A lithium iron phosphate (LiFePO4) deep cycle battery typically lasts thousands of charge cycles, which works out to many years of use for most boaters. The marine lithium batteries we carry are rated by their makers at more than 2,000 cycles (LBP) and 3,000 to 5,000 cycles (Ionic). How long one actually lasts depends on how deeply and how often you discharge it, the temperatures it is charged and stored at, and whether it is charged correctly.
Cycles vs years
A cycle is one discharge and recharge. If you run a trolling motor battery down and recharge it after every trip, the number of trips per year sets how quickly you use up its rated cycles. A weekend angler who fishes 60 days a year uses far fewer cycles than a guide out every day, so the same battery can last very different numbers of years. Partial discharges also count for less wear than full ones.
What shortens or extends lithium battery life
- Depth of discharge: LiFePO4 handles deep discharges far better than lead-acid, but regularly running it completely flat still wears it faster than stopping earlier.
- Charging temperature: charging lithium cells below freezing can damage them. Some batteries, such as the Ionic model we carry, have a built-in heater that warms the battery before charging.
- The right charger: use a charger with a lithium profile that the battery maker lists as compatible.
- Heat: long periods in high heat age any battery faster; keep it ventilated and out of direct sun where possible.
- Storage: store it partly charged rather than empty, disconnect loads over the off-season, and check it every few months.
- Battery management system (BMS): the BMS protects the cells from over-charge, over-discharge and short circuits and balances the cells, which helps the pack last.
Lithium vs lead-acid and AGM
| LiFePO4 lithium | Lead-acid / AGM | |
|---|---|---|
| Rated cycle life | Thousands of cycles | Far fewer, especially at deep discharge |
| Usable capacity | Most of the rated capacity | Lifespan drops quickly if regularly discharged deeply |
| Weight | Much lighter | Heavier |
| Voltage under load | Stays steady until nearly empty | Sags as it discharges |
| Upfront cost | Higher | Lower |
LBP rates its packs at about half the weight of AGM batteries with quicker charging, and Ionic lists its battery as 70% lighter than lead acid. For 24V and 36V trolling motors, see trolling motor batteries: 12V, 24V, 36V and lithium and how to wire a 24 or 36 volt trolling motor.
Signs a lithium battery is wearing out
- Noticeably shorter run time from a full charge.
- The BMS cutting out under loads it used to handle.
- Cells that no longer balance, shown on Bluetooth-monitored batteries as uneven cell voltages.
Lithium marine batteries we carry
The LBP lithium battery bundles ($970.00) pair a LiFePO4 battery with an onboard charger and tray, in 12V 100Ah and 36V 60Ah versions. The Ionic LiFePO4 deep cycle battery with Bluetooth and heater ($1,599.00) adds Bluetooth monitoring and a built-in heater; confirm the capacity you need with us before ordering, because the listing title and the supplier text state different capacities. Size your system with the trolling motor size guide.
More guides: how long car batteries last · trolling motor run time · lithium vs lead-acid trolling batteries · lithium battery chargers · how many amp hours you need for a trolling motor · LiFePO4 vs lithium-ion · lithium batteries in cold weather.
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