A few things going on here and could be a combo of things.
Your Config Review: (terms - be careful ! )
3 EVE 24V/280AH Standard 8S Battery Packs in Parallel within a single Battery Bank. What Cell Grade and are they Matched & Batched ?*
*Matched & Batched are more $ and come with a cycle report of the 3 pass test, These are NOT just matched for IR at standing storage voltage as most vendors do. Please clarify the Grade of Cells and if B or Bulk or Properly Matched & Batched. No need to chase ghosts.
Pack Config for 8S, Cell 1 is typically NEG and Cell 8 is POS
1) When charging Cell 1 will always be a little higher which is not unusual and this should level down as the battery pack charges.
This is disconcerting at first blush and can be problematic in certain conditions.
2) Loose connections would also present Heat Issues (Big Clue) and if the terminals etc are hot on Cell 1 then ensure the terminals are perfectly clean, that there are no burrs or ridges on busbar or lugs (pending on your assembly) and make sure it's all tight. You'd be surprised that oil/wax and ridges & burrs CAN cause all sorts of nastiness that's a PITA to chase down (everyone checks it last).
3) High Rate of Charge (Current/Amps) when cells are reaching above 80%+. LFP does NOT like that ! CC High Amp to 80-85% and then CV charging to finish them off. Once at 80% cell IR starts to increase and the cells will start reducing the Amps they take. A "RUNNER" cell will certainly standout at this point (usually 3.400 Volts +/- a bit) at which point it can run high. Lowering Amps sent to pack can mitigate this a "bit" and allow the others to continue charging to level up (over simplistic).
REMEMBER: There is a Difference between "Working Voltage Range" (3.000-3.400 Vpc) and "Allowable Voltage Range" (2.500-3.650 Vpc) The Amp Hours the cells are rated for comes from the "Working Range" hence why Grade A Cells will test out a MINIMUM of 10% Over label rating when discharged from 3.650 to 2.500 to ensure the Correct AH is delivered from the working range. Bulk / B-Grade cells will rarely ever be able to deliver full AH from the working range, typically 10% less than stated rating.
Now this can get into a very long set of instructions so instead I will suggest you do the following so we can shorten this up and "deal with it" rather than covering all possibilities.
- Check the connections to Cell-1 to ensure they are good. correct as needed.
- Allow packs to discharge a bit as normal to around 60% or so, so you can do a respectable charge run.
- Set the Charge Voltage to 27.8V (3.475Vpc)
-- Your EndAmps/TailCurrent is 14A for 280AH packs (280AH X 0.05 = 14A) always based on Highest AH pack within a battery bank.
-- You can increase that "a little" up to about 18A. and can add 2A per pack in bank. This triggers the transition from CC to CV (float)
- Set your FLOAT Voltage 27.4V (3.425Vpc) (Float is CV, constant current, variable voltage)
- Charge the Bank as normal and observe (Log if possible) once cells go OVER 3.300Vpc (*1)
- Observe the AMPS being taken by the Packs within the bank, as packs reach target voltage @ Full Amp Charge resistance will start to reduce Amps taken, take note of the amps @ voltage (you should see "little" difference between packs as they all reach the same voltage)
-- You MAY even see a pack disconnect due to a runner, that's ok for now. Let the whole cycle go through (might be tough to watch) till charging is done and system enters into Float Mode... Allow to float at least 2 Hours and stop charge. Batteries WILL Settle (normal) and cells within will balance up within the pack in an hour or so (No heavy or crazy loads during this please, better to have NONE actually)
! TAKE NOTE OF Highest & Lowest Cells at End of CC Charging & at End of Float
--- After of hour of Idle Settling, all packs should be very very close together at "Terminal Voltage" and all of the cells within all of the packs should also be pretty darn close to each other. Again take note of Cell Voltages,
*!* These High/Low cells are essentially the limiters... They will trigger the Hi & Lo Volt cutoffs and so they create a "boundary".
(*1) A runner cell will likely be higher than that while the rest may be lower... This is due to the IR differential, this is made worse by higher amperage being delivered to cells. Higher Amps = Faster Running.
IMPORTANT:
DO Account for Voltage/Amperage drop from charge source to Battery Pack Terminals and correct for it. You have to focus on what the voltage is at the Battery Terminals and NOT the charger ! Verify with a good reliable DVOM. NOTE, there is ALWAYS a little loss going through Battery Terminal Lugs (they are most often Brass and it's not the greatest, worse the more recycled it is). Brass is HIGHLY recycled, there is likely WW2 Casing Brass in the brass item you bought yesterday at the store ! Each recycle makes it a little whiter, the more "orange" it is, the more pure it is.
CHARGE PROFILES = PITA !
Every Charger be it an SCC or Inverter/Charger or dedicated charger, have different profiles, some great and some well not so much. LFP requires 2-STAGE CC Constant Current & CV Constant Voltage Variable Current. The Transitioning from CC to CV is handled differently with various brands of types of equipment. It can never be as simple as we would like eh ! Makes for lots of Blue Air LOL. So this of course makes it fiddly and difficut to just say "use this setting" because every single setup is different. Even worse is some companies use terminology that is far less than clear when describing how their profiles work and how they are staged.
The above info will help to further Diagnose what is happening within the packs and the bank overall.
Please be very clear as with what Grade & Level of cells you purchased and do understand that a video with a Voltage & IR Testers such as a YR1035 Hand Held battery tester is NOT MATCHED ! That is ONLY Voltage & IR Matched at standing storage voltage ! The VENDORS PLAY ON THE WORDS / TRANSLATION factor to excuse this obscene behaviour.
PS: If you are Active Balancing and can set parameters for that, start Active Balancing at 3.300Vpc "During Charge" and allow for 20mv differential.
Hope this helps, Good Luck.
Report back, I'm tagging this thread to watch it.