Using Equalize Function to Periodically “Full Charge”

100 Proof

"Please Lord, don't let me do something stupid."
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Feb 14, 2021
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I have a Morningstar Tristar-MPPT-45 solar charge controller that allows a user to set a DIP switch to only allow equalization by manually holding a button for 5 seconds. The equalization function itself is programmable for both voltage and duration. Much like the normal bulk/absorption functions, it allows for bulk charging at full amps until it hits a voltage limit, and then will hold that voltage for a user defined time. It also allows for a max time in the equalization state in the case where the target voltage is never reached.

I am contemplating setting my bulk/absorption/float functions to bounce between approximately 10%-ish to 85%-ish capacity to extend cell life, but from reading these forums I believe there is potential value in topping up further into the knee of the charge curve periodically, perhaps every 6 months or so. It seems to me that rather than reprogramming my SCC to do this, I could set my equalize function to go to, say, 3.6V/cell for 15 minutes when manually commanded to do so.

My bank (still waiting on cells) will be 2P4S, 460AH EVE cells. My solar array is 465W.

I would value input and a discussion on the pro & cons of this scheme before I move forward with it.

Thanks in advance!

100 Proof
 

Steve_S

Offgrid Cabineer, N.E. Ontario, Canada
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Never EQ LFP, you'll be chucking the cells at Recycle if you do. Why do you think EVERYONE says to never do it?
LFP is NOT Lead and does not need any of that nonsense. CC (Constant Current) & CV (Constant Voltage [float]) Charging only.
 

100 Proof

"Please Lord, don't let me do something stupid."
Joined
Feb 14, 2021
Messages
95
Never EQ LFP, you'll be chucking the cells at Recycle if you do. Why do you think EVERYONE says to never do it?
LFP is NOT Lead and does not need any of that nonsense. CC (Constant Current) & CV (Constant Voltage [float]) Charging only.
This WOULD be "CC (Constant Current) & CV (Constant Voltage [float]) Charging only." Just with different setpoints for periodic usage. Not remotely for the reasons it would used for a FLA bank.

Do you think 3.6V/cell for 15 minutes every 6 months will send them to the recycle heap? I'm thinking it possibly may help with cell balancing through the BMS and can be used to "recalibrate" my Coulomb counter.
 
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RCinFLA

Photon Sorcerer
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Jun 21, 2020
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If you can set voltage level and time for equalize sure you can use it. Many solar charger absorb cycle is just a absorb voltage setting and a timer so it is exactly same thing.

You will not be accurately setting SOC level solely by charger voltage settings however. It also depends on rate of charge current during bulk phase.

With high bulk current (>0.3C) you will not be at 100% SOC when cell hits 3.65v. With low bulk current (<0.05C) you will be at 100% SOC when cell hits 3.45v. There is a kinetic over-potential voltage required to create and move lithium ions which is greater the greater the cell current. This is in addition to I^2 * Rs drop of cell's internal impedance.
 
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time2roll

Photon Sorcerer
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Mar 20, 2021
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2,184
I also have the MS MPPT and I plan to set my equalize up in the 14.4 - 14.5 zone and leave the daily charge a bit lower around 13.8 - 14.0 volts.
 

JimmyL

New Member
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Jun 14, 2021
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The BMS i intend on buying says to do exactly what you are saying. If charging to 3.5v/cell set equalise to 3.55v/cell once a week.
 
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