lipo case split

[snige]

hey lads i have a set of 4900 35c reedy stick pack lipo.i was racing today and noticed the case had open/split in one corner i can squeeze it back together but i think it would be unsafe to use it,whats the best way to get rid of it thanks

[ashleyb4]

Discharge it very slowly chuck it in a bucket of sand for a while.

A

[mark christopher]

Originally Posted by ashleyb4

Discharge it very slowly chuck it in a bucket of sand for a while.

A

Ash has it half correct. Slowly discharge it a low amps .5 till completely flat. Or you can put it in a bucket of salt water and leave it. Only reason you would put one in sand is if it was on fire. unless ash thinks new ones grow in sand?

[Battle_axe]

Before you throw away what may be a perfectly good lip are you saying the hard case has cracked or that the cells inside have swollen?

[ashleyb4]

Yea salt water not sand thats the one had been a long day.

A

[snige]

Originally Posted by Battle_axe

Before you throw away what may be a perfectly good lip are you saying the hard case has cracked or that the cells inside have swollen?

just the seam were two halfs of the case meet had just poped open. i just looked at them just now and the case is back together and very hard to open.does heat affect lipos as sunday was a hot day and were i was pitting the lipo was being charged in direct sunlight could that have a affect on it?

[neiloliver]

If the case has just opened because the case was not joined together very well (rather than it being forced apart due to cell swelling) then pop some cyanoacrylate onto the join clip it back together. if the two parts wont rejoin (because the cells have swollen and are restraining the two halves) then discharge the battery to 6.0V and then dispose of properly (tape up the terminals and place it in the correct recycling box provided by your local council).

[snige]

is there any way to test a lipo to see if its no good any more?

[mark christopher]

If its swollen its dead.

[snige]

ok thanks for the help

[neiloliver]

Reasons Lithium Polymer cells swell (please read carefully as there will be a test afterwards)

(1 )Increased internal pressure from gas expansion as a function of temperature.

(2) Electrolyte reactivity and decomposition is influenced by the type of electrolyte, the type of anode graphite, and the cell formation process used to form protective films on the graphite. The usual solvent used in lithium ion electrolytes are organic carbonates (Propylene and Ethylene Carbonate, DMC) and these are prone to degrade at high temperature releasing CO2. And there's nothing in the cell for this gas to combine with.

(3) Impurities in the cathode LiCoO2.

(4) Electrode binder swelling as electrolyte is absorbed by the PVDF resin, this is a factor of PVDF crystallinity and molecular weight and can be as high as 20-30%.

(5) Moisture present in the cell.

(6) Additional swelling on cycling may result from volumetric changes of the active electrode materials, (graphite and LiCoO2). In order for Li ions to intercalate into the graphite the crystal structure must expand approximately 10%. Since these cells are anode overbalanced, additional graphite can expand each cycle. Depending on the type of graphite, (flake, fibre, bead) electrode expansion of 100-200% can occur. The cathode, LiCoO2, also expands approximately 2% upon removal of Li due to Co - Co repulsive forces.