Do used Lifepo4 cells need breaking in after being dormant?

[John in CR]

I've seen a lot of mention of the need to break in new batteries before they reach full capacity, but what about used cells that have been on a shelf for up to a year?

I ask because I have several hundred used A123 M1's all charged up and balanced. My plan is to run them through a capacity test, so I can make equal capacity parallel groups to build strings that stay well balanced. Do I need to run them through a few cycles first, or since they are already broken in I can rely on the initial discharge after being dormant to be the true capacity?

 

[adrian_sm]

Unfortunately I think the answer is yes.

I got a heap of headway cells from abused packs. Charged them up and did capacity, self discharge, and internal resistance tests. But when I repeated them again, they seemed to improve. Cells I thought were stuffed, got better. So if you are really interested in balanced packs, you may have to cycle them a few times. But doing this on a cell by cell basis is a huge undertaking, even for 10ah cells, let alone smaller cells. If you have some way of temporarily building a pack that you can charge/discharge in bulk I would really recommend it.

In fact for the headways I ended up judging the cells quality purely on internal resistance. Basically if it was good from an internal resistance test, it was good on the capacity and self discharge. Luckily my cells are already in packs, so I can charge/discharge in bulk a couple of times, then do internal resistance test cell by cell. This was the best compromise for me.

Hope that helps.

- Adrian

 

[stanz]

yes +1

http://sodoityourself.com/reviving-laptop-batteries/

 

[dogman dan]

Makes dog sense to me, to wake em up from a long sleep the same way we advise to treat new cells. It may not be as much a break in even with new cells as a good thorough balancing repeated a couple times. Never a bad idea to look at how a pack behaves for at least a few cycles before letting er rip.

Nothing of mine has ever lain dormant long, so I really can't add anything from experience.

 

[SamTexas]

I'm confused. From what I read Lithium based batteries voltage are never supposed to go below 2.0 volt, or permanent capacity reduction would result. So after 12 dormant months, I would assume that their voltage are at 0 volt or close. Isn't that the whole idea behind LVC?

 

[stanz]

Sam,

We've been reviving laptop batteries in the PC field for years. I've been working with PCs since 1980 and we have always found ways to save a buck here or there. That's why I jumped on those old Thinkpad batteries.

Laptop batteries are shipped at about 40% charge, if they sit in a warehouse for more than a year they're dead before you get them installed. We ALWAYS charged them before giving them to a customer.

Until I get my watt meter from Hobby King I'm doing some rough tests on my packs, actually just the one I tore open. I charged it to 11.6 volts or so, let it sit for more than 24 hours and put a 1amp load on it. (100 watt 110V incandescent bulb is about 11 Ohms, 11V/11Ohms = 1amp.)

So far it's been running for 2.5 hours and it's still over 11V. That's less than 1/4C I know but I don't want to stress the pack on the first charge.

Once I get my watt meter I can do more accurate tests.

The point is, YES you can revive a lithium battery. The only sticky point is that every once in while a cell may develop copper shunts which will short out the cell so you MUST monitor the first charge.

 

[John in CR]

I'm confused. From what I read Lithium based batteries voltage are never supposed to go below 2.0 volt, or permanent capacity reduction would result. So after 12 dormant months, I would assume that their voltage are at 0 volt or close. Isn't that the whole idea behind LVC?

I have LiFePo4 and LiMN cells that have been on the shelf for almost 3 years and they are still at a safe voltage. Self discharge is very very low, and I don't think it occurs in a straight line. I always think of voltage as pressure, so as the voltage goes lower the pressure to leak is less.

The thing to be careful about with storage is having anything connected to the pack that draws a parasitic current and drains and kills a parallel group of cells by bringing it down to too low a voltage.

Regarding LVC, some of the very low voltage cells on a shelf can be brought back to life. The real damage occurs when you draw current through cells that are at low voltage. It causes more chemical breakdown that permanently changes the cells.

 

[scriewy]

SamTexas nop, these cells can hold a charge a few years, only if some electrical circuit is connected to the cells that drains them even the smallest current they will continue to drain faster than if were alone, and if not caught in time will die.

stanz

Laptop batteries are shipped at about 40% charge, if they sit in a warehouse for more than a year they're dead before you get them installed. We ALWAYS charged them before giving them to a customer.

are you saying you revived those dead cells, or you saying if they're dead then they're dead ?

 

[SamTexas]

Stan,

I will be watching your battery built thread closely. I hope you're correct. I still have a bunch of 2.5AH Lithium cells that have voltage of 2.0 or below. I was going to discard them. I'm holding onto them now, pending the result of your battery built.

My question remains the same though: There must be a real/valid reason why manufacturers STRESS that voltage should never go below 2.0 and that batteries must be stored PARTIALLY CHARGED. ZERO Volt is definitely not partially charged.

 

[SamTexas]

SamTexas nop, these cells can hold a charge a few years, only if some electrical circuit is connected to the cells that drains them even the smallest current they will continue to drain faster than if were alone, and if not caught in time will die.

That's my understanding. But Stan thinks otherwise (if I'm not misunderstanding), thus my confusion.

 

[Ypedal]

You can take nicad and nimh cells to 0v , but do not do this with Lithium cells.

I've revived Lifepo4 cells ( PSI 10ah cells ) from 0v to full capacity, but it's not a good thing to do.

Regarding dormant cells, good cells like M1's and such i think should be cycled at least twice to weed out any runts but generally will not need much breaking in.... either they are good or they are not.

 

[SamTexas]

I've revived Lifepo4 cells ( PSI 10ah cells ) from 0v to full capacity, but it's not a good thing to do.

To full capacity? That sounds like a good thing to do to me. So (again) why do manufacturers (and we assume they know theirs stuff) tell us to keep the voltage above certain level.

 

[stanz]

SamTexas nop, these cells can hold a charge a few years, only if some electrical circuit is connected to the cells that drains them even the smallest current they will continue to drain faster than if were alone, and if not caught in time will die.

That's my understanding. But Stan thinks otherwise (if I'm not misunderstanding), thus my confusion.

I have read and experienced that laptop batteries die due to the attached BMS circuitry.

The batteries I have showed zero volts at the output terminals before I charged them. My 100 watt bulb still has a dim glow in it from the current passing through it. Obviously if it were more than 10V the glow would be brighter but the cells appear to be ok.

Like I said it's a crude test since I only have a multimeter right now but so far so good.

 

[liveforphysics]

I was given a 14p12s pack of A123 M1 cells sitting at 1-1.5v/cell.

First charge it only took 4Ah (out of a pack that should be ~32Ah when healthy)to bring it to 3.65v...

It dropped down to the 3.3v plateau on it's own sitting (which I think was the potential in the current collector opening up new active areas for intercalation. It only discharged about 2Ah (which is a good sign, as charge energy was performing work on the cells internally).


Next charge it took around 10Ah to get up to 3.65v, and discharged around 8Ah.

After around 10cycles of nursing the pack, it does around 25Ah now, doesn't self-discharge, and the impedance dropped to something usable for high current discharge again.

 

[stanz]

OK, obviously a 100 watt 110V bulb doesn't draw one amp at 11V since my test has run for four hours and I still have power. The battery pack is only rated for 3.8ahr.

Until I get better instrumentation I'm stuck with rough tools that I have laying around.

 

[John in CR]

OK, obviously a 100 watt 110V bulb doesn't draw one amp at 11V since my test has run for four hours and I still have power. The battery pack is only rated for 3.8ahr.

Until I get better instrumentation I'm stuck with rough tools that I have laying around.

Just measure the current with your multimeter. DON'T FORGET TO SWITCH THE PROBE BACK IMMEDIATELY AFTERWARD. FWIW my dual parallel 100W bulbs only draw .5A on a 12V battery.

Regarding my OP, since it looks like I have to do some cycles, how many do you guys think is reasonable to "wake up" the idle packs, especially the healthiest cells? I have my iCharger 206B running a set through cycles right now, and evaluate how much capacity changes. I'll worry about rehabbing the weaker ones later, and skim 171 of the best cells off the top.

 

[SamTexas]

I have read and experienced that laptop batteries die due to the attached BMS circuitry.

But your recently acquired IBM packs have the BMS circuitry attached, don't they?

 

[stanz]

Just measure the current with your multimeter.

Regarding my OP, since it looks like I have to do some cycles, how many do you guys think is reasonable to "wake up" the idle packs, especially the healthiest cells? I have my iCharger 206B running a set through cycles right now, and evaluate how much capacity changes. I'll worry about rehabbing the weaker ones later, and skim 171 of the best cells off the top.

If my multimeter had an amp setting I would have used it.

I would say 10 cycles is a good place to start.

 

[stanz]

I have read and experienced that laptop batteries die due to the attached BMS circuitry.

But your recently acquired IBM packs have the BMS circuitry attached, don't they?

Yes, it's clearly shown in the picture.

 

[SamTexas]

I have read and experienced that laptop batteries die due to the attached BMS circuitry.

Yes, it's clearly shown in the picture.

Yes I know. I've seen the picture. Sounds like you are saying (or rather hoping) that your previous experience would not apply to this new case.

 

[stanz]

Yes I know. I've seen the picture. Sounds like you are saying (or rather hoping) that your previous experience would not apply to this new case.

? I don't understand. I said the batteries were dead, zero volts.

 

[John in CR]

10 cycles of 400+ cells is a mountain of work even bulk charge/discharging.

 

[SamTexas]

? I don't understand. I said the batteries were dead, zero volts.

Sorry. Let me try again:

In the past, you have experienced batteries getting killed because the attached BMS has drained the batteries to zero volt. Now you just acquired packs that were in the exact same condition: Zero volt because the BMS was attached, and the whole thing has been sitting untouched for year. Yet you are planning to revive them?

Or may be I'm not understanding you at all.

 

[stanz]

Or may be I'm not understanding you at all.

Yes, dead doesn't mean killed. I meant that the batteries had no charge, zero volts. That doesn't mean they can't be revived.

If revived, perhaps we can call the "undead"! Zombie packs

 

[SamTexas]

OK. Please keep me updated on your battery "undead" effort. I wish you success so I can "undead" a bunch of cells I have now.