NINTHCIT Grade A 3.2V 120Ah LiFePO4 cells - Out for Delivery

[OnTheRoadAgain]

One other crazy note.......

Earlier as I mentioned, I had charged the cells in parallel to 3.377volts.

Well, I stopped charging them for about 2 hours.

When I started charging them again, they were back down to 3.6v and it's taken several hours just to get them back up to 3.363v

I'm still undecided about these cells. They seem to be having a LOT of trouble getting up past about 3.360 volts

Even when I tested them individually they did the exact same thing individually. (Got to 3.377 then started losing voltage)

At least they are al consistent.

 

[Gazoo]

The voltage doesn't drop but the current does a bit at the PSU.
But it does drop on the Meter directly at the battery terminals.

Ok so if you mean the voltage is lower at the cells than the PS that's normal. There will always be some voltage drop.

Only happens when it hits around 3.377v - 3.380v
then it'll just creep slowly back down to about 3.6v

I don't understand this. 3.6 volts?

BTW...the PZEM-15 says I've put 185Ah into the battery so far (it's a 120Ah battery).

It's probably not calibrated and might not be as accurate at the lower voltage. Not familiar with that meter so I really don't know.

Now, I can get 10A flowing to the battery if I crank up the voltage. 4v or higher.

But at 3.65v it only goes to about 6amps.

This has me wondering if it's because the IR of those cells is lower that the EVE or other larger cells.

When I started charging them again, they were back down to 3.6v and it's taken several hours just to get them back up to 3.363v

Do you mean 3.36 volts or something?

Even when I tested them individually they did the exact same thing individually. (Got to 3.377 then started losing voltage)

And that's while charging? Strange. Something is not right obviously but I don't know what it could be. Can you post a photo?

Here is how it's supposed to work:

The voltage of the power supply must be set to 3.65 volts before connecting to the cells.

When you initially connect the power supply to the cells, the voltage displayed on the power supply will go down and the current will output close to the full current the power supply is capable of. Towards the end of charge the voltage of the power supply will increase and the current will start to drop.

At this point the power supply should switch from constant current to constant voltage mode. It's very important to take a voltage reading at the cells terminals with a DVM during this process to be safe especially towards the end of charge. Eventually the voltage displayed on the power supply will be 3.65 volts, and the cells, and the current will taper down to zero. It's ok to disconnect the power supply when the current is .500ma's or less.

 

[OnTheRoadAgain]

Arh...yeah I keep typing 3.6 when I mean 3.36

 

[OnTheRoadAgain]

Ok so if you mean the voltage is lower at the cells than the PS that's normal. There will always be some voltage drop.

I don't understand this. 3.6 volts?


It's probably not calibrated and might not be as accurate at the lower voltage. Not familiar with that meter so I really don't know.


This has me wondering if it's because the IR of those cells is lower that the EVE or other larger cells.


Do you mean 3.36 volts or something?


And that's while charging? Strange. Something is not right obviously but I don't know what it could be. Can you post a photo?

Here is how it's supposed to work:

The voltage of the power supply must be set to 3.65 volts before connecting to the cells.

When you initially connect the power supply to the cells, the voltage displayed on the power supply will go down and the current will output close to the full current the power supply is capable of. Towards the end of charge the voltage of the power supply will increase and the current will start to drop.

At this point the power supply should switch from constant current to constant voltage mode. It's very important to take a voltage reading at the cells terminals with a DVM during this process to be safe especially towards the end of charge. Eventually the voltage displayed on the power supply will be 3.65 volts, and the cells, and the current will taper down to zero. It's ok to disconnect the power supply when the current is .500ma's or less.

Here's exactly what I did......

Disconnected leads from battery.

Turned on PSU

Set VOLTAGE to 3.65v

Set Current knob to Maximum

Turned off PSU

Connected Leads to battery.

Turned ON PSU

PSU has a green light next to the voltage display (indicating constant voltage mode)

Current goes to between 5A and 6A

Battery finally reaches 3.377v...then the voltage on the meter at the terminals begins to fall back slowly...eventually stopping around 3.360v.

It's almost as if these cells have a cell protection circuit in them set at 3.377v....which makes no sense.

My PZEM meter now says I have put 188Ah into the cells but they are in Parallel so I'm not sure the significance.
Meanwhile, Watt Hours is only 650 (out of 1440 because this is a 120Ah battery)

Not sure this set of cells will ever reach 3.65v. If not by tomorrow it's Return time (yet again)

At least this set of cells is balanced and the resistances were good. Baffling what's going on. Magic.
(Or bad PSU?)

The kicker is that even when they are going backwards in voltage....my clamp meter STILL says current is going to the battery....unless it's actually saying current is LEAVING the battery?

 

[Gazoo]

PSU has a green light next to the voltage display (indicating constant voltage mode)

It should be in constant current mode.

My PZEM meter now says I have put 188Ah into the cells but they are in Parallel so I'm not sure the significance.
Meanwhile, Watt Hours is only 650 (out of 1440 because this is a 120Ah battery)

The battery is actually 480ah's. Because you have 4 120ah cells connected in parallel.

The kicker is that even when they are going backwards in voltage....my clamp meter STILL says current is going to the battery....unless it's actually saying current is LEAVING the battery?

You need to verify that. Again it "could" be a faulty power supply. I doubt the cells are bad. Do you have anything else you could use to verify? Something like the variable voltage wall warts Radio Shack used to sell. If you do you could connect it to the cell and see if the voltage of the cell comes up.

The fact your power supply is not in constant current mode isn't good. Did it ever go into CC mode? I don't know how you have everything connected which is why I asked you to post a photo. Nevertheless, I suspect either bad connections, a bad power supply or both based on what you have said.

battery finally reaches 3.377v...then the voltage on the meter at the terminals begins to fall back slowly...eventually stopping around 3.360v.

I get that. Please verify which direction the current is going when it does that using your clamp meter.

 

[OnTheRoadAgain]

It should be in constant current mode.


The battery is actually 480ah's. Because you have 4 120ah cells connected in parallel.


You need to verify that. Again it "could" be a faulty power supply. I doubt the cells are bad. Do you have anything else you could use to verify? Something like the variable voltage wall warts Radio Shack used to sell. If you do you could connect it to the cell and see if the voltage of the cell comes up.

The fact your power supply is not in constant current mode isn't good. Did it ever go into CC mode? I don't know how you have everything connected which is why I asked you to post a photo. Nevertheless, I suspect either bad connections, a bad power supply or both based on what you have said.


I get that. Please verify which direction the current is going when it does that using your clamp meter.

Ah! Forgot all about that. Thank you Gazoo !!

I can get it into CC mode by adjusting the current down from maximum.
But that does not change the current amount going to the battery.
But now the indicator light is next to the Current display so it's in Constant current mode.

I understand what you mean about constant voltage. But I have been sitting here next to it the entire time watching it carefully.

 

[Gazoo]

You are not using banana plugs and have the ring terminals connected to the power supply too right? Which power supply are you using? If you can verify which direction the current is going using your clamp meter that would help. Something about all of this is not making sense. Sounds to me like you are doing everything correctly.

Considering cells are generally shipped with a 50% SOC, and your power supply is putting apx. 6 amps into them, it would take apx 40 hours to top them up.

Here's a pic of mine when I parallel top balanced. Show and tell....lol. I used 12AWG copper stranded silicone insulated wire.

 

[OnTheRoadAgain]

No banana plugs. about 50 hours charging now and 202Ah, 684Wh.

Cheap Dr.Meter PSU.
5.5A is ALL I can get out of it unless I crank up the voltage.

 

[Gazoo]

The PS is in CC mode but I guess that's because you turned the current down as you said. I don't know why it's doing that. Everything looks good to me. I would just leave it as is and see what happens, but keep a close eye on it.

When the voltage of the power supply reaches 3.65 volts or so, it should then switch into CV mode. And then the amps will taper off.

 

[Gazoo]

I took a look at the voltage and current on my PS when I took that photo. Notice I have it set to 3.40 volts and it is in CV mode. And the amps is only 5.84 amps. That's because I was going to use the step method to parallel top balance. Once I turned the voltage up to 3.65 volts the PS did go into CC mode, and it was putting out very close to 12 amps. Just wanted to make that clear in case anyone questions it...lol.

 

[OnTheRoadAgain]

I finally found a thread where someone else had the exact same issue as I am having.....

https://diysolarforum.com/threads/lifepo4-battery-bank-not-charging-completely.9246/

I'm trying one last time with a different PSU.
If it does it again, they're going back.

 

[OnTheRoadAgain]

Gazoo,
Thanks again for your assistance.

Let me ask you this......

If it was in fact a bad PSU......

How could the voltage rise, then begin to fall every time the battery pack reached 3.377 - 3.380v ?
All, while a clamp meter still shows full current flowing to the battery?

What problem in a PSU could cause that behavior?

 

[Gazoo]

Gazoo,
Thanks again for your assistance.

Let me ask you this......

If it was in fact a bad PSU......

How could the voltage rise, then begin to fall every time the battery pack reached 3.377 - 3.380v ?
All, while a clamp meter still shows full current flowing to the battery?

What problem in a PSU could cause that behavior?

Honestly I don't know. If your clamp meter is showing current going into the cells the voltage should be rising. You have a unique situation and I still suspect it's the power supply and not the cells but I could be wrong. There is a point during the process it will appear the voltage is not increasing due to the flat part of the curve. Has the voltage of the cells come up at all since yesterday. Even a millivolt or 2?

 

[cinergi]

It's normal for the voltage to sit at these values for a very very very long time. Don't underestimate h ow long it takes to top balance using this method.

I saw my voltages at the cell terminals DECLINE while top-balancing. It was minor (millivolts) but I consider it normal - the internal resistance of the battery is changing as it's being charged and other factors will easily contribute to observing small voltage changes while charging in the flat part of the charge curve for this chemistry.

 

[OnTheRoadAgain]

Gazoo.....

You were spot on correct.

This ended up totally being a faulty power supply issue. Dr. Meter, Black 10A unit. Brand new from Amazon.
So somehow, this bad PSU would get to 3.377v - 3.800v and then just go nuts and the voltage would begin dropping....even while the clamp meter still showed nearly the full amps indicated on the display going to the battery? This is an electronics issue.
I'm not even sure how this happened?

I have an older 5 Amp power supply on hand and connected it to the batteries......

Sure enough within one hour the battery pack reached 3.4 volts for the first time. I was surprised because I had more faith in the new PSU than the batteries. You were the one who correctly zeroed in on that. A BIG Thank you!

But VERY relieved to know it's not the batteries after all. I said no way I'm going to spend $200 on a PSU....may have to eat that.
Got the batteries fully charged, put them in series, hooked up the BMS and running a capacity test now.

How much was that Riden unit?

 

[Gazoo]

You can find the Riden on aliexpress and that's where I ordered it from. Other places might have it for a little less. I have the 12 amp model. Last I looked they are now up to 18 amps. I bought the complete kit including the case and the power supply. No regrets. It has come in handy for other things and I used it to balance one of my cells that was a bit weak on the top.

 

[cinergi]

I love my Riden, too. But if you series-charge the cells through a BMS first and then parallel top-balance them, this process will go a lot faster (assuming you have a higher-power 12v source) and it's still perfectly safe and you don't need a fancy PS for the 3.65v stuff.

 

[OnTheRoadAgain]

After being led astray by a bad brand new Dr. Meter 10A power supply (since returned), things have gone smoothly.

The 120Ah cells tested out at 124Ah.
Resistances were in specs.
Arrived flat as pancakes.
Price was about as good as I have found state side.
From all I can gather, they do appear to be new, grade A cells as advertised. At least my batch.

I would give these cells a top notch rating.

But always keep i mind, YMMV

By the way...I found out the power supply was seriously bad 4 days after the Amazon 30 day window closed.
They accepted the return....but I had to pay a 20% restocking fee.
Check and double check all those Amazon goods quickly after they arrive. It's ALWAYS possible to get something defective yet brand new.

 

[OnTheRoadAgain]

You can find the Riden on aliexpress and that's where I ordered it from. Other places might have it for a little less. I have the 12 amp model. Last I looked they are now up to 18 amps. I bought the complete kit including the case and the power supply. No regrets. It has come in handy for other things and I used it to balance one of my cells that was a bit weak on the top.

Gazoo,
Just before I learned my new Dr.Meter PSU was bad, I had said I would not be spending $200 on a PSU.
Then after the failure of the new PSu I decided a good PSu was something I needed on hand.
I ordered the Riden 18Amp unit like what you have.

I hope it's not too difficult to learn to use. All the old ones I had just required a twist of a few knobs.

 

[Gazoo]

Gazoo,
Just before I learned my new Dr.Meter PSU was bad, I had said I would not be spending $200 on a PSU.
Then after the failure of the new PSu I decided a good PSu was something I needed on hand.
I ordered the Riden 18Amp unit like what you have.

I hope it's not too difficult to learn to use. All the old ones I had just required a twist of a few knobs.

It can be a little intimidating at first but once you play around with it it's not bad. Carefully read the manual. I downloaded it before I decided to order mine and became familiar with it. I am sure you will be happy with it.