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Top balancing taking forever

Are you certain you always adjusted the voltage before connecting the leads .... then no changes to the power supply after connecting?

Sorry ... but had to ask. The mistake most people make is to make changes to the power supply after connecting it to the battery.
No that's okay to just double double check. I have seen this mentioned many times so am extra careful to turn off and disconnect before adjusting the voltage. An example is that I noticed upon plugging the batteries to the PSU last night(already set to 3.65V without attached), the PSU jumped to 3.66 - 3.68. I turned it off, disconnected and THEN readjusted the voltage to 3.55V and the reconnected the terminals before turning on the PSU.
 
Thin wires, slow charging.
And cooked supply?

"My suggestion to everyone is if you order equipment that is manufactured in China and that equipment comes with wire, check the wire thickness. We had this wire issue on multiple devices, not just the power supplies. Hopefully this article will expose a simple solution for you to extend the life of your electronic devices that you spent your hard earned money on."

Excellent. Lesson learnt!

On another note, my clamp meter just arrived.

PSU is at
3.64V
Playing a jazz solo between 5.5A - 5.7A

The clamp meter is reading roughly the same as the PSU on the DC setting of the clamp meter. Clamp meter reads 5.6-5.15A

What an awesome tool :eek:
 
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I will be upgrading to 16 272ah Lishen LFP cells in about 2+ months (24v 8s2p and two BMS config). I have skimmed thru this thread, but wondering for Top Balancing, If I have a highly customizable charger (The Schneider Conext SW4024 inverter/charger):

1. is it better (or Ok to save money) to use the SW to charge to say 3.4v per cell in series and then Top Balance to 3.65v per cell in Parallel using a cheaper 30v 10amp Desktop Power Supply ...

2. OR ... should I just invest in a more expensive higher amp PS like the 15v 40amp unit mentioned here and do the entire 16 cells in parallel?
 
I will be upgrading to 16 272ah Lishen LFP cells in about 2+ months (24v 8s2p and two BMS config). I have skimmed thru this thread, but wondering for Top Balancing, If I have a highly customizable charger (The Schneider Conext SW4024 inverter/charger):

1. is it better (or Ok to save money) to use the SW to charge to say 3.4v per cell in series and then Top Balance to 3.65v per cell in Parallel using a cheaper 30v 10amp Desktop Power Supply ...

2. OR ... should I just invest in a more expensive higher amp PS like the 15v 40amp unit mentioned here and do the entire 16 cells in parallel?
Most people are doing 1. or a variation of 1.
I do a variation of 1.
Instead of paralleling the cells after the serial charge I don't break the pack down.
I and others just top off the cells individually to 3.65 volts in place.
It saved me the time, effort and wear/tear on the cells of reconfiguring the pack for parralel and then back to serial.
That is a non trivial task if you consider buffing, cleaning and nooxing every conductive surface and then torquing each connector.
 
So I can leave the battery in the 8s Conf with busbars attached and just apply 3.65v to one cell at a time?
You betcha.
Make sure to get the polarity correct.
I did 6 amps at 3.65 volts but stopped when each cell got to 3.625 volts as measured at the terminals.
There was still a bit of current flowing that way which meant I had to watch like a hawk.
Also I would do the serial charge to 3.55 volts.
Since cells usually come effectively top balanced the one that trips on the serial charge is very likely your weakest cell.
 
I was having very similar issues as the original post. I received my 4 cells at about 3.29V each and after 4 days charging in parallel, was only able to achieve about 3.34V using a regulated power supply. I even bumped the voltage up to 3.7 to get is closer to 5-6A output.

I finally built the battery in serial and after about 8 hours @ 14.1V and 10A, I managed to get them to about 3.38V. But now my Overkill BMS is saying they are at 99% of the 280AH capacity with just 3.38V/cell. I was expecting them to be well over 3.5V/cell at this capacity?

I did not that my PS seemed finicky - moving the wires caused big deviations in Amp output. I switched to eyelet connectors and that helped a little. However, this capacity and V thing is concerning me. I plan to hit 100% on the BMS, then go back to parallel top balancing to try and achieve the ~3.6V/cell upper limit. Or should I be happy with the ~3.4V/cell I appear to be able to achieve at 280AH capacitance?
 
Are you certain you always adjusted the voltage before connecting the leads .... then no changes to the power supply after connecting?

Sorry ... but had to ask. The mistake most people make is to make changes to the power supply after connecting it to the battery.
Thanks for that info. Definitely something I would have done.
 
I was having very similar issues as the original post. I received my 4 cells at about 3.29V each and after 4 days charging in parallel, was only able to achieve about 3.34V using a regulated power supply. I even bumped the voltage up to 3.7 to get is closer to 5-6A output.

I finally built the battery in serial and after about 8 hours @ 14.1V and 10A, I managed to get them to about 3.38V. But now my Overkill BMS is saying they are at 99% of the 280AH capacity with just 3.38V/cell. I was expecting them to be well over 3.5V/cell at this capacity?

I did not that my PS seemed finicky - moving the wires caused big deviations in Amp output. I switched to eyelet connectors and that helped a little. However, this capacity and V thing is concerning me. I plan to hit 100% on the BMS, then go back to parallel top balancing to try and achieve the ~3.6V/cell upper limit. Or should I be happy with the ~3.4V/cell I appear to be able to achieve at 280AH capacitance?
What is the delta (Voltage Diff) displayed in the app? The BMS will not report the true capacity until the battery has been fully discharged then fully charged at least once. You will most likely need to resume your parallel top balance for best results.
 
What is the delta (Voltage Diff) displayed in the app? The BMS will not report the true capacity until the battery has been fully discharged then fully charged at least once. You will most likely need to resume your parallel top balance for best results.
use 10 guage wire.. you won't need to "bump" the voltage and risk your battery... I posted a link.. post 44
 
After almost 4 days top balancing and only achieving about 3.38V/cell, I ended up building the cells into 4S config with BMS and charged for half-day at 14V/10A - this got me to about 3.6V/cell. I put back into parallel and top balanced the rest of the way. Cells were within about 2mV of each other. My problems seem to have been mitigated with "Patience" being culprit as well as possible Power Supply user error (upper voltage setting prior to connect). THANKS FOR THE COMMENTS!
NEW QUESTION - i have a battery monitor shunt. Does it matter if I mount before or after BMS on negative side?
 
NEW QUESTION - i have a battery monitor shunt. Does it matter if I mount before or after BMS on negative side?
Not much.
If you the shunt between the bms and the battery it will still draw a tiny bit of juice even after the bms has tripped.
 
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