I'm looking for some insights on the best way to wire eight LiFePo 12V 100Ah batteries that come with a built-in BMS. I found a deal for four batteries at $325, which seems like a great price since they tested well. I've also got seven approximately 300-watt solar panels that I got through a trade, and I'm considering a 3,000-watt inverter (with a 6,000-watt surge capacity). I'm not sure whether to use two MPPT charge controllers or just one bigger controller, like a Victron 150/100. Besides buying used gear or potentially risky China imports, how can I keep costs low while also allowing for future expansion, like doubling the system in a couple of years?
3 Answers
First, make sure you know the exact brand of your batteries. Some manufacturers place limits on how many you can connect in parallel or series, and not having Bluetooth monitoring could make it tough to keep track of their charge states. Balancing them might also be tricky. If you have room, you might want to invest in server rack batteries instead of dealing with multiple units.
I recommend going for a 48V inverter, as this setup can handle future upgrades better than sticking to 12V or even 24V systems. You could set up two parallel rows of four 12V batteries in series, and consider checking out Signature Solar's refurbished EG4 3000XP for $599. I've had one running on a portable setup with 4000W of panels, and it powered a 14,000 BTU window A/C for almost two years without issues.
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It might be best to go with two sets of 48V batteries and choose a charger/inverter combo like the Victron Multiplus or Quattro. Victron also offers excellent charge controllers. The 150/100 is a solid choice, but depending on your panel wiring, you might get by with a lower amperage model. Check platforms for used panels; they're available often. Just make sure to match the voltage of your panels to your charge controller’s specs. Victron has a handy calculator to assist with this setup: [Victron MPPT Calculator](https://www.victronenergy.com/mppt-calculator).
"Challenging" is putting it lightly! Managing 8 batteries in a series/parallel setup will definitely test your skills. And about that price—$325 for four 100Ah batteries? That's pretty cheap considering reputable brands are usually over $130 each. I’d be cautious about going for those.