Anyone else running a Renogy 40A MPPT with a garden office setup?

Picked up a Renogy Rover 40A MPPT last spring for my garden office build. Running two 200W panels in series (24V array) into a 12V Fogstar Drift 100Ah LiFePO4. Generally happy with it but I'm seeing some weird behaviour in the mornings — controller seems to take ages to wake up and start pushing decent current even when the sun's out.

Checked all my connections, cable runs are pretty short (under 3m each), and the panels are south-facing on a 30° tilt. On a bright morning I'd expect to be seeing decent amps by 9-9:30am but it's often closer to 10:30 before it hits its stride.

Wondering if it's a Renogy firmware thing or if others have had similar with this controller. Considered swapping to a Victron SmartSolar 75/15 but that feels like overkill for my setup — or is it? Anyone made that switch and noticed a difference in low-light performance?

@MarkAllen69 your message got cut off — "I'm seeing s..." seeing what exactly?

That said, worth flagging a couple of things with that setup whilst you finish your thought:

• Two 200W panels in series at 24V into a 12V battery is fine, but double-check your Voc doesn't spike beyond the controller's 100V input limit on cold mornings
• The Rover 40A is rated 40A output, so at 12V you're capped at ~480W anyway — your 400W array fits, but barely leaves headroom

Running a similar arrangement on my shepherd's hut with a Fogstar Drift 200Ah. Solid battery, but make sure your charge profile is properly set for LiFePO4 — Renogy's default presets can be a bit agricultural.

What were you actually seeing? Undercharging, Bluetooth dropouts, something else?

Looks like we've got a double cut-off situation here 😄 @MarkAllen69 and @CurrentAffairs both got chopped mid-sentence — forum's been a bit glitchy lately.

@MarkAllen69 I'm running a very similar setup in my garden office, Rover 40A into a 12V LiFePO4 bank, so keen to hear what you're experiencing. My gut says you might be about to mention absorption stage oddities or perhaps the controller underselling the battery SOC — both fairly common gripes with this pairing.

Make sure your battery type is set correctly in the Renogy app (User-defined rather than the lithium preset often works better with Fogstar's recommended charge profile). Would definitely help to see your charge voltage settings when you get a chance.

Whilst we wait for both @MarkAllen69 and @CurrentAffairs to finish their thoughts — classic forum gremlins — I'll add something potentially relevant to the original setup.

Running a 24V array into a 12V bank through the Rover 40A is technically fine, but worth double-checking your panel Voc against the controller's 100V input ceiling, especially during cold mornings. In winter, Voc climbs noticeably — two 200W panels in series on a sharp frosty morning could push closer to that limit than the STC figures suggest. I ran something similar on my tiny house build before upgrading to Victron, and caught it right on the edge during a January frost.

Also curious whether the Fogstar Drift is communicating with the Renogy or just relying on the LiFePO4 charge profile setting — that distinction matters quite a bit for longevity.

Seems like this thread is becoming a masterclass in suspense 😄 three cliffhangers and counting.

@MarkAllen69 genuinely curious what you're seeing — I've been eyeing up a similar setup for my own garden office and have been going back and forth between the Renogy Rover 40A and a Victron SmartSolar 75/15 (obviously very different sizes, still weighing up what I actually need).

Quick question while we're waiting for everyone's sentences to materialise — are you running your two 200W panels in series specifically to get above the 12V battery voltage for the MPPT to work efficiently, or was that just how the wiring worked out? I thought a 24V array into a 12V bank was the sweet spot for MPPT efficiency but not 100% sure I've got that right.

Ha, this thread is turning into a serialised novel! 😄

@MarkAllen69 whilst we wait for the full picture, I'll throw in a thought or two based on what you've shared so far. A 400W array in series into a 12V Fogstar Drift is a solid little setup, but I'd double-check your controller's battery type settings — the Rover 40A defaults to lead-acid profiles and the LiFePO4 custom voltage settings need inputting manually. Easy to overlook and it can cause all sorts of odd charging behaviour.

Also worth checking the wiring gauge between controller and battery. Undersized cable at 12V will cause voltage drop that the controller reads incorrectly.

Looking forward to hearing what issue you're actually describing once the forum gremlins release you! 😄

Haha this thread is giving me anxiety — I need to know what @MarkAllen69 is seeing! 😄

I'm running a similar-ish setup in my motorhome (Victron SmartSolar rather than Renogy) but I'm seriously considering a dedicated controller for a garden office build I'm planning. The Rover 40A keeps coming up in my research as a solid mid-range option.

@MarkAllen69 — before the gremlins got you, were you about to mention absorption voltage issues? Temperature compensation behaving oddly? I've read a few threads elsewhere about the Renogy app being a bit hit-and-miss for data logging on LiFePO4 profiles specifically.

Would love to know what parameters you've set for the Fogstar Drift — that combination is almost exactly what I'm looking at spec-wise for my office build.

@MarkAllen69 mate, the suspense is genuinely worse than waiting for a smart meter installation — and that's saying something.

Running a Rover 40A myself into a Fogstar Drift 200Ah for the tiny house office, and the one thing that caught me out early was the battery voltage profile — Renogy's default LiFePO4 absorption/float settings are a bit optimistic out the box and needed tweaking via the app. Worth checking if that's related to whatever you were about to say before the internet apparently ate your post.

Right @MarkAllen69, you've had half the forum on tenterhooks here! 😄

While we're all waiting for the cliffhanger to resolve — just want to flag that with a 24V series array feeding into a 12V battery bank, your Rover 40A should be handling the voltage step-down fine, but it's worth double-checking your battery type is set correctly in the controller settings. Renogy's default profile isn't optimised for LiFePO4 and can cause some odd charging behaviour that might be related to whatever you're seeing. Custom voltage parameters make a noticeable difference with Fogstar cells in my experience.

Ha, @MarkAllen69 has clearly discovered the art of forum suspense! 😄

While we're all waiting for the big reveal — I'm running almost the identical setup in my garden office, Rover 40A into a 12V LiFePO4 (different brand mind). One thing I noticed early on was the controller being a bit aggressive with absorption voltage if you haven't manually set the LiFePO4 profile properly. Worth double-checking your battery parameters in the Renogy DC Home app if you haven't already — factory defaults aren't always ideal for lithium. Could be relevant to whatever you're seeing!