I am looking to produce 50kW for an off grid solar project. Ideally, I'd like to have a high voltage DC battery system with a high power battery inverter and charge controller.
I have only found a couple high VDC (384V) inverters and charge controllers, and they are from Chinese manufacturers. I'm a little hesitant to buy from them.
All of the big companies only use 12, 24, and 48 VDC. I understand that it's the most common and you don't need much power for a home, but if I want to produce 50kW at 48 VDC that's over 1000A! If I run that in parallel to 48V inverters I would need 10 or more inverters. That is a lot of wire and work.
Is there an electrical reason why they would cap these products at 48 VDC?
Best Answer
60VDC is the cut-off for Safety Extra Low Voltage, or SELV, as spelled out in UL 60950-1. Besides being lower voltage, SELV circuits are also isolated from the mains by reiniforced insulation, which has specific spacing and materials requirements.
In general terms, SELV voltages are ‘touch safe’, meaning that they don’t present a shock hazard with direct contact. 48V falls below this SELV threshold with some margin. It’s also conveniently four ‘12V’ lead-acid batteries connected in series (really up to about 58.8V at full float charge.)
Voltages above the SELV level are considered in the same class as line voltage, and typically require an electrician to install. Reason? Electricians are familiar with codes and techniques to protect against inadvertent contact with potentially lethal voltages, including use of proper materials, fusing, fault protection, enclosures and cable routing.
More here: https://www.edn.com/electronics-blogs/power-supply-notes/4414411/What-does-SELV-mean-for-power-supplies