Discharging LiPos To Non-Reactive Levels

[Greywolf74]

I like to discharge my lipos to levels where they are no longer reactive once they go bad so I know they are safe. Personally I shoot for a combined pack voltage of no more than .5v/c

For a long time I've used various methods to achieve this. Salt water bath, automotive bulbs, small DC fans, LEDs, etc but each one of those ways has draw backs. I have found the simplest/best solution by far and I dont know why I never did this sooner.... Wire wound aluminum resistors.

You can get them right off of Amazon and they are fairly inexpensive.
Resistor specs per cell:
1-2S = 8 ohm 100W resistor
3-4S = 2x 8 ohm 100W run in series
5-6S = 2x 15 ohm 100W run in series
7-8S = 2x 25 ohm 100W run in series
9-10S = 2x 30 ohm 100W run in series
11-12S = 2x 40 ohm 100W run in series

Attach the resistors and leave them plugged into the lipo for 3-5 days and it should be less than .5v/c. Let the pack rebound for a day without the resistor and then check voltages.

DISCLAIMER:
You do not have to mount the resistors to a heat sink and cool them with the specs I provided but they might get pretty dang hot. I would make sure they are laying on a non flammable surface and dont touch them for the first few hours of the discharge process. They shouldnt get crazy hot but they might get up to about 170-200F depending on voltage, ambient temps, etc. I haven't tested these exact specs so I'm not 100% sure what temps you'll see but I'm getting temps upwards of 200F but I'm only using 50W resistors currently. The 100W resistors will run cooler, just not sure how much cooler.

Also, I've only done this so far on up to 4S lipos so my specs while they should be accurate, they are theoretical. Those are the specs id use, just be careful and check temps. Also you can always user higher ohm ratings then what I listed. It will take longer to discharge but the resistors will run cooler too.

 

[CreepyQuarryCrawler]

That outdoor fire pit is beggin for some smoke!

I like the post. I remember Venom back in the day recommended the salt bath for one of their packs that went bad.

Recently I was introduced to the @Doom! method for discharging. It's entertaining!

 

[Greywolf74]

That outdoor fire pit is beggin for some smoke!

I like the post. I remember Venom back in the day recommended the salt bath for one of their packs that went bad.

Recently I was introduced to the @Doom! method for discharging. It's entertaining!

All the lipos outside the ammo box are already under .5v/c so they're safe. The risk of fire is pretty small anyway though because the discharge is fairly slow over the course of many hours. Still possible but i have yet to have it ever happen from discharging slowly.

@doom is a pyro, we keep a close eye on that guy

 

[RustyUs]

If a charger has the capability, they make good use of the external discharging feature as well.
I'm glad you put that disclaimer in there.

 

[9x19]

Good tip.

I've been using 5W ceramic resistors since the old days (before Lipos)

 

[CertifiedMike]

Good tip.

I've been using 5W ceramic resistors since the old days (before Lipos)

And now, after all these years, you know how to use them correctly!!!

Earings!!!