Sveinung L. Johansen avatar image

BYD B-Box Pro 7.5 unable to start.

Last year (Nov 11 2020) I posted a question regarding my BYD B_Box that within 2-3 days SOC dropped from 90% to 7%. I got an answer from Guy Stewart that said:

This model of batteries have an issue where they are not very good at measuring very low power demand, anything less than 50W ~1A per module is not very reliable.

This is not normally an issue if the battery is recharging to 100% - 55.1+ V. At that voltage, it will recalibrate the SOC reading.

It seems like something has changed in that time that meant the battery was no longer reaching that 'recalibration' voltage threshold.

I can only speculate why that might be the case, but that is surely the explanation for inexplicable SOC drop

So I shut down the inverter (remotely) and only left the charger and the CCGX on and since this is an off-grid system up in the mountains in Norway I haven't been able to visit before now.

When I arrived yesterday the batteries was totally "dead" the solar charger MPPT 250/60 said that it was not charging due to lost connection to the BSM and the CCGX did not list the BYD box at all.

The BYD BSM module have a blinking green led that blinks two times and then have a pause. According to the manual this means lost connection to the batteries - no surprise since they don't turn on.

Then the question - Is the batteries totally dead or is there a way I can get the batteries back to life? Like trying to charge each battery individually by bypassing the BSM or telling the MMPT to ignore the BYD "BSM"....?

The system consists of the following components:

•Color Control GX

•MultiPlus-II 48/5000/70-48

•BYD B-Box Pro 7.5

•SmartSolar Charger MPPT 250/60



Sveinung Johansen

MPPT ControllersCCGX Color ControlBYD
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1 Answer
byd-service avatar image
byd-service answered ·

Hello, could you open a ticket in

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Yes, but I have no account there..

byd-service avatar image byd-service Sveinung L. Johansen ·

It just takes a minute, plus it is a requirement to issue a replacement. I believe the front panel might've stopped working so we would need to replace it.

When you open the ticket please add the voltage in B+B- (not P+P-)

I tried, but since I'm and end user and you register form requires a company name I'm not sure how to proceed.



byd-service avatar image byd-service Sveinung L. Johansen ·

Can you put me in touch with your supplier?

Hi, took some time since my contact had quit the company, New contact person / is. Kristoffer Pedersen <>

He said that he thought that the problem was low temperatures that we have experienced this winter and that the batteries has shut them self down.

The problem is how to best bring them back to life. He was not sure how to do this..


Sveinung L. Johansen

byd-service avatar image byd-service Sveinung L. Johansen ·

I will contact him as, even in the case of an overdischarged battery the front panel would switch on so I'm guessing the fault is in the front panel.