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Old 07-06-2012, 12:08 PM
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Daox Daox is offline
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Default Mottcell 39Ah cell test results with PowerLab6

I don't post too much on this forum, but I've been working on rebuilding my Prius' PHEV kit (made by Enginer) since I had some issues with it, and I just wanted to share my findings.

The first step of this rebuild is evaluating every single cell in the PHEV kit's pack. The pack is made up of 32 "39Ah" Mottcell cells. The configuration is 16 in series, 2 in parallel. I've been using a Revolectrix PowerLab 6 charger to evaluate each cell. The process charges each cell up to 3.65V at 38A (~1C), then discharges it to 2.8V at 38A, and then recharges it. The Mottcell cells I've found with this cycling setup only give a max of 35Ah of capacity. This is from brand new unused cells. Some of my older (~2yr) used (and abused) cells are showing capacities of around 30Ah. This is quite disappointing to see that you don't even have the rated capacity. But, its what I have to work with and it'll have to do.

Here are the test results:
(highlighted cells are under 30Ah)




I'm a bit curious why some of the cells tested higher on the 2nd and 3rd tests. My strongest cell (#20) didn't see this effect when cycled multiple times.


The second step of the project is finishing up my BMS system I've been developing for a while now. I'll be sharing more info once I get everything in the car and working. I'm pretty excited about it though because it has some very nice features and is the cheapest BMS I've seen. Its just a little over $7/cell in materials for my 16 cell setup and gets cheaper as you add cells. The current design is made for my PHEV and will need some tweaking for a full electric car though.
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File Type: jpg cell_capacities.jpg (70.0 KB, 64 views)
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Last edited by Daox; 07-06-2012 at 12:11 PM.
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