Battery voltage between 13.6 - 14.4 concidered fully charged?

[sunshine_eggo]

Well yeah...I assume there could be a imbalance in cells inside, they use pouch cells actually as far as I know...

So how would I balance them if needed, keep the absorb or float at a certain voltage for a longer period of time? Since It's not a self built battery, and I cannot balance each cell, they are pre-balanced pouch cells, so the only way maybe is..?

From above:

I'm still not convinced this voltage drop isn't a cell balance issue. Try setting float to 13.8V and hold for 24 hours.

 

[TomC4306]

That ^

 

[Vigo]

Try only charging to 14v, then disconnect and check a few hours later and see if they don't settle at a higher voltage

So is the idea here to stay below an ‘activate balancing’ threshold, with the theory being that if the entire battery voltage drops LESS when it doesnt balance , then the assumption would be that the bms is draining good cells into a bad cell until the battery falls below a ‘stop balancing’ threshold which happens to be around ~13.25?

 

[TomC4306]

So is the idea here to stay below an ‘activate balancing’ threshold, with the theory being that if the entire battery voltage drops LESS when it doesnt balance , then the assumption would be that the bms is draining good cells into a bad cell until the battery falls below a ‘stop balancing’ threshold which happens to be around ~13.25?

No .. completely no. You misunderstand how BMS works.
The battery can fully charge at 3.45 volts per cell just requires more time.
The idea here is I don't think he's fully charging the battery and therefore he's not getting full capacity from the battery. He's charging to 14.6 every time he's tripping cell over voltage protection every time he charges. In my opinion.
So, lower the charge voltage to something that will still produce 100% state of charge but will not cause one cell to go over voltage there by causing the BMS to shut off charging.
And he seems not to understand this theory.

 

[teddysx3]

From above:

So hey, got back to the batteries today, fully unhooked from each other and from the system. I charged them yesterday all 3 together absorb 14.4 and float to 13.6. I got to float and stayed for about 1 hour, unhooked them and left them at 13.6 even. Today all of them were at 13.31,13.25,13.25, which I think it's a pretty close voltage drop for all of them together.

I'm thinking that I really did not somehow charge them all they way up, for them to always fall to 13.2-13.3ish. Do you think my smart shunt has something to do with the settings that I used to charge them, that they were wrong?
Charged voltage: 13.2v
Tail curretn 4%

I charged to 14.4 then float 13.6, and the current dropped to almost nothing, and I assumed that they are charged.

I will change the smart shunt settings to 14.2 for charged voltage, and 6% tail current like you suggested, but do you think I did not charge the batteries, and should I leave the charger for longer periods of time, or even change the float voltage?

Thanks!!!

 

[sunshine_eggo]

The smart shunt has nothing to do with charging. The parameters are for when the shunt determines when it synchronizes and displays 100%.

Current dropping to "almost nothing" at 13.6V may or may not be an indication of a full charge. Imbalanced batteries are not fully charged, but they may behave as you've observed.

I'm still disturbed by that level of drop. It seems excessive. Unless you can verify the battery capacity with a discharge test, I would still recommend holding the batteries at 13.8V for 24 hours and see if the drop behavior changes. I understand this may not be an option, but that doesn't change my preference. If you can leave them at 13.6V for 24 hours, that might help too.

 

[teddysx3]

The smart shunt has nothing to do with charging. The parameters are for when the shunt determines when it synchronizes and displays 100%.

Yea, was 100% sure, but you know when you are searching for the issue, everything is an target lol.

The smart shunt has nothing to do with charging. The parameters are for when the shunt determines when it synchronizes and displays 100%.

Current dropping to "almost nothing" at 13.6V may or may not be an indication of a full charge. Imbalanced batteries are not fully charged, but they may behave as you've observed.

I'm still disturbed by that level of drop. It seems excessive. Unless you can verify the battery capacity with a discharge test, I would still recommend holding the batteries at 13.8V for 24 hours and see if the drop behavior changes. I understand this may not be an option, but that doesn't change my preference. If you can leave them at 13.6V for 24 hours, that might help too.

Let me leave them at 13.6 float, just to be safe, that's the same if you are hooked up to shore power and are trickle charging them. If they are imbalanced maybe 24h of 13.6 could help them, having the fact they have a auto-balancing function through the RJ45 ports.

Thanks a lot for your time and help, answers! I will have to test. I will get another 1 or 2 multimeeters, and see if the one I'm using is not off...Now they read - 13.35, 13.27, 13.29. Have not hooked them up to anything yet.

 

[Vigo]

No .. completely no. You misunderstand how BMS works.
The battery can fully charge at 3.45 volts per cell just requires more time.
The idea here is I don't think he's fully charging the battery and therefore he's not getting full capacity from the battery. He's charging to 14.6 every time he's tripping cell over voltage protection every time he charges. In my opinion.
So, lower the charge voltage to something that will still produce 100% state of charge but will not cause one cell to go over voltage there by causing the BMS to shut off charging.

Sorry about my 'complete' misunderstanding. I failed to infer from your "14v" quoted with no decimals because..there were none, that the point was to hit 3.45+/cell while mitigating to the extent possible, the chance of one cell running away. But i do understand now!

As far as misunderstanding BMS balancing behaviour, that's probably true because the only BMS i've ever interacted with is an Orion for EV packs that is fully configurable and will do whatever i tell it to do, but i have no practical experience observing what the default balancing behavior of pre-built battery bms's is because the only ones i own have no bluetooth. I only know about that, what i have read around here. But my assumption is that a bms would not try to balance in 'the flat part of the curve' because without power-tracking each cell it would not reliably know that one cell was actually lower than another until it was well into the 'knee'. Thus only starting to balance at above "14v". And that if the bms was balancing high cells into a low cell (a circuit, really.. could be connections) which was just turning the energy into heat while staying at a low voltage, that the 'pack' would end up at a lower terminal voltage than if the bms had not attempted to balance at all! Thus my wild left field theory, which turned out to not be what you meant. I thought you were trying to detect a bad cell without knowing individual cell voltages, by watching whetherpack voltage dropped by less WITHOUT balancing, than it did WITH balancing.

 

[teddysx3]

The smart shunt has nothing to do with charging. The parameters are for when the shunt determines when it synchronizes and displays 100%.

Current dropping to "almost nothing" at 13.6V may or may not be an indication of a full charge. Imbalanced batteries are not fully charged, but they may behave as you've observed.

I'm still disturbed by that level of drop. It seems excessive. Unless you can verify the battery capacity with a discharge test, I would still recommend holding the batteries at 13.8V for 24 hours and see if the drop behavior changes. I understand this may not be an option, but that doesn't change my preference. If you can leave them at 13.6V for 24 hours, that might help too.

I was not able to export the file from the shunt, not sure if they even have this option. I snipped a picture and made a small video ot the discharge and charge like you suggested.

 

[sunshine_eggo]

I was not able to export the file from the shunt, not sure if they even have this option. I snipped a picture and made a small video ot the discharge and charge like you suggested.

I can see it.

The abrupt dip in current and then subsequent recovery suggests to me that one of the parallel batteries may be entering into over-voltage protection.

I know it's tedious, but I would discharge them a bit and then charge each individually to see if they all look the same.

 

[teddysx3]

I can see it.

The abrupt dip in current and then subsequent recovery suggests to me that one of the parallel batteries may be entering into over-voltage protection.

I know it's tedious, but I would discharge them a bit and then charge each individually to see if they all look the same.

Sure I will try it out no problem! I'll do anything to troubleshoot it.

Isn't the dip because the battery was almost full before I started charging? I did not drain it at all, just a little before I started to charge again.

Now I'm going to drain all 3 a lot, and then charge each one and let's see how the graphs look.

Cheers mate!

 

[sunshine_eggo]

Sure I will try it out no problem! I'll do anything to troubleshoot it.

Isn't the dip because the battery was almost full before I started charging? I did not drain it at all, just a little before I started to charge again.

It may be. that's why I suggested draining them a bit.

Now I'm going to drain all 3 a lot, and then charge each one and let's see how the graphs look.

Cheers mate!

 

[teddysx3]

It may be. that's why I suggested draining them a bit.

A little update from today. Keep in mind that all the tests these days are done in around freezing temps, but that should not affect the voltage I assume.

Fully charged left for a couple of hours, from 13.6 the rested at 13.5. The next morning they were at 13.3. I'm starting to think that these Renogy batteries like to rest at 13.3 100%SOC...

I put some load for a couple of hours, I have attached some photos of the load. I syncronized 100% SOC when I left them yesterday "fully charged".

The interesting thing is, even after 24% used (42a), when I stopped the load and waited a bit, the batteries voltage went back up slowly to 13.28.

Now I started to charge each battery one by one, so I can see the trends for each one.

 

[sunshine_eggo]

Well, maybe it's the nature of the beast. Recommend repeat full charge and then do a deep discharge to BMS cut off and then see if you get rated capacity. If so, time to move on and just assume it's an idiosyncrasy with their cells.

I have some oddball CALB cells that PLUMMET within 30 minutes of charging and can get as low as 3.30V (13.2V). Yet they still test to 97% capacity from that level even after extended sits.

 

[TomC4306]

"fully charged

What voltage did you use to achieve this?

 

[teddysx3]

Well, maybe it's the nature of the beast. Recommend repeat full charge and then do a deep discharge to BMS cut off and then see if you get rated capacity. If so, time to move on and just assume it's an idiosyncrasy with their cells.

I have some oddball CALB cells that PLUMMET within 30 minutes of charging and can get as low as 3.30V (13.2V). Yet they still test to 97% capacity from that level even after extended sits.

I will probably buy one of these capacity testers the WIll has a video and see if it holds 100ah of charge, I think you are right, just move on and what really matters is the 100ah charge, not the voltage... Too bad here in Europe they don't sell the good quality batteries you guys have. (Battle born, Relion, ect..)

What voltage did you use to achieve this?

I charge bulk/absorb 14.4, then 13.6 float.

 

[hwse]

Hey guys,

I have it all, all victron equipment.

I charged each battery to 14.4, then float brought it down to 13.6, did that to the 2 betteries. The third one I charged to 14.4, then did not wait for the float voltages to bring it back down to 13.6. The 2 batteries that had 13.6 float were are 13.3, but the other was at 13.5ish. I don't think that the batteries for 1-2 days could have dropped to 70% discharge with no loads connected (13.3)?

Should I cylcle the 3 batteries again one by one to 14.4 and let the float bring it down to 13.6, and then connect them in parallel to make sure the voltages are balanaced? They are now connected and I have ran a charge cycle to 14.4 with all 3 in parallel. Am I overthinking it?

You have said several times said something to the effect of "brought it down to 13.6". I do not believe that there is any charger that applies a load to a battery for the purpose of bringing the charge voltage down to resting voltage. If you are disconnecting one battery from the charging buss and watching the voltage it will likely take a longer time to drop to float. I think what you are seeing as a "pulling down" of the battery voltage is due to the power consumed by the internal electronics of the charger. It is constantly monitoring the pack and using electronics that are powered by the battery to do this work. The other battery that is disconnected from the charger does not have that load, so it takes longer to drop to the resting voltage. There is almost no capacity or amps used when an LFP drops from 14.4 to 13.6.

 

[hwse]

I will probably buy one of these capacity testers the WIll has a video and see if it holds 100ah of charge, I think you are right, just move on and what really matters is the 100ah charge, not the voltage... Too bad here in Europe they don't sell the good quality batteries you guys have. (Battle born, Relion, ect..)

I charge bulk/absorb 14.4, then 13.6 float.

I have not seen anywhere that you identified what type of batteries that you have. I assume that they are drop-ins of some kind. Do you have Bluetooth connectivity? That would greatly help to figure out what is going on inside.

I have two 460Ah packs in sealed cases and one of them arrived very out of balance which prevented it from being charge to anything higher than 13.8v without over volt protection (OVP) cutoff. When the two batteries were connected in parallel to my charger, it indicated that they were both at 14.2v but by looking at the BMS all, I could see that one charged to 13.8v and internally shut off charging and the other battery which was better (but not perfectly) balanced kept charging until it hit 14.0v. The charger then when to 14.2v and stayed there for the 30-minute float time but none of that went to the batteries because both were in OVP. As soon as the charger dropped from absorption to float, the battery monitor showed the voltage drop instantly to 14.0v. It then quickly dropped to 13.8v after which it dropped a bit slower down to 13.6v float.
Without the Bluetooth app, I would not know that one battery only charged to 13.8v and the other to 14.0v