"Sins of a Solar Empire"

chess-equality

Solar Enthusiast
Joined
May 21, 2022
Messages
127
Location
Philippines
(Not promoting any game here, just thought of it as an apt title)

Quite embarrassed to admit, but so far I have had:
  1. Accidentally shorted the positive and negative of one of my 12v batteries. Got sparks that jolted me back to my senses (pun intended). Luckily the battery seems to be fine; needed to wake up the BMS though.
  2. Again another short, this time around when adding an extra 12v battery to my portable. I turned off the breaker but I didn't know that that part was live. YOU WERE TURNED OFF ALREADY!!! AND HOW WILL I KNOW THAT YOU WILL SHORT ALL BY YOURSELF!?!? Another round of sparks! And a small mark on my wire to remind me (cruel!). Luckily the old chap seems to be fine. Given up adding the extra battery as the leads were two crammed to each other.
  3. So I promised myself, no more shorts! Work with only one lead, then protect / tape the other! But then guess what! Today another short, another round of sparks! Strike 3! This time I shorted the leads of my inverter. YOU WERE TURNED OFF ALREADY!!! AND HOW WILL I KNOW THAT YOU WILL SHORT ALL BY YOURSELF!?!? But I violated my own rule. So I added Rule #2: If you are getting excited, see Rule #1! And I remember what happened in my portable. And I also remember the manual saying something about this. Luckily the inverter seems to be fine. Third time lucky!
I hope there will be no more fourth time!
 

ncsolarelectric

Engineering Support CEO
Joined
May 24, 2022
Messages
441
Location
Statesville NC
Rule #1, ALWAYS use a meter to check if there is voltage is present. These inverters and BMS have capacitors that will not self-discharge. If they did, it would be an efficiency loss. They will hold the charge indefinitely. You must use a bleeder resistor (100 Ohms, 10W) to discharge these DC Inputs and verify they are discharged with a meter before you do "anything" else with moving wires or tools around. You're lucky these are LV batteries. Do that with a 1000Vdc solar inverter and you could have an arc flash and plate your skin with copper. Ever seen copper plated skin? Be careful, everyone!
 

tashabay716

Solar Enthusiast
Joined
Jun 16, 2022
Messages
24
Great information, I did not know the inverter would store energy in the capacitors even with the PV turned off. Will be more careful for sure
 

ncsolarelectric

Engineering Support CEO
Joined
May 24, 2022
Messages
441
Location
Statesville NC
Great information, I did not know the inverter would store energy in the capacitors even with the PV turned off. Will be more careful for sure
If it is a grid-tied utility-interactive inverter and you disconnect just the PV side, the capacitors are fully powered by the AC connection on the grid side. They are not only storing energy, they are actively powered until you disconnect the AC side too. Then discharge them with the resistor before proceeding.
 

tashabay716

Solar Enthusiast
Joined
Jun 16, 2022
Messages
24
If it is a grid-tied utility-interactive inverter and you disconnect just the PV side, the capacitors are fully powered by the AC connection on the grid side. They are not only storing energy, they are actively powered until you disconnect the AC side too. Then discharge them with the resistor before proceeding.
No AC on mine. Off grid, but will still be more cautious now
 
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