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USA & SINGAPORE JOINT VENTURE

LiPO Safety Precautions

Most importantly read the instructions and use the correct charger for the job. Lithium batteries are the most energy dense on the market but with that comes the volatility of fires and explosion with misuse or poor quality product.

 

1. always stick to the manufacturers safety limits

2. always use a lithium charger dedicated for the job

3. allow for cooling between charges

4. if you smell electrolyte, dispose of it

5. if the batteries bloat, dispose of it

6. check the temperature you are operating at and stay within the batteries limits

7. use a good charger with active control

8. if you have a extremely low voltage cell.  do not charge

9  if you are not sure. don't do it.  

 

How to use LiPO safely?

How should I store packs?

What is thermal runaway?

Store the batteries at 50% state of charge or close.  Thats around 3.6 - 3.8V per cell.

Be wary of cells or packs that have falling voltages.  They may auto ignite due to internal faults.

Store in a room outside your premisis preferably and avoid high temperatures (automobiles in the sun).

Store in a container that is solid and would contain any type of combustion event.

Storing packs together is dangerous.  If a pack has an event, most likley all of them will burn.

 

No need to store them in refrigerators or freezers.  Keeping them cold has no advantage and it'll take you hours before they are ready to fully run or charge again

Thermal runaway is what we are really trying to avoid. It is important to understand the phenomenon of thermal runaway that destroys Li Ion/Li Po cells. All the things we can do, i.e., cell balancing, proper cut - off, and better resistance to over voltage do help avoid thermal runaway.

 

However, if anything ever happens to initiate thermal runaway, no external device, PCM, polyswitch, internal switch, or the like can

stop it. The most dramatic cause is puncture that shorts the plates or a massive, internal short. Once the cell starts to break down and ignition starts, nothing can stop it except to starve the cell of oxygen. This is why the ultimate safety is to charge in a fire proof safe box. If we keep the cells in a pack perfectly balanced throughout the life of the pack, assure cut-off in the face of massive overload, and use proper maintenance to avoid a dead cell in a pack, the possibility of thermal runaway is almost zero from normal operation.

 

You have to worry about Li Pos becoming unbalanced with age.  Active cell balancing can prevent all of this for either chemistry and nothing else will. Cell balance charge is, in effect, charging each cell in a pack individually to the precise end voltage or capacity at which it is rated. The difference is that LiPos are arbitrarily 100% full when they reach 4.2V while Ni Cd and Ni MH are full when they reach a nominal 1.6V/cell but measurable only by detecting the peak during overcharge at which voltage/time slope goes negative.

 

It is best and safest if all charging is automatic and does not demand of the user that he remember to do anything except plug the pack in for charge and take it off when the charger says it is full. Only a cell balancing charger or very tedious and smart manual checks can provide cell balancing protection. A manual arrangement can prevent cell imbalance so long as you remember to use it and remember to check cell balance as charge progresses.

 

Stages of thermal runaway event

 

1. Cell temperature of 100 - 125degC: anode passive films/electrolyte reaction occurs

2. 125 - 180degC  - venting and accelerated heating/smoke. oxygen release, highly exothermic

3. 180degC and above,  explosive decomposition

 

Thus it Is most important not to reach the first trigger event.  To stay safe don't do anything that will take the pack above 70degC

 

 

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