Quick answer: bring the battery to roughly half charge, disconnect every load, store it in a dry place that stays above freezing, and top the charge up every two to three months. LiFePO4 holds a charge well in storage, but charging below freezing and parasitic drains over winter are the two things that shorten its life.
What Winter Does to a LiFePO4 Battery
A LiFePO4 (lithium iron phosphate) marine battery is a lithium battery chemistry that stores energy for trolling motors, kayaks and off-grid boats. It discharges safely in cold weather, but charging a lithium pack below freezing can cause lithium plating inside the cells, which permanently reduces capacity. Most damage over winter, however, comes from something simpler: a small continuous load - a bilge pump, a tracker, a forgotten switch - quietly draining the pack for months.
Winter Storage Settings at a Glance
| Situation | Recommended practice |
|---|---|
| Storage charge level | Around half charge (roughly 13.2-13.3V resting on a 12.8V pack) |
| Storage place | Dry, out of direct sun, staying above freezing |
| Connected loads | Disconnect everything, including small parasitic drains |
| Check interval | Every 2-3 months; top up to storage level as needed |
| Charging in cold | Typically wait until the pack is above 0°C / 32°F before charging |
Step-by-Step Winterizing Checklist
- Disconnect the battery from the boat and remove all loads and parasitic drains.
- Charge the pack fully with a LiFePO4-compatible charger, then bring it down to roughly half charge for storage.
- Store it in a dry place that stays above freezing - a garage shelf ages better than a bilge or an unheated dock box.
- Check the resting voltage every 2-3 months and top up to the storage level when it has drifted down.
- In spring, charge fully with a lithium-profile charger before the first trip of the season.
- If the battery stays on the boat, a small solar panel with an MPPT controller can maintain the storage charge between checks.
Charging Basics for the Rest of the Year
Innospo LiFePO4 packs carry a built-in BMS that protects against overcharge, over-discharge, overload, overheating and short circuits. Charging speed follows a simple ratio: with a 20A charger, a 12V 50Ah pack typically fills in about 2-3 hours and a 12V 100Ah pack in about 5-6 hours. Use a charger or solar controller with a lithium/LiFePO4 profile so the pack charges to its proper voltage, and remember that up to four identical 12V packs can be wired in series up to 48V for larger trolling systems - the voltage guide covers the wiring choices.
FAQ
Can I leave a LiFePO4 battery on the boat all winter?
You can, if the storage spot does not see charging-below-freezing conditions and the battery is disconnected at around half charge. The risk is not the cold itself but a parasitic drain in a freezing bilge pulling the pack down for months.
Do I need a special charger for LiFePO4?
Use a charger with a lithium/LiFePO4 profile. The built-in BMS protects the pack either way, but a matched profile charges it to the correct voltage instead of a lead-acid absorption curve.
What voltage should a stored 12V LiFePO4 battery read?
At around half charge, a 12.8V pack typically rests near 13.2-13.3V. A reading clearly below that after months of storage means it is time for a top-up.
Related Guides
- Marine Power System Buying Guide - propulsion, battery and charging planned as one system.
- 50Ah vs 100Ah vs 200Ah LiFePO4 Marine Battery - pick the capacity before you store it.
- MPPT vs PWM Solar Charge Controller - keep the bank topped up in season.
Browse the LiFePO4 marine batteries collection for 50Ah, 100Ah and 200Ah options.