Okay, so I top balanced my 8 EVE 304 AH cells today. I don't have a constant voltage charger like the ones so many people use, so instead I tried something that I think should work pretty well.
What I used:
8s JK BMS
MPP LV 2424 Hybrid Inverter charger
Battery shunt that I found on Will's website (not victron, but his budget version. I can't remember the brand.)
The JK BMS has an active 2A balancer within it.
I was able to program the inverter charger (plugged into a 30A plug) to only charge with 2A.
Set the BMS over voltage protection to 3.65v per cell.
Set the inverter charger to a bulk and float charge of 29.2v (3.65v per cell)
Then I monitored what happened through the BMS bluetooth app and a battery shunt that I have.
I noticed that I had a few cells that had seemed to be with all the others, until the voltages started getting higher. On cell in particular was about 0.3 v below the top cell ( roughly 3.36 and 3.65 respectively). Since my inverter charger was just trickling in about 0.6 A (it was using some power to power the inverter itself so 2 A became 0.6A according to my shunt) The active balancer was able to semi keep up. Realistically since the programming of the balancer isn't perfect at choosing which cell to add power to or remove power from, the charger would charge at 0.6A for maybe a minute, and then it would shut off and the balancer would continue balancing for a minute, then the charger would turn back on and the cycle would just keep repeating itself. The BMS was successfully cutting the charging off whenever a cell popped up above the 3.65v. Then the balancer would move some of the power around and the cell voltages would settle around 3.64v before the charger then turned back on. This on off on off, and the fact that the current in was less than 1 A, the battery voltage wasn't spiking too much due to the charging current. Over about 2 or 3 hours of it doing this, all cells were in the 3.64-3.65v range. At the very least, pretty close to fully charged and balanced albeit not 100% perfectly.
I figure even though there is still a slight voltage difference between the top and the bottom cell, it is so small that the active balancer in the BMS isn't even kicking in to attempt to balance.
I just felt like I would document what I did to top balance my DIY battery pack since I wanted to avoid needing to buy a charger in addition to everything else that I had already purchased. I'm curious what you guys think of this method for top balancing? After the cells all seemed top balanced, I dropped the float voltage down to 27.6v and then disconnected the batteries from the system to see how voltage drops overnight. I will change the charging and voltage parameters in the inverter charger and the BMS settings to have 3.45v be seen as 100%. I just wanted to be sure that the cells were reasonably balanced first.
Curious to hear your thoughts!
What I used:
8s JK BMS
MPP LV 2424 Hybrid Inverter charger
Battery shunt that I found on Will's website (not victron, but his budget version. I can't remember the brand.)
The JK BMS has an active 2A balancer within it.
I was able to program the inverter charger (plugged into a 30A plug) to only charge with 2A.
Set the BMS over voltage protection to 3.65v per cell.
Set the inverter charger to a bulk and float charge of 29.2v (3.65v per cell)
Then I monitored what happened through the BMS bluetooth app and a battery shunt that I have.
I noticed that I had a few cells that had seemed to be with all the others, until the voltages started getting higher. On cell in particular was about 0.3 v below the top cell ( roughly 3.36 and 3.65 respectively). Since my inverter charger was just trickling in about 0.6 A (it was using some power to power the inverter itself so 2 A became 0.6A according to my shunt) The active balancer was able to semi keep up. Realistically since the programming of the balancer isn't perfect at choosing which cell to add power to or remove power from, the charger would charge at 0.6A for maybe a minute, and then it would shut off and the balancer would continue balancing for a minute, then the charger would turn back on and the cycle would just keep repeating itself. The BMS was successfully cutting the charging off whenever a cell popped up above the 3.65v. Then the balancer would move some of the power around and the cell voltages would settle around 3.64v before the charger then turned back on. This on off on off, and the fact that the current in was less than 1 A, the battery voltage wasn't spiking too much due to the charging current. Over about 2 or 3 hours of it doing this, all cells were in the 3.64-3.65v range. At the very least, pretty close to fully charged and balanced albeit not 100% perfectly.
I figure even though there is still a slight voltage difference between the top and the bottom cell, it is so small that the active balancer in the BMS isn't even kicking in to attempt to balance.
I just felt like I would document what I did to top balance my DIY battery pack since I wanted to avoid needing to buy a charger in addition to everything else that I had already purchased. I'm curious what you guys think of this method for top balancing? After the cells all seemed top balanced, I dropped the float voltage down to 27.6v and then disconnected the batteries from the system to see how voltage drops overnight. I will change the charging and voltage parameters in the inverter charger and the BMS settings to have 3.45v be seen as 100%. I just wanted to be sure that the cells were reasonably balanced first.
Curious to hear your thoughts!