How to Choose the Best Trolling Motor Battery
With all the available battery models and brands on the market, finding suitable trolling motor battery often can be daunting task, but it shouldn't be. But before getting new battery or battery pack, one should first write down few things, including size and weight of the boat, motor strength, required trolling time and of course, the funds allocated for the new trolling motor battery.
Size and Weight of the Boat
Following table lists the most common sizes and weights of small boats and pontoons commonly used for trolling:
|Boat Weight||2000 lbs
|Boat Length (feet)||<16 feet
|Minimum Recommend Thrust||40 lbs
|Recommended Thrust With Power Reserve||60 lbs
Note that actual required thrust depends on other things too, for example:
- water and weather conditions: calm water and no wind require no additional motor power. On the other hand, strong currents and wind can help the vessel sail faster down the current and wind, but if one has to sail up the current and wind, much more power and larger thrust are required.
- height of the boat: kayaks and most of the inflatable boats are low in the water with relatively modest area of the boat that can act as the sail, requiring very little extra power. However, some pontoon boats and catamarans/trimarans are very tall, requiring extra power and thrust in windy conditions.
- presence of sea grass or similar vegetation: subsurface vegetation increases the vessel's resistance requiring more power and thrust to keep the required trolling speed. Also, the vegetation can wrap around the propeller shaft, greatly increasing the motor load and even causing circuit breaker to go off.
So, feel free to choose required electric trolling motor strength according to the table, just have in mind all (or most of) other possible situations, too.
Electric Trolling Motor Thrust vs. Power
Thrust achieved by electric trolling motor roughly equals to the water mass flow in the unit of time, multiplied by the water speed difference.
In order to stay away from the math as much as possible, just have in mind that electric trolling motor with larger thrust requires more electric power.
The following table lists some of the common electric trolling motors, their maximum thrust, nominal voltage, maximum current and nominal maximum power:
Note: Amazon affiliate links in the table open in the new windows, feel free to check them out.
In order to keep maximum currents at acceptable levels (at most 50-60 Amps), stronger electric trolling motors operate at 24 or 36 volts. For example, electric trolling motors with thrust up to 60-70 pounds operate at 12 V, trolling motors with thrust between 70-100 pounds operate at 24 volts, while electric trolling motors with thrust levels of 100 or more pounds, usually operate at 36 V.
Of course, there are exceptions. For example, Minn Kota Riptide EM 160 operates at 24V with maximum of 116 Amps. However, this is double motor electric drive consisting of two 80 pounds electric motors, requiring 58 Amps each - hence the 116 Amps max.
The Best Trolling Motor Batteries
Trolling motor batteries must be able to withstand regular deep discharge operations and cyclic use.
Common starting/cranking car/boat batteries should not be discharged regularly below 50% of their capacity, or their operating lifetime can be significantly reduced.
Thus, for electric trolling motor battery, one should choose dual purpose or preferably deep cycle marine battery. Such batteries have limited cranking currents, but that is not what they are designed for - they can easily withstand regular deep discharges down to 20-30% without adverse effects on their operating life.
Lead-Acid of Lithium Batteries?
Unless otherwise stated, all of the information presented in this article is about lead-acid batteries, regardless of their purpose and type (starting, dual purpose, deep cycle; AGM, gel cell, wet cell, etc).
Lithium rechargeable batteries initially cost more and are sensitive to charging and discharging conditions, but most 12 V lithium batteries come as drop in replacement for SLA batteries. Such batteries come with protective electronics that monitors battery condition and protect it, if necessary.
Just be aware that such 'drop in replacement' lithium batteries also come as starting (being able to provide huge currents, but for limited time) and as deep cycle batteries (having limited maximum allowed currents, but great capacity).
Lithium batteries cost perhaps 3-5x times more than lead-acid batteries, but they often can withstand 5-10x more charging and discharging cycles and are 3-4x lighter than lead-acid batteries. So, in the long run they are actually cheaper (check warranty conditions!) and save plenty of weight.
The following table lists the most popular deep cycle and dual purpose trolling motor batteries, with their most important features:
|Model||Battery Type||Goup Size||Cell Type||Ah||MCA||RC||Weight (lbs/kg)|
|Battle Born 100Ah 12V LiFePO4 Battery||Deep Cycle||31||LiFePO4||100||-||-||29 lbs; 13.2 kg|
|DieHard 38228||Dual Purpose||48||AGM||70||950||120||-|
|Exide Edge FP-AGM24DP||Dual Purpose||24||AGM||75||930||145||50 lbs; 22.7 kg|
|Exide XMC-31||Deep Cycle||31||AGM||100||1110||200||68 lbs; 31 kg|
|Lifeline GPL-31T||Deep Cycle||31||AGM||105||750||195||69 lbs; 31.5 kg|
|Mighty Max ML35-12||Deep Cycle||U1||AGM||35||-||-||23 lbs; 9.6 kg|
|Odyssey 31M-PC2150||Dual Purpose||31||AGM||100||1370||205||77.8 lbs; 35.3 kg|
|Odyssey 34M-PC1500||Dual Purpose||34||AGM||68||1050||135||49.5 lbs; 22.4 kg|
|Optima 8027-127 D27M||Dual Purpose||27||AGM||66||1000||140||54 lbs; 24.5 kg|
|Optima 8052-161 D31M||Dual Purpose||31||AGM||75||1125||155||59.8 lbs; 27.1 kg|
|Optima 8016-103 D34M||Dual Purpose||34||AGM||55||870||120||46 lbs; 21 kg|
|Trojan SCS150||Deep Cycle||24||Flooded Cell||100||650||150||50 lbs; 22.6 kg|
|Trojan T31||Deep Cycle||31||AGM||102||720||177||69 lbs; 31.5 kg|
|Trojan T-105||Deep Cycle||(6 Volts)||Flooded||225||-||447||62 lbs; 28.1 kg|
|UPG UB121000||Deep Cycle||27||AGM||100||-||-||64 lbs; 29 kg|
|VMAXTANKS V30-800||Deep Cycle||-||AGM||30||350||55||22 lbs; 10 kg|
|VMAXTANKS V35-857||Deep Cycle||U1||AGM||35||390||75||25 lbs; 11.3 kg|
|VMAXTANKS MR96-60||Deep Cycle||22NF||AGM||60||600||120||43 lbs; 19.5 kg|
|VMAXTANKS MR107-85||Deep Cycle||24||AGM||85||700||160||55 lbs; 24.9 kg|
|VMAXTANKS SLR125||Deep Cycle||31||AGM||125||-||260||75 lbs; 34 kg|
|VMAXTANKS MR127-100||Deep Cycle||27||AGM||100||800||200||68 lbs; 30.8 kg|
|VMAXTANKS MR137-120||Deep Cycle||31||AGM||120||900||230||75 lbs; 34 kg|
|VMAXTANKS SLR155||Deep Cycle||-||AGM||155||-||350||90 lbs; 40.8 kg|
|VMAXTANKS MR197-200||Deep Cycle||4D||AGM||200||1400||450||112 lbs; 50.7 kg|
|VMAXTANKS V6-225||Deep Cycle||GC2 (6 Volts)||AGM||225||-||500||72 lbs, 32.6 kg|
Note: Amazon affiliate links in the table open in the new windows, feel free to check them out.
Of course, there are many other models and brands on the market - we are updating the list regularly, so feel free to check it as regularly.
Little Bit of Math
Unfortunately, in order to pick the best trolling motor battery, some math is required.
Lead-acid batteries are know as being very tolerant when operating connected in series (for larger voltage) and in parallel (for larger capacity). When connecting batteries in series and/or parallel, always try to obtain the same batteries from the same manufacturer, preferably from the same manufacturing batch.
Why? Well, even the slightest differences among the batteries can cause one battery to be under larger stress/load, leading to imbalances within the battery pack and ultimately to the battery pack failure. And that can be costly!
Example: If you need/have electric trolling motor that draws 55-60 Amp at maximum power and you want at least 90 minutes of operation at full throttle, you need at least 150-160 Ah battery.
60 A x 1.5 h = 90 Ah
Since we don't want to fully discharge lead-acid battery, we will discharge it down to 20%:
90 Ah / 0.8 = 112 Ah
Nominal capacity of lead-acid batteries drops when they are being discharged faster. On average, when such batteries are discharged within 1.5 h period, their capacity drops to ~70-80% of nominal capacity. Just to be safe, let's assume that our battery capacity drops down to 70% of nominal capacity when being drained at such rate:
112 Ah / 0.7 = 160 Ah
112 Ah / 0.8 = 140 Ah
Although this is calculation for the 'worst case scenario', it is also calculation for the real life situation!
If you don't wish to connect the batteries in parallel in order to achieve desired capacity, a good choices for such requirements are:
- VMAXTANKS SLR155 (AGM, 155 Ah, 90 pounds)
- VMAXTANKS MR197-200 (AGM, 200 Ah, 112 pounds)
However, if you don't mind connecting batteries in parallel, the list of potential batteries is much longer (you just need a pair of them) - practically a pair of any deep cycle batteries with at least 75-80 Ah will be enough.
What about the voltage?
If your trolling motor operates at 12 V, you need one large or a pair of two smaller batteries.
If your motor operates at 24V, you need a pair of larger batteries connected in series or four smaller batteries connected in parallel and series.
If your motor operates at 26V, you need three larger batteries connected in series or six smaller batteries connected in parallel and series to achieve desired performances.
In real life, one rarely uses electric trolling motor at full throttle all the time - most of the time, power is reduced and maximum power is used only in emergencies or when changing fishing locations and similar. If you do use your trolling motor at the full throttle most of the time, perhaps it is underpowered for your application and getting stronger motor (or one more) with more powerful batteries will increase your safety.