How Many Amps Does a Fishfinder Draw?


A fish finder can provide an angler with an excellent way to locate fish far below the water’s surface. However, most fish finders draw their power directly from the boat’s battery. While these fish finders come in a variety of sizes and functions, finding the right one will depend on your needs and battery size.

What Is an Amp?

  • An amp, short for ampere, was originally defined by Andre-Marie Ampere in 1881. The ampere, denoted with A, is the standard measurement for current in a given electrical circuit. The amount of amps drawn gives an important clue to any device's usage requirements. Producing an amp requires one volt of potential difference over the length of a conductor with one ohm of resistance. To measure amps in a circuit requires an ammeter.

Your Battery's Amps

  • Luckily, most batteries already specify the amount of total amps they can produce. This information is often found on the side of the battery. The capacity of most batteries is measured in amp hours, or Ah. A common capacity for a 12-volt battery is 7.5 Ah measured over 20 hours. Therefore, using this common example, a 12-volt battery with an Ah of 7.5 will deliver 7.5 amps per hour to any device over a 20-hour period.

How to Calculate?

  • To figure out how many amps your fish finder draws from the battery, you’ll need to calculate the amount of watts your fish finder uses on average and divide it by the amount of volts required to power it. A common fish finder usually requires approximately 100 watts of power and needs about 14 volts to power it. Therefore, an average fish finder uses about 7.14 amps. If it’s powered with the 7.5 Ah battery, the fish finder will last on average about 20 hours.

Amount Needed

  • The amount of amps your fish finder draws off the power supply will vary from model to model. This number will also rise and fall according to the amount of watts being used at any given time. For example, at start-up, the fish finder will need to draw more watts, which is usually defined as its peak. These specifications can be found in any product manual or on the website of your fish finder's manufacturer.

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