How Many Batteries Does a Trolling Motor Need?

The short version

A 12 V motor needs 1 battery. Most make up to 55 lb of thrust, and a few reach about 62 lb.
A 24 V motor needs 2 batteries. These typically make 68 to 97 lb of thrust.
A 36 V motor needs 3 batteries. These typically make 100 to 120 lb of thrust.
Count one 12 V battery for every 12 volts. Go by the voltage on your motor, not its thrust.
Lithium can cut the count to one. A single 24 V or 36 V lithium battery can replace a set of two or three.

Battery count by motor size

The table lists Minn Kota's published figures for its common motors, plus the newer dual-voltage motors that can run on either 24 or 36 volts and make more thrust at 36.

Thrust	Voltage	12 V batteries	Max amp draw	Breaker
30 lb	12 V	1	30 A	30 A
40 / 45 lb	12 V	1	42 A	50 A
50 / 55 lb	12 V	1	50 A	60 A
70 lb	24 V	2	42 A	50 A
80 lb	24 V	2	56 A	60 A
101 lb	36 V	3	46 A	50 A
112 lb	36 V	3	52 A	60 A
Minn Kota Quest 90 / 115 lb	24 or 36 V	2 or 3	60 A	60 A
Lowrance Ghost 97 / 120 lb	24 or 36 V	2 or 3	See manual	See manual

Thrust ranges overlap between brands. A 97 lb Lowrance Ghost runs on 24 V, while a 100 lb Garmin Force runs on 36 V. Go by the voltage printed on your motor or in its manual.

Why voltage sets the count

Trolling motor batteries are 12-volt batteries. To reach 24 or 36 volts, they are wired in series: the positive terminal of one battery connects to the negative terminal of the next. In series, voltages add but amp-hours do not. Two 100 Ah batteries in series make a 24 V, 100 Ah bank, not a 12 V, 200 Ah one.

Every battery in a series chain carries the full motor current. An 80 lb, 24 V motor drawing 56 A empties each of its two batteries about as fast as a 55 lb, 12 V motor drawing 50 A empties its one. Bigger motors do not need bigger batteries. They need more of them.

Parallel wiring is the opposite: positive to positive and negative to negative. The voltage stays at 12 and the amp-hours add. Two batteries in parallel on a 12 V motor double the run time, but parallel wiring never turns a 12 V bank into a 24 V one. The wiring picture in the Trolling Motor Power Calculator shows the series hookup for your motor.

How big each battery should be

Battery size is measured in amp-hours (Ah). Minn Kota rates lead-acid deep-cycle batteries by group size: a Group 24 (70 to 85 Ah) is good, a Group 27 (85 to 110 Ah) is better, and a Group 31 (95 to 125 Ah) is best. It suggests at least 110 Ah for lead-acid.

How much you actually need depends on how you fish. The table shows the amp-hours each battery needs for an 8-hour day on a variable-speed motor. A casting day assumes 40% speed with the motor running 35% of the time. A steady trolling day assumes 50% speed with the motor running the whole time. AGM batteries are used to half their capacity and lithium batteries to 80%.

Thrust	Batteries	Casting day		Steady trolling day
Thrust	Batteries	AGM	Lithium	AGM	Lithium
30 lb	1	46 Ah	25 Ah	164 Ah	99 Ah
40 / 45 lb	1	65 Ah	35 Ah	229 Ah	139 Ah
50 / 55 lb	1	77 Ah	42 Ah	272 Ah	165 Ah
70 lb	2	65 Ah	35 Ah	229 Ah	139 Ah
80 lb	2	86 Ah	47 Ah	305 Ah	185 Ah
101 lb	3	71 Ah	38 Ah	250 Ah	152 Ah
112 lb	3	80 Ah	43 Ah	283 Ah	172 Ah

Amp-hours needed per battery. On a 24 V or 36 V motor, every battery in the set needs this rating.

Two things stand out. A casting day fits in one good Group 27 or Group 31 battery on almost any motor. A full day of steady trolling needs more than any single lead-acid battery holds. On a 12 V motor you can wire a second battery in parallel. On a 24 V or 36 V motor that means four or six batteries, which is where lithium starts to make sense.

How long the batteries will last

These are hours of motor running time with 100 Ah batteries, at full speed and at half speed on a variable-speed motor. If your motor runs only half the time you are on the water, double them.

Thrust	Voltage	AGM, used to 50%		Lithium, used to 80%
Thrust	Voltage	Full	Half	Full	Half
30 lb	12 V	1.3 h	4.6 h	2.6 h	8.1 h
40 / 45 lb	12 V	0.9 h	3.1 h	1.8 h	5.8 h
50 / 55 lb	12 V	0.7 h	2.5 h	1.5 h	4.9 h
70 lb	24 V	0.9 h	3.1 h	1.8 h	5.8 h
80 lb	24 V	0.6 h	2.2 h	1.4 h	4.3 h
101 lb	36 V	0.8 h	2.8 h	1.7 h	5.3 h
112 lb	36 V	0.7 h	2.4 h	1.5 h	4.7 h

Full speed uses the manufacturer's maximum amp draw, which is a peak, so real full-speed times are usually a little longer. A 5-speed motor at a low setting uses more power than a variable-speed motor at the same speed.

Lead-acid batteries deliver fewer amp-hours the harder you pull on them. A 100 Ah AGM battery feeding a motor at 50 A behaves more like a 71 Ah battery. Lithium barely loses any capacity at high draw, which is a big part of why it runs so much longer in the table.

Flooded, AGM or lithium

Flooded lead-acid

It’s the cheapest choice. The cells have caps that you top up with distilled water, the battery has to stay upright, and it gives off gas while charging, so it needs ventilation. Plan on using about half of its rated capacity.

AGM

It’s a sealed, spill-proof lead-acid battery that never needs watering. It has the same usable half as flooded and is heavy: a Group 31 AGM weighs roughly 60 to 70 lb. AGM deep-cycle batteries typically last 4 to 8 years.

Lithium (LiFePO4)

A 100 Ah lithium battery weighs about 20 to 23 lb and can be used to 80% or more. It lasts 3,000 to 6,000 or more cycles, which works out to 10 to 15 years or more. It costs several times more up front and needs a charger made for lithium. You can also buy single 24 V and 36 V lithium batteries, such as Dakota Lithium’s 36 V, 60 Ah model, that replace a set of two or three.

The weight difference adds up on a 36 V boat. Three Group 31 AGM batteries weigh roughly 180 to 210 lb. Three 100 Ah lithium batteries weigh roughly 60 to 70 lb.

Rules for running more than one battery

Match them. Batteries in a set should be the same make, type, size and age. Do not add one new battery to an old set. Replace the set together.
Keep the starting battery separate. If you have a gas outboard, its cranking battery should not be part of the trolling motor bank.
Use heavy jumpers. Minn Kota recommends jumper cables one gauge size heavier than the motor's lead wire.
Charge every battery. A multi-bank charger with one output per battery charges a series set without unhooking it.
Recharge lead-acid soon. Minn Kota says to recharge within 12 to 24 hours of use. Leaving lead-acid batteries discharged is the leading cause of early failure.
Protect the circuit. Put a breaker sized for the motor on the positive lead, close to the battery.

Common mistakes

Buying by thrust and getting the voltage wrong. Check the motor's voltage before buying batteries.
Wiring a 24 V motor in parallel. Parallel wiring stays at 12 V, and the motor will run weakly or not at all.
Using a car battery. Starting batteries are built for short bursts and generally fail after 30 to 150 deep discharges.
Mixing old and new, or mixing types. The weakest battery drags down the set.
Running lead-acid flat over and over. Regularly going past about half shortens its life.
Skipping the breaker. A short without a breaker can start a fire.

Questions people ask

Do I need two batteries for a 55 lb trolling motor?

No. A 55 lb motor runs on 12 V and needs one battery. A second battery wired in parallel doubles your run time, or you can carry it as a spare.

Can I run a 24 V motor on one 12 V battery?

Not as intended. It will run weakly, if at all. Some motors are built to switch between 12 and 24 V, so check your manual.

Will a bigger battery hurt my motor?

No. Amp-hours only decide how long the motor runs. The voltage is what has to match.

How many batteries does a kayak trolling motor need?

One. Most kayak motors are 30 to 55 lb and run on 12 V. The table above shows that a casting day with a 30 lb motor needs about 25 Ah of lithium, so a 50 Ah lithium battery leaves a comfortable margin and is light enough to carry.

Is lithium worth the money?

It depends on how you fish. If you troll all day, carry batteries by hand, or plan to keep the boat for years, lithium's weight, usable capacity and lifespan add up. For a few casting trips a season, a good AGM battery does the job for much less.