AGM vs lithium vs lead-carbon: the honest comparison

There is no best deep-cycle chemistry, there is the most relevant chemistry for each application. Lithium (LiFePO4) wins on weight. AGM wins on price. Lead-carbon wins on value.

And for anything going into a caravan or motorhome, the placement requirement rules placed upon lithium under AS/NZS 3001.2:2022 decide before the spec sheet does.

One comparison that matters is the total energy a battery will deliver before it's finished, not the sticker price and not the nameplate amp-hours. That figure is cycles multiplied by the depth you cycle to, and every battery on this site publishes its cycle life at more than one depth, so you can work it out. Per 100Ah of nameplate: a NOMAD E2 cycled to 30 percent gives you about 45,000Ah over its life, a NOMAD E2 ULTRA G2 about 78,000Ah, a C2 CARBON about 135,000Ah, and the PROFLEX lead-carbon about 180,000Ah. That's a factor of four across the chemistries we sell and no price tag tells you about it. Lithium's claim is a different one: it gives up far more of its nameplate as usable capacity than lead-acid does and a little more than lead-carbon.

The physical differences drive the applications. Lithium is much lighter than lead for the same usable energy, which is decisive in a camper, on a ute canopy, or anywhere the bank travels. On cold, read the spec sheet rather than the marketing: our AGM and lead-carbon batteries publish a charging window of 0 to 40C and will sit and discharge down to -15C, so an unheated shed is fine to keep them in, and a below zero frosty morning is not the time to start a charge cycle on any of them. Lithium is stricter again, because charging below freezing damages the cells and needs heating or BMS management to prevent it. Lead batteries also sit on a shed floor for years with no electronics at all and fail gradually rather than all at once, where lithium depends on its battery management system to protect it, which is both its safety net and one more thing between you and the cells.

Then there's cost and practicality over the whole life, which the marketing skips. Lithium's sticker price is only the start: it won't accept charge below freezing without heating or management, it depends on a BMS, and it wants a charger and a DC-DC set to a lithium profile, which we supply, rather than a lead one. Lead-carbon asks for less of that. It charges on a staged lead profile and needs no electronics of its own, though it isn't the same profile as AGM: our C2 CARBON wants 14.3V absorption and 13.6V float, where a NOMAD E2 wants 14.6V and an E2 ULTRA G2 wants 14.7V, so the charger setting matters as much as the chemistry choice.

There's a placement rule worth knowing for vehicles, because under AS/NZS 3001.2:2022 a lithium battery in a caravan or motorhome can't live in a habitable area unless it's in a sealed, externally vented enclosure, with a BMS, certified to AS IEC 62619, and our lithium-in-caravans guide covers it. But the reason our home and off-grid quotes usually specify lead-carbon is simpler than any rule: for a bank that isn't weight critical, on price and durability it's the better buy. Where weight travels, an EV, a camper or a ute canopy, lithium's case is strong and we spec the charging for it.