94% on trimetric?

arby
arby Solar Expert Posts: 108 ✭✭
in Off Grid Solar & Battery Systems #1
Hello,
Last weekend we went to our off grid cabin after 2 months away. It is winter here and the last couple of weeks were quite cold.
My trimetric showed 94% SOC. There have been lots of sunny days since my last visit so I was surprised that it did not show 100%
like it does in the summer. We went to my friends across the lake and his system showed 98% SOC. In both cabins the inverters had been turned off.
Is this normal in the cold, or is something not set up correctly.
Thanks in advance.
3310 watts panels, Classic 200 controller, 8 Surette S530's, Xantrex 5548 inverter, Honda EX5500 backup Genny.
· Share on Twitter

Comments

  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #2
    Re: 94% on trimetric?

    Did you get a chance to measure the resting voltage and temperature corrected specific gravity?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
    · Share on Twitter
  • arby
    arby Solar Expert Posts: 108 ✭✭
    #3
    Re: 94% on trimetric?

    No, it was dark out and we had just got in by snow machines after a few problems.
    I forgot to check the voltage, which I could have with the trimetric.
    It always reads 100% in the summer if it has had sun, so I put the low reading down to the cold, but now I am wondering about that.
    3310 watts panels, Classic 200 controller, 8 Surette S530's, Xantrex 5548 inverter, Honda EX5500 backup Genny.
    · Share on Twitter
  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #4
    Re: 94% on trimetric?

    If the batteries never drop below float voltage, many controllers will not start a full absorb charge. The Battery Monitor may not "reset" to 100% until you actually pull a load (at night) and pull the battery bank below 12.7 (50.4 volts) volts for a few minutes so the charge controller will do a >14.x (56.x) volt absorb for >XX minutes (programmable in the BM)?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
    · Share on Twitter
  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    #5
    Re: 94% on trimetric?
    arby wrote: »
    Is this normal in the cold, or is something not set up correctly.

    Do you have temp compensation on your controller? What temperature are the batteries?

    Trimetrics do NOT compensate for temperature. It may be that the trimetric doesn't reset because the end amps does not reach the trimetric's reset current when the batteries are cold.

    Also, if your batteries are cold, they have lower capacity, and unless you program the trimetric to use a lower battery capacity, the trimetric will overestimate the SOC.

    One thing I see with cold batteries is false resets. My trimetric is set to reset when absorb (29.4) voltage is maintained for a minute with battery current 6 amps or less. In the winter the temp compensated absorb voltage is about 30.0. If I am in absorb mode with battery current down to 8 amps and a cloud comes by (or a load turns on), the voltage may sag to 29.5 and the current may sag to 5 amps, which meets the criteria for the trimetric to reset, even though the controller has dropped back into bulk mode.

    So, is your 94% SOC real? Use your hydrometer! If the hydrometer says the batteries are charged, they are. Then adjust your trimetric to match the hydrometer.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
    · Share on Twitter

Categories