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Forum Index : Solar : BMS Cycles Calculated
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Revlac Guru  Joined: 31/12/2016 Location: AustraliaPosts: 961 |
I have had this battery setup (48v 200AH Lifpeo4 battery) running for a while now and is running ok, This is a Daly BMS and the cycles read 182 This screenshot was taken a few weeks back a so the cycle count should be more, also the BMS often only shows/updates the count after it has gone into sleep mode after not being in use, one of the quirks of this brand of BMS. It has been running for roughly 600 days give or take a few (whatever the start date was might have stuffed that up) the average overnight battery consumption is 35 percent. BMS is most likely at 190 or more cycle counts by now.  Question is, Do any other BMS calculate every cycle as 1 cycle or do the calculate all small cycles until it counts 100 percent and then calls it 1 cycle? Cheers Aaron Off The Grid |
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| pd-- Senior Member  Joined: 11/12/2020 Location: AustraliaPosts: 122 |
The ones i have played with just have a empty soc and full soc cycle threshold. so a cycle is only counted if you exceed both thresholds. Battery age can be better estimated by counting total battery what hours |
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| Revlac Guru Joined: 31/12/2016 Location: AustraliaPosts: 961 |
I should have put a meter on the battery when it was built, but I have some idea what what goes through it.  I used to have the BMS read 100 percent SOC when it hit the high voltage setpoint when new and the balance was just a little out, since then everything is setup so the BMS is never triggered from high or low voltage, the inverter works between those points so the BMS is just the safety. When doing this, the (200A) BMS never reaches tho 100 percent SOC anymore, its always about 2 percent lower and gets lower over time, the other 200A BMS has less solar panels connected to it and is 5 percent out or more compared to the other one. I usually just reset the SOC every so often or just before the weather starts looking bad. These Daly BMS are a bit different with every model, have a 175A version in the shed and it always gets back to 100 percent SOC and still has a very small cycle count, although it gets used often it gets shut down over night. Cheers Aaron Off The Grid |
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| pd-- Senior Member Joined: 11/12/2020 Location: AustraliaPosts: 122 |
The SOC counter on my BMS s off with the pixies to, it usually reads higher than the inverter. so i just use the cell balancing function and the cell voltage readings as a failsafe to trip a contactor |
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| Revlac Guru Joined: 31/12/2016 Location: AustraliaPosts: 961 |
I will have to do something like that when all the bells and whistles have worn out.  Another thing I noticed, when the inverter is running and batteries are charging or discharging the amperage measured and reported by the BMS to the phone APP is erratic and all over the place, sometimes twice the real value, I thought that might have something to do with the SOC readings but apparently not so much, with the inverter turned off the charge amperage reading is spot on correct and stable. Recent browsing found this place, https://off-grid-garage.com/battery-management-systems-bms/ has listed some reviews on some BMS and other things, unfortunately most of the stuff is documented using YouTube (that I don't watch) would be better if it written so we could read through the highlights. Cheers Aaron Off The Grid |
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| Old Seagull Man Regular Member  Joined: 21/12/2019 Location: AustraliaPosts: 55 |
On my test setup i have found that the BMS cycle count is approximately half the "real" cycle count. This is just my setup others have different results. At the moment the BMS has me on 49 cycles and 82% SOC And the BMV 702 has me on 77 cycles and 99.1% SOC So Daily i go by the BMV 702. My discharge is never below 50%. The shunt is set on Amp Hours. So in the morning its about minus 100Ah, And by midday its back to Zero Ah discharged. This is enough to make me feel safe, and that's really the purpose of monitoring battery's. I can also monitor the daily output of my charge controller, so today, the MPPT output was 106.439 Ah and the battery usage was 98.78Ah So I know in actually charged up. So if you have concerns maybe this is a way to go. Edited 2022-11-24 15:36 by Old Seagull Man |
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| Revlac Guru Joined: 31/12/2016 Location: AustraliaPosts: 961 |
I agree, that is clear to see and understand what is going on doing it like that  .......I would like to do one setup that way later on, that particular meter is good but a bit pricey for me ATM. Cheers Aaron Off The Grid |
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| Revlac Guru Joined: 31/12/2016 Location: AustraliaPosts: 961 |
Have to make a correction, it is actually a 150Amp Daly BMS, 75Amp charge current.....its being a long time since I checked inside the battery box, forget things sometimes.  Cheers Aaron Off The Grid |
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