Motorcycle NiMH battery pack upgrade –

by Ben N on October 29, 2014

Two weeks ago, I got started on my electric motorcycle battery pack upgrade by tearing apart a Ford Escape Hybrid battery pack.

After that, I was trying to figure out the best way to repack the cells into a size and shape appropriate for the motorcycle. Since I already had the original black plastic battery tray material from the Escape pack, I tried reusing that, cutting it to the size needed.

While working on that, I noticed a few things. One was that there are two different sizes of bus bars used in the pack. That accounts for the fact that every couple of rows of cells, there’s some additional spacing for the bolts that go through and hold the entire pack together. That means that I won’t be able to use an even spacing of the cells in my motorcycle pack design.

Also, the plastic that makes up the original battery tray is really terrible stuff. It’s brittle, smelly, and impossible to cut straight. After making a few cuts to try to create a smaller pack, I also found out that the material is less symmetrical than I thought it was. That means that bolt holes from one piece will NOT line up with those from another.

Back to the drawing board, I’ve seen cylindrical cells mounted through sheet plastic with round holes cut in it. Would this work for my project? Who knows? The only way to find out is to try it. I measured the diameter of one of the cells, and then drew that as a circle on a computer drawing program. I duplicated it 47 more times, trying to arrange it to fit inside the rough shape of the motorcycle frame. That done, I saved the file and took it over to a friend who has a laser-cutter. We put some scrap cardboard in the cutter and used it to carve the holes out of the cardboard.

I arranged the cells through the cardboard template inside a milk-crate (to hold the weight) and saw how the cells were spaced out. Overall, it looked like it should work fine, although without the cardboard templates connected to each other, the entire array was floppy and difficult to work with.

Of course, I really can’t do any EXACT work on the size and shape of the NiMH battery pack without getting good measurements of the inside of the motorcycle frame. And that’s rather hard to do with the existing Optima YellowTops. It was time for them to come out. I set to work taking off the tank, removing the top tie-downs, followed by the electric connections.

After removing the top two batteries, I noticed that I had forgotten how the middle part of the rack also supported the plate that holds the controller, main contractor, fuse, and other important components. I’ll have to support this in some other way when I get the new battery pack in. I removed the bolts going from the middle section of rack to the frame, and was able to get the middle section out.

After that, it was just a matter of disconnecting the power cables on the bottom two batteries before removing them from the frame.

At this point, I now have an electric motorcycle with NO BATTERIES in it. The only thing I can really tell you so far is that it’s considerably lighter and easier to push without battery weight.

So, what’s my next step? Hmmmm. I’m thinking that perhaps I just actually set the cells right down on the bottom of the bike frame. I don’t think it would be too hard to connect them with the bus bars to make a small pack. I could even space out the cells with just some foam or scrap wood for now. A block of cells could be strapped right down to the frame for temporary testing. The next trouble that I see is creating bus bars or cables for connecting the columns of cells together. In the Ford Escape Hybrid, the cells were only in two layers. In the cycle, it’s likely going to be 12 layers high! That’s going to mean MANY more vertical connections – ones that I don’t have bus bars from the Ford battery pack for.

{ 5 comments… read them below or add one }

1 Kirk October 29, 2014 at 7:41 pm

What are your expectations for range and performance from the new battery pack? Will this be a big increase in range/power or just updating the technology and reducing weight?

Kirk (fxsti from ecomodder)

2 Ben N October 30, 2014 at 7:25 am

According to the math, (1.2v x 5.5ah x 240 cells) the new pack should be 1.584KWH capacity. The faceplate on the Optimas is (12V x 55ah x 4 batteries) is 2.640KWH capacity. So, I will NOT be seeing an increase in range. I have heard that nickel is good for current, so I expect that with the updated chemistry, the cycle should be as fun as ever. Mostly on this project, it’s just replacing an old battery pack, but in the most cost effective manner possible. Optima YellowTops are about $200+ each, so a new pack of those would be almost a thousand dollars. Lithium would still cost thousands. On this battery update, I’ve only spent $150 for the Ford Escape Hybrid battery pack, about another $100 for the charger(s), and I don’t expect to spend much more than that. That might also include J1772 charging!

3 Mike G May 11, 2015 at 9:39 am

Has there been any update on this progress? I’m having a hard time finding a hybrid battery pack that cheap from either a Honda Civic or Ford Escape. What is the expected distance from this Ford pack on your bike? Were you able to utilize all the cells from the pack?

4 admin May 11, 2015 at 9:46 am

I put this project on pause because I got such a good deal on the Vectrix electric motorcycle. I’ll keep working on it this summer. The idea is to use 48 out of the 50 battery sticks from the Ford battery. I’m expecting about a 25 mile range on this setup. Unfortunately, those cells aren’t rated with a real high capacity (although 25 miles is a very useful range for me) but they were a good deal. NiMH batteries are actually OLD technology at this point. Lithium batteries would be a better choice for a new project. In my case I need to replace worn out Lead-Acid batteries, and these NiMH cells were a cheap way to do that.

5 Daag June 3, 2016 at 8:28 am

I found your post very interesting. Have you found any specs on how fast lithium ion’s can charge without danger of exploding, compared to NiMh’s that charge relatively rapidly in hybrid vehicles? Ive been considering them as well, but wouldnt want my battery to blow up.

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