I don’t think this is a new question as many seem to touch on the subject but I am yet to understand it, so have to ask. Sorry for the repetition.
I’m not an electrician, sparky or similar, just an old guy having a pure off grid system installed centred around a Multiplus II 48/10000/140, Pylontech US5000 x 4 with Lynx Power In, Shunt & Distributor and RS450/100. Future will include generator input.
I’m trying to understand some of the basics so that with installation complete and everyone gone, I’m not left totally in the dark as to what is what.
The Pylontech manual shows an option of 4 batteries in parallel, battery cable sizing of 4AWG, a capability of 100A constant/peak of 120A charge/discharge (higher for short duration) and if only one pair of cables used a protective device of 125A or smaller.
If I parallel these 4 batteries, I have a potential of 400A running thru 4 AWG cables – is that correct?
The Multiplus manual states, for shorter runs, cables of 50mm sq (2 per neg/pos) are required with fuse of 400A.
A big difference. I’m missing something here. Battery cable size can’t be increased due Pylontech connector style - should the bank be split into 2 sets of paralleled batteries to decrease the cable load or am I way off track?
To sum up, I’m trying to understand for my situation, battery cable sizing and protective device sizing as both manufacturers seem to be at odds – at least to me. Thank you for reading.
Ultimately you need to size for what your system can draw from the batteries and charge them.
What they are capable of does not really matter if you are unable to use it.
With pylons you can use 1 or 2 pairs of +'ve/-'cables to the bus bar, this increases current carrying capacity and the possible bank size before splitting to multiple banks.
If in doubt always follow the manufacturer’s recommendations.
No need to worry about 400A when your system can only draw 200A-ish.
And i am not a fan of daisy chain battery banks, they have issues. And develop more serious ones later.
Rule of thumb - the gauge of wire coming off the bank should at least equal the gauge the inverter uses.
10 kVa uses 2x50mm or 2x70mm depending on return length.
Your batteries could be at minimum in pairs. More ideal is individual connections to the bus bar individually fused. That way if one ever needs to go away on a holiday, the bank will be even in charge and discharge.
Thanks for the reply - sorry I’m slow getting back but life got in the way. The feeling I’m getting from both responses is to increase the amount of battery cables for two reasons, reduction in cable loading and I’m guessing, a more even charge.
Thanks for the response - I think you’ve hit one of my exact confusions
This to me is not possible as you rightly state the inverter uses a much larger gauge than the pylon cable - therefore are you saying that splitting the batteries has the effect of increasing pylon cable size due the increase in cable quantity? Is this a light bulb moment for me!