I have a MultiPlus-II 48/5000/70-50 GX inverter.The manual specifies a 70mm² cable for distances up to 5 meters. However, my battery bank is located very close to the inverter (less than 3 meter cable lenght).
In this scenario, would a 25mm² cable rated for 170A be sufficient for the DC connection? I believe that this cable exceeds the inverter’s continuous current requirement of approximately 104A.
I’m particularly interested in understanding the potential trade-offs in terms of performance, efficiency, and safety if I were to use a 25mm² cable instead of the recommended 70mm².
If the 25mm² cable is to be used would a 170 amp fuse be more appropriate instead of the recommended 200amp fuse?
3m 25mm Voltage drop on 100A would be 0.96% or 0.46V equivalent of 46W heat either way +/- !
It adds up! I think 35mm drop 0.34V if not permanently on full load is OK
It is hard to find any cable size bigger than 25mm² in my area. In the end I managed to find a store that sells up to 50mm². Would this cable size be sufficient?
double the cables but it’s not very secure
Oops but I believe that according to energy regulations (NFC 15-100), it is forbidden to connect two wires in parallel to have a higher cumulative section.
Afterwards on the 8KVA or the 10 KVA the M8 are doubled, so…
The distance is 5m return. So 2.5m to bank. Use the size specified.
The inverter is also capable of 100% overload. And the batteries can produce enough current to blow ithe size specified. (Before the cable burns)
@LifeInGalicia With an inverter the current is being taken from the batteries in pulses synchronised with the ac. The inverter has input capacitors to smooth this, but is relies on a low resistance in the DC cables. Read the Victron free book Wiring Unlimited, the Section on ripple is linked below.
It also depends what batteries you use if using lithium with BMS set DVCC force charge current limit to 50Amp if grid connected set max inverter power to 4000W you could use 50mm
Using Using lithium say sing bank 296Ah the cables from the battery will only be 25mm. Most manufactures use Pylon, and BYD and loads of others use 25mm amphonel connectors which are 100amp rated, if using 2 banks at amp hour rating above will be 592hr and 200amp so effectively be 25x2 50mm so you would need to keep those battery cables as short as possible by using lynx distributor then if distance 2m to inverter 50mm would ok as you have set the max load in VE config
But you should really use victron recommendations just giving you some options to limit this current in the cables etc
I have the same inverter and use 50mm2 DC cables which are at most 1.5 meters. I have measured them at about 50 deg C using a thermal camera, under sustained, maximum DC load. The highest temperature is around the DC fuse, logically its the point of highest resistance.
I have a small fan 120mm unit just cooling the area where the fuse and DC main breaker sit.
You can also try to look for cables used for weldig machines (SMA, MMA), they have very fine strands thus they are super flexible and easy to work with them
In my area these welding cables were even cheaper then the “normal” stranded ones.
