diy solar

diy solar

Charging with benchtop in series

I dont think thats the cause as it charged fine up till a certain point. The bms is turning the chg mos on and off
It could also be a bad connection, what does the BMS say? Is it turning off charging? Is it hitting high cell voltage disconnect?
 
It could also be a bad connection, what does the BMS say? Is it turning off charging? Is it hitting high cell voltage disconnect?
As already stated, the bms is turning off charging. The chg mos light turns on and off
The reason Im doubtful that its the connections is that the clamp meter matches the amps of the PSU

further, the connections charge fine up to a certain point and then the chg mos does this turning on and off again
 
Last edited:
Heck, I have no idea exactly what he is doing other than possibly playing with fire. LOL
Not sure what your comment is attempting to point out? The opening post clearly points out what I am trying to do which is charge the battery in series using my PSU. If you cant help someone in need, dont bother commenting.
 
As already stated, the bms is turning off charging. The chg mos light turns on and off
The reason Im doubtful that its the connections is that the clamp meter matches the amps of the PSU

further, the connections charge fine up to a certain point and then the chg mos does this turning on and off again
Then you might examine cell high voltage disconnect settings. The BMS is likely disabling charging due to the settings telling it to.

The settings are there to avoid over charging and damaging your cells, so do not set it above 3.65v.
 
As already stated, the bms is turning off charging. The chg mos light turns on and off
The reason Im doubtful that its the connections is that the clamp meter matches the amps of the PSU

further, the connections charge fine up to a certain point and then the chg mos does this turning on and off again
I looked at the settings of your BMS and they all look good to me. I may have missed it but have you checked the cell voltages with a DMM to verify they match the voltages displayed by the BMS? I am leaning towards a defective BMS based on the information you have provided so far. The BMS should cut off when the voltage of the highest cell reaches 3.650 volts. Apparently it's not working properly.
 
Maybe I'm missing something, but it looks to me like he must have one cell that is hitting 3.65V and causing the BMS to do a HVD. When charging at a lower voltage it seems fine, but the BMS shuts off charging at the higher voltage.

I think several people in this thread have attempted to tell him he doesn't need to charge at that high of a voltage, but he doesn't seem to be reading those comments.
 
Maybe I'm missing something, but it looks to me like he must have one cell that is hitting 3.65V and causing the BMS to do a HVD. When charging at a lower voltage it seems fine, but the BMS shuts off charging at the higher voltage.

I think several people in this thread have attempted to tell him he doesn't need to charge at that high of a voltage, but he doesn't seem to be reading those comments.
The thing is it's always a good idea to test the LVD and HVD of the BMS. He needs to check the voltages at the cell terminals to see if they match the voltages of the BMS. You are right, one cell could be hitting 3.65 volts causing the HVD. But the voltages of the BMS do not show any cells at 3.65 volts.
 
But the voltages of the BMS do not show any cells at 3.65 volts.
Hey @Gazoo - Bad on me if I missed it, but where did you see that no cells were at 3.65V? He posted a couple of screen shots from the app, but the only thing I could see was a "Cell Characteristics" page, which I took to be where you setup the app for what each cell is like. He didn't show us any page that showed the voltage of all the cells (specifically when the charging was cut off), did he?
 
I fixed this

i already fixed this as per the other posts after I realised it myself.

the problem is still persisting after changing the psu to 5 amps instead. It jumps between 13.7V and 4.95 amps TO 14.49 and 0 ampsUnsure what to do. Any other suggestions? Photos attached for values, changes every 5 seconds
The 13.7v measures to 3.425v per cell. The difference between 3.425v per cell and 3.65v per cell is LESS than an amp hour. Your BMS is turning off charging to protect your cells. You might want to check cell voltages with your meter, if all cells are around 3.4v, you are 100% full, and might want to take the hint your BMS is giving you.

Unless you are using really bad cables to charge with, you can set the power supply to 13.6v and wait until current going in is less than an amp. That will give you 99% capacity.

People only use higher voltages to charge with because they are impatient, with good quality cables and connections the current will drop once you hit 13.4 or 13.5v.
 
Hey @Gazoo - Bad on me if I missed it, but where did you see that no cells were at 3.65V? He posted a couple of screen shots from the app, but the only thing I could see was a "Cell Characteristics" page, which I took to be where you setup the app for what each cell is like. He didn't show us any page that showed the voltage of all the cells (specifically when the charging was cut off), did he?
Cell voltages are displayed at the bottom of this screenshot:

 
You might want to check cell voltages with your meter, if all cells are around 3.4v, you are 100% full, and might want to take the hint your BMS is giving you.
But the BMS HVD is set to 3.65 volts? Why is the HVD kicking in at a lower voltage. I never had this problem with my Overkill BMS.
 
Not sure what your comment is attempting to point out? The opening post clearly points out what I am trying to do which is charge the battery in series using my PSU. If you cant help someone in need, dont bother commenting.
He said you are playing with fire because you are trying very hard to charge above 3.4v per cell. Take it or leave it, seems a helpful comment to me if you understand what it means.
 
But the BMS HVD is set to 3.65 volts? Why is the HVD kicking in at a lower voltage. I never had this problem with my Overkill BMS.
Yes, but he also showed later (without showing cell voltages) a pack voltage while it was charging above 3.4v per cell. I suspect he may have a bad busbar connection that makes it appear as if one cell shoots up causing disconnect, then immediately drops when current is stopped. Even with good connections, trying to charge when average cell voltage is 3.4675v (13.87 divided by 4) is going to trigger the BMS within minutes. Just sounds like a bad idea, to me anyway. Even with good top balancing, one of those cells is likely hitting high voltage disconnect.
 
I suspect he may have a bad busbar connection that makes it appear as if one cell shoots up causing disconnect, then immediately drops when current is stopped.
Yeah, actually that makes sense. That why we have been asking him to measure the voltage at the cell terminals. Doing so would give everyone a much better idea of what's going on.

Even with good connections, trying to charge when average cell voltage is 3.4675v (13.87 divided by 4) is going to trigger the BMS within minutes. Just sounds like a bad idea, to me anyway.
My BMS cuts off when the highest cell reaches 3.65 volts. And disconnects when the lowest cell is 2.50 volts.

Agreed it's not necessary to charge to 3.65 volts except for testing the BMS to make sure it will function correctly if other LVD's and HVD's fail. :)
 
Not sure what your comment is attempting to point out? The opening post clearly points out what I am trying to do which is charge the battery in series using my PSU. If you cant help someone in need, dont bother commenting.
I wasn't commenting to you, just making a side joke as you made a mistake that could have been costly. But I'll offer some help.

First thing is did you ever top balance the cells in parallel?

Second, before installing busbars, were the terminals cleaned?

Third, did you capacity test the pack after top balancing?

Fourth, have you put the pack under load after the attempted charging and pull it down until one cell hits 2.5V?

Fifth, why do you need to charge until charging cell voltage cut out at 3.65V?
 
I looked at the settings of your BMS and they all look good to me. I may have missed it but have you checked the cell voltages with a DMM to verify they match the voltages displayed by the BMS? I am leaning towards a defective BMS based on the information you have provided so far. The BMS should cut off when the voltage of the highest cell reaches 3.650 volts. Apparently it's not working properly.
Not sure how you came to the conclusion that my cell is at 3.650V? They are all roughly 3.4V with the multimeter, as reflected accurately in the BMS app.
Maybe I'm missing something, but it looks to me like he must have one cell that is hitting 3.65V and causing the BMS to do a HVD. When charging at a lower voltage it seems fine, but the BMS shuts off charging at the higher voltage.

I think several people in this thread have attempted to tell him he doesn't need to charge at that high of a voltage, but he doesn't seem to be reading those comments.
DMM reads 3.4V when I last checked and was charging. I think I outlined all of this information in the opening post but maybe I'm wrong.

The 13.7v measures to 3.425v per cell. The difference between 3.425v per cell and 3.65v per cell is LESS than an amp hour. Your BMS is turning off charging to protect your cells. You might want to check cell voltages with your meter, if all cells are around 3.4v, you are 100% full, and might want to take the hint your BMS is giving you.

Unless you are using really bad cables to charge with, you can set the power supply to 13.6v and wait until current going in is less than an amp. That will give you 99% capacity.

People only use higher voltages to charge with because they are impatient, with good quality cables and connections the current will drop once you hit 13.4 or 13.5v.
OK! Excellent post John. So 3.4V is full? I did notice the comments where people where suggesting to charge to 3.4V, but was unsure as most threads Ive seen say to charge to 14.6V/3.65V.
Thank you. It appears people are skipping ahead to comment without actually reading the information I've provided.
He said you are playing with fire because you are trying very hard to charge above 3.4v per cell. Take it or leave it, seems a helpful comment to me if you understand what it means.
Thanks John. Was completely unaware that charging above that voltage was not recommended as every video and post I have seen so far advice to charge to 3.6V at least.
 
I wasn't commenting to you, just making a side joke as you made a mistake that could have been costly. But I'll offer some help.

First thing is did you ever top balance the cells in parallel?

Second, before installing busbars, were the terminals cleaned?

Third, did you capacity test the pack after top balancing?

Fourth, have you put the pack under load after the attempted charging and pull it down until one cell hits 2.5V?

Fifth, why do you need to charge until charging cell voltage cut out at 3.65V?
Thanks Zwy.
1. Yes
2. No, but I may do this. What is the method for cleaning the busbars?
3. No.
4. I haven't run the pack to pull it down to 2.5V
5. I am attempting to charge at 3.6V as that's what I've seen recommened. This is the first time I have had people suggest the cells only need to charge to 3.4V so I am a little confused by this.
 
Not sure how you came to the conclusion that my cell is at 3.650V? They are all roughly 3.4V with the multimeter, as reflected accurately in the BMS app.
I never said any of your cells voltages were 3.65 volts. I said:

" The BMS should cut off when the voltage of the highest cell reaches 3.650 volts. Apparently it's not working properly."

I see you could have taken that the wrong way. But I get your concern.

Thank you. It appears people are skipping ahead to comment without actually reading the information I've provided.
You are welcome. The only thing I wasn't sure of was if the voltages at your cell terminals were matching the voltages displayed by the BMS's app. You have now confirmed they are the same.

Thanks John. Was completely unaware that charging above that voltage was not recommended as every video and post I have seen so far advice to charge to 3.6V at least.
For longevity of the cells it's good to keep the cells between the knees. Charging to 3.65 and discharging to 2.50 will still give you at least 2000 cycles. Damage can happen if the cell is held at a high voltage.

Your HVD is cutting in and shutting off the charge before any of your cells reach 3.65 volts and that should not be happening. Is anyone else concerned about this?

Regardless I have no clue why the HVD is kicking in before your cells reach 3.65 volts. Your app shows your BMS HVD is set to 3.65 volts so your HVD should kick in when the highest cell reaches 3.65 volts....not before.

I always recommend testing the HVD and LVD of the BMS as I have recommended in this thread. For some reason your BMS is not working properly. As John said it could be a bad connection some where. I wonder if your power supply could be putting out spikes? Sometimes it's really difficult to troubleshoot problems on a forum. At this point it might be a good idea to contact Daly and see what they have to say about this.
 
Back
Top