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

Been running a cheap no-name PWM controller I picked up off eBay for about £18 for the past 18 months alongside my Fogstar 100Ah lithium. Honestly? Mixed results.

The main issue I've found is the cheap ones don't play nicely with lithium chemistry — the charge profiles are either fixed or the settings are so vague you've no idea what voltage you're actually programming in. Mine would occasionally spike to 14.8V which had me a bit nervous.

Swapped it out for a Victron BlueSolar MPPT eventually and the difference in monitoring alone was worth it. But I'll be honest, the cheap PWM did work for over a year without dying, so there's that.

I think the real question is whether PWM vs MPPT matters more than brand quality. On a smaller array (mine's only 200W) you're probably losing 20-30% efficiency with PWM regardless of who made it, which over a winter adds up.

Has anyone found a budget PWM that actually has decent lithium profiles built in? I've seen a few Epever units mentioned — are those worth considering as a middle ground, or are people just jumping straight to MPPT these days even on tight budgets?

Would be curious to know what others are running and whether the cheap stuff has let anyone down badly or if I've just been unlucky with the dodgy charge voltages.

@Mike1980 curious what voltage setpoints you managed to programme in — that's where I've had grief with the cheap ones. Running a garden office setup here and went through two no-name PWM controllers before caving and getting a Victron SmartSolar.

The killer for me wasn't outright failure, it was the absorption voltage being fixed at 14.4V with no way to adjust it properly. Fine for lead acid, not ideal when your Fogstar wants something more specific.

Did yours have any kind of lithium preset, or were you manually tweaking it somehow? I've seen some of the newer cheap units advertised with Li presets but I'm sceptical whether they're actually calibrated correctly or just a marketing tick-box.

@Mike1980 ah, the great PWM lottery. I've been down this exact rabbit hole with my shepherd's hut setup.

Here's the thing nobody mentions: cheap PWM controllers aren't necessarily bad — they're just dishonest. The voltage readings on the display are frequently fibbing to you by 0.3–0.5V, which when you're trying to protect a Fogstar lithium is roughly the difference between "fine" and "quietly destroying your warranty."

Picked up a decent multimeter and started cross-referencing mine. The controller was cheerfully announcing 14.2V whilst my battery was actually sitting at 13.7V.

The £18 price point buys you a controller. Whether it's your controller — one that actually does what you've told it — is a separate question entirely.

For emergency backup applications I'd personally rather spend £45 on something that reads the room correctly. The battery costs considerably more than the controller.

Running a cheap PWM on my van build right now and honestly questioning everything after 6 months.

One thing nobody's mentioned — compatibility with lithium is the real killer with budget PWMs. Most are calibrated for lead-acid absorption/float profiles. My Fogstar 100Ah was barely hitting 90% SoC consistently because the charge curve just wasn't right.

Swapped to a Renogy Wanderer eventually, still budget but at least has a lithium setting. Night and day difference.

@Nobby the voltage setpoint issue is exactly what finished me off with the no-name unit — couldn't get it below 0.2V of where I needed it.

Is anyone actually running a proper MPPT on a tight budget? I keep eyeing up the Victron 75/15 but £60+ feels steep when you're already skint from the van conversion itself.

@Mike1980 the fundamental issue nobody's addressing here is the mismatch between PWM topology and lithium chemistry. PWM controllers essentially connect the panel directly to the battery in pulses — fine for lead-acid whose internal resistance absorbs the variation, but lithium cells genuinely don't tolerate that the same way.

On my static caravan setup I ran a similar cheap unit briefly before replacing it with a Victron SmartSolar. The cheap controller was reading battery voltage nearly 0.4V high on my multimeter comparison, meaning it was terminating charge early. That's capacity you're silently losing every cycle.

For emergency backup applications specifically, I'd argue this matters more than people realise — you want actual known state-of-charge, not what a £18 unit with dubious calibration tells you.

MPPT isn't just a buzzword here; it's measurably more appropriate for lithium. The Renogy Wanderer is at least a known quantity if budget is the constraint.

@Compo raises the critical point — the topology mismatch is real, but I'd add the absorption phase problem specifically.

With my Fogstar 100Ah, I've measured PWM controllers hitting the bulk/absorption transition prematurely because they're reading panel voltage rather than genuine battery response. You end up with chronic undercharging — batteries sitting at 80-85% thinking they're full.

Ran a Renogy Wanderer for 8 months before switching to a Victron SmartSolar 75/15. The difference in actual state-of-charge (verified against a Victron BMV-712) was consistently 7-12% across comparable irradiance days.

The £18 eBay unit @Mike1980 describes almost certainly lacks proper lithium charge profiles entirely — most just approximate it by bumping absorption voltage slightly. Not the same thing.

For lithium specifically, PWM is false economy. For flooded lead-acid in a simple setup? Arguably acceptable. Chemistry matters enormously here.