Trolling Motor powered by lithium ion 18650's?

[sikeston34m]

Hi Guys,

I am an avid fisherman and love the outdoors.

I've replaced the trolling motor batteries on my boat so many times, it's getting old.

A regular trolling motor battery will only last about 2 years. It's all I can squeeze out of them.

The last replacement, I opted to go with 2 - 6 volt golf cart batteries. They are supposed to be good for 5 years. Well, they have lived for 3 years so far, but I can tell they are already getting tired.

This quest includes building a great performing lithium ion setup that will outlive anything lead acid has to offer.

The pack itself is going to be constructed from New lithium ion 18650 cells. 180 of them to be exact.

180 Sanyo 2200mah 18650 cells, working together in a 6S30P configuration.

This will make for 66ah at 25.2 volts fresh off the charger. For comparison purposes, this will be equal to 130ah+ at the operating voltage.

Check this out. Aren't they pretty?



Now I bet you're wondering. 25.2 volts? That's gonna fry that trolling motor.

If the pack were directly hooked up, then yes. The magic genie smoke would come out.

But.........that's not what we're going to do.

We're going to use 5 DC to DC Vicor voltage converters that were recently acquired.

Input voltage range is: 18vdc to 36vdc Output voltage: 13.8vdc @ 200 watts each



A couple of things I like about these converters are:

At 200 watts each, they will be paralleled for 1000 watts of total output. They will handle the load, since at maximum thrust, (55 ft lbs) the motor's output will be around 700 watts.

80% to 90% efficiency. I'm hoping to reach up toward the 90% mark, hence the total wattage headroom.

The converter will output a constant 13.8 volts. NO voltage sag. In other words, the charge will be just as fresh at the end, as it was at the beginning of the discharge cycle.

This should be a big improvement over the performance of lead acid since it's voltage sags quite a bit under the load.

One problem I have is:

How do I build this pack? I need 6 individual "Bricks" of 30 cells each.

What's the best way to go about building this?

It needs to be tough and somewhat waterproof.

Any suggestions guys?