Trolling Motor powered by lithium ion 18650's?

[lincpimp]

Well, I would take a copper plate, draw a grid pattern with the lines spaced the diameter of the cells. Punch 1/4" or so holes where the lines intersect and solder the cells thru those holes. Wrap the packs of 30 cells in something that can be removed, such as large shrink, then place them in a waterproof box of some sort that has padding (closed cell firm foam?) on all sides and between each pack. Wire the packs in series with large gauge wire and add a balancing tap for testing purposes.

How much did those cells cost and where did you get them from?

[sikeston34m]

Originally Posted by lincpimp

Well, I would take a copper plate, draw a grid pattern with the lines spaced the diameter of the cells. Punch 1/4" or so holes where the lines intersect and solder the cells thru those holes. Wrap the packs of 30 cells in something that can be removed, such as large shrink, then place them in a waterproof box of some sort that has padding (closed cell firm foam?) on all sides and between each pack. Wire the packs in series with large gauge wire and add a balancing tap for testing purposes.

How much did those cells cost and where did you get them from?

This has been what I've been thinking about doing. My first thoughts were solder to copper plate. But then I thought.........

By doing it this way, it's going to be pretty hard to disassemble should the need arise.

Today, I took an old 18650 cell and soldered a galvanized screw to it. It's a counter sunk type machine screw.

What if I soldered one to each end of every cell. Then installed all the cells to the plate with lock washers and nuts?

This would make wiring hookups very easy and also make the pack easy to take apart. If the need were to arise.

On the copper plate, I've noticed that stuff is pretty spendy. I wonder if 1/8" aluminum plate would work? Afterall, aluminum is pretty conductive and it is used in the aerial cable that feeds our home. Would resistence be a factor if 1/8" aluminum plate were used?

Foam padding. A good idea!

I'm thinking of building an aluminum box to house the pack and the converters. I can caulk it up to make it resist water, plus it will be a natural heat sink.

This would also serve as a nice power station to use with an AC inverter.

I lucked out on the cells. You're looking at $150 bucks worth of cells plus shipping. It was a liquidation sale. I have tested samples. They do go full capacity.

[johnrobholmes]

Why not build the pack for the proper voltage in the first place? Is there some reason that you cannot do this? 3s would work with the trolling motor just fine, and you would have a higher system efficiency without the use of the DC converters. There won't be much sag to the pack anyway. Do you have a low voltage monitor on the pack planned as well?

No matter what you will be looking at a massive pack construction task. The cell body needs to be supported while keeping the connections flexible. I would suggest building smaller parallel chunks of cells that you can gang together in the case that pack work needs to be done.


Soldering will work, it is really the only choice you have. I would probably get some threaded copper bits and solder them on so that bolt on ring terminals could be used for cell interconnects. I like your idea of doing it the other way with the screw on the cell. Just don't support the cell by these.

[J57ltr]

I am not sure why you would really want to use the DC-Dc converters. Why not just run 4s45p and be done with it, At that point you have a 99ah 14.4V battery. Adding the converters in there is going to make your system less efficient. What kind of BMS are you going to run?

[sikeston34m]

Originally Posted by johnrobholmes

Do you have a low voltage monitor on the pack planned as well?

No matter what you will be looking at a massive pack construction task. The cell body needs to be supported while keeping the connections flexible. I would suggest building smaller parallel chunks of cells that you can gang together in the case that pack work needs to be done.

I like your idea of doing it the other way with the screw on the cell. Just don't support the cell by these.

The only type of BMS that I have planned at this point, is a digital display monitoring all 6 cell "regions" of the pack. I will consider other options, but I don't like the BMS circuits that I've seen so far, as they generate a small amount of constant drain to keep an eye on things. The pack will be unplugged when not in use.

One other thing I wonder about is: the input range of the converter array is 18 volts to 36 volts. I have to test this, but if the converters bail out at 18 volts, it would be perfect! 3.0 volts per cell would be a good low voltage cutoff for this.

The connecting endplates will be smaller than the brick. No weight will be supported by these. The cell walls will be it's strength.

After a full day of fishing with my wife, on a trolling motor only lake, I measured with a watt meter how many amp hours the charger returned to fully charge the lead acid batteries we used that day.

You might be surprised. It returned 30 amps hours to the lead acid batteries.

I'm sure this figure is off some, since alot of energy toward the end of the charge is spent "gassing" the cells in lead acid to top them off with that last 10% of the charge. Lead acid has less useable capacity than lithium ion.