DC cable sizes for parallel Multiplus ll upgrade with solar

Q&A and troubleshooting
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1

Hi,

I currently have a battery storage system comprising of the following:-

Multiplus ll 48V/5000/70-50 with 70mm2 cables to the centre of a Victron Lynx Distributor with a 125A fuses

4 X Pylontech US5000s wired as 2 pairs with the two sets of standard Plyontech leads back to the Victron Lynx Distributor on 100A fuses

I want to add another Multiplus ll 48V/5000/70-5 (in parallel), two more US5000s and a lot of solar which would utilise a Victron SmartSolar MPPT RS 450/200-MC4

My plan is do the following:-

Connect another Victron Lynx Distributor for the extra connections

Connect another pair of Pylontech US5000s using standard leads and 100A fuses (spread across the busbar)

Connect the second Victron Multiplus ll 48V/5000/70-50 in parallel

Connect the Victron SmartSolar MPPT RS 450/200-MC4

My question is, what size cable would you recommend for the DC connections from both the Multiplus ll’s and the Smartsolar MPPT and also the fuse rating (assuming that the cables are identical lengths to balance)

2

70mm cable will carry ~194A, so is good for the Multiplus connections.
for the RS 200A charger, it will be a bit thin, so 95mm^2 or 2 x 35mm^2 if you need flexibility ( the 35mm cables in parallel have more surface area than the 70mm cable, so can dissipate more heat)
Fuse ratings should be as per the equipment manuals, the 2 inverters should both have identical fusing. for the RS 200A charger the fuse should be 250 - 300A.

3

Thanks very much for your quick response :+1: