HELP PLEASE I think I may have some bad cells

[Dzl]

Do I need to raise the voltage on my machine until it gets to be 3.6 at the terminals

I think this is not necessary, just be patient, Because voltage drop = Current x Resistance, and current is getting lower and lower and lower, voltage drop (difference between the voltage as seen by the PSU and the voltage at the cell terminals) will get smaller and smaller and should be inconsequential probably at <1A.

Great. So far so good. I believe you are out of the flat part of the curve. Your power supply is set to 3.6 volts. Leave it. As you have noticed the current is coming down. When the current reads 1 amp or less, you are good to go for a capacity test.

One thing I would add, that may or may not be necessary, but wouldn't hurt is this bit of advice from Nordkyn:

"Disconnect the PSU from the cells again and wait. The cells should hold above 3.50V for at least 30 minutes. If not, bring them up again and hold them for a little longer until they do. At 3.60V, you may need to insist a little more than if using 3.65 or 3.70 volts; that’s all."

What c charge cycle am I on at the moment?

Current / Cell Capacity = C rate

I don't remember your cell size or charging amps, but for example:

5A / 200Ah = 0.025C

 

[John Frum]

Do I need to raise the voltage on my machine until it gets to be 3.6 at the terminals

That is a really bad idea.
Its the most common cause of bloated/damaged cells.

 

[Gazoo]

"Disconnect the PSU from the cells again and wait. The cells should hold above 3.50V for at least 30 minutes. If not, bring them up again and hold them for a little longer until they do. At 3.60V, you may need to insist a little more than if using 3.65 or 3.70 volts; that’s all."

Yeah, I agree. All of mine remained above 3.50 for a couple of days. If they fall below 3.50 volts after a 30 minute rest I think there could be other problems.

 

[Just John]

3.359 at cell terminals

Once it gets above 3.4, things go much faster. Once above 3.5, the millivolts can even look like it is counting seconds. Be patient, don't touch the supply, let it bring the cell to 3.65. The amps should drop very quickly once above 3.5.

 

[Just John]

That is a really bad idea.
Its the most common cause of bloated/damaged cells.

Yes, if the power supply is nudged to speed it up, it is very easy to damage the cell. Patience, it will happen.

 

[Fallingaway]

Nice! Glad to see your getting there. This seems to happen to a lot of people. It’s been charging for hours and no improvement so they think there’s a problem etc. Patience grasshopper!!

 

[Moltensurf]

Creeping up out of the curve. Been charging all night

 

[Fallingaway]

Ya it takes a while. My bench top only does 5a and it took me days but like others have said once it get up above 3.4 it will take off quick. Make sure your patient too and let the cells rest for 30-60min and check again. They may settle back down and need to go back on charger. Good luck!

 

[John Frum]

Creeping up out of the curve. Been charging all night

Please show the voltage at the battery terminals.
Also do you trust your meter?

 

[Just John]

Please show the voltage at the battery terminals.
Also do you trust your meter?

Hard to tell, the meter leads disappear in the bus bars, but look like they go up to the cell terminals. Certainly the power supply is showing 3.6 volts and the meter is showing just under 3.4, both of which are very believable values. Do you suspect something other?

 

[John Frum]

Hard to tell, the meter leads disappear in the bus bars, but look like they go up to the cell terminals. Certainly the power supply is showing 3.6 volts and the meter is showing just under 3.4, both of which are very believable values. Do you suspect something other?

I didn't see the meter because of my poor eyesight.
Shouldn't be too long now.

 

[snoobler]

That is a really bad idea.
Its the most common cause of bloated/damaged cells.

This is not instructional... it's to a specific point in the video relative to the discussion... please watch...

 

[Moltensurf]

Hard to tell, the meter leads disappear in the bus bars, but look like they go up to the cell terminals. Certainly the power supply is showing 3.6 volts and the meter is showing just under 3.4, both of which are very believable values. Do you suspect something other?

OK I am all charged up to 3.65. I am letting the battery sit for 30 minutes with no power going to it. My meter is a really good meter it’s right on accurate. I also did have the leads connected to terminals

 

[Moltensurf]

Ok I have everything up and running

 

[Just John]

OK I am all charged up to 3.65. I am letting the battery sit for 30 minutes with no power going to it. My meter is a really good meter it’s right on accurate. I also did have the leads connected to terminals

Nice, you can of course connect the next cell to start charging. I'm interested in what capacity you find on the cells.

 

[John Frum]

@Moltensurf what did the cell settle to before you started to discharge it?

 

[Moltensurf]

@Moltensurf what did the cell settle to before you started to discharge it?

It never settled completely, but after 30 minutes it was still above 50

 

[John Frum]

It never settled completely, but after 30 minutes it was still above 50

Do you mean 3.50 volts?
Please be specific this is not flower arranging.

 

[Gazoo]

It never settled completely, but after 30 minutes it was still above 50

Next time please note the complete voltage measurement immediately after removing the cell from the charger, and after a 30 minute rest. I would like to see how much the voltage drops. All 8 of my cells remained above 3.50 volts after sitting for about 2 days. A 30 minute rest is fine and the fact your cell remained above 3.5 volts is good. Looking forward to your capacity test.

 

[Just John]

Next time please note the complete voltage measurement immediately after removing the cell from the charger, and after a 30 minute rest. I would like to see how much the voltage drops. All 8 of my cells remained above 3.50 volts after sitting for about 2 days. A 30 minute rest is fine and the fact your cell remained above 3.5 volts is good. Looking forward to your capacity test.

Yes, I just let one settle for 24 hours, and then paralleled with 3 others that had been fully charged in the past 3 days. Right now the 4 cells are at 3.531 in parallel so I can capacity test them as a battery this week end.