I just got the Active BMS working.
My battery pack is 16 EVE 280Ah cells connected in a 4P4S configuration.
Chemistry: I the Chemistry settings list is relatively short. Is Winston the best equivalent choice from the list?
Capacity: the manual states this is for a single string... is this a single battery (280Ah) or since I\'m stringing all of the paralleled cells together would this be 1120Ah.
Parallel Strings: likewise would this be 0 or 4 based on my configuration and the answer above 0 if the capacity is 1120, and 4 if the capacity is 280Ah.
Voltages: the max and min cell voltages (3.85/2.8) seemed to include buffers to
the Winston 700ah datasheet (4.0/2.5). My
EVE cells datasheet call for (3.65/2.5)... I\'m assuming I should reset the BMS max/min cell voltage however since the 3.65 seems like it doesn\'t need a buffer. Is this a reasonable assumption? Though I should have enough capacity to leave the low end at 2.8.
Balancing & Charging: I\'m assuming I should leave these unchanged from default as they provide safety margin relative to the datasheet specs?
Thanks in advance for the wisdom.
I\'m running the same basic configuration you are (16 eve 280 cells), and have the same question about voltage settings for these cells. I reduced the max cell voltage for now to reduce wear on the batteries and provide a buffer against over-charging cells.
One additional question: I think the SOC has reset the 100% charge voltage automatically to the new reduced voltage setting, but it\'s hard to be sure. I adjusted the max cell voltage and and charge voltage down, then the next time I looked the system registered as 100% SOC (up quickly from ~70%). It would be good to know what the impact is of reducing the max charge value down on displayed SOC and what should be used for the total battery capacity. If it does adjust downward automatically based on the lower max charge voltage, that may not be ideal as the bank would show 100% charge at partial charge levels, hiding the true SOC.
Very interested to know what the recommended charge settings are for EVE cells and also how they might impact the SOC calculations.
The default chemistries are just meant as a starting point. You will need to find the manufacturers specs for your model of battery and apply those numbers. You may even want to start on the conservative side, as 95% charge capacity is achieved usually under 3.5V for typical LFP cells.
I have found that for the Active BMS you can tweak the balance parameters to start a bit lower.
And when changing your parameters it will take several full charge/discharge cycles for the system to reset itself. Its not a static calculation.
Thank you. This is very helpful I\'ll reference the EVE datasheet and plug in numbers.
Can you clarify the question on Capacity & Parallel Strings?
With a 4P4S configuration of 280ah cells, would the capacity be 1120ah with 0 parallel strings, or 280ah with 4 parallel strings?
If you have 4 parallel \"banks\" of 4 cells in series, you\'re capacity is 1120Ah. Parallelling banks adds capacity, while serializing banks increases voltage. Since you have 4s, you\'re in a 12V system.
Thank you. I understand parallel vs. series . I\'m asking about the specific settings in the \"Battery Pack Data\" section of the software where it asks for Chemistry, Capacity, Cycle and Parallel Strings. In the manual, they are vaguely described, so I\'m trying to clarify these settings for a 4P4S setup. My assumption is they should be \"1120ah\" for Capacity and \"0\" of Parallel Strings. I have no idea what \'Cycle\' is (Number of effective battery cycles. ) is supposed to represent, so I\'m leaving this as is.
However, I could see a scenario where they system is trying to learn the actual number of cells in each pack, and would want to see these defined as \"280ah\" for capacity and \"4\" for paralleled cells from which the BMS could calculate total capacity of the pack as 1120ah.
I\'m just trying to not assume anything here so I can get optimum performance and confidence in the system, since the initial implementation has gone well, but not as smoothly as expected.
Jamie, which parameter asks for Parallel strings?
Anyway, connecting your cells in 4P4S would result essentially in 1 Parallel string with 1120Ah capacity at 12V
In my experience i treat the voltage settings in the cell\'s spec sheet MAX and MIN values. Looking at the trends that usually come with the documentation of your cells, there is very little capacity at the ends - bring your protection cutoffs, a little inside the spec settings, and your control settings a little inside those.
Pieter
this is useful information
Thank you. I understand parallel vs. series . I\'m asking about the specific settings in the \"Battery Pack Data\" section of the software where it asks for Chemistry, Capacity, Cycle and Parallel Strings. In the manual, they are vaguely described, so I\'m trying to clarify these settings for a 4P4S setup. My assumption is they should be \"1120ah\" for Capacity and \"0\" of Parallel Strings. I have no idea what \'Cycle\' is (Number of effective battery cycles. ) is supposed to represent, so I\'m leaving this as is.
However, I could see a scenario where they system is trying to learn the actual number of cells in each pack, and would want to see these defined as \"280ah\" for capacity and \"4\" for paralleled cells from which the BMS could calculate total capacity of the pack as 1120ah.
I\'m just trying to not assume anything here so I can get optimum performance and confidence in the system, since the initial implementation has gone well, but not as smoothly as expected.
Did you ever actually get an answer to your question?
A \"Cycle\" is determined as having been completed by the BMS when the cell pack goes from relatively full condition to a relatively empty condition, and is used to assist in monitoring the health and expected longevity of your pack.
And you capacity is calcuated as the number of cells you have in parallel.
If you have 8 cells of 200aH each in a 2P4S configuration, your \"CAPA\" or capacity is 2 x 200 = 400 aH
