Li -ion battery

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Joined: 14/09/2005
Location: Australia
Posts: 1498
Posted: 10:29pm 05 Mar 2021      

I would like to understand the working of the rechargeable li-ion battery pack ?

I understand ,by opening my flat-pack ,that the batteries are in plastic sealed packets.  There must be plates of metal inside ,plus cables ,I have not touched the sealed packets.

They are swelled from a previous owner ,who I do not know.

Could someone out there explain to me how these packets of rare earth or whatever is a mixture of whatever in there ,how they work ,please. I have no intension of opening them , would just like to understand the mechanical working of whats in there and how does the power ,when they are charged, travel .

its a fairly big unit , says 2500 watts and I've applied 48vdc ,it shows 81 watts into the unit ,don't know if this is charging(no indicators), or this 81 watts is consumed in the battery management system ?. no warm feeling on the packets, been on power for 1 hour.

Bruce (change the topic heading and re-locate to another section ,if Solar is not appropriate..


Murphy's friend

Regular Member

Joined: 04/10/2019
Location: Australia
Posts: 96
Posted: 09:38am 06 Mar 2021      

Hi Bruce,
While I have not taken apart my new Li-ion battery pack cells I did open a shortened LYP cell (200Ah). I assume the Li-ion type is similar with different chemical inside.

Basically its constructed like a very large capacitor (and I understand it works in a similar way, eg. no chemical reaction in an electrolyte).

There are two different, very thin, foil type 'plates', one is aluminium and the other copper. These are coated with the special 'stuff' and are separated by a very thin plastic sheet.

The plates are each connected to its terminal on the top, I think there were nearly one hundred 'plates' of each variety. There are no wires inside unless the cell has an inbuilt balancer.

The 'plates' are only as big as the cell outline but the plastic separator zig zags between the alternating 'plates' and is many many meters long.

There was no liquid  inside the cell I opened but the plastic separator sheet felt wet and smelt funny. It also started to smoke when I bundled it into the rubbish bin, I guess it reacted with oxygen in the air. Threw it  on the lawn until it had dried out.

If you want a better explanation how it works just google it, there are some very good texts on this subject.

My new Li-ion cells are tightly strapped into 4 cell packs with aluminium endplates to prevent bulging.
The LYP cells require one to come up with one's own strapping method and, if not done very well, will swell in the middle too.

Senior Member

Joined: 17/10/2017
Location: Belgium
Posts: 277
Posted: 12:10pm 06 Mar 2021      

Good explanation, what I read/heard was that "pouch cells" should be clamped together so an evenly applied force between anode/cathode that guarantees an evenly spread current draw or charge from the plates. This way it will limit the "hot spots" in the battery cell, this is the place where gassing is created. Limiting the charge/discharge rate will reduce the stress and help with avoiding swelling.
I would discourage using (heavely) swollen cells, it will get worse overtime because the plates won't make good "contact" anymore. Maybe you could take the risk with small lifepo cells, but with li(-ion)po it gets dangerous verry quickly.


Joined: 14/09/2005
Location: Australia
Posts: 1498
Posted: 09:55pm 07 Mar 2021      

Thank You , Murphy,friend,(and mine now) and Nickskethisniks (wow, what a name !).

anyhow, thanks very much for the simple explanation of how they work .  I think I gathered that the salient point is the "closeness" of the "plates' , so mine are badly swollen and therefore may never be recoverable.

Can I buy replacements and would they be worth the gamble or expense ?.

I did apply , very carefully, my 48v battery just by touching the Anderson shells together, BANG. yes, melted the POS terminal . no damage.

Funny thing , 0 volts on my meter before the experiment, then after a micro-second and the BANG, I read something like 0.048 volts ,later back to 0.

maybe this was the capacitor effect ???.

Anyhow, the other idea was a controlled charge , like a gradual increase in charge to see if it really is a dead short or just wanting a huge input til it settles down ????. (bruce is thinking out aloud).

Thanks for the discussion, luv this forum.



Joined: 11/12/2020
Location: Australia
Posts: 5
Posted: 08:51am 08 Mar 2021      

The " plastic sealed packets " pouch cells are best sent of to the recycle center.
There are toxic chemicals in the cells so opening them is not recommended.
Trying to charge them is not a good idea
they are likely to continue to swell until they pop
the gas and liquid inside is flammable and very toxic when burnt

You can contact the manufacture and se what price they will charge for new cells
or take a look on Alibaba

The BANG is a concern there may be damage to the electronics

Senior Member

Joined: 17/10/2017
Location: Belgium
Posts: 277
Posted: 10:40am 08 Mar 2021      

That is bad, I'm not going to encourage you to bring the others cells back to live.  If you want to test the electronics you might want to assemble a small lion pack, with some 18650's, what was the voltage again? 13 or 14s for a 48V is verry commonly used.


Joined: 03/06/2019
Location: Australia
Posts: 838
Posted: 11:43am 08 Mar 2021      

I had one of those Lipo jumper packs.
Was very good and unbelievably powerful and it got a lot of use and I did try to look after it.

One day when trying to start the ute, the thing started smoking a little then obviously had a runaway. I managed to tear it off the battery and hurl it into the yard.
I have NEVER seen anything so compact make so much smoke. I mean it filled the yard and you couldn't see one side to the other.  Only other thing I have seen like it is videos of giant smoke bombs on Yt. There was a bit of orange fire and lots of hissing and jet like smoke emanation but the volume of smoke was astounding.

Luckily it was in the morning and the breeze was gentle and took the smoke away but I guarantee the mosquito population took a month to recover.

If you want a bit of entertainment, short that swollen pouch out and toss it making sure you are upwind.  Don't be surprised if some rescue aircraft  descends thinking it's a distress signal or you are marking an LZ for an insertion team.

I would be very careful where you left the thing and myself would be putting it where it could burn and not matter like in a metal bin outside and away from anything else.
From Videos I have seen these things can also go off in a spectacular fashion if shot so if you want a bit of fun with your bunny gun.....   :0)


Joined: 14/09/2005
Location: Australia
Posts: 1498
Posted: 01:25am 09 Mar 2021      



I'll remove the packets ,Carefully, and take them to a recycler depot .

I'm not interested in even trying to figure out IF. after reading the couple of previous warning posts, thank You.

I'll keep the bus(battery management system) and battery charging module ...Some one further down the track may have a use for it or know of a way to use it again.

Thank You ,



Edited 2021-03-09 11:55 by brucedownunder2


Joined: 14/09/2005
Location: Australia
Posts: 1498
Posted: 02:11am 09 Mar 2021      

I just remember you posted about a car jumper starter pack . I have one of those ,must drag it out and take it to the recycler also ,,,,, could very well be dangerous,thank you.....

There is no warm feeling on these packets . So at least that's a good sign.

Looks like the connections from inside the packets ,from the plates, to the pcb outside ,is  connected by some form of heat compression or maybe crimping ?. I,ll keep the flyleads and connections ,they look good for other projects.

I,ll now warn my friends if they come across these type of batteries, thank you for your warning..



Joined: 14/09/2005
Location: Australia
Posts: 1498
Posted: 11:30pm 04 Apr 2021      


  back to the batteries--  My friend ,Aaron is progressing along the path to bring these "modules-Packets,pouches" back to life.

So far ,after a few light voltage charges, medium current, he's managed to "wake" a pouch up from flat.

I won't jump the gun yet, a long way to go ,but fairly good results so far .

He or I will keep you informed,




Joined: 31/12/2016
Location: Australia
Posts: 459
Posted: 08:50am 05 Apr 2021      

Before attempting to charge this pack I wrapped up the back end with some masking tape to help hold it together.
I tried charging the one that has the black plastic wrap removed, I set the charger to 6v then connected it up turned the charger on and it maxed out at 40Amp for 3 seconds the dropped back. I then gradually increased the voltage as the amps dropped, after about 10 minuets I reached 12v on that pack.

Turned it off and disconnected over night, checked the voltage the next morning and the battery was dead flat, Did the same cycle again the next day  and the battery started to hold a little charge of about 1.5v.

Did the same cycle again, this time it was holding over 6v, looks encouraging.
Will do this with the other packs.

These are Lifepo4 pouch cells, LFP.
What We think has happened with this Flatpack is that it was left sitting flat (Discharged) for a long time.
An overcharged cell that has swollen up would not flatten out with any recharge.

Now in the photo you can see the masking tape is really slack, what is most surprising is the cells (while charging and left for some time) have sucked back down flat most of the way, was expecting that.

While charging this pack I did check every cell often to make sure none of then where going over voltage, it was nice to see all cells in this group where charging and voltage was equal on each cell.

Will have to peel open the cover on the end of the other 2 packs to check the while charging, see if they do the same thing, there is a small chance that they might might all charge up and work, will take some time to go through this process, but definitely worth trying.
Thanks Bruce for letting Me work on this.
Can't say for certain that all this will work, too early to tell, there is also the issue of high resistance that could make the battery difficult to use, will wait and see what happens...


Joined: 14/09/2005
Location: Australia
Posts: 1498
Posted: 12:08pm 17 Apr 2021      

Hi Crew.

Well,Aaron has been busy getting these batteries back to some sort of decent charged state.

He,s done careful voltage charging ,setting the voltage to recommended voltage,and constantly observed the rise. He,s observed  only slight discharge,but more importantly, a big decrease in the physical swelling has occurred,which indicates a positive reaction to the charging cycle .

So, success may be achieved after a few more cycles,well done Aaron,and thank you.

I have been thinking ,that this flatpak unit may have just been neglected from new and or maybe charged incorrectly ,in the first place ?. As it was looking brand new and unused when I obtained it.


Solar Mike

Joined: 08/02/2015
Location: New Zealand
Posts: 781
Posted: 05:46am 18 Apr 2021      

I have had some interesting experiences recently with these type of batteries; have 36 odd 40AH rectangular cells, with heavy hard PVC outer casings, removed from an ups. Charged all cells up individually and did a capacity test using a Cellpro 8 charger, then did a half charge and put them away under the bench for 6 months.

Some have started to swell for no reason at all, they still have 2.6 to 3 volts odd, so they must be really old possibly.
The ones that have this condition I clamped up between pieces of timber and placed on charge, repeated the capacity test; result capacity has halved from previous. Tried a few more discharges and gentle re-charge, made no difference; once they have got to this state, basically they are stuffed and its a pointless exercise to use them.

And ringing around here in Wellington, I cannot find anyone who would recycle them, so off to the dump they go, I will drill a 10mm hole through them and leave them in a bucket of water for a week or so to make them inert.

The remaining 30 seem to still be ok, but I wouldn't trust them, as all coming from the same batch, they could crap out any time. Their capacities are all round the 50% mark.

I hope you have better success.

Edited 2021-04-18 20:34 by Solar Mike