I dont know. My thoughts. Mostly uneducated conjecture based on minimal experiences.
I think that is more than normal, ( new revision ANT algorithm).
I dont know why the old ANT would limit charge current / bleed voltage selection, it makes sense to me that it does not. 10A? Silly. I can charge the batteries in my garage at 2C, 100A, and it will be fine. Rated to take that. An Ant would be worthless here with its 10A.
Now, I know we are talking bout BMS... but bear with me for a little guys... : I like to begin balance at 3.4v, and maximize charge current. However, if you set balance " precision" to close, the BMS will sit there and hunt, all day. A hunting BMS is hot.... a " not hunting" bms is cool. So I set precision to a reasonable level, usually 2 or 3 mV for my big, fine, high cost cells. A small pack this may be way to small. you need 40-50mV or even less precision: for the balance hysteresis, encountered. This is adjustable in the new software?
RG: I propose this: Try two baseline tests: One, balance from 4.1v up, like you describe. The next, begin the balance at 3.4v/cell. Consider the time, the balance bleed current ( resultant in dissipate power ie heat) , and the SOC when charged for result. For each scenario. Measure the heat displayed by the BMS in both scenario.
ANT BMS (previous version) heats to 60c very fast when set to the default 180mA and that's why I always limit it to 100-120mA max and even when 20 rows are balancing it wouldn't go above 55c on a hot day.
What gets hot? This is too general a statement. I do not know if you have a FLIR, RG, but I have looked at the BMS the whole cycle watching on the camera: It is CERTAIN ORDER of bleeding sets, and they toggle, on and off, all the time, through the populated string. You can see it quite clearly on a FLIR camera. They exchange the hots and colds in order, in the bleed bank: If it is getting excessibly hot, I think the balance precision should be lowered ( increased numerically). Hunting.
Do you heat sink your BMS? RG? Have you a chance to try that? Thermal transfer. Might help a little, some of these BMS are just out of limits for the design capability of the resistance bank ( wasting 1w on a resistor made for 500 milliwatt (mW) ma.... Just cannot do it, bleed the voltage, at this current.. ) .
john61ct said:
rg12 said:
Why wouldn't it balance at any charge speed?
Top balancing is intrinsically harmful to longevity.
The ANT BMS has a problem with heat , when it has to balance a few cells at the same time over a longer time. So balancing during the whole charge procedure with higher currents could end in a thermal problem.
... or, give more time to dissipate the talked about dissipate power. This is how i see it?
rg12 said:
I'm setting the balance start voltage at 4.10V
Besides, a normal balance procedure can take from hours to days so the BMS needs to be built for that
Or crapped out secondhand scrap?
Use the BMS for protective functions only, get a dedicated balancer.
I kinda disagree with alot that has been put forth in this thread.
I think the PID loop in alot of modern BMS can use some work ( or changeable variables, of the P, I, or D, for that, but you cant get that with bleed resistors easily)... The PID loop will overshoot, undershoot, repeat. Cause excess heat, that the developer hopes ( hope is a great thing) is good enough, and within the heat capacity of the design.
Overshooting and undershooting ( PID LOOP BALANCER GATE CONTROL) is more important to look out for.. as opposed to charge current itself. We have the hard limits of the charge current in the datasheets: I dont suppose you guys like to ignore them. So we must be in bounds.
You guys see it. Charge a battery at 25A and it goes so far out of balance.. Charge it at 50A and does it goes out faster? I dont really agree with this especially if you never go full empty or full full: I dont know. A cell is capable of a ( rated?) max charge current,. You will know when you go over it ( the BMS isnt gonna be hot.. but the cells will proportionally get hot, and hotter, when you go over the max charge).
Do the math. My best advice. Time is measured in min, they are 1/60 of an hour. Capacity is measured in wHours, or watt days, or watt minutes. Watt seconds, watt weeks, watt months. Percentage is " per hundred".. ie.... 1 percent is 1/100.
How many watts are you wasting? How many watt hours is that per cell string? How long does this, or any specific string, under this balance? You guys ignore the process: They come up, they get in line, they go up more, they top out. For me.
A day, symbol d, is defined as 86 400 seconds. The Second is the base unit of time in SI units. … the duration of 9 192 631 770 periods of the radiation corresponding to the transition between two hyperfine levels of the ground state of the caesium 133 atom.
I begin balancing when the SOC vs voltage comes together and balance the whole time until full charge. This depends on the cells, is usually around 3.4v for my recycled EV cells. I begin balancing there.
From the way you guys describe, you have never done a middle balance. I found a middle balance is the best way to begin the baseline the cells. The log also ends there. I'm weird though. Negates some of the variables but thats my charger, very configurable.
With great imbalances say a delta of 0.1V or higher
Lol.... I dont think I ever saw such imbalance with the cells I use. 1/10? 10%? lol hell no. Most I see is... 0.001v.... ( 1/100) and is usually less, in the range of half a millivolt. Poor BMS trying to balance 10% variation over the pack. Lol. I can only imagine. Sure I have seen that, in beat ToolPacks, but those are small and the balance is bought back into line very low in SOC for my datalogging of baselines.... but when I balance the whole charge ( from 3.2v/cell to 4.25v/cell) they come in line fast. For they are so small. Same with th larger cells, but the variation is not great to start with.
Top balancing is intrinsically harmful to longevity.
High current charging is causing imbalance, only after the main charge is nearly done should balancing start.
This is a blanket statement that I wholly disagree with, from my experiences. I have some of the oldest batteries, strongest, you can find, all top balanced regularly to 4.28v/cell on the big charger.... With its 1A balance current. Mostly bulk charged to 4.28v and settles at 4.195v...
Whether it is 0.5C (7.5A), 1C ( 15A) or 2C ( 30A).. they logs show the same imbalance, from the start of the charge, ( where the charger stopped cause one of the string was going low, empty,, for longevity) and the same coming together... at the 3.4v point for my cells I like to use... They love to come together for me at 3.4v/cell.... right at the beginning of the CC mAh input... When charged from empty.
Never go full empty on any cell string. This is what throws them out. I can stop a discharge datalog at 3.0v/cell... and bulk charge right up to capacity full SOC and max v....
Empty them to 2.8v..... unilaterally.. and some will suffer greatly.. and get even more need for balancing current... ... when you go through the climbs of IR at zero SOC and 100% SOC....
Empty to 2.5v/cell and you see it more.
Shoot for zero (0v?) on a string and then a recharge.. see what is still in balance, and what is not.... ( if the cell strings have not been destroyed... yet)
IR climbs like hell on the 0% SOC and at the 100% SOC... Go for it.. Try to measure the IR of a dead battery.. on discharge...
Or measure IR of a full battery... on charge..... when it goes over 4.4v/cell..
Let us know what kind of heat you make. Why sit there hammering the topped out cells with current in and out ( charge and balance bleed, same time) while waiting for the lesser string groups to " catch up".... Nah . I like them all to come together much much earlier. Around teh place the natural SOC begins to fill the cell... So it can bleed the entire time of the charge.. From 3.4v up. Quick termination at chosen CV value ( whether it be 3.8v/cell, 4.0v/cell, 4.25v/cell, ect). A BMS that cannot hack the balance will sit there and get hot as the charger pounds the current into the last cells as they (dont) want to top balance... the good ones suffer. As the bad ones catch up.
Ok that is all.