LiFePO4 vs AGM vs Gel vs Flooded: Off-Grid Battery Specification Comparison

A 100 Ah lead-acid battery and a 100 Ah LiFePO4 battery do not store the same amount of usable energy, do not last the same number of cycles, do not weigh the same, and do not cost the same per kilowatt-hour delivered over their lifetime. The amp-hour number on the label is close to meaningless as a basis for comparison.

The specifications that decide your system are usable depth of discharge, cycle life at that depth, charge acceptance, and cost per usable kilowatt-hour. This page compares those.

Usable capacity is the number that matters

Depth of discharge (DoD) is how much of the nameplate capacity you can actually use without destroying the battery prematurely.

Lead-acid chemistries are conventionally limited to about 50 percent for regular cycling. Discover Battery’s own guidance puts the recommended maximum there for flooded and AGM alike. LiFePO4 manufacturers rate 80 to 100 percent — Battle Born states 100 percent usable for its 100 Ah unit.

The practical consequence:

Nominal	Chemistry	Usable capacity
12 V 100 Ah	Flooded / AGM / gel @ 50% DoD	~600 Wh
12 V 100 Ah	LiFePO4 @ 80% DoD	~960 Wh
12 V 100 Ah	LiFePO4 @ 100% DoD	~1,200 Wh

Two batteries with the same label, twice the energy. Before comparing prices, convert everything to cost per usable kilowatt-hour, or you are comparing nothing.

Cycle life versus depth of discharge

Every chemistry lasts longer if you use less of it each cycle. The trade is not linear, and the shape of the curve differs by chemistry.

Depth of discharge	LiFePO4 (Victron)	AGM (Victron)	Gel (Victron)
80%	2,500 cycles	400 cycles	500 cycles
50%	5,000 cycles	600 cycles	750 cycles
30%	—	1,500 cycles	1,800 cycles

These are same-manufacturer figures, which is the only fair way to read them: Victron’s numbers for Victron’s products, measured on a consistent basis. Cross-brand comparison is much less reliable, because manufacturers do not agree on the end-of-life threshold, the test temperature, or the charge regime.

Two things stand out.

Gel outlives AGM at every depth in the same manufacturer’s line — roughly 25 percent more cycles. Gel is often dismissed as the obsolete middle option; the cycle data does not support that.

The lithium advantage is larger than the price gap suggests. At 80 percent DoD, LiFePO4 delivers roughly six times the cycles of AGM while also delivering more energy per cycle. Combined, that is close to an order of magnitude more lifetime energy from the same nameplate capacity.

Other manufacturers quote higher lithium figures still — Battle Born states 3,000 to 5,000 cycles at 100 percent DoD, and EG4 claims 7,000 at 80 percent. Treat cross-brand numbers as indicative rather than comparable.

Charge acceptance decides how fast you can refill

This one is routinely overlooked and it constrains real systems badly.

Charge acceptance is expressed as a C-rate: 0.2C means a 100 Ah battery accepts 20 A.

Chemistry	Recommended charge rate	100 Ah battery accepts
LiFePO4	0.5C continuous, 1.0C max (Victron)	50 A, up to 100 A
AGM	0.2C standard, up to 0.5C on premium lines	20 A, up to 50 A
Gel	0.2C maximum	20 A
Flooded	~C/10 to C/8	10–13 A

Winter is where this bites. Suppose you have a short December day with three usable peak sun hours and a 400 Wh deficit to recover. A LiFePO4 bank will take everything your array can produce. A flooded bank capped near 10 A at 12 V — about 120 W — physically cannot absorb the harvest, no matter how many panels you bolt down. The array is not the bottleneck; the battery is.

If your use case involves fast recharge from a generator or alternator, charge acceptance may matter more than capacity.

Note also that gel requires a lower absorption voltage than AGM — Victron specifies roughly 14.1 to 14.4 V for gel against 14.2 to 14.9 V for AGM at 12 V nominal. A charger left on an AGM profile will chronically overcharge a gel battery. Set the profile correctly; this is a common and expensive mistake.

Self-discharge

Chemistry	Self-discharge per month	Source
LiFePO4	2–3%	Battle Born
AGM	<2% at 20 °C	Victron
Gel	<2% at 20 °C	Victron
Flooded	5–15%, temperature dependent	Trojan

Flooded lead-acid is the outlier and the reason seasonal installations kill batteries. A cabin battery left over a five-month winter at 10 percent per month arrives at spring deeply discharged, and a deeply discharged flooded battery sulphates, loses capacity permanently, and — if it gets cold enough — freezes. Seasonal, unattended sites want either a maintenance charger or a chemistry that tolerates sitting.

Weight per usable kilowatt-hour

Chemistry	kg per usable kWh
LiFePO4	8.9 – 13.1
AGM (at 50% DoD)	25.8 – 48.5
Flooded (at 50% DoD)	~41.6
Gel (at 50% DoD)	~50

Three to five times the weight for the same delivered energy. For a shed on a concrete slab this is an inconvenience. For a van, a trailer, or a roof-adjacent install it is often decisive, and it is frequently the reason a lithium bank wins despite the sticker price.

Cost per usable kilowatt-hour

Prices below reflect retail listings observed in July 2026 and will drift. Always recompute with current pricing.

Chemistry	Cost per usable kWh	Example
Flooded	$220 – $356	Trojan T-105
LiFePO4 (server-rack format)	$234 – $264	EG4 LifePower4
AGM (budget)	~$348	Renogy 100 Ah
LiFePO4 (RV format)	~$791	Battle Born 100 Ah
Gel	~$948	Trojan T31-GEL
AGM (industrial)	~$1,047	Trojan 27-AGM

The headline finding: large-format LiFePO4 is now competitive with flooded lead-acid on upfront cost per usable kilowatt-hour, before any cycle-life advantage is counted. The three-to-one price spread within lithium — server-rack versus RV format — is larger than the gap between chemistries, so format and brand tier matter more than chemistry alone.

Fold in cycle life and the comparison stops being close. At 80 percent DoD, a lithium bank at 2,500 cycles versus AGM at 400 cycles delivers roughly six times the lifetime energy for a similar or lower initial cost.

Lead-acid still wins in specific cases: very low cycle counts (a backup bank that discharges twice a year), extremely cold environments where charging below freezing is unavoidable, and situations where a locally available replacement matters more than efficiency.

Where the published data runs out

We would rather tell you what is missing than fill the gaps with plausible-sounding numbers.

Round-trip efficiency for lead-acid is not published. Victron states 92 percent for its LiFePO4 line. No AGM, gel, or flooded datasheet we examined states a round-trip efficiency figure at all. The ~80 percent number circulated for lead-acid is a widely repeated generic estimate that we could not trace to a manufacturer specification, so we are not putting it in a table as if it were one. Flooded is likely worse than AGM because of gassing losses, but “likely” is the honest word.

Flooded cycle life versus depth of discharge is not in the Trojan T-105 datasheet. We checked. Commonly quoted figures such as “1,200 cycles at 50 percent DoD” do not appear in the primary document, so we have left flooded out of the cycle-life table rather than import a number of unknown provenance.

Gel’s temperature range is not separately specified. Victron publishes design life versus temperature for gel but not an explicit minimum and maximum operating temperature.

Manufacturer documents sometimes contradict themselves. Battle Born’s material gives 32 °F in body text and 25 °F in a heading for the same low-temperature charge cutoff. When your battery’s documentation is ambiguous, ask the manufacturer rather than the internet.

Choosing

Choose LiFePO4 for daily cycling, weight-limited installs, fast recharge, or anywhere the lifetime cost matters more than the first invoice. Budget for a Class T fuse and confirm the low-temperature charge behaviour.

Choose AGM for a low-cycle backup bank, a tight upfront budget, or an environment that regularly sits below freezing while charging. Accept the weight and the 50 percent usable ceiling.

Choose gel when you want lead-acid with better cycle life and can guarantee the charger has a correct gel profile. Do not choose gel if your charging equipment is fixed on an AGM curve.

Choose flooded for the lowest cost per usable kilowatt-hour in a stationary, ventilated, regularly maintained installation where someone will actually check electrolyte levels. Do not choose flooded for anything unattended, enclosed, mobile, or seasonal.