I’m one of those dedicated anglers who still uses my truck bed to haul my kayak to and from the river. A kayak trailer adds headaches such as trailer maintenance, storage space, yearly registration, and ramp-only launches that I’m not ready to deal with yet. But that means I’m rigging and unrigging my kayak each time I launch or load up the kayak.
There are tradeoffs whichever route you choose when it comes to kayak fishing. One thing I’m not willing to skimp on is a quality lithium battery for my electronics. I don’t have my kayak rigged to the gills like tourney anglers, but do I have the basics such as a quality fishfinder and navigation lights. With that in mind, the Millertech 12v 40ah Sports Series Lithium battery checked off all my boxes perfectly, although the Sport Series includes batteries with other amp hours too.
A Long Life
The Millertech 12V 40Ah Sport Series Lithium Battery (1240-BT) is a high-performance option for the demands of everyday kayak fishing. Utilizing Lithium Iron Phosphate (LiFePO4) technology, it offers a significant weight advantage at just 14 pounds — roughly one-third the weight of traditional lead-acid batteries — while providing 3,000-plus deep-cycle charges. Mine sits in waterproof housing in the front compartment of my kayak.
When used to power a trolling motor, the runtime for the battery depends on your trigger finger and on-the-water conditions. At a continuous full-throttle setting, a standard kayak motor (drawing 30 to 40 Amps) will deplete the battery in about 45 to 60 minutes. Personally, I wouldn’t use this battery for a trolling motor; instead I’d utilize something from Millertech with 100 to 120 Amp hours. However, for anglers who use moderate speeds for cruising or low speeds for position-holding and slow trolling, the 12V 40Ah battery can produce 3 to 4 hours of operation.
For anglers like myself using the battery exclusively to power electronics, the model offers plenty of longevity. Standard fishfinders with 5- to 7-inch screens draw very little power, allowing this battery to last for several days on a single charge. Even high-demand setups, such as large 10-inch displays combined with power-hungry live sonar systems, can run for a full 12- to 14-hour day without issue.
Watch Yourself
I find myself staring at my phone if I utilize my electronics all day while fishing. That’s because the Millertech Bluetooth App functions as a digital dashboard that communicates directly with my battery’s internal Battery Management System (BMS). Make sure to enable Bluetooth and location services, but then it’s easy to find your specific battery from the device list on the app to view real-time data including the state of charge, voltage, and current amperage.
The app even allows anglers to monitor multiple batteries simultaneously, which is useful for complex setups like trolling motor banks. I don’t use that feature of the app because I haven’t needed to with my kayaks. Additionally, the app also completes diagnostic reporting, which enables you to send technical data directly to Millertech support.
Rigging and Charging
For rigging my battery to my electronics and lights, I used a ready-built harness from Connect-Ease. The YAK Quik model allows me to power three different kayak fishing accessories, bolstered with a convenient easy disconnect when I need to load up my kayak. I’ve hadn’t any issues with my DIY rigging yet, and I’m no electrician.
For charging, I use the Battery Tender 10 Amp Automatic Battery Charger and Maintainer that handles lithium and standard batteries. (Millertech has its own battery chargers as well; I just don’t have one in my garage.) It takes about a full day to completely charge the battery, but often I don’t wear down the battery much during a day’s fishing. So I usually top off the battery after a trip, rather than doing a complete recharge. And that’s a much quicker task to complete compared to a full recharge.
These two products do not come with the kayak battery, and I had to purchase them separately. But both have been great options for me with the Millertech battery. You can also check out our Wired2fish handy guide to lithium marine batteries.
Specs
- Capacity: 40AH
- Voltage: 12.8V
- Weight: 14 lbs
- Size: 7.6” x 5.2” x 7.25”
- Warranty: 10 years
- BMS: Yes
- Chemistry: LFP
- Efficiency: 98%
- Memory: None
- Max Charge/Voltage: 14.6V
- Peak Discharge: 120A – 3sec
- Cut-off Voltage: 10.5V
- Max Charge/Discharge Current: 40A
- Operating Temp: -4°F – 140°F
- Low Temp Charging Protection: Yes
- Cell Type: Prismatic
- Bluetooth: Yes
High Expectations
Over the last couple months, I’ve had great experiences with the Millertech 12v 40ah Sports Series Lithium battery. And I’ve run both Garmin and Humminbird units from the battery at different times. The app is a great feature, even if I don’t always keep my phone available while fishing — but that’s changing as I check to see how much battery power I’m using.
I guess the real test is to see if the battery will last over the years. We’ll be on the lookout, but with Millertech offering a 10-year warranty, they’re definitely putting their reputation on the line. And I feel these batteries will continue to produce trip after trip.
