Wiring
How to wire a 36 volt trolling motor bank
Quick answer
A 36 volt trolling motor bank is three 12 volt batteries wired in series, each positive linked to the next negative, ending with two outer terminals feeding the motor at roughly 36 to 37 volts. Series wiring triples voltage at the same amp hours as one battery, the exact opposite of parallel wiring, which is the mistake that produces no usable voltage for the motor at all.
A 36 volt bank is the same series wiring principle covered in the 24 volt guide, extended by one more battery, and it is also the point at which the consequence of that wiring choice becomes the most physically real: three lead acid batteries in series weigh close to 180 lb before the boat leaves the dock, permanently. That weight, more than the wiring itself, is the actual decision being made when a motor requirement pushes past 80 lb of thrust into 36 volt territory.
This guide covers building the three battery series bank correctly, sizing the cable and breaker for the higher thrust motors 36 volts is built to run, and the single pack lithium alternative that removes two of the three batteries entirely.
On this page
- Wiring three batteries in series for 36 volts
- One 36 volt pack instead of three lead acid batteries
- Cable and connection for a three battery bank
- Breaker sizing for the larger motors 36 volts is built for
- Never mix batteries across a three battery series bank
- Wiring a 36 volt trolling motor bank in six steps
Wiring three batteries in series for 36 volts
Extend the same series principle from a 24 volt bank by one more link: positive of battery one to negative of battery two, positive of battery two to negative of battery three, leaving the remaining outer positive on battery one and the remaining outer negative on battery three as the bank's working terminals for the motor.
Wiring three 100 Ah 12 volt batteries in series produces 36 volts at 100 Ah, while wiring the same three batteries in parallel produces 12 volts at 300 Ah, and only the series bank runs a 36 volt motor.
Published figure A published engineering, regulatory or manufacturer figure. It does not change because somebody disagrees with it.
| Wiring method | Resulting voltage | Resulting capacity | Runs a 36V motor |
|---|---|---|---|
| Series (three batteries) | 36 volts | 100 Ah | Yes |
| Parallel (three batteries) | 12 volts | 300 Ah | No |
Published battery engineering: series wiring adds voltage at the same amp hour rating, parallel wiring adds amp hours at the same voltage. Three batteries in series never produce 36 volts by any other connection.
One 36 volt pack instead of three lead acid batteries
A single 36 volt lithium pack removes two of the three batteries and the interconnect cable between them entirely. The LiTime 36V 50Ah is the cheapest way into a 36 volt lithium bank, and 50 Ah of genuinely usable lithium capacity, at 80 percent depth of discharge rather than 50 percent for lead acid, delivers closer to three lead acid batteries worth of real fishing time than the amp hour number alone suggests. The LiTime 36V 100Ah covers a full day on the largest published motors in this catalog, such as the 112 lb Minn Kota Terrova 112, though the run time calculator linked below is worth working through first, since 50 Ah covers most fishing days and the larger pack is a real added cost that not every boat needs.
Cable and connection for a three battery bank
Two series interconnect cables are needed instead of one, and both carry the full motor current just as the single interconnect does on a 24 volt bank, so they deserve the same tinned marine cable and proper crimp as the run to the motor itself. Use ring terminals rather than spade connectors on every stud, since a ring cannot vibrate loose the way a spade can, and seal every joint with adhesive lined heat shrink. Three lead acid batteries also means three times the physical connections that can loosen or corrode over a season, which is a genuine argument in favor of the single lithium pack beyond its weight advantage.
Breaker sizing for the larger motors 36 volts is built for
Motors sold at 36 volts run at the top of the published thrust range, and the Minn Kota Terrova 112 publishes a maximum draw of 52 amps. The Minn Kota MKR-27 at 60 amps is rated for the full 12 to 48 volt Minn Kota motor lineup and is the manufacturer's own answer for most of these larger motors. The overcurrent placement rule under ABYC E-11 does not change with voltage: within 7 inches of the battery positive terminal exposed, or 40 inches inside a sheath, on whichever battery in the series chain the fuse or breaker sits closest to.
Never mix batteries across a three battery series bank
The same rule that governs a 24 volt pair applies with more consequence across three batteries: match chemistry, capacity and age across all three, and never introduce a new battery alongside two older ones or mix lead acid with lithium anywhere in the series chain. A mismatched battery anywhere in a three battery series bank drags the entire bank down to its own condition, and the larger the bank, the more expensive that mistake becomes to discover after the fact rather than before wiring it up.
Wiring a 36 volt trolling motor bank in six steps
- Confirm all three batteries match in chemistry, capacity and age. Replace the full set together when one fails rather than mixing a new battery into an older bank.
- Wire the two series interconnects. Positive of battery one to negative of battery two, then positive of battery two to negative of battery three, using properly crimped tinned marine cable and ring terminals.
- Identify the bank's working terminals. The remaining outer positive on battery one and the remaining outer negative on battery three feed the motor.
- Size cable to the motor by voltage drop and published draw. Use the motor's published maximum current draw and your actual run length, not a gauge copied from a different boat.
- Install the breaker within the ABYC E-11 distance. Within 7 inches exposed or 40 inches sheathed of whichever battery terminal the fuse or breaker sits nearest to, sized to the manufacturer's published figure.
- Confirm voltage at the motor before running under load. A correctly wired three battery series bank reads roughly 36 to 38 volts at rest at the motor's input terminals.
Sources
- ABYC E-11 standard for AC and DC electrical systems on boats, overcurrent protection placement
- Minn Kota and LiTime published specifications for the motors and batteries listed
Frequently asked questions
How do I wire three 12 volt batteries to make 36 volts
Connect the positive terminal of the first battery to the negative terminal of the second, then the positive of the second to the negative of the third, which is a series connection extended by one link past a 24 volt bank. The two remaining outer terminals, the unused positive on battery one and the unused negative on battery three, feed the motor at roughly 36 to 38 volts while capacity stays equal to a single battery.
How much does a 36 volt trolling motor battery bank weigh
Three lead acid batteries at roughly 60 lb each come to close to 180 lb of permanent weight added to the boat, which is the real cost of a 36 volt system beyond the motor's own price. A single 36 volt lithium pack such as the LiTime 36V 50Ah replaces all three at a fraction of that weight, though at a meaningfully higher purchase price than three lead acid batteries combined.
Can I replace three lead acid batteries with one 36 volt lithium battery
Yes, a single pack like the LiTime 36V 50Ah or LiTime 36V 100Ah replaces the full three battery series bank and its interconnect cables entirely, at a fraction of the weight and with far more of its rated capacity actually usable at a trolling motor's draw. Confirm the physical dimensions fit the existing battery compartment before ordering, since a 36 volt pack is not the same size or shape as a single 12 volt battery.
What breaker size does a 36 volt trolling motor need
Check the manufacturer's published figure first. The Minn Kota MKR-27 at 60 amps is rated across the full 12 to 48 volt Minn Kota lineup and is the size the company specifies for most of its largest motors. Where no manufacturer figure exists, size the breaker at least 25 percent above the motor's published maximum draw and confirm it against the conductor's ampacity under ABYC E-11.
What happens if one battery in a 36 volt series bank is weaker than the other two
The entire bank's performance drops to the level of the weakest battery, since a series connection forces the same current through all three regardless of their individual condition. The weaker battery can also be pushed outside its safe charging range by the two healthier batteries during a charge cycle. Replace all three batteries in a series bank together rather than swapping in a single new one alongside two older batteries.
Is 36 volts overkill for most trolling motor setups
For many boats, yes. Thirty six volts only becomes necessary once the calculated thrust requirement passes roughly 80 to 100 lb, and going there for a boat that does not actually need it adds a real, permanent weight and cost penalty for no performance the boat will use. Work the thrust calculation from the boat's fully loaded weight first, rather than choosing 36 volts because it is the largest motor a retailer sells.
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Researched, not professional advice. This page is compiled from published engineering and regulatory figures, manufacturer specifications and owner-review consensus, not hands-on testing. Figures described as a rule of thumb are boating convention rather than published standards, and they are labelled that way wherever they appear. Marine electrical work is not house wiring. Use tinned, finely stranded marine cable, size it for voltage drop and for the ABYC E-11 ampacity table rather than one or the other, and put overcurrent protection within seven inches of the battery positive terminal, because everything between the post and the fuse is unprotected. A lithium battery needs a charger with a lithium profile. Never load a boat past its capacity plate, and remember that canoes and kayaks carry no federal capacity plate at all, so their stated capacity is the manufacturer own figure. Wear the life jacket, and treat early season water as the hazard it is: cold water immersion takes your breath and then your hands long before it takes your core.