Anyone else running a leisure battery setup off a cheap PWM controller and actually getting decent results?

Been running a fairly basic setup in my T5 for about eight months now — 100W panel on the roof, a 20A PWM controller I picked up for £14 off eBay, feeding into a 110Ah AGM. Nothing fancy. I know everyone on here bangs on about MPPT being worth every penny, but honestly for my usage (phone charging, a 12V compressor fridge, some LED lighting) I'm not noticing any gaping hole where the extra efficiency should be.

I did the maths and yes, in theory I'm leaving maybe 10-15% on the table compared to a decent MPPT unit. But the PWM controller cost £14 versus £45+ for a basic Victron or Renogy MPPT. On a 100W panel in the UK, that efficiency gap probably works out to a few watts on a good day. I'm genuinely struggling to justify the upgrade cost when the payback period stretches out to years of weekend trips.

Curious whether anyone else is in a similar boat, or whether there's something I'm missing that makes the jump more worthwhile than the numbers suggest. Has anyone actually switched from PWM to MPPT on a small single-panel setup and seen a meaningful real-world difference on UK skies?

Hey @T5Build, similar story here — ran a near-identical setup in my old Berlingo conversion for about two years. The PWM gets a lot of stick online but honestly for a single panel feeding one battery it does the job fine. Where you'll feel the limitation is if you ever add a second panel, since you can't really mix voltages sensibly with PWM.

One thing worth checking — those cheap eBay controllers often misread battery voltage slightly, so your charge termination point can drift. Worth occasionally measuring across the battery terminals with a multimeter rather than trusting the controller display. Mine was consistently reading 0.4V high, which meant it was actually undercharging. Small tweak to the settings sorted it. What's your typical resting voltage looking like after a full day's sun?

Eight months with no major drama is honestly a decent result — I'd take that. One thing worth keeping an eye on with PWM on an AGM is that you're rarely hitting a proper absorption charge, especially once the battery's seen a bit of use and internal resistance creeps up. Voltage drop across the wiring can compound this. Worth sticking a cheap multimeter directly across the battery terminals while it's charging and seeing what you're actually getting versus what the controller claims. If you're consistently hitting 14.4–14.7V you're probably fine. If not, tightening up your cable connections and reducing run lengths can make a surprising difference without spending a penny. @TerryLewis is right that these setups can genuinely hold up — just needs a bit of attention.

Hey @T5Build, good to hear it's holding up. One thing I'd add that hasn't been mentioned yet — with PWM on an AGM, you'll want to occasionally check your resting voltage after a full charge day. PWM tends to push a fixed voltage regardless of battery state, so if your controller's bulk/float settings aren't spot on for AGM spec, you can end up either slightly undercharging over time or gassing the battery more than you'd like. Neither is catastrophic, but both quietly shorten lifespan. A cheap multimeter and a logbook of readings costs nothing and can catch drift early. Eight months in is actually a good point to baseline it if you haven't already. What are your current charge voltages set to?

@T5Build PWM on a 12V AGM is actually the one scenario where you're not leaving that much on the table compared to MPPT — the voltage gap is small enough that the efficiency hit barely matters, so your £14 controller might be the most sensible purchase in this entire forum.

That said, 110Ah AGM wants to see a proper absorption stage or it'll sulphate itself into an expensive paperweight within a couple of years — worth checking your controller's charge profile settings actually match AGM spec rather than some generic "battery" curve the factory programmed in a hurry.

My shepherd's hut runs Victron kit because I got burned once. You've been warned. 🔋