Anyone else finding the Renogy 40A MPPT a nightmare to set up with lithium?

Had a similar headache with mine when I was setting up the battery system for my cabin a while back. The default charge profile is obviously geared towards lead-acid, and the lithium presets felt oddly conservative — I ended up spending a good afternoon cross-referencing the manual with the Fogstar Drift's recommended charge parameters before I felt confident enough to lock anything in.

The main sticking point for me was the absorption voltage. The Renogy kept wanting to sit at a setting that made me nervous for long-term cell health. Did you manage to get into the user-defined profile? That's where I eventually got it behaving properly, but the interface on the unit itself is genuinely fiddly — tiny buttons, confusing menu navigation.

A few questions that might help narrow things down for others:

• Which lithium chemistry are you using? LiFePO4 parameters differ quite a bit from other lithium types
• Are you using the Renogy app over Bluetooth, or just the unit controls? The app makes parameter adjustments a lot more manageable in my experience
• What's your panel array size? I wonder if some of the odd behaviour people see is actually a current/voltage mismatch issue rather than the lithium profile itself

Genuinely curious whether others have found a reliable parameter set they'd recommend for LiFePO4 with this controller. There seem to be quite a few different "correct" answers floating around online and it would be useful to have some real-world experience from people who've been running these setups for a decent stretch of time.

Hey @PartnerNomad, yeah the Renogy software is a bit clunky when you comes to lithium profiles. One thing that caught me out initially was the float voltage — leaving it anywhere near the lead-acid default will slowly stress your cells over time. I ended up disabling float entirely and setting absorption to around 14.2V for my 12V LiFePO4 pack, which has worked a treat.

Also worth double-checking your battery temperature sensor is actually wired in properly if you've got one — mine was reading ambient air rather than the battery surface, so the temperature compensation was throwing everything slightly off.

What BMS are you running? Some of them will handle the top-end cutoff themselves, which means you can afford to be a bit more conservative with the MPPT settings and just let the BMS do the heavy lifting.

Really interesting thread this — has anyone tried setting a custom absorption voltage rather than relying on the lithium preset? I've been faffing about with my Fogstar Drift 100Ah cells and found the preset was pushing slightly higher than I was comfortable with long-term.

My main question is: does the Renogy 40A let you completely disable the equalisation stage, or does it sneak it in regardless of profile? I've seen a few people mention it cycling through even when it shouldn't, which obviously isn't ideal for lithium chemistry.

Also wondering whether a Victron SmartSolar would just make life easier at this point — has anyone made that switch from Renogy and noticed a meaningful difference in how reliably the charge curves behave? Genuinely curious whether it's worth the price jump or whether the Renogy is salvageable with enough tweaking.

@Cleggy yes, custom absorption is the way to go — stop relying on those presets entirely.

On my shepherd's hut setup I run a Victron SmartSolar rather than the Renogy, but I've helped a couple of people sort their Renogy units out. The issue is the absorption duration as much as the voltage. Even if you nail 14.2V for a 12V LiFePO4, if the controller is sitting in absorption for 2 hours by default it's doing nothing useful and potentially stressing the cells.

Set absorption voltage to 14.2V, absorption time as short as the controller allows (ideally time-limited not current-limited), float at 13.5V. Disable equalisation entirely — that should be obvious but people miss it.

What BMS are you running? If it's a Fogstar Drift or similar with its own charge cutoff you've got a safety net, but I wouldn't rely on it as primary protection.

@Cleggy @SolarJunkie — completely agree on the custom absorption voltage. Just to add a practical note for anyone using lithium iron phosphate specifically: I found setting absorption around 14.2–14.4V (for 12V systems) with a very short absorption time — sometimes just 20 minutes — made a noticeable difference to battery longevity compared to letting it sit at the preset.

Also worth double-checking your float voltage. The Renogy defaults felt too high to me when I first configured mine; I dropped float down to around 13.5V and the cells have been much happier since.

@WonkyDrifter mentioned the software being clunky — if you're struggling with the app, sometimes it's easier to use the physical buttons on the unit itself for setting custom parameters. Bit fiddly but more reliable in my experience.