A few things, but mostly it all comes down to bad firmware that can't be updated. I think this firmware issue is specific to my Renogy rebrand, so it's possible the SRNE won't have any of these problems.
- The LFP-specific charge profile never leaves the absorption/boost phase. The manual claims that it absorbs 'until full', whatever that means. But in my testing, that never occurs so you end up floating the battery at absorption voltage, which is obviously bad.
- The USER charge profile has a setting for the absorption time, but it doesn't do anything. Regardless of how you set it, it absorbs for maybe two minutes, and then goes to float. So your options are indefinite absorption (LFP setting) or effectively no absorption (USER setting)
- Approximately every 12 minutes, the SCC drops to zero power and then searches again for the Max power point. The actual loss of energy is small, but again it's just another indication of bad firmware.
- The absorption, float, and float return voltages can only be set in 0.4V increments. Maybe not a huge deal, but for example, I can't set float to 54.2V, I'd have to go with 54.0 or 54.4, because those are the only options.
- The float return voltage (i.e., the voltage below which the controller will again bulk charge the battery) must be at least 1.2V below the float voltage. For a 16S LFP battery under low-ish load, this is significantly discharged before the controller will recharge it.
Also, the inverter won't communicate with anything other than Renogy equipment, even though the SRNE will. I suspect that if I could somehow swap out the Renogy firmware with SRNE firmware, at least some of these problems would go away.
For reference, the Renogy model number I'm referring to is RIV4835CSH1S.
