Magnum BMK SOC tracking issue

Started by qcda1, February 03, 2025, 06:05:54 PM

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qcda1

Hello! Hi changed my battery bank to LifePO4 last fall. Had Trojan L16 before and my Magnum's AGS used the voltages to drive the generator. With the new batteries, voltage can't be used due to the flat voltage variation throughout the discharge and charge process. So I got a BMK to use the % SOC as a control parameter. Got it to work fine for a while once it had a few 100% charges but this week-end, something weird started to happen.The BMK's SOC jumps to 100% while batteries are far from reaching 100%. I added a few pictures to show the behavior. They are graphs that plot the different SOC that I measure to see how similar they're capable to estimate SOC over time. We see in Pict1 that at 08h20 on 2025-02-02, BMK SOC jumped to 100% after a few amps came from the panels... Last pic shows part of the data form the Magnum unit.

Anyone else have or had this challenge? Can't see in the documentation what can cause this.

This is a bugger since I expect the AGS to start the gen at a low SOC, and if BMK surestimate the value, the system will drain the batteries...
1,2kW on tracker, 1,4kW fixed, 2xMidnite Classic150, Magnum MS4448PAE, 4xMapleLeaf 48VDC/100Ah LiFePO4 and Kohler 14RCA with homegrown monitoring/alerting system.

ClassicCrazy

I don't know what a BMK is .
Does it use a shunt that is between the battery negative and everything else ?
Not sure what kind of batteries you have and what bms is in them but on many bms their soc reading can get way out of whack if the batteries are not charged up full after a number of days.
The bms in my batteries ( pace type bms ) can get off compared to the Midnite Classic whizbang reported soc. I know that some of my pace bms don't count any current under half an amp .
I rely more on looking at the batteries voltage at the top absorb setting I have ( 55.2v in my case) and then I watch for the current to drop to their end of amps rating ( I think some call this the tail current ?) . When both those points are met, then I know the batteries are full.  I now have three SOC counters, the one for the Classic / Hawkes Bay , the battery reported SOC, and I recently put on a Victron Smart shunt which is better positioned than where I had the Midnite whizbang shunt. Sometimes they are all close , and sometimes they get off from each other. I am going to put my faith more in the Victron now but I haven't ever run my batteries all the way down to confirm its accuracy.
Larry
system 1
Classic 150 , 5s3p  Kyocera 135watt , 12s Soneil 2v 540amp lead crystal 24v pack , Outback 3524 inverter
 5s 135w Kyocero , 3s3p 270w Kyocera   Classic 150 ,8s2p  Kyocera 225w to Hawkes Bay Jakiper 48v 20kwh  ,Gobel 16 kwh  lifepo4 Outback VFX 3648  8s2p 380w Rec pv EG4 6000XP

qcda1

Thanks for the reply! So the BMK is the equivalent of the Midnite WbJr and allow the AGS (AutoGenStart) module to run the generator based on %SOC instead of battery voltage for example. It shares the same 500A/50mV shunt between the battery negative lead and the rest. My battery bank is made of four Maple Leaf LiFePO4 48VDC/100Ah batteries in parallel. I was able to get BMS data for the pack and each battery. As you mention, I saw the BMS SOC going everywhere at commissionning until the batteries were fully charged (Voltage raise and very low tail current). So with my archived data, I believe I can simulate the 100% "declaration" of the BMK based on their 3 factors:
1. The charging voltage stabilizes over time (see Figure 3-1).
2. The charging current decreases to a low percentage of the AH capacity—normally less than 2%.
3. The AH removed from the battery are within 1% of fully being returned.
And see if the conditions were really met or there is a bug in the unit.

The other thing I can play with is the battery efficiency factor in the BMK. By default it is at Auto. I might experiment with this to see if I can get the thing to behave.
This wouldn't be an issue if it was measuring too low. But measuring too high, this prevent me from setting the generator trigger adequately low to maximize battery's storage capacity in cloudy days...

Daniel.
1,2kW on tracker, 1,4kW fixed, 2xMidnite Classic150, Magnum MS4448PAE, 4xMapleLeaf 48VDC/100Ah LiFePO4 and Kohler 14RCA with homegrown monitoring/alerting system.

ClassicCrazy

You should check into some other monitoring and control programs like Node-Red or Home Assistant where you can take data from a variety of sources and then use it to do what you want to .
Larry
system 1
Classic 150 , 5s3p  Kyocera 135watt , 12s Soneil 2v 540amp lead crystal 24v pack , Outback 3524 inverter
 5s 135w Kyocero , 3s3p 270w Kyocera   Classic 150 ,8s2p  Kyocera 225w to Hawkes Bay Jakiper 48v 20kwh  ,Gobel 16 kwh  lifepo4 Outback VFX 3648  8s2p 380w Rec pv EG4 6000XP

qcda1

Thanks Larry but the issue is not monitoring. It's the generator management modules (ME-AGS-N and ME-BMK) of Magnum Energy that has some issues. I use monitoring to measure the process and try to identify the issue while waiting for an answer from support that might never come... My fallback is to make my own or look at alternatives such as dcautogen.com unless someone in this forum has some other ideas.

Regards,

Daniel
1,2kW on tracker, 1,4kW fixed, 2xMidnite Classic150, Magnum MS4448PAE, 4xMapleLeaf 48VDC/100Ah LiFePO4 and Kohler 14RCA with homegrown monitoring/alerting system.

ClassicCrazy

#5
That is why I mentioned Node Red - it is a controls program that can do lots of stuff.
Home Assistant these days is also pretty easy to configure to control things.
If you get input to either of these programs from your magnum , then you can have it turn on a relay or whatever you need to switch . You can select the actions based on whatever criteria you want.
Larry
system 1
Classic 150 , 5s3p  Kyocera 135watt , 12s Soneil 2v 540amp lead crystal 24v pack , Outback 3524 inverter
 5s 135w Kyocero , 3s3p 270w Kyocera   Classic 150 ,8s2p  Kyocera 225w to Hawkes Bay Jakiper 48v 20kwh  ,Gobel 16 kwh  lifepo4 Outback VFX 3648  8s2p 380w Rec pv EG4 6000XP

qcda1

As displayed in my initial post, I already have everything to monitor all my device's data and control relays. I'm triying to get the purchased off the shelves modules to work bofore tackling a parallel homegrown control. Certainly Node Red and HA can do it but even if easy, it would require new installations, configurations, maintenance,  of these systems, etc.
I also discovered a way to bypass the BMK with what Magnum Energy call the ME-PT1 and PT2 connectors that will control the generator start/stop from an external dry contact. I ordered the part and will use the battery's and WhizbangJr SOC's numbers to control the generator.
I might come back with my results in the spring when I'll have some time to put on this.

As always, I thank you for your help on the matter. Greatly appreciated.

Regards,

Daniel.
1,2kW on tracker, 1,4kW fixed, 2xMidnite Classic150, Magnum MS4448PAE, 4xMapleLeaf 48VDC/100Ah LiFePO4 and Kohler 14RCA with homegrown monitoring/alerting system.

ClassicCrazy

Good - hope you can get it working .
Larry
system 1
Classic 150 , 5s3p  Kyocera 135watt , 12s Soneil 2v 540amp lead crystal 24v pack , Outback 3524 inverter
 5s 135w Kyocero , 3s3p 270w Kyocera   Classic 150 ,8s2p  Kyocera 225w to Hawkes Bay Jakiper 48v 20kwh  ,Gobel 16 kwh  lifepo4 Outback VFX 3648  8s2p 380w Rec pv EG4 6000XP