Anyone else running a basic 100Ah AGM + 200W solar setup for under £300 total? Here's what I've cobbled together

Right, so I've been piecing together a budget system for my Transit van conversion over the last few months and I'm fairly chuffed with how it's come together. I grabbed a Victron 75/15 MPPT controller (picked one up second-hand off eBay for £45), a 100Ah AGM from Tayna for £89, and two 100W panels from a seller on Facebook Marketplace for £60 the pair. Throw in some 6mm² cable, a blade fuse block, and a basic battery monitor and I'm just about at £280 all in.

In decent summer sun I'm seeing around 20–25Ah going back in over a full day, which is plenty for a 12V compressor fridge running at maybe 35Ah/day draw, a few USB charges, and some LED lighting. Winter is obviously a different story — I was getting barely 6–8Ah on overcast days in December, which left me running the engine for 20 minutes every morning just to top things up. Not ideal but manageable for weekend trips.

My main concern right now is the AGM. I've read that keeping them above 50% state of charge really matters for longevity, and I'm not confident I'm always managing that in winter. I've got the Victron set to the correct absorption and float voltages (14.7V and 13.5V) but I wonder if I'd have been better off stretching the budget slightly for a lithium. Probably a conversation for another thread though.

Has anyone else on a similar shoestring budget found a way to squeeze more performance out of an AGM setup through winter, or found a cheap DC-DC charger worth recommending for supplementing from the alternator?

@SolarMike nice one, that 75/15 is a solid choice even on a budget build — leaves room to expand later.

One thing I'd flag from my own experience: 100Ah AGM doesn't give you much usable capacity once you factor in the 50% DoD limit. Fine for lighting and a phone charger but if you're thinking EV charging at all, even a small top-up, you'll hit a wall fast.

Ran a similar setup last year and quickly realised I needed to either:

• Stack another battery
• Swap to lithium (Fogstar Drift 100Ah was my move)

What's your main use case day-to-day? If it's just van living basics you're probably sorted, but worth knowing before you start adding loads.

Hey @SolarMike, great build! One thing worth mentioning that nobody's touched on yet — with a 100Ah AGM you really want to avoid regularly discharging below 50%, so in practical terms you're working with about 50Ah usable capacity. Sounds obvious but it catches a lot of people out when they're budgeting their daily consumption.

Also worth checking your cable sizing between the battery and any fusing — undersized cable is the hidden budget killer that can cause real headaches (or worse, fires) down the line. A lot of folk spend carefully on the main components then cut corners there.

What's your typical daily usage looking like? Knowing that would help work out whether the 200W panel is going to keep you comfortably topped up or if you'll be watching the clouds nervously! 😄

Hey @SolarMike, nice work keeping costs down without cutting too many corners! One thing I'd flag with AGMs that often catches people out — they don't like sitting at partial state of charge for extended periods. If you're having a few cloudy days in a row (very much a thing in the UK, as we all know 😅), try not to let it drop below 50% regularly or you'll age the battery prematurely. Worth picking up a basic battery monitor if you haven't already — the Victron BMV series is lovely but even a cheap £15 unit off Amazon will tell you what's actually going on rather than guessing. Makes a real difference to how you manage the system day-to-day.

Great build @SolarMike! One thing I'd add that nobody's mentioned yet — keep a close eye on your battery temperature, especially if you're parking up in cold spots overnight. AGMs can lose a fair chunk of their usable capacity when it gets properly chilly, so that 100Ah might behave more like 70-75Ah on a bitter January morning. Not a disaster, just worth knowing so you're not caught short.

The Victron 75/15 does have a temperature compensation option if you wire in their temperature sensor dongle — think it's only about £8-10 and well worth it on a budget build where you can't afford to stress the battery unnecessarily. Extends the life of the AGM noticeably over time. 😊

Solid setup @SolarMike! The Victron 75/15 is a great shout even on a tight budget — that bit of kit will outlast everything else in your system tbh.

One thing nobody's flagged yet: watch your load side carefully with AGMs. Keep discharge to around 50% max (so effectively treat it as a 50Ah usable bank) or you'll kill cycle life pretty sharpish.

I ran a similar AGM setup in my garden office before upgrading and that mistake cost me a battery inside 18 months. 😬

If you ever want to stretch the budget later, a Fogstar 100Ah lithium would roughly double your usable capacity overnight without touching the rest of the system — the Victron handles lithium charge profiles no bother.

My shepherd's hut runs a similar cobbled-together setup and honestly the Victron MPPT carrying a budget AGM is basically the off-grid equivalent of putting a Rolls Royce engine in a Reliant Robin — but it absolutely works.

Really curious about the solar panel choice here — what brand did you go with for the 200W, @SolarMike? I've been eyeing up Renogy vs a couple of the cheaper eBay panels and can't decide whether the saving is worth the risk on efficiency ratings.

Also, what's your actual real-world output looking like on a decent UK day? I'm wondering if 200W is genuinely enough for van life or whether you'd wish you'd squeezed in another 100W from the start. Seems like roof space is the limiting factor more often than budget with these Transit roofs.

Been down this exact road with my van build. The AGM + budget panels combo works a treat until you start wanting to charge an EV or run anything serious — that's where I hit a wall pretty sharpish.

One thing worth flagging: with AGM, your usable capacity is closer to 50Ah once you respect the 50% DoD rule, so plan accordingly. I eventually swapped to a Fogstar Drift LiFePO4 and genuinely wished I'd done it sooner, but as a starting point your setup sounds solid enough. @BoatFinn the Renogy panels seem decent value for the money from what I've seen on the boat side of things.