The Best Fish Finder Batteries for Kayaks and Smaller Boats

Fish finder batteries for kayaks and smaller boats must be lightweight and compact but accept charge quickly from various sources and should be able to power the fish finder during the entire fishing session without the need to be recharged before going to shore or starting the main engine (if present).

Fish finder batteries are spill-proof AGM and Gel-Cell lead-acid batteries and Lithium Iron Phosphate (LiFePO₄) batteries. Most fish finder batteries feature a nominal capacity in the 5 - 20 Ah range.

Updated: January 11, 2024.

Fish Finder Battery Required Features

Fishing trips with smaller boats and kayaks that sometimes last for days or even weeks are getting more and more popular, and they all have one common feature - lack of storage space and limited payload.

Even ocean-going fishing kayaks have limited payload, and when going for longer fishing trips, every pound counts.

Thus, the main features of goof fish finder batteries include spill-proof, compact and lightweight design, high capacity, easy charging, reliable power source, compatibility with other equipment as well, maintenance-free operation, acceptable price, and similar.

Basically, fish finder batteries may be Sealed Lead-Acid (SLA) batteries or Lithium Iron Phosphate (LiFePO₄) batteries.

Sealed Lead-Acid (SLA) batteries may be either Gel-Cell or Absorbent Glass Mat (AGM) batteries, with AGM batteries being more common - both Gel-Cell and AGM batteries are maintenance-free batteries, designed to be vibration-resistant and spill-proof. Most of them may operate in any position except upside-down, with some models being able to normally operate even upside-down.

The number of charging/discharging cycles depends on the Depth of Discharge (DoD), and when the batteries are discharged down to 100% DoD, they tolerate 170-200 charging/discharging cycles and 300-500 cycles down to 50%, with some premium models being able to withstand 600-800 cycles down to 50% DoD.

AGM and Gel-Cell batteries are easily charged with smart AGM battery chargers - such battery chargers may even analyze the battery first and then charge it depending on the battery condition, with equalization and maintenance charging modes being the last ones.

Also, AGM and Gel-Cell batteries are fairly cheap.

On the other hand, Lithium Iron Phosphate (LiFePO₄) batteries cost more than lead-acid batteries and should be charged only with the battery chargers intended for such batteries. Some advanced AGM battery chargers feature a special charging mode intended for lithium batteries.

Note: If you don't have a lithium battery charger, don't charge your lithium battery with a common lead-acid battery charger - it may overheat the battery and cause it to burst into flames or even explode. Most lithium batteries do have Battery Management Systems (BMS) that protect the batteries from unwanted events like overcharging, over-discharging, overtemperature, short-circuit, and similar, but better safe than sorry.

Lithium batteries are 2-3 times lighter than lead-acid batteries, considering 20h capacity, and with the increase of discharge current, this ratio is even larger, up to 4-5 times.

Also, lithium batteries tolerate a much larger number of charging/discharging cycles, with some models easily withstanding 2000-3000 charging/discharging cycles down to 100% DoD, 5000-6000 cycles down to 80% DoD, etc.

Initially, lithium batteries cost more, but in the long run, they are both cheaper and great weight savers, which can be very important for applications where payload weight is rather limited.

Fish Finder Battery Power Requirements

Fish finder batteries feature a nominal voltage of 12 volts and a nominal capacity usually in the 5 to 20Ah range, with some vessels being able to carry even larger batteries that are often used as general-purpose batteries for powering fish finders, navigation lights, smaller trolling motor and similar.

Power requirements of most popular fish finders on the market differ greatly and are usually in the 0.2 and 2 Amps range, with some larger models requiring even more than 2 Amps.

For example, if You need the battery for Garmin Striker 4 (Amazon link, the link opens in the new window), which draw ~0.23 Amps @12V, with a runtime between recharges of at least 10h, You will need a rather small battery - even 5Ah battery is able to power such unit for a day. If the weight savings are important, then consider a lithium battery.

On the other hand, if You have a larger unit that requires 2 Amps to operate properly for at least 8 hours, consider a larger 20Ah AGM (~12-13 pounds) or lithium (~6 pounds) battery.

General Purpose Batteries Sizes

The following comparison chart lists some of the most popular general-purpose battery sizes suitable as fish finder batteries:

12V 7Ah General Purpose Batteries

12V 7Ah general-purpose batteries are very popular battery size, very often used in small UPS devices, toys, tools, small electric vehicles, and similar.

As their name suggests, these batteries feature a nominal voltage of 12V and a nominal (20h) capacity of 7Ah.

12V 7Ah batteries feature physical dimensions of (L x W x H) 5.94 x 2.56 x 3.7 inches (~151 x 65 x 94 mm) and come mostly with F1 battery terminals, but also sometimes with F2 battery terminals.

In the case of mismatched terminal sizes, F1-to-F2 and F1-to-F2 battery terminal adapters can be found in local hardware shops or can be ordered from online stores.

The battery terminals are on the right side of the battery, with a positive battery terminal closer to the user.

Most lithium 12V 7Ah batteries feature maximum continuous discharge current in the 7+ Amps range, making them suitable for various electronic devices, fish finders included.

If You are looking for a small and compact fish finder battery, consider batteries of this size, either 12V 7Ah or 12V 9Ah, since there are models with a nominal capacity of up to 10Ah.

For more information, feel free to check our 12V 7Ah General Purpose Batteries article.

12V 9Ah General Purpose Batteries

12V 9Ah batteries share the same physical dimensions as 12V 7Ah, except they tend to be slightly heavier, and most of them come with F2 terminals, which are a little bit larger than F1 terminals - they are not compatible.

The actual difference in weight between AGM and lithium batteries in this group starts to be rather noticeable - most AGM 12V 9Ah batteries weigh 5-6 pounds (~2.3-2.7 kg) and is able to provide 4.1 - 4.3 Amps for 1h (down to 10.5V), while lithium batteries weigh on average 2.5-3 pounds (~1.13-1.36 kg) and are able to provide 8-9 Amps for 1 hour.

Lithium batteries are slightly more expensive and generally require lithium battery chargers, but in the long run, they are cheaper (10x more charging/discharging cycles), lighter (less weight to carry), more energy efficient, etc.

For more information, feel free to check our 12V 9Ah General Purpose Batteries article.

12V 12Ah General Purpose Batteries

12V 12Ah batteries are slightly wider and taller than 12V 9Ah and 12V 7Ah batteries, but there are some lithium batteries in this size that feature a nominal capacity of 18Ah - that is ~2.6 larger nominal capacity than the capacity of AGM 12V 7Ah batteries.

And yes, such batteries do cost more, but what You pay is what You get.

On the other hand, there are very nice lithium 12V 12Ah batteries that can provide 2-3 Amps for 4-6 hours easily and can power Garmin Striker 4 Fish Finder (0.23A @12V) for 50+ hours. Excellent results for still rather compact batteries.

For more information, feel free to check our 12V 12Ah General Purpose Batteries article.

But, with advancements in technology, many brands offer 12V 15Ah batteries of the same size as 12V 12Ah batteries.

12V 15Ah General Purpose Batteries

General purpose 12V 15Ah batteries feature physical dimensions of (L x W x H) of 5.94 x 3.86 x 3.98 inches (~151 x 98 x 101 mm) and come with F2 battery terminals, which are slightly larger than F1 battery terminals, allowing stronger charging/discharging currents.

The nominal capacity of the AGM batteries in this group is mostly 15Ah, while lithium batteries range between 15Ah and 18Ah.

Sealed Lead-Acid (SLA) Absorbent Glass Mat (AGM) batteries weigh mostly around 7.3 - 8.9 lbs (3.3-4.2 kg), while Lithium Iron Phosphate (LiFePO₄) batteries weigh mostly around 3.0-4.6 lbs (1.36-2.1 kg).

Again, the initial price difference can be significant, but if you do need a battery that is lightweight and cycles well, go for a lithium battery and get a proper charger.

For more information, feel free to check our 12V 15Ah General Purpose Batteries article.

Note: some manufacturers offer 12V 15Ah batteries in "tall" form-factor, but most batteries with such form-factor have a nominal capacity of 18Ah or more...

12V 18Ah General Purpose Batteries

12V 18Ah, 12V 19Ah, and 12V 20Ah+ batteries feature physical dimensions of (L x W x H) ~7.15 x 3.03 x 6.59 inches (~181 x 77 x 167 mm) and come with a pair of battery terminals with a positive (red) battery terminal on the right side of the battery.

While AGM batteries in this class have a nominal capacity of 18Ah, lithium batteries range from 18Ah to 23Ah or even more, with maximum continuous currents in the 20-40 Amps range and maximum short burst currents up to 60Amps for 3-5 seconds.

Note: AGM batteries in this class can provide 270-300(!) Amps for 3-5 seconds.

For more information, feel free to check our 12V 18Ah General Purpose Batteries article.

12V 35Ah (U1 and U1R) General Purpose Batteries

Groups U1 and U1R batteries' physical dimensions are (L x W x H) 7.75 x 5.18 x 7.31 inches (~197 x 132 x 186 mm), with the U1 battery having a positive terminal on the left side, and U1R having a positive terminal post on the right side of the battery (hence the 'R' as part of the label).

They are much larger than previous battery sizes, but they can be used for powering a broad range of devices, gadgets, tools, and similar.

After all, some AGM batteries in this class can provide 500+ Amps for 3-5 seconds, while some lithium batteries feature a nominal capacity of 50+ Ah and maximum continuous current of up to 50 Amps and short bursts of up to 100 Amps for 3-5 seconds.

For more information, feel free to check our 12V 35Ah (U1 and U1R) General Purpose Batteries article.

How to Charge Fish Finder Batteries

Generally, lead-acid batteries should be charged using advanced battery chargers that support equalization, desulfation, and maintenance charging modes and also feature temperature compensation.

The maximum charging current should be no more than 0.15-0.2C - for exact values, check the documentation/Owner's Guide.

Lithium batteries should be charged using dedicated lithium battery chargers or AGM battery chargers that feature lithium battery charging mode, which is usually CC/CV (Constant Current/Constant Voltage) charging mode. 

The maximum charging current should be no more than 0.3-0.4C, regardless of the fact that most brands advertise their batteries as being able to accept 1C charging currents - yes, they can accept such currents, but personally, such charging current may shorten the batteries life span. Just my 2c.

Long Story Short: When choosing the right fish finder battery, choose according to your own needs and requirements - it is not the same if you have a weight limit or budget limit. Or both.

In the end, whatever You do, be sure to stay safe.