Thank you! I hope to find other ideas and concepts to show like this. I always loved science shows that had fun demonstrations, I think it'd be a blast to think of more to do. ^_^
Good demonstration. I'm assuming the battery that's higher than the others drains from it to the other batteries via the balance leads. I suppose a simulation of that with this setup would entail a small diameter hose that goes from one bucket to the next. And each bucket would have it's own partner battery with a linked tiny balance hose. I still have to watch more of your videos to get a better idea os what's going on. Good to develop an understanding of control systems involved.
Most BMS units use "passive" balancing that stops charging the pack once any cell reaches a set voltage, eg 3.65 for LPF, and then turns on the bleeder resister for the fully charged cell, slowly draining it. Any you're right, it drains at such a slow rate, that it can take a significant amount of time drain enough so that all the other cells can get to full charge. Even worse, if you have 3 cells fully charged and one cell at a low SOC, all three fully charged cells need to be slowly drained. Imagine a 16S pack with 15 fully charged cells. It would need to bleed 15/16 of the energy being put into the pack to top up that last cell. You can improve the speed of passive balancing by reducing the value of the bleeder resistor so that it draws more power, draining the cell quicker. But of course that has the disadvantage of causing more heat, especially as more cells reach their full charge. In your demonstration, this would be like drilling a bigger hole at the top of the pail, causing your patio to get pretty wet. ;-) In contrary, "active" balancers move energy from one cell to another. That would be like dunking a cup into the fuller pail and moving a cup of water into a pail that is less full, and repeating that until all pails where equal. Less water spills onto the patio, ie, less energy waisted.
The BMS 'balancing' voltage is a little lower, 3.4V than the cutoff of 3.65V so above 3.4V the resistor is working and above 3.65 the main relay/mostfets are shutoff. But as you said they are so small (100mA) that they are effectively useless unless you can use a wall charger plugged in for several days after the first cell hits 3.4V. Even a a 5W solar panel would be too much for 100mA resistors...so yeah, these BMS designers still haven't figured out how to manage solar charging with 10s of amps.
Hi to you and honestly speaking I'm impressed about your videos!!! Is very nice explanation but in my point of view for your application a must is a active balancer that can "move" current from one battery to the other continously and constantly!!!. The discussion over the net is if is necessary balancing "all the time" or only during the nearly full charge and full discharge because is in that area the active balancers can move lot of energy(they all work due to difference of tension and the bigger is the difference, the bigger is the current is moving. with your tension should work great the active balancer!!! Have a nice day!!!
Oh you clever girl. Nice demo. That is how I though it works but know I understand it even better. I wanted you to rotate the right two buckets about 5-10 mins CW to match the print on the left two buckets. I disagree with your last statement. I understand by connecting each battery in parallel and allowing them to rest, the current will pass to the lowest SOC batter(ies) until they all reach the same potential (15-30 days?). Then connect a charger to bring the pak up to your final cutoff voltage. Then all batteries will be at the same SOC. Right? Thoughts? Thanks for sharing.
Excellent explanation and or demonstration. Now my mind running wild, What if there was a controller that instead separated each cell charged it independently and only on the output tied them together? heck even had a mosfet to throttle each cell so they discharged equally... This would solve the 'well the peak solar time is NOW but cant charge because one cell is to high' problem and help keep the cells balanced during discharge. I need to think more on this. Thanks for sharing I am learning a lot!
I've got a BMS I'm going to test soon that has a good approach. Andy showed it on Off-Grid Garage first used it; Basically, it sucks power (water) out of the fullest battery (bucket) into a supercap bank, then dumps it into the cell with the lowest battery (bucket). I've got it, and plan to play with it after I get the battery box rebuilt.
i kind of understand this concept and the BMS how it manages the power, i have often wondered about the charging of AA batteries with a simple plug in adaptor into a standard 240v (UK) house supply, i gather AA batteries have a memory that is depleted, a work colleague who understood these things suggested it is best that when batteries are new to charge fully for the suggested length of time, 4hrs 10hrs etc a few times and totally discharge them in a torch etc, so does that happen here? do these batteries in your system have a memory, will each cell become more damaged than others in due course and can the BMS not just shut off a cell and let the others charge to the same level, or even use the overflow power to charge into the other cells to save on wasting power, if that's a thing or not
Good demonstration. But here is the important part. Solar is like the hose on full power it can fill much faster than the holes can drain. Using a trickle to fill will not put in more than the holes take out and will eventually fill the low buckets and not over fill the high ones. So you can balance just by a low current charger in your setup, which is kind of how all these BMS products are designed(wall charger that tapers current near top voltage). Although, better just to parallel all the batteries and let them sit.
Resistive BMSs don't and cannot work that way. BMS devices that move energy from a high to a low cell can, but the charge input has to be disconnected. Why? Because there's very little energy stored in a LiFePO4 cell at both ends after the 'knee' - and even a very small input can drive a cell over voltage very quickly - even with a BMS attached and actively bleeding current. Resistive BMSs can never fully charge all cells because all charge current flows through all cells - and it takes more current to charge the remaining 3 cells than a single shunt can convert to heat. Balancing is a distant second to the primary BMS function of completely disconnecting all charging inputs once the first cell reaches high voltage, and by disconnecting all loads when any cell reaches low-voltage cut.
Interesting demonstration! I really do appreciate your effort in putting this together. But after some extended thought on this, something really bothered me. That is that this demonstration does not actually simulate a 4S battery pack. Why? Because according to Kirkhoffs Current Law a Serial Connection would draw current through all 4 cells when they are being discharged as a pack. The SAME current. What you have demonstrated isnt even a battery pack. Unless each cell is interconnected directly to the next adjacent cell with a tube of some fashion these are simply 4 independent cells charged and discharged separately..
@Robert Orr While you're correct that current flows from all cells when the cells are being discharged, her demo is of a static battery not being discharged. Also - note that (most if not all) BMS devices use voltage as a proxy for state of charge. The problem with the analogy, and with all BMS devices that use voltage for balancing, is that the cell voltage that results from a fixed charge current varies with the cell's internal resistance. A damaged cell has a higher Ri, and it's voltage sags more deeply (and it hits low voltage cut first) under load, and rises first during charge. Your tube suggestion only applies if cells are connected in parallel.
Great job, thank you Miss.
Absolutely Brilliant demonstration!
Thank you! I hope to find other ideas and concepts to show like this. I always loved science shows that had fun demonstrations, I think it'd be a blast to think of more to do. ^_^
Great demo!
Great visual demonstration of the concept. This should help others better understand top balancing.
Thank you! I hope so, it would make me happy to know it helped other more visual learners "get it".
I have been enjoyed, so thank you for delivering.
Thank you for watching, Frej!
great demonstration!
This was really excellent! Thank you so much :)
Hopefully you catched up your phone soon enough.
Cool experiment and nice backyard :)
Definitely a “bucket” list item! 😉
lol
Brilliant demonstration I couldn't see the point in a BMS when the wires are so thin when the battery is so high amps now I understand thank you.
Good demonstration. I'm assuming the battery that's higher than the others drains from it to the other batteries via the balance leads. I suppose a simulation of that with this setup would entail a small diameter hose that goes from one bucket to the next. And each bucket would have it's own partner battery with a linked tiny balance hose. I still have to watch more of your videos to get a better idea os what's going on. Good to develop an understanding of control systems involved.
Most BMS units use "passive" balancing that stops charging the pack once any cell reaches a set voltage, eg 3.65 for LPF, and then turns on the bleeder resister for the fully charged cell, slowly draining it. Any you're right, it drains at such a slow rate, that it can take a significant amount of time drain enough so that all the other cells can get to full charge. Even worse, if you have 3 cells fully charged and one cell at a low SOC, all three fully charged cells need to be slowly drained. Imagine a 16S pack with 15 fully charged cells. It would need to bleed 15/16 of the energy being put into the pack to top up that last cell.
You can improve the speed of passive balancing by reducing the value of the bleeder resistor so that it draws more power, draining the cell quicker. But of course that has the disadvantage of causing more heat, especially as more cells reach their full charge. In your demonstration, this would be like drilling a bigger hole at the top of the pail, causing your patio to get pretty wet. ;-)
In contrary, "active" balancers move energy from one cell to another. That would be like dunking a cup into the fuller pail and moving a cup of water into a pail that is less full, and repeating that until all pails where equal. Less water spills onto the patio, ie, less energy waisted.
Exactamento.. 👍
The BMS 'balancing' voltage is a little lower, 3.4V than the cutoff of 3.65V so above 3.4V the resistor is working and above 3.65 the main relay/mostfets are shutoff. But as you said they are so small (100mA) that they are effectively useless unless you can use a wall charger plugged in for several days after the first cell hits 3.4V. Even a a 5W solar panel would be too much for 100mA resistors...so yeah, these BMS designers still haven't figured out how to manage solar charging with 10s of amps.
@@jmaus2k Good point about balancing starting before cut off..
Muy bien explicado !!
Hi to you and honestly speaking I'm impressed about your videos!!!
Is very nice explanation but in my point of view for your application a must is a active balancer that can "move" current from one battery to the other continously and constantly!!!. The discussion over the net is if is necessary balancing "all the time" or only during the nearly full charge and full discharge because is in that area the active balancers can move lot of energy(they all work due to difference of tension and the bigger is the difference, the bigger is the current is moving.
with your tension should work great the active balancer!!!
Have a nice day!!!
That is exactly why i think of Some sort of Switching supercapacitor BMS design..
Oh you clever girl. Nice demo. That is how I though it works but know I understand it even better. I wanted you to rotate the right two buckets about 5-10 mins CW to match the print on the left two buckets. I disagree with your last statement. I understand by connecting each battery in parallel and allowing them to rest, the current will pass to the lowest SOC batter(ies) until they all reach the same potential (15-30 days?). Then connect a charger to bring the pak up to your final cutoff voltage. Then all batteries will be at the same SOC. Right? Thoughts? Thanks for sharing.
Excellent explanation and or demonstration. Now my mind running wild, What if there was a controller that instead separated each cell charged it independently and only on the output tied them together? heck even had a mosfet to throttle each cell so they discharged equally... This would solve the 'well the peak solar time is NOW but cant charge because one cell is to high' problem and help keep the cells balanced during discharge. I need to think more on this. Thanks for sharing I am learning a lot!
I've got a BMS I'm going to test soon that has a good approach. Andy showed it on Off-Grid Garage first used it; Basically, it sucks power (water) out of the fullest battery (bucket) into a supercap bank, then dumps it into the cell with the lowest battery (bucket). I've got it, and plan to play with it after I get the battery box rebuilt.
@@TheDigitalMermaid Oh yes that is smart! I'll keep watching and see your test
i kind of understand this concept and the BMS how it manages the power, i have often wondered about the charging of AA batteries with a simple plug in adaptor into a standard 240v (UK) house supply, i gather AA batteries have a memory that is depleted, a work colleague who understood these things suggested it is best that when batteries are new to charge fully for the suggested length of time, 4hrs 10hrs etc a few times and totally discharge them in a torch etc, so does that happen here? do these batteries in your system have a memory, will each cell become more damaged than others in due course
and can the BMS not just shut off a cell and let the others charge to the same level, or even use the overflow power to charge into the other cells to save on wasting power, if that's a thing or not
Somebody has big bucket money.
I really dove in to the life savings for this one... :P
Best comment award
HOWdy D-M,
a VISUAL-AIDE to Battery-TOP-Balancing 🙂
Thanks
COOP
...
I forget one thing....you can install more than one active balancer in parallel and you'll have lot of energy moving from one cell to another.
You dumbed it down so easily even a caveman could understand.Thank you!
Awe, thanks NJ! ^_^
Good demonstration. But here is the important part. Solar is like the hose on full power it can fill much faster than the holes can drain. Using a trickle to fill will not put in more than the holes take out and will eventually fill the low buckets and not over fill the high ones. So you can balance just by a low current charger in your setup, which is kind of how all these BMS products are designed(wall charger that tapers current near top voltage). Although, better just to parallel all the batteries and let them sit.
Resistive BMSs don't and cannot work that way. BMS devices that move energy from a high to a low cell can, but the charge input has to be disconnected. Why? Because there's very little energy stored in a LiFePO4 cell at both ends after the 'knee' - and even a very small input can drive a cell over voltage very quickly - even with a BMS attached and actively bleeding current. Resistive BMSs can never fully charge all cells because all charge current flows through all cells - and it takes more current to charge the remaining 3 cells than a single shunt can convert to heat. Balancing is a distant second to the primary BMS function of completely disconnecting all charging inputs once the first cell reaches high voltage, and by disconnecting all loads when any cell reaches low-voltage cut.
Interesting demonstration! I really do appreciate your effort in putting this together. But after some extended thought on this, something really bothered me. That is that this demonstration does not actually simulate a 4S battery pack. Why? Because according to Kirkhoffs Current Law a Serial Connection would draw current through all 4 cells when they are being discharged as a pack. The SAME current. What you have demonstrated isnt even a battery pack. Unless each cell is interconnected directly to the next adjacent cell with a tube of some fashion these are simply 4 independent cells charged and discharged separately..
@Robert Orr While you're correct that current flows from all cells when the cells are being discharged, her demo is of a static battery not being discharged. Also - note that (most if not all) BMS devices use voltage as a proxy for state of charge. The problem with the analogy, and with all BMS devices that use voltage for balancing, is that the cell voltage that results from a fixed charge current varies with the cell's internal resistance. A damaged cell has a higher Ri, and it's voltage sags more deeply (and it hits low voltage cut first) under load, and rises first during charge. Your tube suggestion only applies if cells are connected in parallel.
And... right at the end.. they bottom balanced.. ;)
lol!
Sorry to hear about your thumb... 😟