Hedges
I See Electromagnetic Fields!
- Joined
- Mar 28, 2020
- Messages
- 21,840
If 20A is sufficient for the charge controller.
Normally we would only run 80%, 16A, through a 20A breaker. But I think Midnight said theirs are OK at 100% (because magnetic/hydraulic, not thermal/magnetic)
Unlike an inverter, your system won't start drawing heavy current, so doesn't matter how long it takes.
Size the resistor so it can handle 48V continuously. If a 10W, resistor, V^2/R = 10W or less. 50^2/10 = 250 ohm or higher.
How long it needs to precharge, I'm not sure. Could be seconds. Check with a voltmeter.
A light bulb could also do it. A 12V bulb may or may not survive (probably short enough pulse it is OK.) A 120V bulb should work. If 60W, would be about 240 ohms hot, 24 ohms cold. Nice thing about a bulb is you see precharge happening, then ending. Wait for it to go out completely, maybe a little longer.
AC rated switches aren't suppose to be used for DC, tend to arc and burn. But knowing this isn't used to interrupt current, I might do that. The light bulb as a snubber might even protect it if accidentally opened while charging.
Normally we would only run 80%, 16A, through a 20A breaker. But I think Midnight said theirs are OK at 100% (because magnetic/hydraulic, not thermal/magnetic)
Unlike an inverter, your system won't start drawing heavy current, so doesn't matter how long it takes.
Size the resistor so it can handle 48V continuously. If a 10W, resistor, V^2/R = 10W or less. 50^2/10 = 250 ohm or higher.
How long it needs to precharge, I'm not sure. Could be seconds. Check with a voltmeter.
A light bulb could also do it. A 12V bulb may or may not survive (probably short enough pulse it is OK.) A 120V bulb should work. If 60W, would be about 240 ohms hot, 24 ohms cold. Nice thing about a bulb is you see precharge happening, then ending. Wait for it to go out completely, maybe a little longer.
AC rated switches aren't suppose to be used for DC, tend to arc and burn. But knowing this isn't used to interrupt current, I might do that. The light bulb as a snubber might even protect it if accidentally opened while charging.