This is where it stopped charging, after tapering off the closer it got to 3.45v per cell, I suppose done by Victron (?), not the BMS … maybe @Louisvdw software (?) … even after I removed all the charge parameters in the driver? Set driver to charge flat-out all the way to 100% SOC.
Note: The above is set on Keep Charged, not ESS SOC.
Comparison of what I see everyday:
The main system is running on ESS SOC, also set to 3.45v per cell, it never gets to 3.45v per cell, always to the “correct” SOC and ah in/out as per BMS, “matches”:
Correct me if I’m wrong:
Running on ESS SOC puts even less strain on the batteries than 3.45v per cell i.e. running 100% in the flat curve all the time, right?
Note 1: If a cell goes out of whack … it all goes to smithereens.
Note 2: Balancing 300ah cells, BMS has NO chance whatsoever. Even an active balancer, wot, 5amps, has no chance. I get why the brand names use smaller cells.
The trick now is to figure out HOW to do it on large ah cells. … when they are out of balance.
I didn’t read all of that… since it is 11PM. But I just want to reiterate: From the Victron side we stop when we reach the voltage we’ve been instructed to aim for. If the BMS limits the current, it might take a bit longer to get there. If the BMS lowers the charge voltage, we will stop at that lower voltage. But the Multi and solarchargers literally don’t care about the SOC, in fact the solarchargers don’t even know what it is… they just aim for the voltage you told them.
Watching a few hours of Andy at The Offgird Garage, that is where I realized something is “off”.
As he alters his MPPT’s charge/absorption volts, he gets a near instant result.
Stupid me, I don’t.
As I’m under the impression that on a Grid-tied setup with ESS, that the MPPT is under ESS control, and not by itself anymore.
Methinks, him being 1) off-grid, 2) no driver on his Venus, and 3) not using ESS … as far as I have seen to date … must have an impact.
So, he alters his MPPT’s, I’m going to alter the inverter settings. Same thing I recon, as on the MP 12v, I don’t have a MPPT.
So now I’m going try:
Setting the charge volts at 3.60v on the inverter, set ESS SOC to 55%, and see what happens, after altering Louis driver too also to 3.60v. I bet the system will stop charging at 55% SOC, irrespective of volts.
If I don’t see what Andy sees, I will remove the driver from the Venus, and try again.
If I still don’t see what Andy sees, I will disable ESS on the inverter/Venus.
Indeed, I’ve seen half of one of his videos. Off-grid makes a difference. If the MPPT is running standalone (not remote controlled by the Multi or a BMS), then you set the voltage on the MPPT. If you are running ESS, the Multi is in charge, you set the voltage there. If there is also a BMS (one with comms), then the BMS runs the show (although the Multi can add a small offset if you run ESS).
The SOC plays no role in the decision to stop charging (there are rare cases yes… but you have to explicitly mess with things to get the to act up). It stops charging when it hits the voltage you asked for.
What happens in this case, as far as I can determine is the BMS/Driver combo reduces charge current based on SOC, which prolongs the charging process. The Multi is still going to do the same thing it always does… aim for the voltage… now it will just take longer to get there
Result 1:
Set Louis driver on the Venus and the inverter to charge at 3.60v.
Set ESS at 55% SOC.
Charging lekker at ±270w, ±3.3v, and ±20.3amps, the cell Delta solid at ±0.004v, it stops charging at 55% ESS SOC as I told it to … as I know it does.
Titbit for newbies: If you set the Grid-Setpoint at say Zero (0), it still spills a wee bit over at about 8-10w charging to the cells. This we know as at these low measurements, that is expected, normal.
To avert that, I set Grid-setpoint at 10w+ depending on the inverter size.
Next step … removing the BMS driver on the Venus, run the same test to SOC of 60% … see if ESS stops it again. How? I make a typo inside the battery.py file, the driver will stop loading.
… and reboot the inverter after having rebooted the Venus/Cerbo/Rpi.
It’s going to stop when the total voltage is where you told it to go. And then it will hold it there. Whatever the estimated SOC is at this point by any particular BMV/BMS/etc… totally up to the setup of that particular device.
Or, without rebooting, just take the service down:
svc -d /service/dbus-serialbattery.ttyUSB0
And remember to vebus reset the Multi after removing the BMS. Otherwise it will go into passthru after some minutes on account of having lost the BMS it once knew…
Yes do that. Cause you are confusing the crap out of me. For all of the typing and titbits there appears to be some information missing as to what you are doing. Are you messing with scheduled charging? Cause that can be told to stop at a particular soc…
If you just put the thing in “Keep Batteries Charged”, and set the right voltage… it will charge to that voltage regardless of what the SOC estimate might be.
The newest beta (v0.9beta1) now include scripts that you can run to disable the driver (and install latest release or local version)
Might be a bit better that breaking the code.
What people are telling me, and what I’m seeing in front of me, are two different worlds.
You state categorically that the MPPT’s/inverter runs the show, I agree … UNTIL you have ESS enabled.
ESS runs on SOC, not the MPPT nor the inverter’s volt settings, from what I see in front of me.
It all stems from that I have never seen 3.45v per cell ever, only 100% SOC. Yet Andy sees 3.45v per cell and 100% SOC by adjusting his MPPT’s settings.
The two differences between me and Andy, I have ESS and a BMS driver. With the BMS driver removed, ESS still controls the system, to CHARGE to the set SOC I pre-set.
That I learned last night when you where asleep … Setting ESS SOC to 100% and setting ESS to Keep Charged, the one stops at 100%, the other stops at the volts set.
EDIT: Result 3: ESS removed … now it keeps on charging, as there is no place to set the SOC.
EDIT: Result 4: ESS still removed, BMS driver back … keeps on charging.
EDIT: Result 5: ESS and BMS driver back … stops charging at 60% SOC I pre-set.
The victron stuff does work on the voltage. However my driver adds the SOC to the mix as well. And it also give the system feedback from the BMS/battery which Andy’s off grid system does not have. Thus the only settings it use is that of the MPPT.
Here is the priority order:
BMS/Battery
ESS
MPPT
Multiplus
If the top priority is not available it will use the settings from the next lower level.
So for off grid it will use MPPT.
Grid tied will use the ESS.
Battery grid tied will use the BMS settings.
Well… I will just have to assume that is some weird interaction with the driver then. Cause I promise you, even with the ESS assistant installed, if you give it a positive grid setpoint* (ie you instruct the Multi to import power from the grid), and if you have somewhere to put the energy (a battery for example, or loads), then the Multi will not stop charging based on the SOC. It will only stop based on the voltage. It may stop if the BMS tells it to dial back the charge current to zero.
I think I should know. I’m the maintainer of that component.
* When you set the ESS mode to Keep Batteries Charged, it sets a very large positive setpoint. That is what happens behind the covers…
ESS in play, SOC rules, not the volts UNLESS you set ESS to Keep Charged.
… but only on a well-balanced bank, the Keep Charged option BUT, that is not the answer.
Must say, fast charging at 3.6v is nogal cool, on the flat curve part. So much faster.
The trick is to stop it before the end of the curve, where the cells can run away. Would be really nice to be able to automatically drop the charge amps when a cells does get excited.
Mmmh maybe I actually know what you are doing wrong. You have a low ESS grid setpoint, and you are activating the Auto Recharge feature (which charges the battery to the minsoc if it drops more than 5% below that).
