Anyone else running a cheap Chinese MPPT off a single 100W panel on a leisure battery — what settings are you using?

Just picked up a Renogy Wanderer knock-off from AliExpress for about £18 delivered — one of those generic EP Solar-style 10A units. Paired it with a knackered-looking but actually decent 100W poly panel I got off Facebook Marketplace for a tenner, feeding into a 110Ah AGM leisure battery I rescued from a mate's caravan. Total spend so far: under £40, which feels mad.

Thing is, I'm not confident the default settings on this controller are right for AGM. Out of the box it was set to sealed lead-acid with a bulk charge of 14.4V and float at 13.8V. I've nudged the absorption up to 14.7V and dropped the float to 13.6V based on what I've read, but I'm getting a bit of paranoid about whether I'm cooking the battery or undercharging it. The unit does let you go into user-defined mode which is handy, but the manual is about as useful as a chocolate teapot.

Has anyone else gone down this budget route and actually dialled in settings that work long-term? Curious what absorption voltage, absorption time, and float voltage people are running for a leisure AGM. Also wondering if it's even worth fussing over this much at 100W input — the panel's unlikely to push more than 5-6A in British weather anyway.

Had almost identical setup for my garden office last summer — same generic 10A unit, single 100W poly.

Key settings that worked for me on a 100Ah AGM:

• Absorption: 14.4V
• Float: 13.6V
• Low disconnect: 11.8V

The default float on mine was set way too high out of the box (14.4V!) which would've cooked the battery over time. Worth double-checking yours @Turbo19.

One thing — those units can read voltage a bit optimistically. Grabbed a cheap Victron Battery Protect and a decent multimeter to cross-reference. Made a noticeable difference knowing what's actually going on.

Also disabled the load output entirely and just used the battery terminals direct — the load port on cheap units like that can be dodgy.

Great setup for the price, @Turbo19! A few things worth checking on those generic units — the default bulk/absorption voltage is often set for sealed lead-acid, so if you're running a flooded leisure battery you'll want absorption around 14.4-14.7V and float at 13.6-13.8V. Worth double-checking what chemistry profile is selected.

Also, those EP Solar clones sometimes have the load output LVD (low voltage disconnect) set aggressively low from factory — I'd bump that up to around 11.8-12.0V to save your battery's health.

One gotcha: the temperature compensation is usually enabled by default but with no sensor attached, so it may be applying incorrect corrections. Either disable it or grab a cheap NTC sensor if your unit supports one.

With a single 100W panel you're unlikely to stress a 10A controller anyway, so mostly it's just protecting the battery correctly.

Running this exact combo on my narrowboat for a couple of seasons now. One thing nobody's mentioned yet — watch your absorption time setting on these units. The generic default is often absurdly long (sometimes 2+ hours), which on a small 100W panel basically means you're sitting in absorption all day burning nothing useful. I dropped mine to 30–40 minutes and bulk charging improved noticeably.

Also check the equalization voltage — many of these units default it enabled on a timer. On a single leisure battery that's just punishing the cells unnecessarily. Disable it entirely unless you're running flooded cells that genuinely need it.

@Dizzy70 what was your load reconnect voltage set to? I've seen these units default to something daft like 11.1V which lets the battery get hammered before cutting loads.

Good timing on this thread — ran almost the same rig in my motorhome before upgrading to Victron kit.

One thing worth adding: those EP Solar-style units often have the load output enabled by default, which quietly drains your settings memory if the unit loses power. Took me an embarrassingly long time to figure out why my absorption voltage kept resetting back to 14.4V every time I disconnected.

Also worth sticking a cheap inline fuse between panel and controller — the generic units rarely have adequate internal protection, and a £2 blade fuse holder from Halfords has saved at least one of my leisure batteries from a dodgy connection going warm.

@SunnyDrifter's point about amp-hours is spot on for narrowboat use too — on a motorhome I found logging with a basic shunt meter transformed how I managed the single-battery setup.

Good points from @BayPete and @SunnyDrifter above. One thing I'd add specifically for a single 100W poly panel into a standard 100Ah leisure battery — keep your absorption time short, around 1–2 hours maximum. At 5–6A real-world current you're simply not pushing enough charge to justify the voltage-hold that most of these controllers default to (often 4–6 hours). You'll cook off electrolyte unnecessarily on a flooded battery, or stress AGM/gel unnecessarily.

On my shepherd's hut build I ran a similar EP Solar unit for 18 months. Setting absorption to 14.4V and float to 13.6V worked well. The equalization function on these cheap units is worth disabling entirely unless you really know your battery needs it — the default cycles are aggressive and poorly controlled.

Worth grabbing a cheap Bluetooth battery monitor too; you'll immediately see what the controller is actually doing versus what it claims.