48 volt safety

[BigIslandRyan]

I am building my first 48 volt system, and I hear Will's comments about getting shocked and being careful, but im not finding much information on how to put safety in practice. Does any have a resource or list of DONT's when it comes to working around 48volts? When a discharge capacitor is needed? I plan on putting my 4 SOK batteries (serial connected) inside a plywood box, but when connecting the batteries, is there a good video on exactly how to do it to avoid a huge spark? And what about earth grounding? Any concise safety resource is appreciated.

 

[Hedges]

Biggest hazard is high current. If battery gets shorted (e.g. by a wrench) it will melt and splatter metal.
No metal jewelry, insulate handles of tools, wear goggles. A class-T fuse on battery is a good idea (but a small piece of metal causing short can still splatter without blowing fuse.)

Nominal 48V charged to about 60V is a moderate shock hazard. Avoid letting it conduct through your body, don't be soaking wet, and secure a cover to keep other people away.

Lithium battery connected to capacitors of inverter causes a high surge, could damage switches and blow fuses. People use a precharge resistor. Search for threads in this forum on the topic.

Inverters probably discharge their capacitors when disconnected. Mine have safety instructions on time to wait before opening.

My inverters say grounding battery isn't required. I think the U.S. NEC requires it for this voltage.

 

[OffGridInTheCity]

In my jurisdiction I've been told that anything 48v or higher has regular NEC rules - because it enters the relm of shock danger.
One example of NEC rules that I had to follow is that that DC wiring must be in conduit (unlike regular AC house wiring). So my wiring from the PV array to the controllers all had to be in conduit - a real pain!

OK enough grousing, bottom line, I think there's a specific NEC body rules that would answer specific questions for US stuff.

 

[BigIslandRyan]

Fortunately I am doing this system under a "no permit required" situation so i dont have to follow all codes, but I don't want to kill myself either. And as safe as I try to be, on my 24v system I caused a short across battery terminals TWICE, just by being sloppy. It was enough to cause small melts on terminal posts. Fortunately this time i am dealing with 4 batteries instead of 16 individual cells like before.

 

[OffGridInTheCity]

OK - the bottom line (from what I understand) is that there is 'shock' risk at 48v and higher. The top 3 things that come to mind for you to consider:
- Grounding *Mine is to the house ground.
- Fuse/Circuit Breakers for short/overload protection (wire melting protection) *Pretty common for everyone
- A DC GFP (Ground Fault Protection) circuit breaker in your control box. *This came as part of the Midnite Classic charge controllers - but they sell these as specialized circuit breakers.

 

[tnt4him]

I am building my first 48 volt system, and I hear Will's comments about getting shocked and being careful, but im not finding much information on how to put safety in practice. Does any have a resource or list of DONT's when it comes to working around 48volts? When a discharge capacitor is needed? I plan on putting my 4 SOK batteries (serial connected) inside a plywood box, but when connecting the batteries, is there a good video on exactly how to do it to avoid a huge spark? And what about earth grounding? Any concise safety resource is appreciated.

Work with one hand. That way your heart wont' be in the center if you get shocked using two hands.