Can I recover drained lipo?

[kudos]

Somehow I managed to not only leave my lipo battery connected on my bike for a few days, something I never do, but also left the controller on, a double stupid mistake.

So anyway my 20s lipo battery made up of two 10s nano-techs register less than a volt per cell.

My cellog won't even power up.

I had to use a multimeter to measure the cells.

My Icharger won't charge them, just says balance voltage low.

Is it worth trying to rescue these? If so how?

Kudos

 

[Drunkskunk]

I did this a few weeks ago. ruined 1337 watts worth of battery too. I feel your pain!

If you have a fire proof area, it might be worth trying to bring the cells back. But in my experiance, not all the cells would come back. I managed to get 8 packs to charge, although balancing them is a real problem now. And the 20C batteries now heat up and experiance voltage sag so bad I can't pull more than 4c from them.

 

[neptronix]

Less than a volt per cell? hate to be the bearer of bad news, but that's basically a firebomb waiting to happen if you recharge it. It has changed inside, chemically.

The lowest voltage you can salvage is about 2.5-2.7 and the only way you can do it safely is to charge it at the lowest rate possible - like 0.1-0.01 amps.

 

[dnmun]

what are the individual voltages? measure before charging so you have some idea of which went below 2.5V. can you use the bulk charge setting for lifepo4 or nicad? then put a resistor in series with the top of the pack to keep the charging current low.

 

[neptronix]

If your goal is to produce an amazing amount of fire and smoke by recharging the most dangerous chemistry possible and completely ignoring what i'm talking about, nicad charge form mode will work.

Just do it outside, so that the death metal pyrotechnics show does not occur near anything flammable.

Do not expect anything other than puffing timebomb cells at best, and scaring the frock out of your neighbors and maybe getting a visit from the fire department at worst :lol:

 

[dnmun]

but measure first so we can tell if the ones that don't discharge below 2.5V have different behavior than the ones that discharge to low voltage. some may be zero if you were using average voltage from the pack voltage measurement.

 

[Matt Gruber]

this is why i like makita konions, i brought back 11 from spending months at 0 volts and they work fine and have good capacity. slightly more than half came back, the others RIP (no fires),
.
Put a LED that you can't miss so this will never happen again!
on a scoot that lacks a led, i blip the throttle now and then when it is parked. sure enough i've found it left on! And this habit has saved the battery, it is now 10 years old! a record for me.
.
now i click on my stopwatch anytime i'm riding, charging, or cooking something and leave the kitchen. yesterday i looked at my watch, it said 3:22 at 2pm. That reminded me that my ebike was on charge and was about done. Can't forget for too long as i'm in the habit of looking at my watch. When i shut the bike, charger, or burner off, i reset my watch to normal time.

 

[kudos]

FYI

I was measuring the cell voltages using a multimeter by using the point on the small tabs on the balance leads which may have been giving me a slightly poor reading.

When I hooked up my iCharger the voltage for the 10S was around 12.5V so approx 1.25V per cell average.

Before reading all your replies I just told my charger I had a 4S battery, turned current down to 0.1A and started charging.
As the voltage increased I stopped and changed the cell count up to 5 and so on.

The voltages got back up to around 3.2V per cell when I read some of these posts and stopped.

I'm still tempted to charge it up to storage voltage 3.7V and leave it for a while and see how it behaves.

One of the cells out of the ten is lower than the others. I've ordered a Battery Medic to do a balance because my icharger won't balance charge when it's that far out.

I am keeping the battery in the garden away from anything flammable just in case.

Kudos

 

[izeman]

... I'm still tempted to charge it up to storage voltage 3.7V and leave it for a while and see how it behaves...

sure you can. why not. as you said, you're taking precautions while charging. so you're fine in case anything happens.
charge is to 4.20v and let it sit. a poor cell will go down faster then the others.
then do a high amp discharge watching the cell's voltages to calculate internal resistance. after that you have a good guess about the battery. of course it will never be "safe" - as safe as rc lipo can be anyway.

 

[dogman dan]

You might be able to bring them back. But, they will be potentially ready to fireball after that, especially during charging.

So keep them with your other extremely hazardous materials from now on. Outside charging ONLY!!!

Use them only till your new battery arrives. Then chuck em. DONT even think of selling them used on this website.

 

[kudos]

I would never do that dogman!

So, the next question is, how do you dispose of lipo?

 

[dnmun]

so you have no way to know which cells were below 2.5V?

the risk of ignition is really only when you have them fully charged and pushing current into them.

you may wanna charge them and then do a discharge into a load and see how much the internal resistance has changed for each cell in the series and see if some stand out from the others.

 

[izeman]

...So, the next question is, how do you dispose of lipo?

discharge as far as your rc charger allows. then let sit for some more days. should be 0 volts by then. a battery with 0 volts contains no energy and imho is safe to dump into the recycle center near you.
i tried all imaginable (perforating, hammering, cutting ...) of a zero volt cell. nothing happened.

 

[Ykick]

To dispose my RC Lipo - once they're completely discharged I usually solder a jumper between +/- leads in order to insure no voltage can creep back up once they leave my care. Then to the trash or battery recycler.

 

[dnmun]

it would be more useful to actually do more testing to see what can be learned, rather than just throwing them away. just don't try bulk charging with high currents to full charge without babysitting them.

is there some way you can monitor the current flowing into each cell when charging? does your balance charger tell you that? maybe build an experimental JST plug jumper that you could insert your ammeter into the individual channels to measure the charging current and then see if there is a difference in charging currents for the cell that were the most deeply discharged versus those that only dropped to above 2.5V.

self discharge rates would be useful too. that would require a single cell charger and ability to measure the current pushed back into the cell for each channel. you could do that with the test rig built up wit the JST plugs.

 

[cal3thousand]

If you have an iCharger, does that model read cell IRs?

I would take a look and make sure none are out of whack. If they didn't build some huge IR differences, you might be able to get away with what you did.

I'm under the impression (just a hypothesis) that slow drain down like this doesn't cause the same damage as if you rode the battery pack down this low.

 

[kudos]

Yes it will read cell internal resistance, never done it before so good time to try.

Once the cells got up to 3.5v per cell, turns out the iCharger was happy to start balance charging as well. Haven't done so yet though.

Kudos

 

[dnmun]

you should go read the manual and find a big resistor to use to discharge the pack into. if you use the little internal resistor they provide you risk burning up the connection inside that ties the pack to the charger when the internal resistor gets too hot.

if you do use the internal resistor then keep the time of discharge short to keep the heat down.

 

[e-beach]

You can also go the slow and methodical way....separate all the cells, mark them each with their own individual number. One at a time, charge each to full capacity on your icharger, and then discharge at a low amps to 3v or so. If the battery seems ok, no heat or puffing then recharge to 4.2 (if possible) and discharge at a higher amperage.

Keep track of your numbers, write them down and post them here for fun.....

As dogman said, baby sit them during the process and do them out side in a terracotta flower pot or something fireproof.

After this process you will have a good idea of what each cell can handle.

 

[gwhy!1]

one thing that I have always wondered is do lipo get warm/hot as they expand just before they blow up ? .. or do they just start expanding without rising temps, I know undamaged cells have very little ( if any )temp rise when charging. Im thinking along the lines of how I used to fast charge nicads,, (many years ago) and used to terminate the charge cycle when a certain temp was reached.. i guess lipo do/can get warm because all my lipo chargers has a temp sensor input that can be connected to the battery.

 

[izeman]

Yes it will read cell internal resistance, never done it before so good time to try.

to my findings icharger IR measuring is FAR from perfect. but i guess it's still good enough to tell good cells from bad ones. you may measure a new cell first to see what readings to expect.

 

[izeman]

one thing that I have always wondered is do lipo get warm/hot as they expand just before they blow up ? .. or do they just start expanding without rising temps, I know undamaged cells have very little ( if any )temp rise when charging. Im thinking along the lines of how I used to fast charge nicads,, (many years ago) and used to terminate the charge cycle when a certain temp was reached.. i guess lipo do/can get warm because all my lipo chargers has a temp sensor input that can be connected to the battery.

yes. bad lipo get's very hot and soft. during charge and during discharge. bad lipo has a higher internal resistance. this causes the cell to become hot when you put some current into it. and heat is strictly to avoid as this (and other chemical processes) causes (the name says it all) thermal runaway.

 

[dnmun]

this experiment is not to determine good ones and bad ones. all of these that were discharged below 2.5V are damaged. it is not clear how much damage has been done.

but if there is some measurable variable that could be used by others to evaluate the condition of the pouches they have in similar situations it would be useful knowledge.

all of these need to be monitored imo and if there is no BMS to prevent overcharging then they should always be charged on the balancing charger.

 

[gwhy!1]

one thing that I have always wondered is do lipo get warm/hot as they expand just before they blow up ? .. or do they just start expanding without rising temps, I know undamaged cells have very little ( if any )temp rise when charging. Im thinking along the lines of how I used to fast charge nicads,, (many years ago) and used to terminate the charge cycle when a certain temp was reached.. i guess lipo do/can get warm because all my lipo chargers has a temp sensor input that can be connected to the battery.

yes. bad lipo get's very hot and soft. during charge and during discharge. bad lipo has a higher internal resistance. this causes the cell to become hot when you put some current into it. and heat is strictly to avoid as this (and other chemical processes) causes (the name says it all) thermal runaway.

so can a lipo be charged without fear of popping if the current is kept low enough not to get the lipo warm even if its damaged.. basically is it just the thermal runaway that causes the pressure to build up or is there something else going on as well .

 

[e-beach]

Since there is no posted standard of what used what lipo is supposed to do, the only thing I can think of is to go with new standards. Can the cells still charge to full capacity? Can they discharge at high "C's"?

Also, someones personal charger may not be calibrated perfectly, so equipment may be dissimilar to manufactures standards. So some sku to the numbers is to be expected within reason.

I think the individual charge and discharge test is the only way to know characteristics of each cell as they stand today, to see how "great of little the damage."