Batteries by size
300Ah Lithium Boat Batteries: 12V Capacity and Runtime
These examples allow 240 Ah usable from a 300Ah battery using an 80% planning allowance. This is a reserve assumption, not a universal battery limit. Everything below is worked from 240 Ah, not from the number on the label.
On a single charge
300Ah battery runtime by appliance
Run times if that load were the only thing on the boat. Real boats run several at once, which is why the calculator sums them rather than letting you read a single row.
| Load | Draw | Run time on 240 Ah |
|---|---|---|
| VHF + AIS on standby | 0.9 A | 11 days |
| Fans | 1.2 A | 8 days |
| Cabin + nav lights | 2.0 A | 5 days |
| Instruments + chartplotter | 2.2 A | 5 days |
| Laptops, phones, tablets | 3.5 A | 3 days |
| Freezer | 4.0 A | 3 days |
| Autopilot (passage days) | 4.5 A | 2 days |
| 12 V fridge (45% duty) | 5.0 A | 2 days |
| Freshwater + shower pump | 7.0 A | 34.3 hours |
| Watermaker | 25.0 A | 9.6 hours |
Against real boats
Example overnight loads and battery bank capacity
| Hull | Daily draw | Nights on one 300 Ah | Cases for one night |
|---|---|---|---|
| 12 ft tinnie | 14 Ah | 17.1 | 1 case |
| Bowrider | 50 Ah | 4.8 | 1 case |
| Half cabin | 75 Ah | 3.2 | 1 case |
| Offshore centre console | 110 Ah | 2.2 | 1 case |
| Trailer sailer | 55 Ah | 4.4 | 1 case |
| 38 ft cruising yacht | 149 Ah | 1.6 | 1 case |
| Cruising catamaran | 260 Ah | under one | 2 cases |
| Houseboat | 320 Ah | under one | 2 cases |
| Liveaboard | 220 Ah | 1.1 | 1 case |
Daily draw is the load profile published on each hull page, quoted in 12 V amp-hours. Cases are the number of 300 Ah batteries needed to cover one night with nothing coming back in — before solar, and before the reserve you should be holding for weather.
The options
Compare listed 12V 300Ah lithium batteries
| Battery | Price band | Per usable Ah | Weight | Warranty | Bench |
|---|---|---|---|---|---|
| Amptron 12 V 300 Ah | $1,950–$2,600 | $9.48 | 34.5 kg | 5 yr | claimed |
| Revolution 12 V 300 Ah | $2,100–$2,750 | $10.10 | 34.5 kg | 4 yr | claimed |
| Enerdrive 12 V 300 Ah | $2,600–$3,400 | $12.50 | 34.5 kg | 5 yr | claimed |
Pricing is indicative and not yet independently verified. Bands are compiled from published market pricing, not from quotes we obtained. No brand has paid to appear or be ranked.
Asked most
How long will a 300 Ah lithium battery last?
A 300 Ah LiFePO4 gives about 240 Ah usable using this site’s 80% depth-of-discharge planning allowance. On a boat drawing 10 A continuously that is roughly a day. The honest answer depends entirely on your loads, which is what the calculator is for.
Is 300 Ah enough for my boat?
On its own, 300 Ah covers a night at anchor for 7 of the nine hull types we publish load profiles for, including a 12 ft tinnie. Bigger boats need it multiplied: size the bank from your own loads rather than from a capacity you have already picked.
What does a 300 Ah lithium battery cost in Australia?
Indicatively $1,950–$2,600 at the budget end and up to $2,600–$3,400 for the marine-specific brands. Those bands are compiled from published pricing and are not quotes; confirm with the retailer.