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

Had a couple of these on my shepherd's hut build a few years back. Picked up a 30A unit off eBay for about £12 and honestly it did work — panels charged the batteries, lights came on, job done.

But here's the thing — PWM vs MPPT aside, the cheap ones have a habit of dying at the worst moment. Mine gave up mid-winter when I needed it most. No warning, just gone. Had to scramble for a replacement.

Switched to a Victron SmartSolar (even the small 75/15) and the difference was night and day — proper app monitoring, reliable as anything, and I've not touched it since. Worth every penny on the hut.

On the motorhome I did keep a cheap PWM clone running as a secondary for a small 100w panel on the roof. That one's actually held up fine for 18 months, so maybe it's the lottery.

My take:

• Tiny setup, short-term use? Cheap PWM probably fine
• Anything you rely on? Don't risk it
• Got panels over 100w? Get an MPPT, the gains are real

The false economy angle is real though — one failed unit plus the hassle of rewiring can cost more than just buying decent gear upfront. Fogstar do reasonable budget MPPT options if Victron feels too steep.

Curious whether anyone's had better luck with the branded Chinese stuff like Renogy or EPever vs the no-name eBay units — feel like there's a big difference there that doesn't get talked about enough.

@FrostySocket yeah I know where this is going...

Had exactly the same on my shepherd's hut. £15 job off Amazon, worked fine for about eight months then just quietly stopped doing low-voltage disconnect properly. Batteries went flat repeatedly before I noticed. Did more damage to my leisure cells than the controller ever cost me.

Switched to a Victron 75/15 MPPT and haven't looked back. Yes it's £80-odd. Yes that stings when you're building on a tight budget. But it actually reports what it's doing via Bluetooth, so you can catch problems before they wreck your bank.

The maths isn't complicated — one ruined 100Ah battery costs more than the controller upgrade. PWM also wastes potential in partial shade which matters more than people realise in the UK climate.

False economy? Almost certainly, in my experience.

Has anyone actually tested the charging efficiency difference on a boat install? I'm wondering whether the losses from PWM vs MPPT are more pronounced when you've got longer cable runs to contend with — mine are about 8 metres from panels to batteries.

Also curious whether these cheap units handle the damp environment at all. I've seen corrosion eat through budget electronics surprisingly fast on the water.

I've been looking at a proper Victron SmartSolar but the price jump is significant. Is there a middle ground — something like a Renogy Wanderer — that's actually reliable without spending Victron money?

@FrostySocket what was the failure mode when yours eventually gave up — did it just stop charging or was there a more dramatic exit?

@OakSeeker I actually did a rough comparison on my boat last summer — ran a cheap PWM unit alongside a Victron SmartSolar 75/15 on identical panels for about a fortnight. The PWM was pulling noticeably less into my Fogstar lithium bank, especially on overcast days when the panels were operating well below their Vmp.

The Victron was consistently pulling 15-20% more usable energy. Over a full season that's significant if you're relying on limited roof space.

The thing people don't always factor in is that with PWM your panels are essentially throttled down to battery voltage. On a 12V system with a 20V Vmp panel, you're leaving a lot on the table.

For a tiny cabin with minimal loads, maybe the £12 option is fine. For a live-aboard situation? I wouldn't go back.

@NicolaTaylor72 that boat test is genuinely useful data, cheers for doing the legwork.

My two penneth: I ran a no-name PWM on my van conversion for about eight months before the magic smoke escaped on a particularly warm August afternoon. Replaced it with a Victron MPPT 75/15 and honestly, in the UK's famously generous sunshine, squeezing every last watt out of panels matters more here than somewhere sensible like Spain.

The real kicker isn't just efficiency — it's the battery health side. My Fogstar lithium cells weren't best pleased with the PWM's idea of "bulk charging." The Victron actually talks to them properly.

£12 controller + prematurely aged batteries = false economy written in fire.

That said, if you're running a tiny 50W panel into a basic lead-acid for a weekend shed? Crack on with the cheap unit. Horses for courses. 🐴

@NicolaTaylor72 that boat data is exactly the kind of thing I needed six months ago before I wired up my static caravan with a £15 mystery controller and watched it cook my Fogstar batteries like a Sunday roast 🔥

Swapped to a Victron SmartSolar 100/30 and honestly the difference in how the Bluetooth app actually tells you what's happening is worth the price alone — the cheap unit just sat there silently judging me.

For garden offices and low-wattage setups I'd say PWM is fine, but the moment you're protecting a decent lithium bank or trying to charge an EV off a bigger array, just spend the extra £80 and stop lying to yourself about "it'll be fine."