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

Been down this road twice now with my static caravan setup, so here's my honest take.

First controller was a £12 jobber off eBay — lasted 14 months before it started giving completely false battery readings and eventually fried itself during a warm spell. Second was a slightly more reputable Chinese brand (Epever, which I'll admit is a step above the truly anonymous stuff) and that's actually been fine for two years.

The real question isn't PWM vs MPPT — that's a separate argument — it's whether the cheap PWM units are actually regulating properly or just pretending to. I've measured the output on a few of these things with a decent multimeter and the numbers are, let's say, optimistic. Your £80 of Fogstar lithium doesn't deserve to be overcharged by a fibbing £11 controller.

That said, for a small panel setup — say a single 100W panel running lights and USB charging in a shed — a halfway decent PWM controller is probably fine. Nobody needs a Victron SmartSolar for that application and anyone telling you otherwise is either sponsored or doesn't understand the law of diminishing returns.

My rule now: spend at least £25-30 minimum, stick to Epever or Renogy's basic range, and actually check the output voltage with a meter when you first install it rather than just trusting the display.

What's everyone else's experience? Particularly interested if anyone's running the truly anonymous stuff long-term without issues, because I want to know if I've just been unlucky.

@FormerTeacher 14 months is actually not terrible for a £12 unit tbh — I got about the same from a no-name PWM before it started cooking my battery overnight.

Switched to a Victron SmartSolar MPPT for the garden office and honestly it's a different world — the Bluetooth monitoring alone is worth it for peace of mind. Yes it's £80-100 more upfront but it's been solid for 3 years.

That said, for a very small setup (single panel, tiny load) I reckon a decent mid-range PWM like the Renogy Wanderer is a reasonable compromise — at least it has proper over-charge protection that actually works.

The real false economy isn't the controller itself — it's pairing a dodgy PWM with quality batteries. Learned that one the hard way with a Fogstar cell I'd rather not talk about. 😅

@FormerTeacher PWM vs MPPT is the real question nobody's asking — even a decent £35 Renogy PWM is leaving 20-30% of your panel's potential in the bin compared to a proper MPPT, so "cheap controller that works" is still a false economy if your panels are mismatched to your battery voltage.

That said, if you're running a dead-simple 12V panel → 12V battery setup with matched voltages, PWM losses are minimal and a mid-range unit like a Victron BlueSolar (not the bargain-bin stuff) sits around £45-60 and will outlast the caravan.

The £12 eBay units aren't just unreliable — half of them lie about their rated amps on the label. Tested one myself that claimed 30A and thermally collapsed at 14A. Bin fodder.

@MarineGeoff is right on the MPPT point — that 20-30% loss stings even more in the UK where we're already fighting weak winter sun.

My garden office ran a cheap PWM for about a year. Bin fire waiting to happen honestly — the thermal regulation was garbage and it got hot.

Switched to a Victron SmartSolar 75/15 and the difference in winter harvest was immediately obvious. Yes it cost ~£65, but it's been rock solid for 3 years now.

For anything boat-related like my other setup, I wouldn't touch PWM — moisture + dodgy components is a bad combo.

The maths usually works out: cheap PWM dies faster, wastes solar, potentially damages your battery. A decent MPPT pays back pretty quickly, especially if you're running Fogstar or any other lithium that needs tighter charge control.

@MarineGeoff @CE_Builds — the 20-30% figure is worth expanding on slightly, because it's angle and temperature dependent.

On my narrowboat, where the panels are flat on the roof and I'm frequently moored under bankside trees in the Exmoor combes, I've measured closer to 35-40% loss versus my Victron SmartSolar in similar conditions. Weak winter sun at shallow angles is precisely where MPPT earns its premium.

The irony of cheap PWM controllers is that the people most likely to buy them — folk on tight budgets with modest arrays — are exactly the people who can least afford to waste a third of their harvest.

False economy doesn't quite cover it. It's more like paying for a round and someone quietly tipping a third of every pint down the sink.

@ExmoorNomad makes a fair point on the variables, but here's where it got real for me — I was running a PWM on the garden office for about eight months, convinced I was being sensibly frugal. Then I fitted a Victron SmartSolar MPPT and watched the app data over a fortnight. The difference on overcast February days was genuinely eye-watering.

The boat's a different story — smaller panel array, shorter cable runs, and I did the maths carefully first. PWM can make sense there, but only because the numbers actually stacked up for that specific setup.

The cheap Chinese units aren't just inefficient — they're unpredictable. False readings mean you're flying blind, and that's where batteries quietly die. False economy doesn't really cover it when you're replacing a Fogstar battery pack.

@JennyThomas57 that garage setup story is exactly why I'm skeptical of the "it's only a controller, buy cheap" argument.

Running a boat with Victron SmartSolar — the difference in data alone is worth the premium. PWM gives you nothing to diagnose problems with. When my batteries started behaving oddly last autumn I could actually see the charge curves and pinpoint a duff cell. With a £12 eBay unit you're flying blind.

That said — small panel, fully matched voltage, always in float? PWM probably fine. The false economy really bites when:

• Panel voltage significantly exceeds battery voltage
• You're in the UK fighting for every watt October–March
• You need any kind of monitoring

The Renogy Wanderer isn't expensive and at least it won't lie to you about your battery state. Start there if budget is genuinely tight.