What Cable should I run to for a backup battery

[ricardo100671]

We are doing a refurbishment and want to plan for the possibility of adding a Battery backup, like Anker SOLIX or Mango Power E, in the future. 

 

The grid supply and Main CU are located in the middel of the house and the batteries would be in an outside Plant Room, which Has a CU supplied with 16mm2 cable from the Main CU. In the future we would like to run the house entirely from Batteries, charged either by solar or overnight on cheap tarrif.

is the current 16mm2 cabling coming into the Plant Room adequate for charging the battery from grid and I assume I would need an additional cable inplace to  run power back to the Main CU to power it of the batteries, as well as CAT for any controll pannels?

 

Am I missing anything please ?

 

Thank in advance

[sharpener]

16mm^2 cable is what was formerly used for meter tails on a supply with an 80A cutout.  But 25 mm^2 meter tails and 100A cutouts are now standard so at first glance it might not be thought to be enough.

 

However for charging you will almost certainly be OK as 80A at mains voltage will in theory allow you to charge a 48V battery at nearly 400A (neglecting losses).

 

For discharging it depends on the inverter rating and topology, I assume you will locate the inverter in the plant room to minimise losses. The existing cable will handle anything up to 18.4 kW; in a domestic setting you would be more likely to need 8 or 10 kW at most. We have a Victron 5kVA and it is fine for nearly all purposes, and 10mm^2 is adequate for input and output as even in pass-through mode it is limited to 50A.

 

Whether you need to run a second cable also depends on the inverter circuit topology. With a Victron you could get away without it by wiring everything to its AC-In terminals but that is a bit unusual, separate inputs and outputs are more the norm.

 

You might also think about other heavy current users like HPs and EVCPs which have their own particular wiring requirements. And also putting in cable runs for the various current transformers needed. Maybe a duct would be better if you don't yet know what you will be needing.

 

Earthing is a whole topic in itself. Many Chinese inverters are not compliant without extra kit.