Batteries won’t stay at full change after reaching float.

Jarvis442
Jarvis442 Registered Users, Users Awaiting Email Confirmation Posts: 1 ✭
in Advanced Solar Electric Technical Forum #1

Hi,

I'm having a problem that I'm hoping someone can help me with.

Once my batteries get through the float phase and reach %100 charged, they start gradually losing their charge, even in the middle of a bright sunny day in Phoenix Arizona. My system will reach float by 9-10 AM, start discharging, and then creep down to below 90% by 3 PM.

My understanding of what float mode should do is that once reached, the controllers should keep the batteries at float voltage and/or 100% SOC while providing enough e power to run the extra loads. It should also continue doing this all the way up to where there’s not enough sunlight/PV capacity BEFORE it starts using the batteries. I do see that after float, the OpticsRE shows more power coming from the charge controllers than going to the load, but apparently not enough to keep the batteries topped up.

I’ve had this problem for years now, since the system was new, but I have always written it off as the PV array being too small to keep the batteries topped up while loads are running.

However, I recently expanded/doubled my PV array and charging systems and still have the same problem.

I am now running 4 PV arrays totaling about 15k watts, 4 flexmax 80 charge controllers via a Mate 3 and/or Optics RE.

My battery bank is 16 Outback 200re batteries arranged in a 48v battery bank.

I’ve read forums about 2 other people with the same problem.

One person fixed it with changing the Flexmax auto restart mode from 0 to 1, which I’ve tried and had no effect. The other person found their Flexnet DC mis-wired which is little beyond my wheelhouse.

I will say that it doesn’t seem as pronounced while in Grid Use Mode than it does in HBX mode.

Thoughts?


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Comments

  • JRHill
    JRHill Registered Users Posts: 429 ✭✭✭✭
    #2
    I haven't used lead batteries for some time now but yes, that happens and I believe it is to be expected. The FNDC is merely tabulating the energy going into the batteries and that going out along with factoring in some other variables. So after the absorb finishes and the batteries drop to float voltage some energy is leaving the batteries and the SOC drops accordingly to some level. It should be relatively consistent every day or is it not?

    "...controllers should keep the batteries at float voltage and/or 100% SOC..." The FM80 will keep the float voltage up but in my experience the SOC will drop some amount as the system drops to float. This also happens with my LFP04 batteries.
    Off Grid. Two systems: 1) 2925w panels, OB VFXR3648, FM80, FNDC, Victron BMV-712, Mate3s, 240 xformer, four SimpliPHI 3.8; 2) 780w, Morningstar 30a, Grundfos switch, controller and AC/DC pump, 8 T105. Honda EU7000is w/AGS. Champion 3100. HF 4550, Miller Bobcat.
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