LiFePO4 vs AGM — which should I choose?

Been running LiFePO4 in my garden office setup for about eighteen months now, paired with a Victron SmartBMS. The jump from AGM was worth every penny.

Key thing nobody's mentioned yet — temperature. My batteries live in an unheated outbuilding. LiFePO4 gets grumpy below 0°C (won't charge properly), whereas my old AGMs didn't care. Sorted it with a cheap stick heater on a thermostat, but it's a real consideration if you're off-grid somewhere cold.

The DoD advantage is genuinely massive though. I was replacing AGM packs every four years. LiFePO4 should go ten-plus if you're not hammering it flat constantly.

Budget-wise, yeah, you need the right kit. But honestly? A basic Victron MPPT and a decent BMS costs less than replacing AGM twice. False economy keeping old chemistry.

Also got a smaller Fogstar 48V setup on the boat for weekends — same reliability, just different form factor.

If your usage is steady and you can sort the charger compatibility, LiFePO4 wins. Only stick with AGM if you've genuinely got physical space or thermal constraints.

Right, I'll chip in with the narrowboat perspective. Had AGM in the cabin for donkey's years, and the thing about them is they're forgiving — you can abuse them a bit, forget to top up the water, leave them sat, and they'll still sulk along.

LiFePO4 is like upgrading from a temperamental old diesel

Cheers for the insight there, @ExFirefighter11. Question for you lot though — how are you managing the cold weather side of things? I'm looking at a setup for a mountain cabin (Scottish Highlands, so winters get properly grim) and I've read conflicting stuff about LiFePO₄ performance below 0°C.

My current AGM setup just keeps chugging regardless, but I'm hearing the smart BMS on LiFePO₄ units like the Victron ones will essentially lock discharge in cold temps to protect the cells. That's brilliant for longevity, but useless when you actually need power in January.

@CE_Builds — does your garden office get much subfreezing use? Wondering if a low-temp heating blanket round the battery is worth the faff, or if I should just stick with AGM for emergency backup duty up there.

The lifecycle cost argument makes sense for year-round use in milder climates, but I'm struggling to see how it pencils out when half the year you're running at reduced capacity anyway. Am I missing something obvious here?

The cold weather question @PartnerNomad raises is where you really see the difference between the two. LiFePO4 will throttle its charge acceptance below about 0°C — it's a chemistry thing, not a fault. I've got a Fogstar unit in the motorhome and learned this the hard way during a winter trip to Wales. Tried charging it in a frost and got nothing but "battery cold" errors from the Victron.

With AGM, you don't have that limitation, which is why they're still solid for vehicles or seasonal setups where you can't control the environment. They'll accept charge in a blizzard without complaint.

That said, if you've got any control over your installation — heated compartment, insulation, keeping kit indoors — LiFePO4 absolutely wins long-term. Deeper usable capacity, longer lifespan, way better efficiency. The AGM will need replacing every 5-7 years; the LiFePO4 should give you 10+ years easily.

Where are you based? If you're somewhere consistently cold, AGM might genuinely be the better call unless you can manage temperatures.

Had AGM in the boat for years and it was like watching paint dry in winter — literally, the output just vanished. Switched to a Victron LiFePO4 setup and the difference is mental: same capacity, half the weight, actually works when it's freezing.

Only catch is the BMS needs to be decent quality or you'll spend more time troubleshooting than cruising. And don't cheap out on the charger — a Victron or Fogstar will play nicely with LiFePO4, whereas some dodgy 30A unit will stress it into early retirement.

That said, if you're running basic stuff and don't mind the weight penalty, AGM still works. Just budget for replacing them every 5-7 years versus LiFePO4's 10+ if you're not hammering them. The maths usually favours the lithium once you factor in all that.

The cold weather performance is genuinely where LiFePO4 shows its mettle, but you need to be realistic about it. I'm running a 15.36kWh Victron LiFePO4 setup here and it handles winter reasonably well, but there's a catch — you absolutely need a BMS with integrated heating or you'll be throttled.

My system uses a Victron SmartBMS which manages cell temperature. Below about 5°C, discharge starts limiting itself regardless. That said, it's still miles ahead of AGM in that regard. My old Fogstar AGM would lose 30-40% usable capacity in January; the LiFePO4 loses maybe 15%.

The real cost difference though is upfront capital. You're looking at double, sometimes triple, for equivalent capacity. If you've got the budget and plan to keep it 10+ years, LiFePO4 wins on lifespan alone — 6000+ cycles vs 1000 for AGM. But if you're on a tight budget and only use the system seasonally, AGM might still make sense.

One thing

Mate, LiFePO4 in winter is like comparing a kettle to a candle — sure the candle still works, but you're not getting your brew on quick. That said, if you're serious about off-grid living (not just a weekend jolly), the cost-per-cycle works out properly. My Victron setup with a decent BMS has been solid, though I'll admit the upfront hit made me wince.

The real kicker nobody mentions: AGM forgives you when you're thick and forget to check water levels. LiFePO4 demands respect — get the charge profile wrong and you're looking at a very expensive paperweight. Worth it if you're disciplined, but not if you're the "I'll sort it later" type.

What's your actual usage pattern, @ExFirefighter11? That's what actually decides it, not the specs.

Been running LiFePO4 in the motorhome for about eighteen months now and it's transformed how I work from the garden office setup. The real difference isn't just winter performance — it's the usable capacity and charge cycles.

With AGM you're looking at maybe 50% depth of discharge if you want decent longevity. LiFePO4 lets you actually use 80-90% without degradation, so a 200Ah LiFePO4 genuinely gives you what a 400Ah AGM would. That's before you factor in the charge acceptance rates — my Victron MPPT pushes current into the LiFePO4 far more aggressively than it ever did with AGM.

@BoatMark's right about winter though. Cold kills the output, no getting round it. I fitted a basic heating blanket (nothing fancy) and that sorted most of it. Costs buttons to run.

The cost differential has compressed loads in the last couple years too. Fogstar and Renogy pricing is getting competitive with quality AGM now. If you're in it for ten years or more, L

Right, couple of things worth adding here. The real decision hinges on your actual usage pattern and ambient temperature range, not just the headline specs.

I'm running a Victron LiFePO4 setup in my narrowboat and yes, winter performance is the crux of it. The chemistry genuinely struggles below 0°C for charging — your BMS will throttle or cut out entirely. That said, discharging in cold isn't nearly as problematic, so if you're mainly drawing power in winter and charging when it's mild, LiFePO4 still wins.

AGM's advantage is pure robustness in neglect. You can leave it half-charged for months, it won't sulphate catastrophically, and you'll get decent cycle life. It's also significantly cheaper upfront — roughly half the cost of equivalent LiFePO4 capacity.

Where LiFePO4 justifies itself: usable capacity (you get maybe 80-90% vs AGM's 50%), lifespan (4,000+ cycles vs 500-1,000), and charge speed. On a narrowboat or van with limited

LiFePO4 in a van is brilliant until you're parked up in the Cotswolds in January and realise you've bought an expensive brick that won't discharge below 0°C — learned that one the hard way with my motorhome setup. That said, if you've got a heated space like @ExChippie's garden office or somewhere you're actually living (shepherds hut, van conversion with proper insulation), they're genuinely superior: better cycle life, faster charging, way less faffing about with equalisation. AGM's still the sensible choice if you're running it in an unheated shed and only checking in monthly though. The real kicker is battery management — LiFePO4 needs a decent BMS, whereas AGM will forgive you for being a bit slack. Victron and Fogstar units are solid if you're going the lithium route, just make sure you've got heating or a low-temp cutoff unless you fancy an £800 paperweight come December.

I've got both setups running on the boat actually — LiFePO4 for the main house bank and a couple of AGM units tucked away as backup. The real difference I've noticed is performance degradation in the cold.

Those AGMs just... keep going. Sluggish as anything at -5°C, but they'll still give you what they've got. The LiFePO4 shutters down its BMS below about 0°C, which caught me out last winter moored near Dulverton. Dead calm, nobody around, and suddenly no power for the heating because the battery had decided it wasn't playing.

@BitsAndBobs has hit the nail on the head there. Where I'd genuinely recommend LiFePO4 is if you're using the system hard and regularly — charge cycles, high discharge rates, that sort of thing. The efficiency gains and cycle life make the cost back after a few years. But if you're topping up sporadically or live somewhere properly cold, AGM's still the sensible choice.

The trap I see folks fall into is thinking LiFePO4 is universally better

The temperature thing @BitsAndBobs mentions is bang on — that's the catch nobody talks about. My static caravan setup taught me that the hard way. LiFePO4 basically sulks below 0°C, and you'll lose a fair chunk of usable capacity.

That said, if you've got decent insulation and can keep the battery box heated (even passively), it's less of an issue. I run a small 12V heater pad on mine during winter — costs bugger all to run but keeps the chemistry happy.

The real win with LiFePO4 for me is cycle life and the fact you can actually use the full capacity. With AGM, you're looking at 50% DoD if you want decent lifespan. With LiFePO4, 80-90% is fine. Over five years, that's genuinely more usable energy.

Cost-wise, LiFePO4 is still pricier upfront, but the maths work if you're off-grid long-term. If you're just topping up from the grid regularly, AGM's probably fine and simpler

Running both in my van conversion actually — LiFePO4 for summer months when I'm touring, but I keep a smaller AGM bank as backup for winter when temps drop. The cold performance thing is real, not just forum chat.

LiFePO4 wins hands down for efficiency and cycle life if you've got the budget and can manage the temperature side. My Victron BMS has built-in heating logic but honestly it's another layer of complexity. AGM just... works, even when it's frozen solid.

Worth asking yourself: are you stationary (like @ExFirefighter11's setup) or mobile? Static installs can justify LiFePO4 more easily since you can add proper thermal management. Vans and boats are trickier because weight and space matter.

Also depends what you're running — if it's just a fridge and lights, AGM's fine. If you're drawing 100A+ regularly, LiFePO4 pays for itself faster.

What's your use case? That'll tell you more than specs ever will.

I'm running LiFePO4 in my cabin setup and honestly couldn't go back to AGM now. The depth of discharge is the real winner here — I can use 80% of the capacity without degradation, whereas AGM you're really only getting 50% usable if you want longevity.

That said, @ExSquaddie's right about temperature. My Victron system handles the monitoring brilliantly, but in winter when I'm not actively heating the cabin, the LiFePO4 won't accept charge below about 0°C without the heater running. It's an extra cost most people don't factor in.

Cost-wise, LiFePO4's come down loads in the past couple years. My initial outlay was hefty, but the cycle life (4000+ cycles vs 500-1000 on AGM) means the per-cycle cost is actually lower. Plus no maintenance — AGM needs checking and watering if you go flooded rather than sealed.

If you're on a strict budget and don't mind the maintenance, AGM's still fine for backup banks. But for a primary system where you're

Had both systems on my narrowboat actually, and the real deciding factor for me came down to what I was actually doing with them. Switched to LiFePO4 about eighteen months back, but it wasn't as straightforward as "better battery wins."

The thing nobody mentions is the charging profile. My Victron MPPT had to be reconfigured completely — AGM's forgiving if you're a bit sloppy with voltage settings, but LiFePO4's fussy about it. Worth doing properly though, because once it's dialled in, the charge times are genuinely half what they used to be.

Space-wise, that's the real win. Got nearly double the usable capacity in the same locker. And @VanAnne's spot-on about seasonal use — LiFePO4's happier just sitting at partial charge, whereas AGM sulphates if you leave it discharged. That matters if you're only cruising seasonally.

Cost-wise though, you're looking at three times the upfront spend. Only makes sense if you're drawing serious daily power. For a shepherds hut or static setup like