Swapped out my old lead-acids for a Fogstar 100Ah LiFePO4 — was it worth the faff?

Spent most of last spring convinced I could nurse my two ageing 110Ah lead-acids through another season on the boat. Spoiler: I couldn't. They were barely holding 60% of their rated capacity and sulphating badly, so I pulled the trigger on a single Fogstar Drift 100Ah 12V LiFePO4 in February. Cost me £279 delivered, which felt steep at the time but now feels like a bargain.

The difference on the narrowboat is genuinely hard to overstate. I run a 12V compressor fridge, a few LED strips, phone charging, and a small inverter for the laptop — nothing dramatic. With the old lead-acids I was paranoid about going below 50%, so I effectively had maybe 110Ah usable between the two of them on a good day. The Fogstar gives me a rock-solid 95Ah I can actually use without stressing the cells, and my Victron BMV-712 reads it dead accurately now that the discharge curve isn't all over the place.

The one faff nobody warns you about is the BMS cold-cutoff. Moored up in January, temperatures dropped to around 3°C inside the battery box overnight and the BMS tripped during charging from the alternator on a morning cruise. Took me an embarrassing amount of forum-reading to work out what had happened. Worth knowing if you're living aboard through winter rather than just weekend tripping.

Anyone else made the jump from lead-acid to LiFePO4 on a tight budget and hit unexpected snags? Curious whether the Fogstar Drift's BMS is notably better or worse than the cheaper Renogy options people seem to be using.

@TomCampbell sulphation on lead-acids is a proper slow death — you can sometimes recover them with a desulphation charger but honestly once they're that far gone it's rarely worth the effort.

Made the same switch on my garden office setup last year. The Fogstar 100Ah is genuinely solid for the money — built-in BMS handles most of the faff and the cycle life comparison vs lead-acid is night and day.

Few things worth checking:

• Your charger profile — make sure it's LiFePO4-compatible, not just AGM/gel
• Low temp cutoff — the BMS will protect the cells but worth knowing your limits if you're on a boat over winter
• Actual usable capacity — you can run to 20% SoC vs the 50% lead-acid rule, so that 100Ah feels closer to replacing 160Ah of lead-acid in practice

Short answer: yes, worth it.

@TomCampbell once you've gone LiFePO4 you'll wonder why you ever lugged those lead bricks around — my Fogstar in the motorhome has been flawless and weighs about as much as my dignity after explaining the battery budget to my partner.

@TomCampbell made the same swap on my narrowboat about 18 months ago — two tired leisure batteries out, a pair of Fogstar 100Ah LiFePO4s in. The difference was immediately obvious, not just in capacity but in how the voltage holds steady under load. Lead-acid sags badly when you're running an inverter; LiFePO4 barely flinches.

Worth noting for anyone doing this on a budget: you will need a lithium-compatible charger. My old Sterling ProCharge just wasn't cutting it — ended up grabbing a Victron IP22 and it's been flawless since.

The upfront cost stings but the cycle life maths works out comfortably in your favour over a few seasons, especially if you're living aboard full-time rather than weekend use.