Newbie - what motor and battery?

-- Last Updated: Aug-01-15 10:01 AM EST --

Dear padddlers!

I am a total newbie in paddling. I live in Greece and bought a BIC Trinidad to paddle at sea and lakes with my partner. We have been a few times in the water and love it. Now we want to buy an electric motor, but I am overwhelmed by the offers. I don't know how many lbs I need - the more might be better but then I need a huge and obviously very heavy battery that we have to carry arround all the time. How many lbs do we need if we are to use the motor at sea with some waves and what type of battery would you suggest (how many ampere)?

Thank you so much for your input!

how far/fast are you going?

– Last Updated: Aug-01-15 12:15 PM EST –

Most people on this site don't use motors, though a minority do. I do, and have posted regarding them. I use the motor for two reasons:
1. the canoe I have is a hassle to paddle. It's too wide, and is primarily a platform for fishing.
2. I'm recovering from an injury, and can't paddle the way I want to. After I recover, I will keep the motor and use it to increase fishing range without exhausting myself before even starting to fish.

All this is to say, be clear as to why you want a motor. Do you want speed or range? For speed, a Torqueedo would be great. The propeller pitch is optimal for pushing a small craft quickly. A 55 lb Minnkota would be good also, and less expensive. If your primary goal is range, a 30 lb Minnkota would do just fine, especially if it has a "digital maximizer", aka, a "pulse width modulator" (which saves on battery usage). Minnkota is a great brand. Carry a spare paddle and motor prop (w/ instalation screwdriver and wrench) in case of problems.

You want a "deep cycle" marine battery. There are four types: lead acid (with subtypes: standard, glass mat; aka "AGM", and gel), as well as Lithium Ion.

If price is no object, and you don't mind the battery failing after three years or so, get a lithium ion. If price is a major concern, standard lead acid is the cheapest. I use a glass mat, since it doesn't need filling, lasts through more years of use, and very importantly (for me), can be stored in any position.

If you capsize, there's a good chance that the weight of all this will sink your craft. I have extra flotation. The battery and motor would probably be ruined, but I would not lose everything.

As for how large a battery, look at current draw over time (amp hours) in relation to current draw of the motor (for a 30 lb minnkota, it's about 30 amps/hr, full duty (on highest setting). There are plenty of resources on the internet if you search for "what size trolling motor battery for kayak". At lower speeds, the pulse width modulator (pwm) will increase range considerably; and won't increase range at all at max speed. Make sure you secure the battery. It's heavy, and you don't want it bouncing around.

For what it's worth, I use an Interstate Battery DCM0035. It's 35 amp hours (a small battery) and 25 lbs. For a sit on top kayak, like yours, you need a waterproof case for the battery also. good luck!

why not car battery?

– Last Updated: Aug-01-15 2:40 PM EST –

Wow, thank you so much, this really helped. Well, we want the motor in order to be able to reach further distances in a small amount of time, and my partner is a bit afraid of the open sea and needs it as a reassurement. So we need distance, not speed, so you really helped a lot cause I was looking at some 30 lbs models and found out that for these you would need a 60 Ampere battery.

What is the difference between a marine battery and a car battery? Why better gel / glass mat than acid?

Would a Lithium battery still need to be 60Ah?

Thank you so much!


– Last Updated: Aug-01-15 9:12 PM EST –

You're welcome.

A car battery puts out a lot of power all at once for a short period. A "deep cycle" battery is meant to be drained slowly over a long period. Using a car battery for a trolling motor (or anything that drains it slowly for while until the charge goes down) will destroy the car battery in short order.

When you have a device that places a load on an electrical system, voltage needs to be matched. If a trolling motor says that it runs at 12 volts (v), use a 12V battery- not a 24v and not a 6v. And, some trolling motors do run at 24v. I wouldn't recommend these. Among other things, they generate more heat in the battery/wires when run.

When running a system with proper voltage, you need the system to provide enough amperage (amps). Motors will draw more amperage the harder they are run. If your motor draws a maximum of 30 amps, then unless you have a system that can provide 30 amps or more, the motor will not run at full speed. This is very different than "amp hours". Amp hours refer to how long a battery will last (in theory) at a given load. So, if you have a motor running on full, drawing 30 amps, and the battery is rated at 35 amp hours (ah), then the battery will last for: 35 amp hours/30 amp draw = 1.16 hours = 70 minutes. If the motor is run on low, and draws 5.5 amps, then: 35 amp hours/5 amp draw = 7 hours. This is not exact, however. There is a little more to it than this. So, the maximum amperage that a battery can provide and the "amp hours" the battery is good for are two different things.

As for using a motor as a "backup" over paddling, it should be the other way around. If your partner doesn't feel comfortable in an area paddling, he certainly shouldn't be in that area with a motor. A motor can fail much more easily than a paddle. Whenever I'm using a trolling motor, I keep in mind the following before getting on the water: "If the motor fails, how far can I paddle myself to get to safety?" and "If I get tossed in the water, and can't get back in the canoe, how far can I swim to get myself to safety?"

As for the differences between the lead acid, glass mat and gel, there are pretty detailed sources online. In terms of lasting for the most years, the order is gel, glass mat, and lead acid. gel and glass mat are sealed, lead acid is not. gel can be used in extremely cold temps (not an issue for you).

Thank you
Thank you so much for your input, this helped me so much!

Interesting comment on the life of a
lithium ion battery for trolling motor. Been considering one due lighter weight, but 3-year life you mention has me rethinking. Seems they are touted as able to stand deeper discharges and many more cycles? Tks, Rick

I don’t know

– Last Updated: Aug-03-15 11:03 AM EST –

I don't have any experience with them. I decided to avoid them because of articles I read that state that they start to age as soon as they are manufactured, and are in pretty bad shape after about three years. I've read different things regarding this, though. One thing that everyone seems to agree on, is that temperatures over 86 degrees F (30 degrees C) are bad for the battery. Lithium Ion batteries use different chargers than lead acid batteries. DO NOT charge a battery inside of a building. By the way, when a 12V battery discharges to about 9.6 volts, it's dead, and won't run a motor any more. The manufacturer of your specific battery can answer this more precisely. I'd recommend testing your setup either with a barrel of water or in shallow water next to shore before going too far with it. It's better to find problems then.

How are you paddling your kayak? If you are using single bladed paddles, and are in deeper water and don't have to push off rocks all the time, "beaver tail" paddles might make things somewhat easier. Check out the company "bending branches". Of course, paddling and motoring are still completely different things...

By the way, if you're interested in serious distance at increased speed (but also increased noise) a square-back canoe with a gasoline engine of about 2 horse power is also an option, albeit a far more expensive one (look at the "MacKenzie Sport 15'" by clipper canoes and the 2.5 hp outboard by yamaha).

Some sources: