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Best Deep Cycle Battery for a Trolling Motor: Lithium vs. AGM vs. Flooded
Short answer: The best deep cycle battery for most trolling motors is lithium (LiFePO4). You can use nearly all of its capacity, it holds full voltage until it's almost empty, and it weighs a fraction of lead-acid. One Pro-Guide 36VM60 powers a 36V motor at 44.1 lb, compared with about 218 lb for three Group 31 AGM batteries. If you'd rather stay with lead-acid, a sealed AGM deep cycle battery is the next best choice. The Group 31 AGM (205 minutes reserve capacity) and Group 27 AGM (175 minutes) are maintenance-free. Flooded batteries cost the least but need watering.
Your trolling motor's voltage, how long you fish, your boat's weight limits and your budget all affect the answer. This guide compares the three chemistries and gives a pick for every motor voltage.
Key Takeaways
- Use a deep cycle battery, never a starting battery. A trolling motor pulls steady current for hours.
- Match the motor's voltage: one battery for 12V, two in series (or one 24V pack) for 24V, and three in series (or one 36V pack) for 36V.
- Lithium gives the most usable runtime per pound and keeps the motor at full speed all day.
- AGM is the best lead-acid option: sealed, maintenance-free and rated by reserve capacity.
- Plan for half: lead-acid batteries are usually discharged only about halfway to protect their life.
Lithium vs. AGM vs. Flooded for Trolling Motors
| Factor | Lithium (LiFePO4) | AGM deep cycle | Flooded deep cycle |
| Usable capacity | Nearly all of the rating | About 50% | About 50% |
| Motor speed late in the day | Full speed; voltage stays flat | Slows as voltage sags | Slows as voltage sags |
| Weight | Lightest | Heaviest | Heavy |
| Maintenance | None | None (sealed) | Check water levels |
| Cycle life | 3,000+ cycles at 100% depth of discharge | Typically a few hundred | Typically a few hundred |
| Up-front cost | Highest | Middle | Lowest |
| Where to buy | Online | Online | Through Pro-Guide dealers |
The voltage curve matters more than most anglers expect. As a lead-acid battery drains, its voltage falls and the trolling motor loses thrust. A LiFePO4 battery holds its voltage under load, so the motor performs the same in the afternoon as it did at launch.
Best Picks by Motor Voltage
| Motor | Best lithium | Best AGM | Best flooded (dealer) |
| 12V | 24M100: 100Ah, 23.8 lb | 1 x Group 31 AGM (205 min RC) or Group 27 AGM (175 min RC) | 1 x 27M180 (180 min RC) |
| 24V | 24VM90 or 24VM115 (one pack), or 2 x 24M100 | 2 x Group 31 or Group 27 AGM in series | 2 x 27M180 in series |
| 36V | 36VM60 or 36VM75 (one pack), or 3 x 24M100 | 3 x Group 31 or Group 27 AGM in series | 3 x 27M180 in series |
For deeper lithium detail, including continuous discharge ratings and Group 31 Tall fit, see our best lithium battery for trolling motors guide. For series and parallel wiring, read One Pack or Three?
Why these lead-acid picks
- Group 31 AGM Deep Cycle: 205 minutes of reserve capacity, the most in our lead-acid lineup, sealed, with a 24-month free replacement warranty. It weighs 72.75 lb.
- Group 27 AGM Deep Cycle: 175 minutes of reserve capacity at 50 lb, for boats with Group 27 trays or tighter weight limits.
- 27M180 flooded: 180 minutes of reserve capacity at 50 lb for the lowest up-front cost. It is sold through dealers.
Three 12V batteries wired in series is the traditional way to power a 36V trolling motor.
The Weight of a Full System
Weight adds up fast on a 24V or 36V boat. Here is the battery weight of a full trolling motor system, using Pro-Guide specs:
| System | Lithium | Group 27 AGM | Group 31 AGM |
| 12V | 23.8 lb (24M100) | 50 lb | 72.75 lb |
| 24V | 41.9 lb (24VM90) | 100 lb | 145.5 lb |
| 36V | 44.1 lb (36VM60) | 150 lb | 218.25 lb |
On a 36V boat, switching from Group 31 AGM to a single 36VM60 removes about 174 lb. That can help hole shot, top speed and fuel use.
How Much Runtime Do You Need?
For lithium, divide amp-hours by your motor's average draw. A 100Ah battery at 30A runs about 3.3 hours. For lead-acid, plan on about half the rated capacity, because draining it further shortens its life.
Lead-acid deep cycle batteries are rated by reserve capacity: the minutes a fully charged battery can deliver 25 amps before its voltage drops to 10.5V. A higher number means more runtime. The Group 31 AGM's 205 minutes beats the Group 27 AGM's 175 minutes and the 27M180's 180 minutes.
Motor draw varies with speed, wind and boat weight, so check your motor's manual and watch your state of charge over a few trips to learn your real use.
Charging Trolling Motor Batteries
- Lead-acid and AGM banks are usually charged one battery per bank on a multi-bank on-board charger. A 36V series bank needs three banks, plus one for your starting battery.
- Use the right profile. Pro-Guide on-board chargers charge flooded batteries at 14.1 to 14.3V, AGM at 14.3 to 14.7V and 12V lithium at 14.4 to 14.7V.
- Single 24V or 36V lithium packs need a bank built for that voltage, such as the 12V & 36V 2-Bank Charger or 12V & 24V 2-Bank Charger.
- Recharge lead-acid promptly. Leaving it partly discharged shortens its life.
Need help sizing a charger? See our on-board marine charger guide.
Frequently Asked Questions
What is the best deep cycle battery for a trolling motor?
For most anglers, a LiFePO4 lithium battery: it delivers nearly all of its rated capacity, keeps the motor at full speed and weighs far less than lead-acid. The best lead-acid option is a sealed AGM deep cycle battery, such as the Pro-Guide Group 31 AGM with 205 minutes of reserve capacity.
Is AGM or lithium better for a trolling motor?
Lithium gives more usable runtime, steadier motor speed, lower weight and thousands more cycles. AGM costs less up front and is a sealed, maintenance-free upgrade from flooded batteries.
What is the best AGM battery for a trolling motor?
The Pro-Guide Group 31 AGM Deep Cycle has the most reserve capacity in our lineup at 205 minutes. If you need a smaller or lighter battery, the Group 27 AGM Deep Cycle has 175 minutes at 50 lb.
Can I use a starting battery for a trolling motor?
No. Starting batteries are built for short, high bursts of current. A trolling motor needs a deep cycle or dual purpose battery that can deliver steady current for hours.
How many batteries do I need for a 36V trolling motor?
Three 12V batteries wired in series, or one 36V lithium battery such as the Pro-Guide 36VM60 or 36VM75.
Are lead-acid batteries still good for trolling motors?
Yes, if you want the lowest up-front cost and don't mind the weight. Flooded batteries also need regular water checks. Pro-Guide flooded batteries are sold through dealers.
Choose Your Trolling Motor Battery
Match your motor's voltage, decide how much weight and maintenance you'll accept, and pick the chemistry that fits your budget. Lithium is the long-term best value for most anglers who fish often.
Prefer AGM? Browse AGM batteries, or call our team at 1-800-827-3232 to find a dealer for flooded batteries.
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