I’m trying to determine the correct bulk/float voltages for my batteries to set in my inverter.
- Inverter is growatt 12000T
- Batteries are an LG NMC Lithium battery. Each battery is 6.5KW, so over the 7 batteries in the pack, 45kw total. These batteries were planned for an off-grid desalinization plant, but some were never used. They are a bit obscure, LG Model #: M48128P6BA. The battery modules built by LG contain 28 pouch style NMC cells (14 series, 2 parallel) and a module-level BMS.
- I currently have the bulk and float voltages set to 54V, per guidance from my vendor here in Mexico. I don’t have high confidence that these numbers are precise given other issues with this guy.
- Sun came up, and batteries started charging, peaking at 68.9 amps
- At 10:43:20 – battery charge current started dropping from 68.9 Amps, tapering down to 9 Amps at 11:09. So a 25 minute gentle curve.
- Charge voltage climbed from 53.2 at 10:28:00 to 53.5 at 10:42:40, and 53.6 at 10:43:20.
- It remained at 53.5 for the rest of the day until the sun went down (even though inverter is set to 54 float).
- Load was relatively constant in this period at only 200w.
- Batteries are actually 99% full at 53.6 volts and not 54, and hence batteries are unable to accept more current. Setting should be changed to float voltage of 53, and maybe bulk of 53.5.
- Even though inverter is set to 54v for both float and bulk, it’s actually tailing off charging early. This seems unlikely. I thought current was controlled entirely by how much the battery could accept, subject to the max charge current and max voltage setting in the inverter.