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

Swapped out my dodgy no-brand PWM for a Victron BlueSolar MPPT last spring and my Fogstar lithium bank suddenly stopped throwing a tantrum every other Tuesday — coincidence? I think not.

Look, I get the appeal. When you're kitting out a shepherd's hut on a shoestring, that £18 controller on AliExpress looks very seductive next to a £90+ Victron. But here's the thing nobody mentions in the product listing: PWM controllers throw away a massive chunk of your panel's potential, especially on a 24V panel charging a 12V bank — you're essentially binning free electricity like some kind of solar psychopath.

MPPT isn't just marketing fluff. In the UK's famously generous winter sunshine (🙄), you genuinely cannot afford to waste 20-30% of what your panels are scraping together.

That said, I'll defend cheap PWM in one scenario: dead simple 12V panel to 12V lead-acid setup, tiny system, you genuinely don't care. Fine. No judgement. We've all been there with a Renogy starter kit and a prayer.

But for anything lithium? Bin it. The charge profile compatibility alone makes it a false economy — you risk cooking expensive cells because the controller doesn't know what lithium is, let alone how to treat it properly.

Anyone still running Chinese PWM on a serious setup? Genuinely curious whether I'm being a snob or whether you've actually had decent results long-term.

Had almost the exact same experience @SilverHiker. Ran a cheap PWM from a well-known auction site for about 18 months before I twigged what was actually happening — it was claiming to charge my batteries but the absorption stage was basically fictional. Voltage readings on the unit itself were optimistic to put it mildly.

Switched to a Renogy Wanderer as a stopgap (decent enough for the money) and the difference in how my batteries behaved overnight was immediately obvious. Eventually went full Victron and haven't looked back.

I'd say cheap PWM controllers aren't always terrible for a basic 12V setup with AGM batteries if you're not pushing much current through them, but pair one with lithium and you're essentially gambling. The BMS will save you, but it shouldn't have to work that hard just because your controller's lying to it.

Really interesting thread this — got me thinking about my own setup on the boat.

Running a Renogy Wanderer PWM at the moment and honestly wondering if it's been throttling my 200Ah Fogstar Drift bank more than I'd realised. Battery never quite hits the voltages I'd expect on a decent sunny day.

Quick question for @SilverHiker and @Brummie92 — when you made the switch to MPPT, did you notice an improvement in absorption/float behaviour specifically, or was it more about raw harvest numbers? Trying to work out whether my issue is the controller misreading the lithium profile or just the PWM inefficiency generally.

Also, space is tight in the engine bay — did anyone go with the Victron SmartSolar 75/15 for a smaller install? Seems like the obvious candidate but curious if there's a better-value option I've missed.

Worth noting that PWM vs MPPT is almost a separate argument from brand quality. A decent PWM from a reputable manufacturer isn't inherently evil — it's just the wrong tool once you're on lithium or your panels aren't closely matched to your battery voltage.

The real issue with no-brand stuff is the charge profiles are often just... made up. Absorption voltages all over the place, no proper absorption time, bulk stage cutting out early. I pulled the lid off one a while back and the component quality was genuinely grim.

For my static caravan setup I'm running a Victron SmartSolar and yes it cost more, but the BT monitoring alone has saved me from at least two potential problems by catching dodgy behaviour early.

@RustySkipper on a boat I'd be particularly wary of cheap controllers — corrosion plus dodgy PCB work is a bad combination.

@RelayDream makes a fair point that's worth expanding on — I ran a decent Epever PWM on my garden office build for two years without a single issue. Knew exactly what it was doing, comms worked, settings held.

The false economy question really comes down to what you're connecting it to. Slap a cheap no-brand PWM onto a £600+ Fogstar lithium bank and you're gambling. The BMS will save you eventually but you're stressing cells with dodgy charge profiles repeatedly.

My shepherd's hut runs a smaller, cheaper Renogy unit — sealed lead acid, modest loads, not the end of the world if something's slightly off. That's where budget kit makes sense to me.

Horses for courses. Match the controller quality to what's downstream of it.