Has anyone used Startmonkey or Lithium equivalent ?

Submitted: Friday, Feb 28, 2014 at 13:23
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I note that the shop is carrying ads for the more powerful 400A version of Startmonkey lithium jump starter and I find the specs confusing and wonder if anyone has more detail.

I get a little worried when I see statements like "delivers a jump-start current of 12Volts at 400Amps" and " Maximum jump-start current: 400A, 4,800watts in 6-8 seconds "

In reality its a secondary battery of 21AH that is used to dump some charge into a good but flat battery which together then start the car, in this mode everything is fine and I'm sure it delivers.

Implied in these specs is that it can deliver 400A and start a car which isn't really true.

It may deliver 400A for an instant but its own spec 4800 watts in 6-8 seconds" is an average of approx 66 amps.
(I also don't think the leads on Smartmonkey wouldn't handle 400A for long).

I.E. Its unlikely to start a car which has a destroyed (and hence disconnected) battery.

Ever since the manual option was deleted from the GU 4800 patrols I love and I had to go automatic, I have carried my own version which is a 21AH GEL Cel permanently connected to car via a low volts drop diode.
It has Anderson plugs connected for quick jump starts and running inverters etc.


This Smartmonkey appears to be much the same functionality as my Gel Cell system, however if its weight claim of 1.1kg for 21AH is true then its represents an incredible capacity/kg specification as gel cells are around 5kg and for this reason alone would be worth my consideration .
Robin Miller

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Reply By: tim_c - Friday, Feb 28, 2014 at 16:28

Friday, Feb 28, 2014 at 16:28
Lithium Ion batteries have amazing capacity for the size and weight when compared to older technologies such as gel-cells (lead acid), NiMH, etc. - hence the attraction to use them in aeroplanes, though as Boeing is now painfully aware, it's not always without other issues!
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Follow Up By: Robin Miller - Friday, Feb 28, 2014 at 18:14

Friday, Feb 28, 2014 at 18:14
They are pretty good al right Tim but this one must be exceptional.

21AH for 1.1kg is the best figure I have ever seen , for a long time Lithium has been about 1/2 the weight and I note some new types claiming 5:1 (with some issues as you say) - we still seem to be some way from a car battery replacement without side issues at 5:1 though.

Fingers crossed, one day !
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Reply By: chisel - Friday, Feb 28, 2014 at 16:35

Friday, Feb 28, 2014 at 16:35
4800W is 400A if delivered at 12V. There's no mistake there. They're saying they can sustain (an average of, I assume) 4800W over 6-8 secs. It's not that surprising. Modern lithium batteries can deliver that sort of power.

66A at 12V would be 792W. Not sure where your 66A comes from.

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Follow Up By: Bonz (Vic) - Friday, Feb 28, 2014 at 17:15

Friday, Feb 28, 2014 at 17:15
4800w in six seconds is 800watts per second, which equates to 66 amps continuous over the six seconds to deliver the 4800w.

That's where is comes from chisel I reckon.

400 amps at 12v or 4800w for 6-8 seconds is about 0.66 Amp-hours delivered very fast from a battery, and it would be exciting to see what it did to anything less than 70mm2 leads I say.
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Follow Up By: Robin Miller - Friday, Feb 28, 2014 at 18:02

Friday, Feb 28, 2014 at 18:02
Hi Chisel

Thats not correct actually , watts is power and can only be delivered over time - Oops I just noticed Bonz also said that.

That amount of current flow (66amp average) just wouldn't start my Patrols engine - without the extra assitance of the cars own battery.

Hence no real value over Gel cell - and in fact is probably less versatile as some Lithium types are a little sensitive to discharge/charge.
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Follow Up By: Allan B (Member, SunCoast) - Friday, Feb 28, 2014 at 18:36

Friday, Feb 28, 2014 at 18:36
I'm afraid that expression is not correct either Robin.
Watts certainly is 'power' but it is instantaneous. It only becomes 'energy' when it flows for a period, hence 4800 Watts for 6 seconds is 28,800 Watt-seconds or 8.0 Watt-hours. And at 12 volts it would be a current flow of 400 Amps.

I am guessing that the product specifications are incorrectly expressed as "IN 6-8 seconds'. They probably meant to say "FOR 6-8 seconds".

I have no experience or knowledge of the performance of these Polymer Lithium jump starters but do know that these batteries can deliver very high currents without harm. Their major problem, other than price, is being over-discharged which will render the cells ruined without hope of recovery. I expect the product has protection against over-discharge.

As for the connecting cables, it is surprising how much current a cable can carry for a few seconds without becoming damaged by overheating, and the cables on the product are very short so there would not be a lot of volt-drop during a start effort. Having said that, I expect that the product is aimed at typical petrol car engines, not high compression large diesels with high cranking demand.

I have yet to discover an unbiased reliable review of this or similar products, only supportive 'sales' expressions. It would be useful to view a competent unbiased review.

Cheers
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Follow Up By: chisel - Friday, Feb 28, 2014 at 20:42

Friday, Feb 28, 2014 at 20:42
As Allan B has said power is instantaneous. Wh (or Ah) would be the energy or work measurement. (eg. if you had 4800Wh delivered over 6 seconds that's 800Wh/s which is, err, very large current and power!).

Many "jumpstarters" are rated to much higher than 400A. Normal jumper leads will deal with that current over a short period.
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Follow Up By: Robin Miller - Friday, Feb 28, 2014 at 21:01

Friday, Feb 28, 2014 at 21:01
I agree it appears to be use of bad terminology in a couple of places, and thats why I question it.

To keep it simple I am trying to find out if it can deliver 400A for 6 to 8 seconds.

Its a critical question because if it does then it could be used to start a car by itself with the car battery disconnected.
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Follow Up By: Bonz (Vic) - Friday, Feb 28, 2014 at 21:27

Friday, Feb 28, 2014 at 21:27
yep 400A for 8 seconds is going to be fun to watch
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