A while back, I ended up at a salvage yard a few hours drive from my house. While I was there to get a transmission, I also ended up walking away with a Ford Escape Hybrid battery pack.
The battery came out of a truck that had been rear-ended, and there was a bit of a dent in the back of the battery case, but not bad. For $150, it was worth it for me to buy the pack and take it home.
So, the hybrid battery has been in my garage since then, just waiting for the right time for me to crack it open and pull out the cells. Theorically, this battery pack has 300 volts at 5.5AH, or about a 1.6KWH capacity. Not huge, but most hybrids use are constantly charging and discharging their battery to best overall vehicle efficiency. I figured that if I pulled out the cells and re-packed them, I could create a lower voltage pack at a higher AH capacity.
So, I set to work taking the pack apart. (Warning: Many battery packs are 300V+DC and potentially FATAL electric shock hazard. Kids, don’t try this at home!)
First, I removed the top cover. Pretty easy, just LOTS of bolts to take out. A power screw driver comes in handy here.
Next, I pulled out all the bolts holding on the black plastic cover over the cells. The larger bolts were very long and went all the way through the pack and into the bottom of the housing.
I was able to grab the part of the pack that held the cells and shake it a little. It was mostly loose, but still held in by connections at the service disconnect and main contractor. I also removed the cables going to the cooling fans and the physical connections of the ducts to the cooling fans. I was extra cautious working around both the service disconnect and main contractor. The cables to them are always color-coded orange, indicating high voltage wiring, typically in the neighborhood of 300V.
The cells are actually arranged in two layers, an upper and a lower. The service disconnect is between the two. So, when you disconnect the battery pack, you not only break the circuit, but also make the battery into TWO 150V battery packs, instead of one 300V pack.
With the service disconnect and main contractor both disconnected, I pried on the upper block of cells, and had several pieces of oak firewood handy to use as spacers to set the cells back down onto. This would give me a way to get a good grip on the block of cells and also see what other wiring might remain and need to be unplugged.
After disconnecting a few more wires, I was really to remove the upper block of cells. (Lift with the legs not the back…)
OOOOOOOOmmmmmmfmmffff! I got the cell block out and carried it over to a pair of saw-horses, where I would have better light and more room to work.
On top of the cells was an array of sensors – temperature sensors and a large circuit board for cell management, held in by about a zillion screws. I set to work removing them. I also tested the block of cells with my volt-meter and found that this half of the pack was at about 166 volts, which sounded about right for a full charge.
I removed the BMS and then trim covers on both ends of the pack. Those with the cell connections. I used the multimeter to test and saw that they were connected in a serpentine pattern so that each electrical connection was about 24 volts higher than the previous one. I removed those interconnect bolts, which finally brought the pack down from a 150V+ down to a mere pile of 6v components.
The cells in the pack are Sanyo NiMH “D” cells, with 5 connected in series to make 6V sticks. The entire battery pack is composed of 50 of these 6V sticks.
I checked the polarity of each with my multimeter and then marked the Negative end (-) with a black Sharpie marker. Then I pulled them out, one at a time, and stacked the sticks, all pointing the same direction.
Once I had this all figured out on the first half of the pack, I pulled out the lower layer of cells and did the same, carefully stripping out the cells.
Next, I took a look at the area on my motorcycle taken up by the lead-acid battery pack. Essentially, it was a rectangle that was 14 inches wide, 17 inches tall, and 7 inches across on the bottom. (The batteries are a different orientation on the bottom vs the top of the pack, but I’m just going with the smaller size, figuring I want the NiHM cells to be packed as a rectangle.
The NiHM cell sticks are over 13 inches long including the terminals. 14 inches is probably about right for a little space to work around them. I packed the cells into a milk crate in a 4 x 12 grid. That would mean that every two rows of four is 8 sticks (which makes 48V) and it would be 6 of those groups of 8 sticks in parallel to make the entire 48V pack for the motorcycle.
Next, I’ll have to figure out how to mount all the cells together. I’m thinking about laser-cutting circles in acrylic to make a clear case where all the cells would just slide through the holes to make an array. I’m not sure how much heat will be made during charge and discharge, so allowing an air-gap between the cells and adding something like a computer fan might be a good idea. I’ll probably base the spacing of the cells on reusing the bus-bar interconnects from the Escape Hybrid battery pack.
That’s it for now. I am showing off my motorcycle at an alternative-fueled vehicle day two days from now. Maybe after that, I’ll pull the lead-acid pack, to be able to take some real measurements for the NiHM cells.
Til next time, stay charged up!
-Ben
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That was a fascinating article.
Nice work Ben!
Do you still have any of the components of the escape pack? I need one and am terrified it will cost a fortune from Ford.
I think my contactor is bad, and it seems from your video, I could replace it myself.
Please let me know.
Jon
Hi Jon, I have some of the cells from the Escape, but I don’t think any of the other components. If you need a cell module, let me know.
Thanks Ben,
I bought a parts car, 2005 and opened up the battery. I got out the contactor (the last part before the hv output to the vehicle) and when I opened up my 2009 battery I discovered the electronic components and the wiring and plugs inside are not the same (aluminum computer box on passenger side is different, and aluminum computer box on drivers side doesn’t exist). Since the contactor seemed to be the same, I cut the wires from the 2005 contactor and soldered them to the plugs to fit the 2009. Put it all back together and the 2009 started and ran fine! I was able to start and turn it off several times with no problems. I was very excited until I drove around and then left it outside in the cold for a half hour and then my no start issue came back. Super sad. I have no idea what is wrong with it. I wont need any cell modules from you as I have an entire spare pack. Thanks for the response. Thanks for the great photos that made it possible for me to attempt this repair.
Very interring project you did here. I just crashed my 2008 Ford Escape Hybrid and was thinking of salvaging the hybrid batteries but I am not sure what I can do with them. I sell solar panels for homes and am very into that technology. In fact I built a mini solar house that you can see on my web page. Any suggestions to build a solar back up or golf cart back up with these? I’m not as tech savvy as you so this may be over my head.
I was even thinking maybe a battery atorage up for a backyard entertainment center that would stay charged up with Solar. Let me know your thoughts, you are very knowledgeable and I respect any input and ideas you can give.
Since you have experience with solar, a stationary solar-charged battery would probably be a good use for those cells!