Bulk MPPT reading as the sun goes down. What does this reading mean?

Started by showme, December 24, 2023, 06:42:15 PM

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showme

I recently got my system fired up (again) after having some issues with my PV array circuit breakers. I have a Classic 150 and a 150sl with (2) NOS (new old stock) Trace SW5548 inverter/chargers and 500ah SOK LiFePo battery bank. The master 150 has been 'resting' most of the time, while the sl has been in absorb for the few days it's been up. It's at a property we own, and there have been no loads on it except when i turn the light on in the shed it's in, and when I gave it a quick test when I hooked it up to the 5th wheel we have down there. (I'm not leaving that on until I get a new deep cycle battery for it). Anyway, yesterday I happened to be there as the sun was going down behind some pines on a far hill and also popping in and out of some cloud cover. At this point I noticed the controllers readings bouncing around, as would be expected, but the master cc was showing "Bulk MPPT" instead of resting, bulk or absorb. The sl was still on absorb at the time. I still haven't seen float on it yet, although the minimal absorb charge would seem like it would actually be on float. (around .4 to.7amps and 25-35w. My questions are- What does Bulk MPPT mean, and why am I not seeing 'float' when the only thing drawing current would be the cc's and the inverters, which, BTW, are set on 'search' every 3 seconds and not inverting? Thanks for any help on this. Lee
"Knowing is not enough, we must apply.
          Willing is not enough, we must do."
                                                       Goethe

Wizbandit

You have some settings different between them or difference on voltage drop in the wiring or voltage calibration is out of adjustment on one or both.  Lithium don't use absorb, that's a lead battery setting so unless the manufacturer gives time to you set absorb time to 5 minutes.  EQ time to 00:00 minutes.  Set EQ and ABSORB voltages to the needed CHARGE VOLTAGE, set FLOAT to what the manufacturer wants or if not given 2 volts less than CHARGE VOLTAGE (Absorb).  Set REBULK 2 volts less than FLOAT.

showme

Thanks, whizbandit. My batteries (SOK 100amp x 5) give the parameters for setting up the system and definitely include an absorb voltage and time. I think you mean lithium batts don't need equalizing? Even there, Current Connections says that although most other types of lithium batts don't need EQ that if that stage is cut out completely, the BMS system may not completely top off some cells in the batteries, and although the batteries can self balance, if the difference in cell voltage gets too great, the BMS may not be able to recoup those cells. So Current Connected, SOK's distributor, tells me that it's best to keep the equalization near the absorb time, if for nothing else but to make sure all the cells in all 5 batteries are equalized.
"Knowing is not enough, we must apply.
          Willing is not enough, we must do."
                                                       Goethe

ClassicCrazy

Quote from: showme on December 30, 2023, 09:36:00 AMThanks, whizbandit. My batteries (SOK 100amp x 5) give the parameters for setting up the system and definitely include an absorb voltage and time. I think you mean lithium batts don't need equalizing? Even there, Current Connections says that although most other types of lithium batts don't need EQ that if that stage is cut out completely, the BMS system may not completely top off some cells in the batteries, and although the batteries can self balance, if the difference in cell voltage gets too great, the BMS may not be able to recoup those cells. So Current Connected, SOK's distributor, tells me that it's best to keep the equalization near the absorb time, if for nothing else but to make sure all the cells in all 5 batteries are equalized.

Just set the absorb time longer if the bms need longer for the cells to balance.
SOK seems to have some odd parameters set in their bms. You can see what they are set for by using their software and looking at the parameters tab ( by using Read button). Then if you want to evaluate the SOK settings you can compare to what Off Grid Garage suggested for Jakiper batteries in videos he made on them. They both use the same Pace BMS and the cells are similar enough compare. You can get software to make changes to parameters if you wanted to .
Larry
system 1
Classic 150 , 5s3p  Kyocera 135watt , 12s Soneil 2v 540amp lead crystal for 24v pack , Outback 3524 inverter
system 2
 5s 135w Kyocero , 3s3p 270w Kyocera  to Classic 150 ,   8s Kyocera 225w to Hawkes Bay Jakiper 48v 15kwh LiFePO4 , Outback VFX 3648 inverter
system 3
KID / Brat portable