The failure nobody warns you about
Both boxes arrive. Both work. Then the well pump starts and the whole house goes dark, because the inverter asked for 250 amps and the battery was built to give 200. Or the charge stage runs past what the BMS allows and the pack protects itself by disconnecting on the sunniest day of the year.
Every one of those failures was predictable from figures the manufacturers already publish. They publish them in separate PDFs, in different words, with no mention of each other’s equipment. Putting those numbers in one place is the entire job here.
Start with a pairing
The ones people ask about most, worked through in full.
EG4 6000XP with EG4 LifePower4 48V 100Ah
Specs align on every checked field. Checked as 2 packs, 10.2 kWh against a 6,000 W inverter.
EG4 18KPV with EG4 LifePower4 48V 100Ah
Specs align on every checked field. Checked as 3 packs, 15.4 kWh against a 12,000 W inverter.
Sol-Ark 12K with Fortress eVault Max 18.5kWh
Specs align on every checked field. Checked as 2 packs, 37.0 kWh against a 9,000 W inverter.
Sol-Ark 12K with Pytes E-BOX 48100R
Specs align on every checked field. Checked as 2 packs, 10.2 kWh against a 9,000 W inverter.
Sol-Ark 15K with Fortress eVault Max 18.5kWh
Specs align on every checked field. Checked as 3 packs, 55.5 kWh against a 12,000 W inverter.
Victron MultiPlus-II 48/5000 with Pytes E-BOX 48100R
Specs align on every checked field. Checked as 1 pack, 5.1 kWh against a 4,000 W inverter.
Or start with the part
Inverters
40 units, with the voltage window and charge current that decide most pairings.
Batteries
50 packs, from bare case imports to floor standing cabinets.
How the checks work
The four tests, the three results, and the words this site refuses to use.
Field notes
The questions that come up over and over in the forums, answered from manufacturer documents rather than from other people’s guesses.
How many batteries does your inverter actually need
Battery count is set by the inverter’s charge current, not by how much energy you use in a day.
Your inverter says 100 percent, then 40 an hour later
A LiFePO4 voltage curve is nearly flat through the middle, so voltage based state of charge guesses badly.
Your battery is not on the inverter’s protocol list
What to do when the inverter menu offers a dozen brand names and none of them is yours.
Battery over voltage fault at the end of a sunny day
The absorption setpoint and the BMS cutoff are two different numbers, and the gap between them is where this fault lives.
Busbar or daisy chain, and why the first battery ages fastest
Unequal cable paths make one pack in a parallel bank do more work than the others, every cycle.
Split phase or single phase, and what it costs to get that wrong
A 120 volt inverter cannot run a well pump or a dryer, and finding that out after delivery is expensive.
Buying this month
The parts most builds need, priced live on Amazon. Check the pairing here first, then buy.
48V inverters48V batteriesCable, fuses, busbarsAffiliate links. As an Amazon Associate this site earns from qualifying purchases, at no extra cost to you. Prices and stock change often, and a listing appearing here is not a statement that the pairing above is approved.