Anyone else using cheap Chinese PWM controllers or is it false economy?

Been running a cheapo PWM controller on my shepherd's hut build for about 18 months now and honestly… it's fine? 😅

Not great, but fine. Cost me about £12 off Amazon and it's still chugging away. That said, I'm only running a couple of LED strips, a phone charger and occasionally a small fan, so it's hardly being pushed hard.

The real question I keep coming back to though — am I actually losing enough from the panels to make the upgrade worthwhile? I've got 2x 100W Renogy panels and I suspect a proper Victron MPPT would squeeze meaningfully more out of them, especially on those classic British overcast days when every watt counts.

So my actual questions for the hive mind:

• At what panel wattage does the switch to MPPT genuinely pay for itself?
• Has anyone done a direct before/after comparison?
• Are the slightly pricier Chinese MPPT units (Epever, Epsolar etc.) worth considering or is it Victron or bust?

Running the hut mostly spring through autumn, so not doing full-year calculations. Would love to know if anyone else has gone through this exact dilemma rather than just reading the theoretical specs. Real world numbers from real setups always beat a datasheet 📊

@StormyWelder Ah yes, the £12 controller — I remember it well. Bought one for the boat back in 2019, gave it a name (Derek), and Derek lasted fourteen months before quietly giving up the ghost on a Tuesday afternoon with all the drama of a damp firework.

The real cost isn't the unit — it's the efficiency losses

@StormyWelder Genuine question — what happens when it eventually packs in mid-trip? I've got a static caravan and a motorhome to think about, and I got burned once with a no-name controller that took out a battery bank with it when it failed. Not a catastrophic fire or anything, just cooked the cells.

Is there any actual data on failure modes with these cheap units? That's what bothers me more than the lifespan. A Victron or even a half-decent Renogy controller failing gracefully is one thing, but do the £12 jobbies fail safely or do they take something expensive with them?

Curious whether anyone's actually monitored what these controllers do at the point of failure rather than just how long they last.

@StormyWelder Curious about something specific — what's your panel Voc versus your battery bank voltage? Because with a PWM controller, if your panel's open-circuit voltage is significantly higher than your battery charging voltage, you're essentially throwing away a substantial chunk of potential capacity. That's the bit that bothers me about budget PWM units.

I'm mid-conversion on a van build at the moment, wrestling with exactly this decision. I've been looking at whether the MPPT efficiency gains actually justify the price jump to something like a Victron SmartSolar 75/15 — probably yes in a low-light UK climate where you're already losing output.

What's your actual amp-hour throughput looking like over a typical day? Have you measured it or just going by feel?

@FormerMariner1 raises a really important point that often gets glossed over in these budget discussions. PWM basically just shorts the panel down to battery voltage, so if your panel Voc is significantly higher than your bank, you're leaving a fair chunk of potential generation on the table regardless of controller quality.

That said, @StormyWelder, if your numbers are reasonably well matched — say a 12V nominal panel on a 12V bank — then yeah, a cheap PWM is perfectly serviceable for a small static setup like a shepherd's hut.

Where I'd urge caution is reliability of the protection features. The BMS circuitry on the really budget ones can be dodgy — overcharge protection that doesn't quite trigger at the right voltage can quietly cook your batteries over months without you noticing until it's too late.