Anyone else running a cheap PWM controller with decent results, or is MPPT always worth the extra?

I've been running a Victron 75/15 MPPT on my shed setup for a couple of years now and it's been brilliant, but I'm putting together a second small system for my campervan and trying to keep costs right down. The van will have a single 100W panel feeding a 100Ah AGM battery, so nothing complicated. I keep seeing 10A PWM controllers on Amazon for £12-15 and wondering if I'm just being daft spending £60+ on a proper MPPT for a system this size.

From what I've read, MPPT really earns its keep when your panel voltage is significantly higher than your battery voltage — so with a standard 18V nominal panel into a 12V battery, the gains are maybe 10-20% in good conditions, less in low light. On a small 100W system in the UK, that's not exactly going to set the world on fire. A cheap PWM might genuinely be fine, especially if the van isn't my primary power source and I'm not trying to squeeze every last amp out of grey November skies.

Has anyone actually run one of those budget PWM units long-term without issues? I'm not asking about the £5 no-name horrors, but something like an EPSolar LS1024B or similar mid-range PWM. Curious whether the reliability holds up or whether it ends up being a false economy after 18 months.

@FL_Solar funny you should ask this — I went through exactly this debate when I first set up my narrowboat system a few years back.

Ended up starting with a cheap PWM from Amazon (can't even remember the brand, it was that forgettable) on a single 100W panel. Honestly? For summer it was fine. No complaints.

But come October, living aboard full-time, I really felt the difference when I swapped to a Victron 75/15 like yours. Those low-light, overcast days — which in the UK is basically most days — the MPPT genuinely pulls noticeably more. On a 12V system with higher voltage panels the maths just works in its favour.

My rule of thumb now: if it's a seasonal/occasional-use setup, PWM is probably acceptable. If you're relying on it through a British winter, just spend the extra.

Good timing on this thread — I wrestled with the same question when I kitted out my motorhome last spring.

Ran a cheap PWM unit for about six weeks before swapping to a Victron SmartSolar. The honest truth? On a small, well-matched system the PWM worked, but I was losing a noticeable chunk of harvest on overcast days — which, living in the UK, is basically every other day.

The maths that shifted my thinking: if your panel voltage is significantly higher than your battery voltage, MPPT claws back efficiency you simply cannot get from PWM. On a campervan where space limits you to one or two panels, that recovered wattage genuinely matters.

For a tight budget I'd look at a Renogy Wanderer if staying PWM, but honestly a Victron 75/15 second-hand off eBay regularly appears under £50 and it's a different league entirely.

The maths really does depend on your panel voltage relative to your battery bank. Where PWM genuinely holds its own is when your panel's nominal voltage closely matches the battery — a 12V panel on a 12V system, you're losing very little. The moment you start clipping higher Voc panels down to charge voltage, you're burning potential harvest as heat in the controller.

On a campervan specifically, you're also dealing with partial shading from roof bars, aerials, and whatever's parked next to you. MPPT handles partial shading curves considerably better than PWM, which just gets confused and sits on a suboptimal operating point.

The Renogy Wanderer is a reasonable cheap PWM if your panel matching is ideal. Otherwise a Victron SmartSolar 75/15 is only around £60–70 from Bimble Solar — the payback in extra harvest on a modest 100W panel is genuinely measurable within a season.

Good points all round, but nobody's mentioned the seasonal angle yet.

I ran a cheap PWM on my first van build — worked fine through July and August, then come October I was scratching my head wondering why my 100W panel was barely keeping up. Turns out PWM really struggles when your panel's running cold and the voltage climbs well above battery voltage. All that extra potential just gets thrown away.

Switched to a Victron 75/15 (same as your shed unit, @FL_Solar) and the difference in winter was genuinely surprising — probably 20-25% more usable charge on grey November days.

If you're only running the van in summer, a quality PWM like a Epever Tracer might make sense on a tight budget. Year-round van life? MPPT pays for itself before Christmas.

Really glad this thread came up — I've been going back and forth on exactly this for my tiny house build too, so it's not just the van crowd asking!

@SussexVanLifer makes me curious — what sort of difference were you seeing percentage-wise in winter vs summer with the PWM? Because that's genuinely the bit I keep second-guessing myself on.

My gut feeling is that for anything under 100W with a well-matched panel-to-battery voltage, PWM is probably fine? But the moment you're in the UK from October onwards, does that calculus just fall apart completely?

Also — has anyone here tried the Renogy Wanderer as a budget option? Seen it mentioned elsewhere and wondering if it punches above its price bracket or if it's just cheap for a reason.

@SussexVanLifer seasonal angle is the one that finally broke me — my van spends November through February looking at a grey flannel sky in a Tesco car park, and that's exactly when a PWM controller decides to have a proper sulk about panel voltage.

Swapped my old no-name PWM for a Victron 75/15 mid-winter and genuinely felt like I'd added an extra panel without bolting anything to the roof.

For a campervan specifically @FL_Solar, MPPT pays back fastest when you're relying on it most — which is unfortunately when British weather is doing its absolute worst impression of weather.

@SussexVanLifer @PanelRob — the seasonal thing hits even harder when your panels aren't flat on a roof. My shepherd's hut setup has panels at a low angle, and winter sun barely grazes them. MPPT genuinely saved my skin there, squeezing what little it could from those weak harvest days.

That said — for my emergency backup kit I actually kept a cheap PWM. Dead simple, nothing to fail, and it's only babysitting a 100Ah battery through summer. Context is everything. Ask yourself what the system actually needs to do, not what looks impressive on paper.