Urgent advice required. I have just spent $12K replacing my clients 15kwhrs worth of Pylontech with 20Kwhrs of BYD LVS as Pylontech is blaming the Victron Gear for the fault and I want to keep my client happy so I have paid for it myself. The system incorporates a 8kw Q, 2 x 250/100mppt, Cerbo. The system is live in the VRM portal. I have many live systems with no problems. The batteries hit their 100% mark early most days but that is followed by continuous high cell alarms which have led to the eventual failure of the Ptechs (as ther was a period of no internet). The mppts and cerbo all indicate DVCC and External Control is functional. The BYD’s have been in for 5 days and whilst one might expect a couple of high cell alarms as the BMS finds the floor and ceiling I am extremely nervous that in fact the DVCC is not adequately winding back the input voltage and current as requested by the Battery BMS and that as soon as the batteries are at 100% the BMS is actually charge controlling and the Mppts are not winding back.
Anyway to get a Victron professional to have a look at the system on the portal and advise.
That new algorithm for holding back when the cell voltage is too high, is implemented only for Pylontechs with 15 cells.
Also because the Pylontechs are sending the min and max cell voltages.
Question: Are the BYD sending min and max cell voltages?
Why? Because then you can ask Victron (or do it yourself) to modify the dvcc.py script to prevent those cell overvoltages.
any update on this? did you have sufficient comms between the pylontechs and the cerbo? it should have forced DVCC on with settings for the 15 cell pylontech loaded… If you had for example charge voltage of 56.8 Volt, you would have had 3.8 Volt. Is the screenshot that you posted from the BYD battery? Those cell voltages look not good at all… you are hitting almost 3,8 V. Which is really really high. I think EVE calls it the highest allowed voltage, above that you have guaranteed damage. From my experience, BYD is very nicely balanced from the get-go.
For troubleshooting, can you post more pictures of the physical installation? Also what exactly happened that made pylontech blame victron? Can you give more insight? this is a really serious situation and if there is a victron related fault, it ought to be investigated properly…
When you say this, what do you mean exactly? BYD has to be in charge of charging. DVCC is just a way to distribute control easily. It does not actually control charging, unless you do a custom script in nodered, altering the charge voltage limit. The mppt’s are either in control, or the byd BMS is. Both are possible, but for BYD, definitely put the BMS in control and make sure the mppts have external control turned on. (see BMS menu setting)
does the topic starter @brian woodham, have solved the problem?
Usually, the BMS is also sharing there Charge limits (CVL, CCL, DCL), which can be made visible in the VRM (widget of the BMS)… this might give an insight in what the BMS is communicating and if the MPPTs are using these settings accordingly…
What in case you have the mppts in external control, but SVS (shared voltage sense), SCS and/ or STS disabled by coincidance? maybe there is a wrong setting, saying, the mpps takes an other voltage as reference, instead of the one of the BMS? could that be?
Update, As suspected the system has been operating perfectly since the installation of the BYD batteries. I commenced the warranty claim process through Pylontech and to date have been getting the run around, the CN office responds relatively quickly with a referral, and then the Australian office pretends to not have received the extensive documentation which has been provided to them 3 times. Will be forwarding the documentation to the ACCC (Australian Consumer Protection Commision) and OFT (Australian Office of Fair Trading) if i don’t get a resolution soon. Will also let you all know and publish the System Details Logs Pylontech emails etc here.
My supplier hier in portugal (solarshop) has stopped using pylontech all together. seems like there are just too many issues arising after a few years of use.
There have been a fair number of complaints over PT batteries later in life, usually where cells are failing, though they seem quite good at swapping the cells out.
You can see the delta between min/max cell voltages in the OP’s charts.
What isn’t clear is the size of the setup and the age, it looks like 3 x US5000 but which inverter isn’t clear.
PT have aggressively pushed their deep discharge over the years, and where I have seen problems, the only common thread I can find, tends to apply to many other manufacturers as well.
The battery pack is often undersized, especially for off-grid, with a larger inverter than would be recommended. Sites often don’t get to spend extended periods at high SOC to balance, or cycle more regularly on a daily basis (mismatched loads vs solar). Then add warmer temps into the equation.
These aren’t environments kind to 15 cell batteries.
I have seen a local battery manufacturer updating their warranty terms to limit charge/discharge rates due to problems later in life.
Probably normal when you push newer battery models to market and promise long warranties and good performance without knowing how they will fare in the real world.
I have older banks of PT which are absolutely fine, but are operated comfortably within conservative specs.
Recent changes to the charge algo for PT batteries applied via the GX should improve the experience for newer systems.
They also changed the error description from high-voltage to high cell voltage to be less confusing, as it indicates a cell imbalance, not overcharging from the system.
The 16-cell BYD bank, is a better battery with superior real-world performance and imo a better BMS, it isn’t quite a fair comparison to the previous setup, time will also tell how it stands up under similar loads.
