Trolling Motor Battery Life Calculator

Motor Kayak

Battery Life Calculator

If you have the attention span of a hungry child and you know a bit about batteries just go straight to the chart below. If you are normal, keep reading.

So you’re thinking of getting a motor for your kayak? Great idea! You’re in for some fun! And also for some involuntary weightlifting! Those batteries can be stupid heavy! And it can be difficult to know how big a battery you need. . .
You’re in luck! We’re here to help. This article explains exactly what you can expect from most motor-battery combinations.
You know we don’t beat around the bush unless we’re dragging a yak and a rod behind us! So here is the info you need:

What kind of battery? If you’re feeling super rich you can grab a lithium battery. They’re about a third the weight and triple the price of ‘standard’ batteries. If not and you’re feeling normal you need an AGM battery. AGM = Absorbed glass mat. No spillage, no venting. Can be used upside down, sideways, etc. They are “deep cycle” meaning, unlike a standard car battery, they are OK to drain down and re-charge regularly, although it’s best not to drain them below 30-50%. More on that later.

—————-  —————————————  ——–

Dream Kayaks War Horse Motor Kayak is Amazing. Click here for more info.

—————-  —————————————  ———-

Your battery size is rated in “Amp-hours” or Ah. What does this mean? Well, a 5Ah battery fits in your hand and is the size of a mobile phone from the 90s. A 120Ah battery weighs 35kg and is liable to hurt your back permanently if you pick it up the wrong way.

The thing you need to know about AGM batteries is that you can only drain them down to 50% if you want to maximise battery life (~10 yrs). You can push it to 30% and still get a decent battery life (maybe 3-5 yrs). Draining an AGM battery below 30% regularly will probably destroy your battery pretty quickly. To be clear about this, it means if you have a 100Ah battery and you regularly drain it below 30Ah you will probably damage it.

What this means is that a 100Ah battery only really gives you 70Ah of usable power. Pity, but that’s life…

Of course once in a while if you need to drain your battery lower as a one-off it’s probably fine – but it is important to make sure you charge it back up to 100% as soon as you can. Always store AGM batteries fully charged. Storing them in a depleted state damages them.

So the question we get all the time here at Dream is this: “how long will the battery last?” Well, it depends – primarily on 3 things:

  • how big your motor is
  • what speed you are on, and
  • how big your battery is

The chart below shows you how long the battery will last depending on the size of the motor, the speed, and the size of the battery. The numbers below assume you only use 70% of the battery power and draw it down to 30% of its original potential. They also assume you stay on the one speed the whole time, which you won’t of course – but it give you the info you need to average it out.

Battery Life Calculator

So if you have a 24 lb thrust motor, and your battery size is 33Ah, you can go at high speed for 1.2 hours, or about 72 minutes. After the 72 minutes your battery will still have about 10Ah left in it – but if you want it to last you will need to stop motoring and charge it back up as soon as you get home.

Dream Kayaks has a range of motors, motor kayaks and motor accessories. Click here for more info.

Motor Kayak


Massive Thanks to Rodney for loads of help writing this article!!

War Horse with Motor Drive

by rusty

Leave a Reply

Your email address will not be published. Required fields are marked *