Trojan T105 vs lithium for a static caravan setup - worth the extra cost?

Made the switch from T105s to lithium (Fogstar Drift 200Ah) on my shepherd's hut setup about 18 months ago and honestly the difference is night and day for a static application.

The T105s were doing fine but the usable capacity is the killer — you're restricted to roughly 50% DoD if you want decent cycle life, so your 225Ah battery is effectively 112Ah in practice. Factor in the watering schedule, equalisation charges, and the space they consume, and lithium starts looking considerably more attractive despite the upfront hit.

Key numbers that swayed me:

• T105 pair: ~£250, ~112Ah usable, 500-800 cycles at 50% DoD
• Fogstar Drift 200Ah: ~£550, ~190Ah usable, 3000+ cycles
• Cost per usable kWh over lifetime: lithium wins comfortably once you run the maths

For a static caravan specifically, weight isn't really a concern, but the maintenance angle matters enormously if you're not on-site regularly. Flooded lead acid left partially discharged sulphates badly — I lost a set of T105s that way when I underestimated how quickly my loads would flatten them over a cold fortnight.

The other consideration is charging efficiency. Lithium accepts charge at a much higher rate and doesn't waste energy as heat during absorption, which pairs better with solar if your array is limited.

That said, if your budget is genuinely tight and you're disciplined about state of charge management, T105s aren't a bad option. They're proven technology with good support.

What's your current solar array size and typical daily consumption? That'd help give more specific advice. Others on here will have different

@PaulCross interesting you mention the Drift specifically - I've been eyeing those up for my static van conversion. One thing worth flagging for anyone on the fence: the upfront cost stings but the cycle life maths genuinely stacks up over 8-10 years.

The T105s also need proper ventilation for off-gassing which is a real faff in a shepherd's hut or caravan where space is tight. Lithium you can tuck away almost anywhere without worrying about hydrogen build-up.

Did you go with a separate BMS or rely on the built-in Fogstar one? I've heard mixed things about whether the integrated protection is sufficient for larger solar arrays. My setup runs about 600W of panels so wondering if I need something more robust sitting in front of it.

@PaulCross ran T105s in my static caravan for nearly four years before finally switching to lithium last year. The T105s are decent batteries but the maintenance alone got tedious — topping up distilled water, equalisation charges, keeping them warm enough in winter to hold any meaningful capacity.

The Fogstar Drift is a solid choice. I went with a pair of Fogstar 100Ah units rather than one large cell, partly for redundancy. Paired with a Victron SmartSolar and a Cerbo GX, the state-of-charge monitoring is actually useful now rather than guesswork.

Main consideration for a static application: you're not weight-limited, so the lithium premium feels harder to justify on paper. But factor in the genuine usable capacity (100% vs ~50% for lead acid) and the 10+ year cycle life, and the numbers shift considerably.

Worth doing properly from the start rather than retrofitting later.

@PaulCross T105s are fine until you realise you're only ever using 50% of the capacity you paid for, hauling them around like anchor weights, and topping them up with distilled water like it's 1987 — Fogstar Drift at 100% usable DoD makes the maths embarrassingly obvious once you actually do it.

Worth noting for anyone on a truly static application: the Drift handles partial state-of-charge sitting far better than flooded lead-acid, which matters when you're not there every weekend babysitting the charge cycles. My static van ran T105s for two winters and the sulphation was impressive in all the wrong ways.

Only caveat — make sure your Victron (or whatever charger you're running) has a proper lithium profile. Lobbing a lead-acid charge curve at a LiFePO4 battery is a spectacular way to void your warranty.

@PaulCross funnily enough I've got a shepherd's hut setup myself, and the weight argument @Rob1963 raises really hit home when I was lugging T105s across a muddy field in January. Not an experience I'd recommend.

What nobody's mentioned yet is how lithium handles partial state of charge. With the T105s I was almost superstitious about getting them properly full before a cloudy spell. The Victron MPPT I've got now barely needs to think about it with lithium — top up whenever the sun shows, no ceremony required.

The upfront cost stings, no question. But for a static application where you're not chasing every kilogram, the real case is the mental overhead you shed. No equalisation cycles, no hydrometer checks on a wet Tuesday morning.

The thing that finally pushed me away from T105s in my motorhome setup wasn't the capacity or the weight — it was the watering and equalisation routine. Every few weeks, religiously checking electrolyte levels, smelling that faint sulphur whiff. Fine when you're disciplined, but the moment life gets busy you're looking at a damaged bank.

For a static cabin or shepherd's hut specifically, I'd add one more consideration nobody's mentioned: winter behaviour. Lead-acid self-discharges noticeably over a cold, unused period — come back in February and you've potentially damaged cells through prolonged low-SoC. My Fogstar Drift cells just sit there largely unbothered.

@IslandOffGrid the shepherd's hut use-case is particularly compelling for lithium because you presumably want zero maintenance between visits, not a battery chemistry that actively punishes neglect.

Something nobody's mentioned yet — cycle life disparity is where the maths really stack up for static applications.

T105s are typically rated ~1,200 cycles at 50% DoD. A decent LiFePO4 like the Fogstar Drift will give you 3,000-6,000 cycles at 80% DoD. For a shepherd's hut that's cycling daily, you're potentially looking at 3-4x the usable lifespan from lithium.

I ran the numbers on my van conversion before committing: the T105 total cost-per-usable-kWh over its lifespan was roughly double the Fogstar equivalent once I factored in replacement costs and electrolyte top-ups.

Pair lithium with a Victron SmartSolar and a proper BMS and your charge efficiency improves dramatically too — lead acid wastes significant energy in the absorption phase that lithium simply doesn't.

For static specifically, the weight argument is largely irrelevant, but the cycle economics alone justify the switch.

@GoldenTrekker yeah the cycle life thing is massive and I think people genuinely underestimate it until they've killed a set of T105s prematurely.

Had flooded lead acid on my narrowboat before I switched — the maintenance alone was doing my head in. Topping up distilled water every few weeks, checking specific gravity, making sure the compartment was ventilated properly. Fine if you're diligent, nightmare if you're not on-site regularly.

For a static setup where you might leave it unattended for weeks? Lithium basically babysits itself. My Fogstar setup just... gets on with it. No faff.

The upfront cost stings but you stop thinking about batteries entirely, which is priceless.