These are the steps I use to rapidly discharge my broken LiPOs and prepare them for safe disposal. If you are reading this bear in mind that discharging and charging lipos is always risky and require that these be done in a safe place, preferably outdoors with no combustible material nearby.
Lipos are not known to explode but they can generate a lot of heat, smoke and yes sometimes a bit of fire. So place the lipos in a non flammable material like a lipo sack, metal box or, in my case, on top of some ceramic or rock.
There are two common ways to skin this cat: a) Use a discharger exclusively or b) Use a discharger and some bulbs. If you want to use the discharger exclusively go to step 1 and jump to step 3. I like the combination since it allows me to discharge different sized batteries at the same time.
1) First bring down total battery voltage to 3v (or less) per cell using a discharger. This assumes you have a 12v halogen bulb which will be used to do most of the discharging. On the other hand, if you will be using a discharger exclusively set the discharge rate at 1C of your LiPO and discharge to the lowest voltage then jump to step 3.
2) Rapid Discharge with a target of 3-4V for the entire pack using halogen bulbs. I use Two (2) 12v 50watt halogen lamps in parallel as the primary and rapid discharger. The pair generates 8.3A of pull. Obviously for 5S and above the bulbs needs to be placed in series (with optional parallel) to accommodate the high voltage.
The 8.3A rate brings a 4S with 12v charge to 3-4v in about 30minutes. Once the bulbs show no light whatsoever, let it stay that way for at least 5 minutes before removing the pack. The halogen lamps are very hot so be careful.
Note that because of the high discharge rate and below minimum voltage this process induces on the lipos, they will almost always puff.
3) Drip Discharge on last Vs. After reaching use a charger to discharge at a lower amp. Set the charger to use NiCd (LiPo has a min termination voltage of 3V so it won’t do) and set to DISCHARGE at 1A without attaching the balancing cable. Set the target voltage to the minimum allowed by the charger, in the case of the Turnigy Reaktor its 0.10V. Discharge.
4) Set the second cycle using the charger to half an Amp (0.5A). This will be quick. And will bring the voltage to around 2V after a 3-5 minute pack rest.
5) 3rd cycle we use 0.2A discharge rate. This will take a few minutes and bring the voltage to about 1.5v. Once done make the pack rest for 3-5 minutes.
6) 4th onwards cycle set the discharger to 0.10A (the lowest setting) and discharge. This will take some time (8-10minutes) and is designed to really squeeze most of the remaining juice out of the pack. Let the pack rest for 5 minutes. After rest, it will bounce back to about 1.5v-2v. Do this same same (step #6) 3 to 5 more times making sure to make the pack rest for 5 minutes per discharge. Each cycle will be quicker than the previous one as the chemicals in the pack loses its capacity to regenerate charge.
7) Repeat until 1.5V is reached. After at least 3 cycles of step #6 the packs will have a voltage of about 1.5v. Wait for 15minutes and verify that the voltage is steady at 1.5v. If the pack goes beyond this after this longer rest period, discharge it using step #6 a couple of times.
8) Cut off charging lead. At 1.5v the battery is basically dead but still has residual charge. You can reuse the red and black charging wires and plugs by cutting off the wires leaving just enough to short the battery. In my case I also cut off the balancer wire. After cutting the charging wires, use a pair of long nose pliers to expose a bit of both wires and twist them together to short the battery.
9) Safe store for a day. Tape the exposed lead and balancer wires and place in a secure place with no flammable material. It will take 2-12 hours for the residual charge to finally zero out depending on the battery’s capacity. In my experience a 3S 2200mah charge was completely depleted after 3 hours, a 4S 5000mah about 6 hours, leaving me with just inert material. This means I get to throw these tomorrow with the rest of the trash.