I'm feeling a bit cautious about dealing with 200 Amps in my 12V system and would love some recommendations about safety. Here's what I've got:
- Battery: I'm using an EcoWorthy 12.8v LiFePO4 that shuts off at 10v when fully discharged.
- Inverter: I have a Renogy 12V 2000 watt inverter.
This means at the bottom of the discharge, the inverter could pull up to 200A at 10V, or around 156.25A at nominal voltage, which feels like a lot of current. I don't plan on doing anything risky, but I'm wondering how careful I should actually be with normal outdoor conditions.
Also, how should I size the breaker? I'm considering a 200A DC breaker based on the nominal voltage calculation (156.25 * 1.25 = 195), but I don't want it tripping when my battery is low; should I go for 225A instead? I'd prefer not to drain the battery completely, but I'm unsure.
Lastly, the inverter comes with 3' 1/0 cables. They're probably sufficient for my typical usage, but I'm curious if I should consider upgrading to 1' 2/0 cable. I've seen ampacity charts that suggest 3/0, but that seems excessive; would 2/0 be overkill too?
1 Answer
You're definitely right to be cautious with a 12V system. Here are some key points you should consider:
- LFP batteries usually have a 1C discharge limit, which means for 200A output, you'd need around 200Ah capacity. Make sure your battery's BMS can handle that.
- Don’t forget that inverters are around 85-90% efficient. So, if you’re pulling 2kW, your input might be more like 2.25kW.
- For breakers, aim for one around 250A since you'll be pulling 225A at the lower end of the battery.
- Also, pay close attention to wire sizes. Thicker wires will help minimize losses from heat, especially since you’re dealing with high current.
Make sure all connections are solid to prevent any fire risks; use quality terminal connections and torquing practices to look after safety.
Wow, this makes a lot of sense! I'm mainly using it for backup on a chest freezer, but I'm definitely starting to think about my inverter efficiency now. I'll follow your advice on the 250A breaker!