Sciencemadness Discussion Board - Large Li-ion battery packs, compact jump starters and truth in advertising?

Large Li-ion battery packs, compact jump starters and truth in advertising?

Bert - 15-12-2017 at 14:23

Researching the compact Li-ion based vehicle jump starters which have proliferated recently. The first thing I learned was that specifications given by manufacturers are largely bogus, or at least written in a deceptive manner.

I can find a few videos and posts by people who actually disassembled these and checked out their true cell capacities or ran them into test loads while measuring Amps delivered at 12 Volts, proving what the packs really WILL output under vehicle starting loads.

And quite a few half assed (can you HEAR me, Consumer Reports? "Wirecutter"?!) comparisons and ratings of "the ten best" or such, done without any proper measurements. At best, the writers just tried to start various engines and noted which size/types would crank over and start. A few bothered to try the same starts at different temperatures.

Has anyone run across a properly engineered test run on a good sized sample of the different brands/models available?

Anyone here got one, did their own testing and could report methods and results?

Twospoons - 15-12-2017 at 14:52

I've seen a few ads for those things, and I'm deeply suspicious of the claims. Given the size of the things they can't be running cells much bigger than 18650 size. The high current versions of li-ion cells top out at about 30A - and have a capacity in the region of 2Ahr. That's the type used in e-cigs. Pack 6 in a box you could just get 12V 60A - a bit short of the 100+ amps most car starters need.

Its going to be pretty rough on the cells too.

Then we add in competition and the race to the bottom: cheaper units that will have crappy chinese cells that will probably die under that kind of abuse.

I wouldn't buy one myself.

DJF90 - 15-12-2017 at 15:12

I have one of these: https://www.amazon.co.uk/gp/aw/d/B01KZFUW98?psc=1&ref=yo...

I bought it originally to jump a sportsbike I'm currently repairing before buying a new battery for it. It also saved my arse this morning when my winter hack wouldn't start (it has been having issues for a couple of weeks now, due to increasingly cold weather and what I now think is a battery on its way out).

These engines are very much on the small side of things (750 and 400 cc respectively) but they both started "on the button". Its certainly something worth carrying in a backpack or glove box, in my opinion.

[Edited on 15-12-2017 by DJF90]

violet sin - 15-12-2017 at 15:32

I have regularly jumped a '94 Ford escort with an 18v dewalt battery for a cordless screw gun. Got stuck out in the middle of nowhere after work hours, 30min drive for a jump. So I figured it out.

The car battery does most the hard work, you basically just up the voltage in the system. I know my cordless battery, nickel cadmium guy, could not turn over the starter on its own.. 18.2v @ 3Ah new and mine was third hand pass on kind of Tired. My theory is the extra voltage allows the auto battery to effectively dump it's amps into the car.

My battery still works great on the jobsite, as far as I can tell no damage or loss of power. But I've made it home more than a dozen times because of that gem. Now I use the 20v li job, paid for new from pocket at store... So no I'm not gonna just use those to jump my car.

Bert - 15-12-2017 at 18:35

I have a Cummins 6.7 litre turbo diesel in a 3/4 ton Dodge Pick up (a Ute, to the ozzys). It has two large Lead acid batteries in parallel, something on the order of 800A being required to turn over and start.

Additionally, there are glow plugs that need several seconds of run time before cranking and ditto on a grid heater for incoming air on really cold days. These things suck down the voltage on the batteries fast, if they are at all marginal, the starting relay just chatters by the time the plugs and grid have cycled and the truck asks to be cranked.

So, I ordered one of these: Noco Genius Boost 150 It has not arrived yet, I am guardedly optimistic after watching a couple of tractor trailer engines jumped with one on YouTube videos.

Someone who had enough of a tech background disassembled one, made a youtube video of the guts, including the markings on battery pack, and then ran it into a variable, instrumented load. It put out a measured 425 Amps at 12 V for 20 seconds, then the thermal overload protection kicked it off. Looking at the cables on these, I suspect more than the battery would have cooked if it ran longer at that output.

One also wonders how many such cycles the batteries are good for. If/when it shit cans the battery pack, I would be tempted to salvage the electronics and make up a replacement battery pack with a cooling fan for hot days/long cranking and a pre heat circuit for cold days to being the batteries up to optimum temperature. That still would be smaller and lighter than ONE of the original batteries.

Anyhow. This is not a cheap tool. I wondered if I would have been better served by buying two of the smaller, cheaper units and placing one across each battery... But since there is no 3rd party verified information on capacities and outputs, there is no good way to estimate which of the many advertised units would do the job.

(Edited because our OLD NiMH batteries were nominally 24V, the NEW Li-ion batteries are 18V)
We have 20+ Makita (18V) Li-ion drills, impact wrenches and grinders for our crews, and around 60 battery packs, 2/3 1.5 AH, 1/3 are 3 AH. Also, another truck (M35-A2) with a 24V system and a 7.6 liter diesel engine. I should make a rig with those Makita batteries for jumping that bastard on cold days too.

[Edited on 16-12-2017 by Bert]

NEMO-Chemistry - 15-12-2017 at 18:41

Quote: Originally posted by Bert

I have a Cummins 6.7 litre turbo diesel in a 3/4 ton Dodge Pick up (a Ute, to the ozzys). It has two large Lead acid batteries in parallel, something on the order of 800A being required to turn over and start.

Additionally, there are glow plugs that need several seconds of run time before cranking and ditto on a grid heater for incoming air on really cold days. These things suck down the voltage on the batteries fast, if they are at all marginal, the starting relay just chatters by the time the plugs and grid have cycled and the truck asks to be cranked.

So, I ordered one of these: Noco Genius Boost 150 It has not arrived yet, I am guardedly optimistic after watching a couple of tractor trailer engines jumped with one on YouTube videos.

Someone who had enough of a tech background disassembled one, made a youtube video of the guts, including the markings on battery pack, and then ran it into a variable, instrumented load. It put out a measured 425 Amps at 12 V for 20 seconds, then the thermal overload protection kicked it off. Looking at the cables on these, I suspect more than the battery would have cooked if it ran longer at that output.

One also wonders how many such cycles the batteries are good for. If/when it shit cans the battery pack, I would be tempted to salvage the electronics and make up a replacement battery pack with a cooling fan for hot days/long cranking and a pre heat circuit for cold days to being the batteries up to optimum temperature. That still would be smaller and lighter than ONE of the original batteries.

Anyhow. This is not a cheap tool. I wondered if I would have been better served by buying two of the smaller, cheaper units and placing one across each battery... But since there is no 3rd party verified information on capacities and outputs, there is no good way to estimate which of the many advertised units would do the job.

I was going to suggest one them hand held devices that can start from a dead battery. But noway would it handle a beast like that, well i doubt it.

Some of the professional type Capacitor type starters are pretty good, but again I have zero knowledge with a motor that big. Wouldnt want to crank it by hand though

Melgar - 15-12-2017 at 18:46

Had a friend who rigged up his car with a supercapacitor bank so that he could start it using a golf cart battery. And those things are the deep-cycle kind that last for a really long time. With supercapacitors, you can immediately blast the starter motor with enough power to get it acting as an inductor, at which point it provides enough resistance that the battery will suffice.

RogueRose - 15-12-2017 at 18:52

I'm not sure the battery packs are supposed to be able to jump them from the pack alone, but IDK. If your car battery is like 11v and you put on the jump pack that is 14.4, the pack is going to discharge into the battery until they are even voltages (as far as I understand electricity to work).

So, if you need 12v (let's say 12.6v for a healthy car battery) for 3-4 seconds and maybe 400A, then putting that 14.4 pack on the battery for a couple minutes is going to dump 20-60A into the battery for that entire time. So, given the lowest amount of 20A, 3 minutes (180 seconds) = 3600 Amp seconds (made that up, but you know what I'm saying) but you need 4 seconds to turn over (high estimate) so you have about 3600Amp seconds/ 4 seconds = 900A for the start.

Now add in internal resistance and what not for 20% reduction = 720A. But then you also have the jump pack on and that should give a few extra amps (at higher V as well) to get things working.

I know I found that my car wouldn't start by putting the pack on and immediately turning it over, but allow it to sit for a couple minutes and it starts right up.

I've thought about the 18v ni-cd packs as well and might give it a try on charging a dead battery to see how much it ups the V over a few minutes. If it works, these may be the better choice over the car jump packs as they have MUCH more capacity than 4 18650 cells.

Bert - 15-12-2017 at 18:59

This company offers a supercapacitor jump start unit, claimed to charge in 2 minutes off vehicle 12V oulets or able to charge itself on any residual power remaining in the weak vehicle battery when clamped to the terminals. Once again, no good figures on just what that capacitor and the discharge circuit can really do-

Rockford CED1000 Capacitor Based 12V 700A Portable Jump Starter

[Edited on 16-12-2017 by Bert]

NEMO-Chemistry - 15-12-2017 at 20:04

Quote: Originally posted by Bert

This company offers a supercapacitor jump start unit, claimed to charge in 2 minutes off vehicle 12V oulets or able to charge itself on any residual power remaining in the weak vehicle battery when clamped to the terminals. Once again, no good figures on just what that capacitor and the discharge circuit can really do-

Rockford CED1000 Capacitor Based 12V 700A Portable Jump Starter

[Edited on 16-12-2017 by Bert]

Thats the kind of thing I was on about, a guy came out and started my mums car with one a couple of months ago. I cant remember the brand but it was a professional one and had a little printer on it. She has a Diesel with a fairly big battery (car is Mondeo estate).

The device did its tests and came back with 'fucked battery', it was well shot!! But the little device took the last few volts in the battery and started the car no problem.

The guy was from the UK's main call out service (AA), so it wouldnt be a cheap unit, if i can remember the name i will grab you a link, it was astounding seeing this thing start a car that couldnt even light up the head lights.

It wasnt snapon brand, but it was a high end brand like that.

XeonTheMGPony - 16-12-2017 at 07:09

lead acid batteries form whats referred to as a surface charge, it forms fast and leaves fast.

So what these do is create this skin charge, and essentially the car battery acts as a capacitor in this scenario and dumps a far larger current then the little pack you used to get this skin effect going, that is why most tell you to leave it on for several minutes befor trying to start.

DJF90 - 16-12-2017 at 09:05

The one I have doesn't require any "warm-up period" - you hook it up and turn the ignition. It has not failed to start the engine despite the battery being so flat that the instrument panel wouldn't even light.

NEMO-Chemistry - 16-12-2017 at 18:43

Quote: Originally posted by DJF90

The one I have doesn't require any "warm-up period" - you hook it up and turn the ignition. It has not failed to start the engine despite the battery being so flat that the instrument panel wouldn't even light.

The same situation we had, i think its a case of buy a half decent one. Not sure if this is what Bert wants though... Might be cheaper to buy a new battery?

Bert - 16-12-2017 at 23:41

Would be TWO new batteries. Last time, two interstates with 6 year guarantee were over $500.00 US... So a booster for $275 is not a bad stopgap, plus it will be useful for all the other trucks, boats and cars we use in our work.

We used to have a start cart, a large transformer on wheels that needed to be plugged in to mains power. We wore it out in 3 years, and it cost more than this booster.

[Edited on 17-12-2017 by Bert]

XeonTheMGPony - 17-12-2017 at 07:15

In the logging camps we just made one from taking an alt from a d8 excavator and throwing a Honda engine on it, portable, cheap, and worked every time all the time, best part is if truck wasn't needed you could properly charge the batts on the field too!

every 3 months good to disconnect and do a full over night trickle charge on truck batteries then hit them with a hard current till all cells are bubbling to stir the electrolyte and balance the cells, while at it adjust water levels. get the full 10 year life of the battery that way

L.A. Cells rarely die they are mostly murdered.

RogueRose - 17-12-2017 at 09:35

If you need something where space isn't a major issue (that is why these are nice), then get a standard car jump pack for about $50-70. It has a 17 AH 12v SLA (sealed lead acid) battery and can be used to jump 4-10 cars on one charge and they last a LONG time. We used them all the time where I worked b/c 1/2 the cars we had to pick up had dead batteries.

https://www.overstock.com/Home-Garden/Speedway-4-in-1-Power-...

This one has a 120 PSI compressor with it for $60!
https://www.walmart.com/ip/Stanley-1000-Amp-Peak-Jump-Starte...

[Edited on 17-12-2017 by RogueRose]

aga - 17-12-2017 at 09:56

The only direct experience i have with Li-Ion batteries is with flying models, as that is the 'normal' battery these days.

3S 2200 mAH at 40 Amps are the ones i have these days, although i did have a couple of big ones, 5000mAH 6S once for a 700-size helicopter which scared the bejeesus out of me - the rotor diameter was about 1.4 meters, a bit like flying a scary garden table with spinning swords attached.

Those batteries certainly pack a serious punch of energy.

After a lot of cycles they started to puff up.
Just to see what happens i charged a 'puffy' one up and then stood it in a field and shot it with a .22 air rifle.

When the slug hit it (after 30 misses) immediately a 6" flame like a blowtorch shot out of the cell, which then ignited the others in quick succession.

Lots of energy can rapidly go into and out of Li-Ion battery devices in more way than one !

Edit:

Turns out it was a 600-size heli. It was a few years ago.

Here's a demo of the energy in one of the larger cells :
https://www.youtube.com/watch?v=icXbEiUg9i0

[Edited on 17-12-2017 by aga]