Flat spell survival: winter storage for electric boats

The season is over. The lake has gone from glassy to grey, the jetty is empty, and your boat is heading into storage.

Petrol owners spend this weekend changing oil, fogging cylinders and draining fuel. You have a much shorter list. But the one item on it, the battery, is the one that matters most.

We collected what makers and safety bodies say about storing lithium batteries, so the boat that comes out in spring is the one that went in.

The set wave: store part-charged

Lithium batteries do not like sitting full or empty for months.

ePropulsion recommends charging its Spirit battery to 60 to 80 percent before winter storage. The battery then slowly discharges until it reaches 60 percent and goes into a deep sleep mode (Oceans EV).

Other makers use different figures. Check your manual and use your maker's number. The principle is the same across the line-up: part-charged, not full, never flat.

Keep it warm and dry: no frozen sessions

Cold and damp are the enemies.

ePropulsion recommends storing its batteries in a dry place at 15 to 25 °C and avoiding temperatures below freezing. It also says the battery should only be charged between 5 and 30 °C (Oceans EV).

For a portable battery, that usually means bringing it home. For a battery built into the boat, ask the maker or dealer whether it can stay aboard in your storage conditions, and what heating or protection it needs.

Check every few months: don't let it wipe out

A stored battery still loses a little charge over time. Left long enough, it can fall too far.

ePropulsion suggests checking its batteries every three months and recharging to 60 to 80 percent if the level has dropped well below 60 percent. It also says a Spirit battery that discharges fully to 0 percent cannot be recovered and must be replaced (Oceans EV).

Put a reminder in your calendar. It takes minutes and protects the most expensive part of the boat.

Charging safely in storage: watch the line-up

Winter is when batteries sit unattended for long periods, so charging habits matter.

The Boat Safety Scheme advises using only the maker's charging equipment, disconnecting batteries once charging is complete, and not leaving equipment on charge when you are asleep or away from the vessel, unless the instructions say it is safe (BSS). The Broads Authority adds that larger batteries should be charged off the vessel where possible, on a stable hard surface (Broads Authority).

Our guide to battery safety and fire on board covers the warning signs.

The rest of the boat: the usual flat spell jobs

Electric changes the engine bay, not the boat. The usual winter jobs still apply:

• Clean the hull and let it dry.
• Rinse the motor and drive with fresh water, especially after salt water.
• Check the anodes and the propeller.
• Dry and cover the charger, cables and plugs.
• Air the boat and keep moisture out.

Before the first spring session, charge the battery fully, check cables and connections, and run a short test before you head far from the jetty.

Our verdict: five minutes now, a season later

So, how hard is winter storage for an electric boat? Easier than for a petrol one. No oil, no fuel, no fogging.

The battery is the whole job. Store it part-charged, warm and dry, check it every few months, and never let it run flat. Get that right and it will be ready the day the water goes glassy again.

For the full routine, read electric boat battery care.