You can buy range extenders or transmitter/receivers. Look for Bluetooth 4 or 5.
But what is the problem? If it's inside something with metal walls like a boat, might not work.
I have my smart shunt connected to my solar setup in my carport. My work desk is 6 metres from the gear and no walls interfering and cannot connect . I can move to my door, 5 metres from shunt and works but of course that's bloody annoying...
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