There we go. Got the BMS and BMV close as damn together last night and discharging, follows closely too.
An interesting observation.
Saw this morning, when the sun took over, that the BMV can still show up to 1amp going into the batts, the BMS sees none of that:
Methinks I’m going to keep the BMV in place … BMV is more accurate ito SOC and BMS more accurate ito each cell’s voltage. If the two are in “sync” iot SOC it points to a healthy bank for me.
Will be using the BMS SOC for a while though.
Ps. HomeAssistant also adjusted to use BMS SOC.
Pss. Cell 4 seems to be about ±0.03v below the rest hen discharging and also very quick to recharge … but is less “excitable”. Seems to be slowly catching up again. But if I had spare cells I would have been replaced no 4.
It’s an interesting experiment, but without some tailor-made specific test cases (eg low power discharge, running several days without a full charge), I think the only result you can expect is that they will drift into- and out of sync
In my unscientific casual observation, I see the SOC is close when discharging from the same top SOC.
The difference comes in when charging, the BMS going up faster from the similar low SOC only to slow down, or stop, at ±80% SOC, where it then sits for a while whilst the BMV still slowly climbs to full SOC - similar what you have seen with other brand names.
Unless a cell shoots out, my BMS SOC does not “jump” that often, if at all.
BMS volts/SOC, methinks it is funny thinking about that other forum and the continuous ragging of Axpert users that did not have a BMV. They will have a field day now that with lithium’s the volts drives the SOC more than a BMV.
If someone had the interest, my system is online, it would been have been fun to offer my system as a test. Especially when cells are out of whack and all that marakas with getting an accurate SOC with coulombs and cell volts thrown in the mix, and how the BMS software does all the calcs.
So MY wife discovered Tjhoko paint … no one is safe, you sit too long still and she paints YOU!
She told me she has a surprise, I’m not allowed to look … her having an astute sense of humor.
So with me ever so often swearing earning my Master Doctoral Degree in “WTF NOT to DO!” … she decided to “help” me out a bit with some salient warnings …
She even got the color nearly spot on @mmaritz , and she made it into my favorite brand @plonkster
@TheTerribleTriplet
I just snipped the " precision guesswork" and quickly added it as the closing slide of a PowerPoint presentation I have just given to 20 odd power system engineers.
This is interesting, I’d like to explore this a bit.
Just so I am clear, when did you drop it to 3.3V?
If you dropped it when it was above 3.3V, then the battery would discharge a bit, relieving the load of the solar.
But, that wouldn’t be the normal running situation.
I think, ( and only think, mind you) that if you had changed that setting when the average cell voltage was below 3.3V, the the solar production would’ve remained high, until 3.3V was reached.
Whereupon it would’ve reduced to the your level of consumption.
Everything happening just like normal but just at 3.3V.
Your comments?
@TheTerribleTriplet,
If you can sit through this, (it’s long), it is the most comprehensive video I have seen on the subject.
He actually uses the same ZKE tester that I have.
Since before COVID, I have wanted to do these same tests.
I can only fault him that he should be using 40A, to be closer to reality. The curves and voltages would be affected.
Some nice conclusions though, actual tests not theory.
Notice how the charge and the discharge curves are different.
I would revise my previous 3.3V recommendation to 3.37V + long absorption times if I had similar test results.
Your theory is interesting, but me, I want to be told, do this, do that, and just Nike it …
From THAT I can then take cautionary steps and tune a wee bit more.
Right now it is try this, that, it makes logical sense …
For he tried the 3.35v test and LONG absorption:
I’m still stuck with dropping volts too low = lower panel production.
And THIS is how it looks if you adjusted the voltages over the entire system, and then forgot to set the BMV back.
