Good Day All from sunny South Africa,
I’m hoping to get some insights from the community regarding my VE system and battery performance. I live in the Cape Town area and have a system installed in May 2023, consisting of:
2 Multiplus II 5 kVA in parallel
3 MPPT 150A
4 x BSLBATT 7 kWh LiFePO4 batteries (28 kWh total)
17 solar panels with a peak output of 9.5 kW
The BSLBATT batteries were installed according to VE guidelines.
In summer, with ample solar yield, the system performs without issues. However, during winter months with reduced solar production, the discharge pattern of my BSLBATT batteries becomes very erratic. Specifically, under a load of 3-4 kW, they unexpectedly “cave in” (shut down or significantly reduce output) at approx. 30% SoC.
BSLBATT’s marketing boasts an 80% DoD. I can only achieve this DoD reliably if the batteries have reached a full charge (100% SoC/float) prior to discharge. If the batteries only reach 80% SoC or less during charging, their discharge performance is notably poor.
Two of my batteries have been sent to the agent in Johannesburg, where only cell rebalancing was performed. The firmware was updated once, and I also conduct regular bottom balancing myself. Despite these efforts, the battery performance remains unreliable. I find myself constantly monitoring them via VRM/ESS and carefully managing the load, which is frustrating.
Is anyone else experiencing similar erratic discharge behavior with BSLBATT batteries?
Is this discharge problem (sudden “caving in” at higher SoCs when not fully charged) typical for LiFePO4 batteries in general, or is it specific to certain brands/firmware? I previously had a smaller system with 4 x Pylontech 2.4 kWh batteries and never encountered such issues.
Any comments or advice would be greatly appreciated.
Many thanks,
Joerg
I burnt my fingers with BSL a while ago, as did others.
They use a generic BMS from PACE which is used in various other batteries locally.
They often seen to have similar issues that relate to the BMS’s inability to reliably track the SOC, so if you don’t charge often, or sufficiently, it drifted significantly.
So, it could under or over-report, in some cases you would see it leap up from 80% to 100%.
If you aren’t charging it regularly or with sufficient power you are probably running into two problems:
-The SOC it is reporting is not correct, it is probably lower.
-Cells may be imbalanced, triggering the BMS when one gets too low.
You can report on the battery voltage which will give you an idea of how charged it really is relative to the charger settings and cut-offs set.
You can also report on the min/max cell voltages which will show if any are hitting a lower threshold.
These issues aren’t unique to BSL, some batteries are better than others. The better the BMS, the better the behaviour.
All charts are available in VRM advanced.
You would be better off setting it to regularly charge from grid so the BMS can properly sync, or changing ESS to use batterylife so it has a better chance of fully charging.
The SOC jumps up particularly when charging hard if something like a load on the house (when grid charging ) or solar drops off (cloud cover) the amps take a dive 100% SOC is triggered, even when well below even float voltage.
So lesson 1 -Dont trust the soc.
I have had a few with a weak cell in it (and had it replaced) but that was fun and games on its own.
I realised after cracking one open, they used second life cells, and was not happy. Since it is not stated.
I have never daisy chained them as some do but see that made zero difference to them.
If you have mixed firmwares and generations, all kind of strangeness happens.
Out local distributor has dropped tham as a product line, so that tells me all i need to know. And they have their own internal fixes so they can honour their warranty period.
One fix includes a cell balancer that is retrofitted.
My experience is quite different but then, I have used them lightly for about 1 year and where I’m located, they charge fully almost daily. I have 800ah and my loads are about 3000w on average. The cells are normally balanced though I don’t do any manual balancing. The only thing I have noticed is SOC sometimes jumping from about 85% to 100% for no obvious reason but that has not proved to be a problem so far. I initially had a highly recommended brand that didn’t last even a month but I think it was badly wired.
F.
Where there is no shortage of charging power and stable loads, they behave because they can sync.
Provide iffy charging and variable loads, then the wheels can come off.
I had a personal set as well which I threw back at the distie as the SOC calculations were hopeless which made them not fit for purpose, something no amount of firmware updates could fix.
A decent battery should work reliably under all conditions.
But, then, you get what you pay for.
Many thanks Everybody,
I agree with Nick. BSLbatt is not the best choice on the market but I think I will have to live with them. Hopefully, they will last longer than the warranty period.
For the time being, I have adjusted my charging strategy. I will not go lower than 30% SoC in winter. At the moment, I have put the system on ESS “Keep batteries charged” and add grid power to ensure balancing of the cells. I will do that for a couple of days in a row. I monitor the cells with PBMStools 2.5. During the night, I will not discharge lower than 75% SoC. Let’s see. Many thanks again. Joerg