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

Ran three of the cheap eBay specials across my van build, my cabin setup, and a mate's motorhome — two died within a season and one lied through its teeth about the charge percentages so convincingly I nearly killed a brand new Fogstar lithium.

The maths just doesn't add up when you factor in replacing them every 18 months plus the potential damage to your batteries. A Victron SmartSolar MPPT isn't cheap upfront, granted, but it's been rock solid for two years and the Bluetooth monitoring alone is worth it when you're trying to diagnose why your setup's behaving oddly at 6am in a field somewhere in Wales.

PWM vs MPPT is almost a separate argument — PWM controllers in general are fine for smaller, simpler setups where you're not chasing every watt. But cheap PWM is where it gets dicey. The decent ones from Renogy or similar at least have some quality control behind them.

The real false economy question is whether you trust a £12 controller to protect £300+ worth of battery.

Anyone actually had a long-term positive experience with the budget Chinese ones, or is it always just a matter of when rather than if?

Foggy80 | Posts: 847

@MoorKev that third one lying about percentages is actually the worst outcome of the three if you ask me — at least you know when something's dead. A controller confidently telling your batteries they're full when they're sat at 60% is doing real silent damage over time, especially through winter.

I went through two cheap PWM units on my shed setup before biting the bullet on a Victron BlueSolar. Night and day difference, and the Bluetooth monitoring alone has saved me from a few nasty surprises.

That said, I've heard decent things about Renogy's budget MPPT range if proper MPPT is out of reach price-wise — not glamorous but they seem to actually do what they claim on the tin. Anyone else had long-term experience with those?

@Foggy80 is right about the lying being the worst outcome — at least a dead unit tells you something's wrong.

Ran a no-name PWM on my static for about four months before I got a Victron SmartSolar. The difference in actual data quality alone justified the switch. The cheap unit was consistently reading 12.8v as "100%" regardless of time of day or load — completely meaningless.

The other issue nobody mentions: PWM vs MPPT aside, even a decent-quality PWM like a Renogy Wanderer will at least be honest with its readings. The problem isn't always the charge algorithm, it's the rubbish firmware underneath.

False economy in my view, particularly for anything static where you're depending on it longer-term. For a weekend-warrior setup you might get away with it, but I wouldn't gamble my batteries on it.

@MoorKev I had a similar experience with my shepherd's hut setup — binned a cheap PWM after one winter and moved to a Victron SmartSolar MPPT. Night and day difference, and the Bluetooth monitoring actually tells you what's really happening.

That said, I'd push back slightly on writing off PWM entirely. For a tiny fixed panel setup with flooded lead-acid, a decent branded PWM (not eBay lottery stuff) is perfectly adequate. The problem is nobody's buying decent branded PWM — they're buying the absolute bottom of the barrel and expecting miracles.

The lying display is what kills me though. You can't make any sensible decisions about your system if your controller is feeding you fantasy data. At that point it's not even a false economy, it's actively harmful.

@ExPostie curious which Victron unit you landed on for the hut — I've got a SmartSolar 100/30 MPPT on mine and the difference versus the PWM I started with was genuinely eye-opening, particularly through the low-angle winter sun we get up here.

The efficiency gain from MPPT alone justifies the cost on anything above a trivial panel array, but the data logging via VictronConnect is what really changed my understanding of what my system was actually doing day-to-day.

@MoorKev the lying percentage issue you describe is almost certainly the PWM reading panel voltage rather than true battery state-of-charge — completely useless for protecting your batteries from chronic undercharge. With lithium especially (I'm running Fogstar Drift cells), that kind of inaccurate reporting will quietly wreck your pack before you realise anything's wrong.

False economy doesn't really cover it.