Portugal
Visit site
Are we sure it's a lithium battery. Price of £50 ish is more in keeping with the old motor bike size lead acid ones I would have thought. Unless prices of lithium have dropped.
 

lw395

Well-known member
Joined
16 May 2007
Messages
41,951
Visit site
Are we sure it's a lithium battery. Price of £50 ish is more in keeping with the old motor bike size lead acid ones I would have thought. Unless prices of lithium have dropped.

If you look for 'ducati lithium' on ebay, there are lots of lithium bike batteries not much over £60 delivered.
36W.hr for £63 delivered.

Lithium batteries are indeed still getting cheaper.
 
Top