low voltage in harvested cells

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Oz18650

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Oct 2, 2017
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199
I am wondering about low voltage in harvested cells.


Some people seem to discard low voltage cells, while others seem to charge them up and use them.

I would like to discuss which is the way to go.

Zero voltage means that the cell has discharged, but is there any way of knowing if the low voltagewas because
a) the cell has been sitting for a very long time and discharged at a normal rate
Or
b) the cell has a problem which made it lose voltage

What do you do with low voltage cells and why?
 

Matthew Oliver

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Sep 20, 2017
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If you feel its safe, Try and charge them up while keeping a very close eye on them incase of overheating or leaking or worse. then if they manage to take charge safely let them stand for a week or so and see if they are self discharging.

Some may be saveable but there is only one way to find out
 

daromer

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Oct 8, 2016
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thats why we test every cell. We dont know about why it went down to 0 volt. Ie capacity + self discharge test will tell you alot. And of course internal resistance.

If they dont take charge, get hot or self discharge then bin the cell. Its not harder than that.
 

dougal

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Sep 13, 2017
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Oz18650 said:
...
Zero voltage means that the cell has discharged, but is there any way of knowing if the low voltagewas because
a) the cell has been sitting for a very long time and discharged at a normal rate
Or
b) the cell has a problem which made it lose voltage
...

Zero volts cells should immediately be checked for open circuit.

If there is no connection internally between + and - then it can be discarded without wasting any more of your time - it has been abused.
If it isn't open circuit, you could see if it can be recovered, if you so choose.
 

TheBatteries

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dougal said:
Oz18650 said:
...
Zero voltage means that the cell has discharged, but is there any way of knowing if the low voltagewas because
a) the cell has been sitting for a very long time and discharged at a normal rate
Or
b) the cell has a problem which made it lose voltage
...

Zero volts cells should immediately be checked for open circuit.

If there is no connection internally between + and - then it can be discarded without wasting any more of your time - it has been abused.
If it isn't open circuit, you could see if it can be recovered, if you so choose.

I wouldn't waste your time trying to recover 0v cells. There is a reason they're at 0v and honestly, it's not worth the risk. Just discard and move on to another pack.
 

owitte

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Oct 19, 2016
Messages
245
well, from my opinion, it all depends... on how much packs you can get and on how much time you want to spend for testing. I always check 0V cells, even though I have a continous supply (get a box with 50-70 batteries every week from a local electronic recycler). So, I'm not doing that because I'm short in cells, but because I want to keep using as much cells as I can.

Low voltage cells -if they're not tossed immediately- need to be tested thoroughly, because they went way under the voltage level they were made for. By the way, have you ever thought about which voltage/SOC a newly produced cells in the factory has? Will they be 'born' at 3.7V or at 0V...? However, if they not shorted, I think they deserve a test.

I always put them in my TP4056 bulk charger. If the TP4056 starts to charge them, I watch the charging process (temperature!) and check the cell voltage regularily. If it charges full, I then check if it holds the charge (constant voltage over a few days). If a low voltage cell passes this test, I consider it as good.
 

DarkRaven

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Sep 2, 2017
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I consider 0V cells to be dead. Everything above 0V is tested, everything at 0V is discarded.
However, if you are desperate and need every single cell, then even the 0V cells can be tested and then you can find out why they are at 0V. Some will work, some won't. You can't determine what it is without testing.
 

neilmc

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May 22, 2017
Messages
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I'm ok with using low volt cells if they they have usable capacity and behave normally.

When I started testing cells, I discarded a few that came out of the batteries under 1v. I regret that now, since I've had many low volt cells test over 2000mah without getting hot etc. While it's not ideal for a cell to get really low, they've probably not been repeatedly charged and discharged super low.

If I find a zero volt cell, I test resistance. If it's open circuit (probably popped CID) I bin it. If it's not open circuit, I still test it. I haven't tracked it accurately, but I think I have got a few decent working cells from 0v cells. The percentage of rubbish cells seems to be higher in 0v cells, but they're not all bad.

I charge low volt cells 8 at a time ona RC hobby charger set to 1A on the NiMh setting initially to bring them up to about 2.5v (usually takes about 5 minutes) and then switch them to lipo charge at 2a. (so a really gentle charge to bring them up) Then into the Lii-500 for capacity testing.

Almost all of my hot cells have performed normally after letting them sit for a while and retesting. I wasn't retesting these early on.

I pulled out a couple of Sanyo's from a box marked "dead" that had HOT written on the side of them. They were probably cells I discarded months ago. I retested them yesterday and they came up at 2100mah and stayed cool.

Does anyone know if Sony and Sanyo shared cell manufacturing? I'm not getting as many Sony cells as Sanyo, but a lot of the green Sony cells start out hot too and test ok after sitting for a while.
 

Oz18650

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Oct 2, 2017
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Just to clarify:
When talking about zero volt cells, do people mean "0.00v" or is anything with "0.01v through 0.99v" also "zero voltage"?
 

neilmc

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May 22, 2017
Messages
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Oz18650 said:
Just to clarify:
When talking about zero volt cells, do people mean "0.00v" or is anything with "0.01v through 0.99v" also "zero voltage"?

I consider 0v to be 0v or very close to it. Eg I just grabbed an old green samsung from my 0v pile and it reads 0.09mv or about one ten thousandth of a volt. Cells at 0 or really really close to it seem to yield good capacity cells less often, but someare still 1700-2000mah.

I've just tested 8 cells from my low voltage pile. They started off between 0.1 and 0.4v. They got 1696mah, 2330,2288,2321,2139,1497,2192.2275. I certainly wouldn't exclude any low voltage cells. Actual zero voltage cells might be a lower priority for testing though.

edit... I wouldn't consider a random sample of 8 low volt cells to be that good typically. I think some of them came from the same battery. I don't think low storage voltage (say 0.1v or above) is much of an indication of the health of the cell. IMO still test them.

If I see 0v and then get no continuity, it's trash. I'm not going to mess around trying to bypass a CID.
 

Tostaki

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Sep 20, 2017
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Hello

I was not planning to test the cells below 1v. After reading, I'll start to test a bunch of them.

The only ones ( I got 2 of them) I will not test are the ones with reversed polarity. I asume something went wrong with chemistery.
 

neilmc

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May 22, 2017
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Tostaki said:
Hello

I was not planning to test the cells below 1v. After reading, I'll start to test a bunch of them.

The only ones ( I got 2 of them) I will not test are the ones with reversed polarity. I asume something went wrong with chemistery.

I'd definitely be interested in how you go with cells under 1v. In my experience, voltage isn't much of an indicator of how well a cell will test except I've had a lower success rate with cells at zero volts.
 

dougal

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Sep 13, 2017
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Oz18650 said:
Just to clarify:
When talking about zero volt cells, do people mean "0.00v" or is anything with "0.01v through 0.99v" also "zero voltage"?

The ones you absolutely doneed to discard are the 'no continuity' cells.
They will be among those showing 0.00v.

I indicated that it was a personal preference thing what you dowith the others, and the responses above bear that out!
 

neilmc

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May 22, 2017
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only a small sample, but for what it's worth:

I grabbed 16 cells out of my zero voltage box yesterday. This box doesn't have cells with zero continuity.

7 of the 16 wouldn't take or hold a charge. To get them started, I connected them in parallel with a 1.5v cell long enough to get my charger to begin a 100ma charge in NiMh mode. I took them off at 2v. Some of them were already back to zero by the time I got the multi meter near them. Others you could see rapidly dropping as I checked them. Maybe these could be turned around with more charge (don't know) , but I discarded them.

The remaining 9 held a voltage around 1.7 to 1.8v. I put them back in the charger and brought them gently up to 2.8v in NiMh mode, and then switched to LiPo to complete the charge at 200ma. They were then put through a full test cycle. The results were:

6x Red Sanyo with green top : 1238 1320 1348 1869 1958 2070
2 x Panasonic (light green without the black stripes around the top): 1800 1666
1 x bright orange Chinese generic 1704

So that's only one cell out of 16 over 2000mah. only 4 out of 16 over 1800mah. I think if you have plenty of cells available, it's fair enough to discard the zero voltage cells because of the time taken to check them. If you're finding cells scarce where you are though, you might want to put them aside to work through them last.

I'll sit these 9 aside for a few weeks and check them for self discharge.
 

Rad

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Aug 18, 2017
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If a cell reads 0 volts and is not damaged or corroded then I always try to revive them. Charge at 100mA for about 3 hours, I use a current limited power supply. Measure voltage again, if over 3.0V then charge normally. Let it rest for a minimum of 5 days, check for voltage loss, capacity etc.

I have recovered a surprising number of cells using this technique, a recent batch of 26 zero volt cells, 20 could be revived, 6 are dead. I reckon it is worth the effort, especially as I do not have a good source of packs.
 

Oderus420

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Oct 1, 2017
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Tostaki said:
I'll let you know. Just ordered some more Opus BT-C3100 and proper PSU to increase my throughput.

Does everyone get a lame PSU with their OPUS?

I noticed it shows 12V@0.8A on the Power Supplywhich is much less than the 12V@3A that shows on the device itself.
 

daromer

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That was the first i scrapped. Im running with a proper 12V PSU.
 

Oderus420

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daromer said:
That was the first i scrapped. Im running with a proper 12V PSU.

Good to know. I ordered a second OPUS and with it, 2 x 12VDC adapters that do 3A. We'll see if I see any differences.
 
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