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mufmur avatar image
mufmur asked

BYD LV Flex not working

I have 1pc BYD LV flex 5kWh connected to a cerbo GX, Multiplus II 5KVA and 2pcs bluesolar 150/45. I commissioned the battery, made sure all the cables are connected correctly including the special VE Can to BMS Type A cable but the battery doesn't work. Both the BMU and battery continuously blink white and then blue alternatively. I connected the cerbo to a separate 12V battery and accessed the console. It detects the battery but shows it at 0% with no voltage or current. The inverters and controllers are also not turning on or being detected on the cerbo. When measuring the battery voltage at the terminal there's less than 1V. However when accessing the BMU with Wifi, it shows that the battery is at 33%.

BYD
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2 Answers
nickdb avatar image
nickdb answered ·

Have you followed the setup doc?

https://www.victronenergy.com/live/battery_compatibility:byd_b-box

Also, that is not enough battery for that system, it may well be the lack of precharging that is tripping the battery or just not enough of it.

Would suggest you read up on these topics.

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mufmur avatar image mufmur commented ·

I managed to sort it out. It was a minor issue with the inverter cabling on one of the busbars which was causing the battery to self protect.

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Alexandra avatar image
Alexandra answered ·
@mufmur

If you see on page 11 of your BYD battery manual you will see that it means the battery is initialising.

The battery will not initialise if you have not programmed the BMU or the system cannot precharge the system. You will not see voltage until you have programmed and the system has precharged, that is why they ask you to have the fuses/breaker closed on start up, do not connect the inverter after battery precharge. (9.1 commisioning battery system in the BYD manual)

And yes alot of your problems will be related to the lack of battery.... your system will shut down alot... The BYD is very aggressive with its discharge current limit. In your case 60A. You have enough battery for a 3kva.


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mufmur avatar image mufmur commented ·

I managed to sort it out. It was a minor issue with the inverter cabling on one of the busbars which was causing the battery to self protect.
The client's load does not exceed 3kva, we had to go for 5kva since we couldn't find 3kva/48v with any of the distributors nearby.

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Alexandra avatar image Alexandra ♦ mufmur commented ·
Appreciate sometimes circumstances are what they are, however the battery is not sized for loads so much as the inverters needs on the minimum sizing. just be aware that you may run into problems further down the line.
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hanco avatar image hanco commented ·

Hi @Alexandra , do you think 1 x BYD LV flex 5kWh would be enough for a 3kva multiplus-II, when configured for a UPS system (i.e. loadshedding, SA) ? According to the victron/byd docs, 1 battery is enough for grid-connected, while 2 is required for off-grid. Does a UPS system count as off-grid ? Continuous power from the 3kva is 2.4 kW, which is more than enough for this installation. The max possible output from the inverter is 5.5 kW which 1 battery won't be able to handle, but I won't require that. The docs also state that "You must have the minimum number of battery modules to supply the inverters startup inrush surge currents that charge the capacitors when the inverter is first connected, this occurs prior to any loads being connected"... but it doesn't state what current is required to charge the capacitors.

For the BYD:
Max Cont. Output Current [2] 70 A

Peak Output Current [2] 105 A, 5 s

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Alexandra avatar image Alexandra ♦ hanco commented ·
@Hanco

It is a tricky one... since we have one foot on either side ;).

Technically a UPS type system is on grid. So one is ok.

For the 2 battery requirement I think they are expecting that the user is power up the system from the batteries and possibly with load and possibly even a self recovery black start.

The BYD precharge is the most elegant one I have used and is hands down my favourite. It is very clever it ramps up the voltage to precharge so by the time you are at full voltage there is no big amp draw.

One battery does start up a 3kVa with no load easily.

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