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epever settings for lithium, what to do with boost/absorb and float voltages.

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  • unexpected
    replied
    Its weird that this is the most popular cheap MPPT and very few discuss charging lithium batteries with it. Unless everyone is just slapping cheap bms boards on top and crossing their fingers. I've been using 18650s for a few years so at least I have that, most fall off at 3.2/3.3 which is probably closer to 30% discharge. The high point and the inability to completely cut charging is where I'm having doubts.

    Leave a comment:


  • Mike90250
    replied
    That's why engineers study for a long while to get this stuff right. Knowing what happens under all conditions leads to longer component lifetimes.

    You want to stay away from fully charged (no more than 85%) and deeply discharged (no deeper than 20% remaining) Figuring those points for your cells will take a while.

    Leave a comment:


  • epever settings for lithium, what to do with boost/absorb and float voltages.

    I'm getting 2 nissan G1 lithium packs, need some help setting up the epever tracer AN. I've deduced the following:


    Each battery is a 2s2p, 2 of them should give me ~16v and still work with a non 24v+ voc panel. A kind of "turbo" 12v system.

    [B]Empty voltage[/B] 2.5v per cell
    [B]Nominal[/B] 3.75v per cell
    [B]Max[/B] 4.15v per cell
    [B]Knee[/B] 3.2v per cell (from users of large banks on youtube)

    Operation temperature range -25 ~ 60 ℃ (which i will just program)

    So now for the epever,30A: less straight forward. It claims to support lithium but these settings can only be set up from the user parameters in the PC software. I don't know if the "lithium" parameter page settings all even work or what oilengine control is.

    This is what I have so far:

    [B]Over Voltage Disconnect:[/B] 16.6 (4.15)
    [B]Over voltage reconnect[/B] 16.2 (4.05)

    [B]Equalization:[/B] 16.4v (4.1) time 0,disabled
    [B]Boost Voltage:[/B] 16.4v (4.1) time 0, disabled
    [B]Float Voltage:[/B] 15.6v (3.9) ??
    [B]Boost Reconnect[/B] 15.2v (3.8) ??

    [B]Charge limit:[/B] 16.4v (4.1)
    [B]Discharge Limit[/B] 12v (3.0)

    [B]Low Voltage Disconnect:[/B] 12.8v (3.2)
    [B]Low Voltage Reconnect [/B]14v (3.5)

    [B]Under voltage warning:[/B] 13.2v (3.3)
    [B]Under volt end[/B] 14v (3.5)

    Aiming to get an SOC in the low 90s and discharge to about the knee voltage where current output will drop anyway.
    What I don't know is if the float voltage should be lower/higher and if I should be completely disabling the boost/absorb stage. With the time at 0 the controller will charge in bulk to 16.4 and then drop into float, which is hopefully low enough to not stress the cells but still allow the panel to directly drive loads.

    Not sure what voltage will bring back the bulk charge unfortunately or if that boost should act as a buffer in between.

    What it looks like in the software:

    Lithium page:

    lithium.png

    Classic page:

    regular.png
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