Trolling Motor batteries can get heavy. If you want to keep the weight of your gear to a minimum, your Battery is a good place to start.
Choosing a light trolling motor battery is important for kayakers and inflatable boaters looking to cut back on the overall weight of their gear.
The compromise?
With AGM batteries, it is power capacity. Light AGM batteries will store less energy, meaning that their Amp Hour (Ah) rating will be lower than that of larger batteries.
With lithium batteries, it is the price. They weigh 3-4 times less than similar AGM batteries, but cost 4-8 times more.
Let’s have a look at a few light AGM and lithium batteries.
| VMAX V35-857 | Mighty Max ML35-12 | ExpertPower EXP12180 | Renogy 50 Ah | Smart Battery - 50 Ah | |
|---|---|---|---|---|---|
| Weight | 25 | 23.15 | 11.68 | 14.77 | 15 |
| Capacity | 35 Ah | 35 | 18 | 50 | 50 |
| Size (inch) | 7.7 x 5 x 6.1 | 7.68 x 5.16 x 7.13 | 7.1 x 3 x 6.6 | 7.75 x 6.53 x 6.73 | 7.7 x 6.45 x 6.75 |
| Type | AGM | AGM | AGM | Lithium | Lithium |
| Price check | Amazon | Amazon | Amazon | Amazon | Site |
Best lightweight AGM batteries for trolling motors
AGM batteries are the number 1 choice for use with boat trolling motors. Without going into the technical working of this type of battery, suffice it to say that AGM batteries are great because they are:
- maintenance-free
- spillproof
- low self-discharge rate
- fast charging
- resistant to vibration
Here are the most popular lightweight marine batteries you can use to power your trolling motor.
VMAX V35-857 – 35 Ah
Weight: 25
Capacity: 35 Ah
Group size: U1
Dimensions: 7.7 x 5 x 6.1 inches
Type: AGM
This is a very high quality battery, thus the premium in price. I have personally used this battery paired with a 40 lb thrust Minn Kota trolling motor, and got around 3 hours of boating out of it at a low-medium setting.
It always held the charge and never had any issues charging it either.
Here it is on Amazon.
ExpertPower EXP12180 – 18 Ah
Weight: 11.68 lbs
Capacity: 18 Ah
Group size: –
Dimensions: 7.1 x 3 x 6.6 inches
Type: AGM
This battery is super thin and light, but of course, the trade-off is that it only has an 18 Ah capacity.
If you have a light kayak and a sub-30 lB trolling motor, this battery will suffice. I would not use this with stronger motors though, as it just won’t be able to give you much time out on the water.
The opinions on Amazon customers are overwhelmingly positive, so if the low Ah is OK with you, go for it.
Mighty Max ML35-12 – 35 Ah
Weight: 23.15 lbs
Capacity: 35 Ah
Group size: U1
Dimensions: 7.68 x 5.16 x 7.13 inches
Type: AGM
Mighty Max batteries are good quality as well. I have a friend who uses this battery with a 30 lb trolling motor, and he says it just keeps on going like the energizer bunny.
Of course, you have to watch wrist if you want to get hours of boating out of small batteries like this one.
Here it is on Amazon, check out what other people who have bought it think,
Best lightweight lithium batteries for trolling motors
If we’re going to talk about lightweight batteries for trolling motors, we need to talk about lithium batteries as well.
They are 3-4 times lighter than comparable lead-acid batteries. They are not widely used due to their high price, but their weight to power ratio is unbeatable for now.
Another advantage lithium marine batteries have is that they have a lifespan of around 5000 cycles, while lead-based AGM batteries typically have 300-500 cycles in them.
If you use your trolling motor daily though, you will end up saving money in the long run. You would need to be a professional angler or similar for this though.
For most recreational boaters, the price of lithium batteries makes them an inhibiting factor. I have personally never used one either, and don’t know of anybody that has. The tech behind marine grade lithium batteries is new, but it is here to stay.
Let’s have a look at a few of them, so we can compare their weight and capacity to AGM batteries.
Renogy Lithium-Iron Phosphate Battery – 50 Ah
Weight: 14.77 lbs
Capacity: 50 Ah
Group size: –
Dimensions: 7.75 x 6.53 x 6.73 In
Type: lithium iron phosphate
The light weight and small size of this lithium battery are truly marvelous when compared to an AGM battery of the same capacity. For example, this 55 Ah AGM battery weighs 37 lbs and is 9.02 x 5.43 x 9.13 inches in size.
It is rated for 7000 cycles, while an AGM battery is rated for around 600.
The bad part? It costs 5x more than the AGM battery.
Here it is on Amazon in case you are interested in reading what customers have to say about this super lightweight battery.
Smart Battery – 50 Ah
Weight: 15 lbs
Capacity: 50 Ah
Group size: –
Dimensions: 7.7 x 6.45 x 6.75 In
Type: lithium iron phosphate
This is another 50 Ah lithium battery. It’s specs are great, but the price tag is daunting. It costs more than $600.
How long does a lightweight marine battery run a trolling motor?
How much trolling motor operating time you get out of a battery will depend on 2 things:
- the thrust of the trolling motor
- the speed setting you are using
Lightweight batteries in the 30-35 Ah range will power trolling motors up to around 35 lb of thrust. Anything stronger will have your reaching or your paddles before you can start enjoying your boat trip.
To calculate how long a battery will run a motor, let’s have a look at an average setup:
- 30 lb thrust Minn Kota trolling motor – max 30 amp draw
- 35 amp hour (Ah) AGM battery
- and a 50 Ah battery as well
| Amps drawn | Runtime with 35 Ah | Runtime with 50 Ah | |||||||
|---|---|---|---|---|---|---|---|---|---|
| Speed setting | Max | Medium | Low | Max | Medium | Low | Max | Medium | Low |
| 30 lb trolling motor | 30 amps | 15 amps | 5 amps | 1.2 hours | 2.3 hours | 6 hours | 1.7 hours | 3.3 hours | 10 hours |
The table above will give you an idea of how long a 30 lb trolling motor will run with a 35 Ah and a 50 Ah battery at various speeds.
Running the motor at full speed will draw 30 amps per hour, draining the battery in a little more than an hour.
Running the motor at half speed will draw 15 amps per hour, meaning you will get 2:20 minutes runtime.
Running the motor at the lowest speed setting will draw 5 amps per hour, so you will get 7 hours of run time.
That’s not that bad!
Ways to increase the runtime of a light trolling battery?
Battery performance is directly linked to how you use the trolling motor. This is a skill you need to learn that they don’t teach in school.
Here are the things you need to keep in mind if you want to get the most out of your battery:
- Do not run the motor at maximum thrust. This will drain the battery quickly, and will subsequently reduce the capacity of the battery by 10-15% as well.
- Run the motor at the 2-3 speed setting most of the time. This will protect your battery in the long run, and not drain it too quickly.
- Sharp speed changes will affect battery performance and cost power. You want to increase/decrease your speed gradually, instead of going from speed 1 to 5 in one twist of the wrist.
Taking care of your battery will keep its capacity at maximum throughout the life of the battery, meaning that you will get more time out on the water with each charge.
AGM marine batteries are maintenance free, you just need to keep these in mind:
- Always keep your battery charged when not in use. Discharged batteries will sulfate, thus lower the capacity and service life of your battery.
- Get a good charger. A rule of thumb is that the charger should supply power at around 10-20% of the battery’s amp hour capacity. So for a 35 Ah battery, a 4-6 amp charger is ideal.
