Left my Lipo attached to the ESC. Any hope?

[markkat 87]

I have a relatively new 2S 5000mAh lipo and accidentally left it plugged to the ESC for a few days. I believe it fully discharged, and doesn’t seem to be taking a charge.

Is there any hope for it at all? I has no damage or swelling.

[Mad Ax 6702]

OK - there might be a way to recover it, but it is dangerous and done entirely at your own risk.  Considering an unrecovered battery is junk anyway, you need not worry about possibly destroying the battery during recovery - you need only worry about destroying your house through fire or your lungs through fume inhalation.  In other words, DO THIS AT YOUR OWN RISK AND OUTSIDE ON A FIREPROOF SURFACE, a place where you'd be happy for a burning LiPo to rest until it runs out of chemicals.  Keep the battery in a charging sack.  Wearing heat resistant gloves and a face shield would also be a good idea just in case.  Possibly connect your charger with an extension lead that is connected away from the fire zone so you can switch it off without having to get close to the fire, if necessary.

Check the battery for puffing.  If it's new, it shouldn't have any puffing at all yet.  If it's an old pack and started to expand a little, consider throwing it anyway as it may not survive much longer.

Set your charger to NiMH mode for a 6-cell NiMH pack.  Set it to a low current, around a 10th of the battery capacity (i.e. if the battery is a 5000mAh, set the charger to a 500mAh charge).

Connect the discharged LiPo to the charger.  Don't worry about the balance leads.

Start the charger.

Monitor the fire sack for heat and for any puffing in the cells.  If you hear the hardcase splitting or see the back shifting, stop the charger immediately and disconnect the battery.  Leave it for a while before checking if it has puffed.  If it has, it's junk.

Otherwise - monitor the battery voltage on the charger.  As soon as the battery voltage exceeds the low-voltage cut-off (6v), stop the charger.  This may only take a minute or two.  The battery should not stay on a NiMH charge any longer than absolutely necessary.

Disconnect the battery from the charger.  Check the leads and fire sack for heat.  If the battery is hot, don't open the sack.  This battery is now dead and dangerous.  Leave it until it cools down, then make it safe for disposal (plenty of threads about this online).

Open the fire sack and check the battery for puffing.  If it has puffed since starting the charge, it's dead and dangerous.  Get rid of it.

If the battery looks fine and isn't warm, connect a voltage monitor or connect it to the charger to inspect the cell voltage.  Ideally each cell will be at or above 3v.  If not, you may need to repeat the process.  If it looks like one cell isn't taking a charge, it's probably too late - continually pushing voltage into the battery will probably cause a fire, so get rid of it.

If each cell is at or above 3v, try a normal LiPo charge.  Monitor the cell voltages closely and make sure the battery stays in its charging sack.

Once complete, test-run the battery.  If it survives a charge it should be OK.  In theory it will have been weakened by its experience and won't have as long a life as it did before, but I've had the exact same thing happen to a nearly-new LiPo before.  It was one of a pair bought at the same time and used in the same car.  Both packs lasted many years giving the exact same performance, both showed signs of puffing as they aged.  One of them eventually broke its case and expanded to 3 times its size during charging, so both were retired at the same time.

[Wooders28 4273]

What voltage does the charger say, is  in each cell? 

[markkat 87]

All right. It sounds dangerous. I'll try it on the driveway!

Thanks, @Mad Ax!

@Wooders28 stand by. I need to dig out my reader.

 

[Howards 439]

9 minutes ago, markkat said:

I need to dig out my reader.

Wait - you mean you don't have a charger that reads the individual cell voltages via the balance lead? 

 

[KEV THE REV 2246]

it does sound un-nerving

 

[markkat 87]

25 minutes ago, Howards said:

Wait - you mean you don't have a charger that reads the individual cell voltages via the balance lead? 

 

No. This is the setup. I am flying blind... O_o

I do have an old meter though. I'll try it first.

[howaboutme 224]

9 minutes ago, markkat said:

No. This is the setup. I am flying blind... O_o

I do have an old meter though. I'll try it first.

I'm a fan of Spektrum. I use their radios for my helis (but not batts or chargers). They do a lot of good things to get people into the hobby and for this hobby to be less intimidating. However, I think they are doing no one any favors with their mini charger offering. If you've decided to take the plunge w/ lipos, do yourself a favor, get a real charger that provides all of the basic information (it's basically standard in a full sized charger) you need to stay safe and keep your batteries healthy while understanding the information behind it. At some point, being "smart" is too smart by giving someone a false sense of security or awareness.

[markkat 87]

Thanks everyone! It worked. I did about 3 min on mi NiMH charger, then switched to the lipo charger, and it recognized it.

No swelling, no heat. No explosions.

I’ll take it for a spin tomorrow.

[Wooders28 4273]

On 7/7/2020 at 4:47 AM, markkat said:

Thanks everyone! It worked. I did about 3 min on mi NiMH charger, then switched to the lipo charger, and it recognized it.

No swelling, no heat. No explosions.

I’ll take it for a spin tomorrow.

Keep an eye on the voltage of each cell, and maybe up the cut off value on the esc.

The Lipo I last had to do that on, one now discharges quicker than the other , maybe 0.5v of a difference, so @6v cut off, one would be 2.5v and the other 3.5v.

[NobbySideways 112]

Funnily enough I did exactly this technique myself to rescue an old LiPo. Worked like a charm, but as mentioned I did it somewhere it could burn without causing damage to anything and I did have a twitchy ring througout.

[KEV THE REV 2246]

14 hours ago, NobbySideways said:

I did have a twitchy ring

Always remove any jewellery before attempting anything like this