Can I recover this Lipo?

[Chuck Plains]

Me.

I forgot to set the ESC to switch to reduced power to indicate low voltage. So 3 cell Lipo went to around 1% as the slow stick ditched, but still seemed to be showing around 3.5 volts per cell, when I could check it several hours later. (yes, I also forgot to take the checker.)

My Turnigy Accucell 6 charger has not been able to balance charge it back up further than 60% charge and keeps saying full. But the cell voltages keep jumping around after that, even if I try to storage charge it from there. It is balanced though, as my Power Analyzer confirms.

Is there a method I might use to get this pack into some reasonable sort of shape? It's not puffed and was completely cold after being dumped, as was the ESC.

[Denis Watkins]

Unlike other cell chemistry's, lipos complex full discharge chemistry is irreversible in most cases, and every hour it spends in a no charge state accelerates the less useful chemistry in the cells, sorry

[Chuck Plains]

Yes, thanx Denis, you've confirmed what was lucking in the back of my mind. I'm not minded to try and strip the pack to make a 2 cell. I can't be bothered with that malarkey. I'm disappointed, as my packs haven't had a had life and have been resting for nearly 18 months. I shall discharge it tonight and park it in some salt water for a day or two. Though I don't have that much salt on hand today, so it can live in the charging sack till then.

[Peter Beeney]

We have managed to revive some packs that have been left flat for quite a long period, such as a colleague that lost his model in a treetop in the middle of a large wood for six months. We had to wait for the leaves to fall to find it. Zero volts on test, quite understandably, but it charged up ok and he continued to use it. I’ve sorted a number of packs, including brand new ones that occasionally can be very reluctant; but the older ones certainly don’t always oblige; probably more failures than not, as it happens; it’s just pot luck; but always worth trying, there’s nothing to lose. And I have to admit I do have a very old but still serviceable variable bench supply which makes it all very easy to do. I do appreciate that few modellers will have one of these.

I’d tinker with that for a while, try a bit of a discharge and re-charge. Two or three cycles might improve it. Also, if you have to bin it is it such a good idea to put it in salty water first? I take all old cells and packs to our local Civic Amenities Site, where they have a couple of heavy duty plastic tubs for small cells. A modern battery recycling plant will be more than capable of handling anything that’s thrown at it. If lithium cells do contaminate liquids that salty water has to be poured away somewhere, probably a drain, and you may just be passing it on. See the past record of Nicads to see where this goes…….

Just simply an observation, Chuck, not meant as any form of criticism or even advice really… It’s just the way I do it….

PB

[ken anderson.]

m y experience with a 1300 m/a/3s lipo that i ran totally flat...i charged it up and according to the charger it put 1301 m/a back in...and it still working / charging ok today...

ken anderson...ne....1......save the lipo dept.

[gangster]

I am in total agreement with Peter firstly that I would not be ready to give up yet without a few more charge discharge cycles. And secondly the salt water idea has been discredited for a couple of reasons. One as mentioned pollution and secondly it may not be effective. I have been pulled up on this very forum for suggesting the old salt water thing

if you really feel the need to discharge use a car bulb

[Cuban8]

[AJ]

There is an easier way to recover a lipo. Just parrallel up the dead battery with a second fully charged lipo through the balance connector and leave it somewhere safe for a day or so. This will equalize the voltage between the two batteries. Both will need a proper balance charge afterwards.

A.

[Simon Chaddock]

I have to agree there is a chemistry issue with a discharged Lithium cell. It not strictly the voltage it can be charged to (it will quickly get to 4.2V which the charger will detect as 'full' regardless of the charge that has been put in.

The real issue is the cells resting voltage after being charged. My own experience suggest a damaged cell will quickly drop to around 4V where as a new cell will only drop a few hundreths of a volt even after several weeks.

Then there is the issue of the cell internal resistance. This rises with use anyway and even more so if the cell is mistreated. This will reduce the voltage available at high discharge rates which in turn raises the amount of heat that is generated within the battery which makes it deteriorate faster!

If you can reduce the duty the battery has to perform (a plane that does not work the battery so hard) it can go on being used.

For example my oldest LiPo - a 5 year old 5000mAh 2s 15C - actually now only has about half its rated capacity and C rating but that did not prevent me from using it to fly for 70 minutes yesterday in my 'Endurance' plane but then it only needs 1A continuous from the battery to stay up!

[Peter Beeney]

Generally speaking I don’t have many problems hooking up cells together, either in series or parallel, or at any state of individual charge, but I might be a little itty bitty cagey about using just the balance leads as the only connecting link. It’s certainly true that there will be little or no current passing down the intermediate wires but it might be that the first outside positive and the last outside negative will carry all the current resulting from the voltage discrepancy between the two packs, which in theory could be up to 1.2 volts/cell. Unless the packs are really adrift, when it may be even higher. When I tried whacking 1 flat and 1 charged 3S together at sometime in the past it yielded an instantaneous inrush 18 amps, although this was only momentary.

And the balance leads are definitely not power wire sizes……

But I’ll agree about connecting them together as I’ve always liked the idea of parallel charging anyway. I have some 4 way parallel boards that piggy back with each other in series nicely, so providing all the packs are vaguely in the same ball park I just daisy chain them all together, switch on the charger and let them get on with it. Packs of any capacity flavour; but they all have to be the same number of cells; and as I don’t ever watch any batteries charging it’s never really a chore.

One thing I’ve done, and I’m sure with many others too, is to utilise the nickel charge regime to get started. If your charger is capable, select nimh auto charge, set to say a 200mA rate for a 2000mAh pack. In theory this would take 10 hours to complete, so I’m sure you could leave it for an hour or so. Hopefully this would raise the voltage enough for the lithium charge to take over and when this gets as far as it will parallel it with another pack. If after a couple of cycles of this it still won’t play the game properly then probably the only option is to banish it to the tip!

I never throw any batteries away, my own or other people’s, unless I’ve established beyond doubt they are not recoverable…

PB

[Kevin Wilson]

At risk of a 'me too' post.

I would certainly give it a few cycles and see what the capacity (out) is looking like.

You say you don't give your cells a hard life Chuck, so an increased internal resistance may not be that important to you.

I always consider the recovery up to a voltage that a LiPo charger will start a balance at (>3v) to be the most dangerous as that part is usualy done in NiCd or NiMh mode. After that I use my normal LiPo rules balance@1C in a fire resistant space.

Edited By Kevin Wilson on 21/04/2016 18:10:40

[Chuck Plains]

Thankx for all the input you guys.

I was that busy at work today that I forgot to

GOTO TESCO

IF SALT = 0 THEN ADD SALT

Yes, I used to be familiar with basic, but have forgotten most of it.

Sooo, the pack is now storage charging, in a safe sack, and the charger visible from where I'm sitting, with all three cells are behaving themselves and milling around the 3.8v mark.

All my battery charging etc is done via a 300w PSU from an old PC that I stripped 18 months ago.

Once it bleeps out, I'll balance it again and see if it gets any higher this time.

[Chuck Plains]

Now very close to full voltage on balance charge. If I recall correctly, the Accucell 6 is the type that uses charge and discharge to finally balance the cells. Is that right? It's probably going to take a while to complete it.

[eflightray]

It has not been mentioned in a thread title for a while, and maybe it isn't the problem it used to be, but is a 'puffed' Lipo still classified as similar to an 'unstable explosive device capable of flattening half a city' ?

The only time I generally stopped using them was when they no longer fitted in a narrow fuselage.

luckily, I don't seem to get them these days, perhaps the problem, (poor/cheap chemicals ?), has been reduced enough not to be mentioned.

Do people still have some modern cells suffering from 'gas' ?

Ray.

[Chuck Plains]

I have two 2200 3s packs that are mildly puffed. They still work ok.

[Chuck Plains]

So, after after balancing to 97%, the pack dropped to 45% and unbalanced overnight. I discharged it till it was around 8.6v, re-balanced it again, but the cell voltages appeared to jump about and the charger didn't like it. I then left it on storage charge and after more than an hour it bleeped out saying FULL. It appeared to be balanced so I left it overnight again and now it's sitting at 40% and balanced.

As I'm getting something ready for flying later today, I'm leaving this as is for now and will check it's condition each day, if I remember. If it goes unbalanced again I might mess with it again, but as I can't walk away from it it's becoming more of a nuisance than it's worth in some ways.

Edited By Chuck Plains on 23/04/2016 09:36:40

[stewart BAKER]

The idea of recovering a flat lipo sounds ok . BUT when the model goes in weeks/ months later is it worth the uncertenty of not knowng the reason for the crash..trannie ...reciever dodgy connections OR battery failure? makes me wonder how many beginners will try this then when the £10 battery fails and the model goes up in flames start a thread blaming Spektrum or jr ?