Good Morning, Have been lurking around and reading , but this is one of my first posts. Please be kind/patient.

I bought a Back Plate solution form a Co in Kaya Sands (it has a Victron Multiplus II 5KvA Inverter, a Victron MPPT and a BlueNova 52V- 77Ah-4k Battery. I also have 8 x 410w Art Solar panels. I am really happy with the Victron and Solar panels, but am unsure how to feel about the battery. 

I'm hoping someone can tell me how to tell if the battery is performing as one would expect from such an expensive battery.

I have set the ESS to Optimized( with Battery life) and set the Minimum SOC (unless grid fails) to 75%.

During the day when the PV are producing, it works beautifully and I power almost all consumption from PV.

However, when the sun goes down within an hour or 2 the battery is down to 75%.

I run almost everything through the system (more like trying to be off-grid than as a Back-up).

so Yes, the configuration of my loads and if I should rather have essential and non-essential loads etc is a separate conversation.

So, yes, the drain on the battery can be as a result of so many loads, but how do I test it.

How can I confirm that the BlueNova isn't under performing?

 

Since that is supposedly a 4kWh battery, then to use 25% (down to 75% SOC) is only 1kWh. So if you use between 500W and 1kW then it will take 1 - 2Hours to go down to 75% SOC. Although in reality the "77Ah / 4kWh" BlueNova battery is actually a 60Ah 3.12kWh battery (You can open it up and check for yourself. The capacity of the cells is printed on them by the manufacturer). So 25% of the real capacity is actually only 0.78kWh

A 4kWh Lithium Battery is undersized for a 5kW Inverter. Take a look at the Pylontech battery recommendations for example. You should also typically set your minimum SOC to around 30% - although this depends on how much battery reserve you need to keep for loadshedding.

I have a 12kWh BlueNova battery with a 3kW inverter so I generally only discharge to about 65% SOC overnight. My battery appears to have a larger capacity than advertised - cell voltages still looked okay when I once discharged it close to the full rated capacity (as measured by BMV712).    

Thanks. It seems that the 4K is just too small, and that it is not under performing.

I'l now start the saving for a new 8k BlueNova.. together with my 4k, it will therefore be 12K and that should carry me through an Eskom load-shedding of 4+ hours.. I hope

Yes, 4kWh (or 3.2kWh in reality) is way to small for your inverter size.

I know you may actually be able to get quite a bit more than the 'rated' energy from a new cell, but I still have to wonder about the fact that the manufacturer rates these as 60Ah cells. Surely they would rate them higher if they could. Here is a picture of a cell from a BlueNova 77Ah / 4kWh battery

There are 16 of these cells in the battery. Each cell is clearly printed as 60Ah / 198Wh. 198Wh x 16 = 3.168kWh

http://en.winston-battery.com/index.php/products/power-battery/item/wb-lyp60aha?category_id=176

Hi Stanley, do you know which cells are being used in the BN13V-310-4k_NG from them? Are BN still using the 123Smart BMS?

 

Regards

Henk

Hi Henk,

I don't know which cells exactly (I only ever looked at the BN52V-77-4k and a big custom built battery that was a high voltage and a few hundred kWh) but BlueNova use Winston cells (you can check the link I posted above to the 60Ah cells). In the large custom bank, they used bigger Winston cells (I don't remember which ones exactly) and still paralleled 2 cells (Then they had lots of series connected pairs of cells).

The last I knew they were still using the 123Smart BMS, but that was maybe 2 years ago now. They did say at the time that they had developed their own bespoke BMS, but when asked if they had a battery with the new BMS they said they didn't have one available yet. I have never seen a BlueNova battery with anything other than the 123Smart BMS (but then I don't really see a lot of their batteries anymore since I prefer other brands), so I don't know if they did end up using their own BMS or not.