The simplest way to charge trolling motor batteries is an onboard marine charger with one bank per battery, plugged into shore power after every trip. On a 24- or 36-volt system, a multi-bank charger charges each 12-volt battery separately even though they are wired in series, which keeps them balanced. Lithium batteries need a charger, or a charger mode, made for lithium.
Ways to charge trolling motor batteries
| Method | Good for | Notes |
|---|---|---|
| Onboard multi-bank charger | Most boats | One bank per battery; plug in at home or the dock |
| Portable charger | Single batteries, small boats | Charge each battery one at a time on a series bank |
| Outboard charging output | Topping up while running | Usually through a relay or DC-to-DC charger; small motors provide little current |
| Solar panel and controller | Maintaining charge, camping | Slow; use a charge controller matched to the battery type |
Charging 24-volt and 36-volt banks in series
A 24-volt system uses two 12-volt batteries in series, and 36 volts uses three. Charging the whole string as one battery can leave them unbalanced. A two- or three-bank charger connects to each battery individually; leave the series jumper in place unless the charger instructions say otherwise. See how to wire a 24 volt trolling motor and trolling motor batteries.
How long does it take to charge?
Charge time depends on how deeply the battery was drained, its capacity and the charger’s output. As a rough example, replacing 50 amp-hours with a 10-amp bank takes about five to six hours once charging losses are included, and longer for the final topping stage of lead-acid batteries. Lithium batteries charge faster and do not need a long absorption stage.
Charging on the water or without shore power
- A DC-to-DC charger or relay can feed the trolling batteries from the outboard’s charging system while you run.
- A generator or portable power station can run a standard charger at camp.
- Solar panels help keep batteries topped up between trips, but rarely replace a full charge after a long day.
Charging tips
- Recharge after every trip; leaving lead-acid batteries discharged shortens their life.
- Use the correct charger profile for flooded, AGM or lithium batteries.
- Keep terminals clean and tight, and charge in a ventilated area.
- Store batteries fully charged and use a maintainer over winter; see how long lithium batteries last.
Batteries that never seem to fully charge may be worn out; see how long a trolling motor battery lasts and our trolling motors, or the 12V 300Ah LiFePO4 lithium battery ($1,599.00).
More guides: lithium vs lead-acid · boat battery keeps dying · lithium battery chargers · trolling motor wiring · lithium batteries in cold weather.
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