johnpcunningham

So you left your battery on your RX and forgot about it. You spent $55 to $90 on that expensive lipo and now it is dead. What do you do? This is what I did.


The quick method (11.1 V Thunderpower Lipo)
I took the battery and charged it for a few minutes using the NiMh charge setting - I set it for 8 cells set at 0.5 amp current charge rate. If you try to charge fully with the NiMH setting, what you will find is the overall voltage of the pack is about right, but one cell is something like 4.5 volts and another one is 3.9 volts, giving the average to be about 4.2 volts per cell for the pack, but grossly out of balance. When you try to balance, the balancer will give you an error message saying one cell is overcharged. Unfortunatley, discharging the pack means all of the cells discharge at the same rate so it always stays out of balance.

The cells voltage stabilize fairly fast using the NIMH setting so keep an eye on the overall voltage of the battery. The cells will be fairly close but may be off more than 0.2 volts. Once you get the charge up enough, charge at the normal LIPO rate and use your balancer to balance the cells. If your balance balks at you because the cells are too far off, then charge each cell one at a time through the balance plug. Stick some small jumper wires in the balance plug and charge each cell individually to 4 volts. Then, charge as normal with a balancer. Set your charger for a single cell and move down the balance plug. Typically, the balance plug has a black wire and then each other wire is coneected to the (+) of the next cell. Start on the black wire and the wire next to it to charge. Once at 4 volts, simply move the two jumper wires over - this allows you to charge only one cell at a time.


The best method
Purchase the Hextronik Balancer/charger from unitedhobbies for $27.68

It charges up to 4 lipo cells and can do two 7.4v lipos at the same time. If you have Thunderpower batteries, get the adapter cable from www.maxamps.com for TP to Align (3S)

http://www.maxamps.com/categories.php?cat=173

The nice thing about the above listed charger is that it is cheap <$28 and charges and balances at the same time through the balance adapter. It charges each cell one at a time whereas a typical balancer only discharges the highest charged cells until they are all at the same voltage and within about 3.6 to 4.2. This charge can take a completely dead Lipo and alternates charging each cell until they are fully charged.

Safety
As usual, be very careful. Don't EVER leave the LIPO batteries unattended and monitor the voltages closely. Stop everything if the LIPO starts to puff up or gets very warm. I assure you, if you leave a LIPO on a NiMh or NiCd charger rate for too long, it will puff up and probably explode. You only want to charge it up to get the voltage up and then move over to a LIPO charger. A Lipo-Sac is of great value in case of fire or explosion.

JC

J-MICHAEL

Whew...Isn't that a relief saving our precious lipo's...Lol.. My dad did a similiar thing as you on a Bantam BC-8 charger. Trickled it on Nimh mode for his Trex 600 Air-Thunder batt...This was advised by the Reps at Air-Thunder on how to do this, and worked excellent ! I guess if there's a will, there's a way.... But caution should always be present when dealing with the lipo's....I agree....

~ Jeff

rocket_jim

Several points from my reading and my personal experience several times with mixed results:

Expect mixed results from flattened LiPos. Different brands and different cells in a pack can act differently.

Take the recommended safety precautions now and forever on any pack that got flattened.

Use a very low charge current when trying to bring the cells back up from zeroishland.

Know that the slower the discharge occurred and the longer and lower the pack was discharged, the higher the possibility of irreversable cell damage.

Watch the cell voltages during and after charging. Sometimes one cell (or all of them!) will appear to come back up to voltage, but it will immediately head back towards zero when charging is stopped. If so, that particular cell (or pack!) is probably toast! Don't ever try to charge at a high rate to burn thru the short like we used to do with Nicads!

Consider using the pack at much lower C discharge and/or for non-flight purposes. I use several to run my string trimmer now.

Jim

J-MICHAEL

Jim ~

I definately agree there..... My dad being somewhat new, was just going to let it trickle on that low rate in his office while he went and did some other things ! I said NO YOUR NOT...! I showed him some You-Tube videos of there destructive behavior, and that immediately grabbed his attention. It was only done as a desperate measure for his 6-cell lipo, as they are spendy suckers, but so is your house/property and personal safety among that...............


~ Jeff

Cashpoboy

My Feedback: (7)

I am in the process of recovering one right this minute. It is a brand spanking new 3S 2100 20C battery that I have not even had a chance to fly with yet.javascript:void(AddText('','')) I left it connected to the ESC and forgot about it all day. I found it this evening to my horror that one of the cells had died.

So far so good. It appears to be coming back to life just like John's initial post says.

I will post the results after I use it a few times to see. Hope it lasts.

Cashpoboy

My Feedback: (7)

It Works!
After several runs it appears to have come back from the dead.
I will be using this restoration process in the future.

WhoDaMan

My Feedback: (164)

so it does work

LuckyArmpit

Doing one now myself.
Got a 25C 2200 3 cell pak from hobbypartz. It is the blue lipo brand. And like a dummy, I checked the voltage before I put it on a charger. It read 8.32 volts.
Hmmm....instead of sending it back, I decided to try and re-vive the pack and put it on slow charge (about 400 miliamps) for 15 minutes. Pack reads 11.8 volts.
Connected it to my equinox balancer and tried to do a normal charge. The Triton charger will error out in about 2 minutes (it thinks the battery got disconnected).
So, will try and charge this pak on my poly charger with a "blinky" balancer. Just gonna do a 1/2C charge rate or 1 amp/hour.
I know this sorta works with old nimh's that have been sitting a while, slow charge them and they are fine. This will be the first for lipoly tho.

Lucky...

cjg

I tried this with a Lipo that I left plugged into the charger after I inadvertently turned the power strip off. I didn't find it for several days.

The charger of course completely discharged the cells. One cell never recovered, even though it appeared to charger properly on a charger through an equinox balancer.

I tried to take it apart to make the 3s ad 2s, but gave up when I realized it was getting dicey to try to carve the thing apart.

Results on LIPO recovery do vary.

eddieC

My Feedback: (2)

You toss it and chalk it up to experience. Be more careful next time.

Will they cover your loss and possible hospital bills if the Lipo goes up in flames? Is this something viewable on their website or via e-mail? I hope so, their insurer will have a field day.

I can't believe people are so desperate and/or cheap that they would not only try this, but post it so others get the idea it's OK!

You are, of course, within your right to try anything you like, but to post it here for others to see is needlessly endangering them. Lipos have enough of a bad history while being handled normally, to encourage folks to 'recover' them is foolish and risky in the extreme. I couldn't believe this post when I first saw it, I thought someone was testing the RCU viewers.

I'd like to see what the battery mfgr's would say to this. I can tell you now, NONE of them would endorse it!

I see lots of guys in our club buying the low-cost lipos, the few that are DOA get pitched and they feel they're still money ahead.

johnpcunningham

eddieC,

If you look at the bottom of my post, you will see a big block that says SAFETY. Please go back and read it.

Since it seems you may not fully understand battery technologies I will try to explain it. NiCD, NiMH, PB, Lipo all charge by putting more charged electrons into the battery. You run the battery in your plane and deplete these charged electrons and then you charge again. The main difference in the charging of the batteries is the charging profile and the voltage. Lipo is 3.7 V per cell, NiCd and Nimh is generally ~1.2V, PB is ~1.5v per cell.

Many of the lipo chargers look to see if the lipo is within a range of voltages before it will begins the charging process. Those that charge with the balance plug look at all of the cells and they should all be within a range of voltages, somewhere around 2.7 to 4.2 volts. If the voltages are outside this range, the charger will not charge. This is a software programming of the charger, not of the battery itself. So, if your battery is out of this range and not damaged or too old, it is quite possible to bring the battery voltage up enough where you can charge it normally with a Lipo charger.

I respect that everyone on the forum can have an opinion and yours is against this. But I am sure if you asked a battery MFG if this is an acceptable procedure, I'm sure they would say no. Why not, just buy another battery - sounds like good marketing to me.


Also, your quote:

I can't believe people are so desperate and/or cheap that they would not only try this, but post it so others get the idea it's OK!

Unless something has changed, RC flying is filled with patched planes, invented contraptions, and other crazy ideas that come from enthusiasm. If I tossed out a plane every time it got dinged or damaged because I was "too cheap" to just by a new one does not make sense to me. And neither does not trying to "safely" recover a battery.

My 2 cents,

JC

eddieC

My Feedback: (2)

JC,

I read your entire post before responding. Don't confuse posting a safety disclaimer with defusing an inherently unsafe practice.

Too funny! Save the condescension. I'm what's called an early adopter. We were buying and playing with nicads from the electronics supply store in the late '60's. I'm well aware of charging protocols - lead/acid. nicad, nimh, lipo, life, rcg, etc.

The fact you were charging lipos using a nimh/nicad setting indicates (1) you were using the charger in a way it wasn't designed for, and (2) you were charging using the output side of the pack, and hopefully monitoring voltage using the balance port (which sadly puts you in close proximity to any thermal event even if using a lipo-sack or other shield). Monitoring voltage via the charger is not very accurate, as most chargers display inaccurately. I've checked enough, most are off by at least .5v on displayed voltage during charging of nicad/nimh. (BTW, nicd and nimh nominals are 1.25v, not 1.2v.) Using the nicad/nimh setting is a different charge protocol. Read the charger manual. If it's well-written (most hobby chargers aren't) it will explain why nicad/nimh is not compatible with lipo. It's not just blindly cramming in electrons.

Your procedures go well beyond seat-of-the-pants hobby innovation. Experimenting is fine, as is patching, making do, shortcuts, etc. But dangerous practices need to be addressed also. The risk/benefit ratio of your experiment is inverse and thus too dangerous. Your safety data lacked any directions for the charging environment and dealing with an accident. I hope you were outdoors during this experiment.

.
Marketing is probably last. How about, good, safe, repeatable practices? Liability?

Using that rationale, it's OK to glue broken prop blades together. I find nothing 'safe' in this experiment. Even test pilots have established means for finding limits. Your procedure is akin to trying to plug in an AC plug in a dark room - you may be successful, but there's a good chance you'll get a shock, too. If you can afford to be in the hobby, you can afford the occasinal $100 mistake. Your choice is to walk away, or take a chance on personal injury and property damage.

I haven't even touched on the lipo status after this abuse. One or more cells were below 2.5v, how far is anyone's guess, and so will not fully recover. This pack is now highly suspect for further use and should be closely monitored during each charge/discharge cycle. I don't keep track of individual packs, too many for that. If one is bad, I'll check/cycle/balance it. If it fails, it's gone
Lipos don't magically 'fix' themselves. Once run down completely, they decay quicker. This is why using 3v for a cutoff (under load, not free voltage) is a more conservative practice. When lipos first came out, we were told 2.5v was the limit. Went through many packs as a result.

I don't need to touch the stove to know I'll get burned, and use the same reasoning for lipo safety. I know they are the most volatile chemistry we use, I don't need to experiment and risk my welfare and property.

BTW, I always remove lipos after use, not just turn a switch off. That way, they won't damage anything else if there's an 'event'.

billhass

My Feedback: (1)

I disagree with eddiec. If you do this while montering the voltage closely thru the balance plug you will be doing it safely.

I have done this several times to 2 cell 7.4 volt lipo packs with very good results.

You have to use a balancer once you get the voltage up to 6 to 6.5 volts.

I have tested them after charging by discharging, and have them last for over 2 hours.

Sinai

Thanks this thread's first post was helpful. Of course the safety reminder in itwas clear too.

Teenage Pilot 14

Hmmm.... Since when?

Sorry, but this has to be one of the dumbest statements I've seen ANYWHERE in a LONG time.

I can build an entire plane, from the ground up, starting from absolutely nothing, for less than $100. Ain't gonna be fancy but it's gonna fly as well as anything out there, I can tell you.

Don't bother replying/arguing; I very rarely come around this site anymore.

eddieC

My Feedback: (2)

I'll bet. The discussion wasn't about building a cheap airplane. Do try to keep up. The point I'm making is you shouldn't risk more than you can afford to lose in this hobby. 'Recovering' a dead Lipo is potentially dangerous, and you'll still have a battery that's iffy at best. Same with old Nicads. If they get to be 5-6 years old, I pitch 'em. Not a question of if, but when.
Same with the cost of a plane or heli. I don't put anything in the air that I can't afford to lose. Saw one club member total 3 IMAC planes in a month. He hasn't been flying since.

Darn! Probably 'cruising' Justin Bieber fansites. Good riddance.

johnpcunningham

eddieC,

I can validate some of your points. I don't think I would want a 12 year old kid trying this blindly in the garage with no supervision. That certainly could be a recipe for disaster. On the other hand, I have a Masters in Electrical Engineering and have a deep understanding of the battery technologies. I have all of the electronics equipment (Fluke, Agilent, HP, etc) that I use to monitor voltages and current rates.


Anyway, thanks for the input and keeping the forum active.

JC

Teenage Pilot 14

I'm keeping up just fine, and it would have made a substantial bit more sense to just say what you meant rather than trying to put a number value on it. That's the part that you screwed up on.

For the record, if I have a lipo that's dead I'm not gonna screw around with it; I'm harvesting the connectors and getting rid of it. I have done it in the past but the lipos never perform as well as they used to, and to me it's just not worth it.

As for why I'm not here very much, that's a matter of incompetent, arrogant moderators of the past. "Don't let the RCU mods get any little extra bit of freedom or they'll go crazy and wreck stuff" was a common phrase awhile back. I like how you tried to insult me; it was very mature and had me in tears for a good couple of hours

lorih

I have recovered lipos using this method.

It CAN work.

If you don't like the method or are afraid it can cause a problem...DO NOT DO IT.

Now, wasn't that simple?

Cliff

robertwilkerson

This Hobby is all about experimenting we would never have used nitro if all the safety warning wana be out there had there way omg the stuff burns blue and you are compressing it that will create and explosion. Ya lipo's burn they are so dangerous that we put them next to our head daily (cell phones) set them on our laps (lap tops). And for all you that have that much money that can trow it away $$$ you need to lose your job! If some one has a trick, tip it should we welcomed and not badgered Glue a prop? JB Weld how crazy is that!! Come down from your ivory tower you will get a nose bleed or worse a sun burn.

johnpcunningham

UPDATE.

Been a while since I touched this thread but wanted to revisit some points (besides being CAREFUL and using SAFETY)

1) I would NOT suggest trying this on a battery that has had some good use and is showing a dead cell. The cell is probably gone. In a typical 3 cell Lipo, you can actually see over 11 volts when one cell is dead. This happens when you do not use a balancer and do a normal charge. Since the charge current goes through all 3 cells, the dead one provides nothing and the other 2 charge up to > 5.5 volts.
2) I WOULD recommend this for the Homer Simpson "DOH!" moments when you leave a good battery plugged in an RX or something and you get a slow discharge until the battery is too low or seems dead. This is where I have always succeeded. A fully charged Lipo is around 4.20 volts per cell. The typical minimum for a Lipo is 3.20 per cell for LIPO chargers to work, but may vary slightly from different mfgs. When trying this, try to get each cell above 3.6 volts and then move to the LIP mode of charging.

3) To measure voltage on each cell, use a volt meter and check them at the balance plug. Starting at the BLACK wire, measure between the black wire and the wire right next to it. That is cell 1. Now shift over 1 wire and measure those two. Remember the positive of the previous cell is the negative of the next cell, like in flashlights.

JC

nonstoprc

My Feedback: (90)

In my opinion, lipos are much more dangous than nicad or nimh types. Any lipo cell can catch fire or explode when charged above 4.2v. This has to be in your mind when charge a lipo pack with whatever charger.

The best way to avoid revive a lipo pack is to disconnect it at the end of the day and store it in a safe box. I would not leave a lipo pack on the model.