Please understand that at 3.65V the cell is at Max Allowable Voltage, it is beyond full.
LFP Nominal Voltage is 3.200, The full working voltage is 3.000-3.400, and typically we look at 2.900-3.450 and the 90% we want to use, because this is where the majority of the power is.
Charging above 3.500 is for all intents & purposes a waste of energy because you can charge your cells, to 3.65V and 100% SATURATED meaning taking <1A, stop charging and the cells will settle to 3.500 within an hour. Above 3.500 and below 2.900 the voltage curve is very short and only represents about 5% total capacity.
Now another Solution that actually may be the cause of your problem with overdriving the cells, is your charge profile. If charging to 29.2V you're overdriving the cells. 3.500V x8 cells = 28.0V
I've done testing including extreme hard-edge limit Thrash Testing with Grade-A Matched, & Bulk cells as well as EV Grade LFP cells and came up with a profile that works well.
NOTE: LFP only requires CC (Constant Current) which will charge the pack to 90% or so and CV (Constant Voltage) with decreasing amperage to finish the last 10%. Technically they do not require Absorb and they NEVER need Equalization by a charge controller (which is for Lead Acid only).
This is my Charge Profile that I use with a Midnite Classic-200 Solar Controller. My Samlex Inverter has identical settings.
All equipment MUST BE Voltage Corrected & Calibrated (VERY IMPORTANT) see link in my signature on how to do it.
Divide Values X2 for 12V. Multiply X2 for 48V.
Absorb: 28.2 for 15 minutes (3.525vpc) (some call this boost)
Equalize: OFF
Float 27.9V (3.4875vpc)
MIn Volts: 22.0 (2.750vpc)
Max Volts: 28.7 (3.5875vpc)
Rebulk Voltage: 27.7 (3.4625vpc)
End Amps: 14A (*1)
(*1): End Amps is calculated from the Highest AH Battery Pack in a Bank. IE: 200AH X 0.05 = 10A 280AH X 0.05 = 14A.
NB: Victron Forum discussion says EndAmps = TailCurrent
This get's the bank charged to full with high amps (Constant Current) and then float (Constant Voltage) tops off so the cells are on average between 3.475-3.500. I am running 7/24/365 so float is used up by the Inverter + provides whatever the packs will take to top off.
** Coulumbic Efficiency for LFP is 99%
NOTE that ABSORB (which is Bulk) is at 28.2 / 3.525Vpc,
Try adjusting your Solar Controller settings to match the above and you may see better results as it "should" not overdrive the runner and allow the other cells to top up more.
Regarding Active Balancers: (
Consider only AFTER changing charging profile & testing that for 3 days of good sun - charging weather.)
There are many types and some are chemistry specific and various features. You want Active Balancing of at least 5A or more... Higher Amperage = Higher cost of course.
There are a vast amount of them out there. They are very specific and quite "quirky". Many are junk !
Known Good are:
QNBBM by Deligreen,
Deligreen / Alibaba link
Heltec,
Heltec / Alibaba Link
Hankzor, (is a VAR Value Added Reseller)
Hankzor Alibaba / Link
Hope this helps.
Steve