Here’s my personal experience in discharging a LiPo pack. I found this how-to scattered all over the inter-webs but the main source (Thunder Power?) seems to be lost forever. At any rate, I’m cross-posting it here for posterity.
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Unlike NiCd batteries, lithium-polymer batteries are environmentally friendly. For safety reasons, it’s best that LiPo cells be fully discharged before disposal (however, if physically damaged it is NOT recommended to discharge LiPo cells before disposal – see below for details).
The batteries must also be cool before proceeding with disposal instructions.
To dispose of LiPo cells and packs:
1. If any LiPo cell in the pack has been physically damaged, resulting in a swollen cell or a split or tear in a cell’s foil covering, DO NOT DISCHARGE the battery.
Jump to step 5.
2. Place the LiPo battery in a fireproof container or bucket of sand.
3. Connect the battery to a LiPo discharger. Set the discharge cutoff voltage to the lowest possible value. Set the discharge current to a C/10 value, with “C” being the capacity rating of the pack. For example, the “1C” rating for a 1200mAh battery is 1.2A, and that battery’s C/10 current value is (1.2A / 10) can be used, such as a power resistor or set of light bulbs as long as the discharge current doesn’t exceed the C/10 value and cause an overheating condition.
For LiPo packs rated at 7.4V and 11.1V , connect a 150 ohm resistor with a power rating of 2 watts (commonly found at Radio Shack)to the pack’s positive and negative terminals to safely discharge connecting it to an ESC/ motor system and allowing the motor to run indefinitely until no power remains to further cause the system to function.
Json Comment:
My first attempt at discharging was using a Turnigy Reaktor 250W, I used NicaD setting instead of Lithium so I can set the minimum discharge voltage to 0v. My first test was a 3S 2200 which I discharged at 1A with a preliminary target of 6v. After 20minutes the LiPo warmed up and puffed more (it’s already puffed to begin with and has 250-300 internal resistance across the cells) creating a small tear in the packaging. So yes, there’s a reason why the suggested discharge current is 10% of the effective C (i.e. I should have discharged it at 0.20-0.25A).
4. Discharge the battery until its voltage reaches 1.0V per cell or lower. For resistive load type discharges, discharge the battery for up to 24 hours.
5. Submerse the battery into bucket or tub of salt water. This container should have a lid, but it should not need to be air-tight. Prepare a plastic container (do not use metal) of cold water. And mix in 1/2 cup of salt per gallon of water. Drop the battery into the salt water.
Allow the battery to remain in the tub of salt water for at least 2 weeks.
6. Remove the LiPo battery from the salt water, wrap it in newspaper or paper towels and place it in the normal trash. They are landfill safe.
Reposted from these sources (there could be others):
http://www.sefsd.org/index.php/ct-menu-item-95/ct-menu-item-107/971-disposal-of-lipo-batteries
http://www.simivalleyflyers.com/Disposal%20of%20LiPo%20Batteries.pdf