A123

So I did some testing but still have more to go. I found that when they say don't charge above the recommended limits. Even with the recommended limit they can be fast charged in 20 minutes. I tried to charge at 40amps and that is well above the limits and just when the cell was nearly full the PowerLab shut itself down due to overheating. The cell was filled but well over the maximum temp limits. So charging too fast will overheat the cells and put them in the danger zone. The temp was up in the 150 degree range and the upper limits are 130 F. So at 10 amps the cells respond quite well and don't overheat but they do get a bit on the hot side of warm. The discharge at 40 amps is quick and they don't overheat. I am not sure if they can handle a discharge of a constant 50 amps but they may. As for peak discharge I'd say if you decide to do 120 amps then stick to the 10second rule. That is like 48C. Not to bad for a cylinder cell of LiFePO4. I think it was rumored that they could do 70C but that is not so. It is only 48C peak. 120 amps from a 2.5ah cell is a whole lot. They do have a safety vent on top so if you do tab weld them you should have a hole punched so the vent is not covered.

Here are a few discharge/charge graphs. The average rating is 2.3 ah but I am doing a charge of 10amps and a discharge of 40 amps. So fast charge and normal discharge will lessen the total ah of the cell. True usable capacity that is actually usable I'd say is 2.1 ah and that is doing fast charge and normal discharge. So a 40 amp discharge is like 16C. Better than the prismatic. Not sure how well they live in this condition but they can do it for short periods.

I am hunting for a way to test for 120 amps out of one of these suckers. I am also looking to build a spot welder so I can have better connections for building larger packs for higher amperage loads to test them. As a single cell they get hot fast. It could be because of the way I have my connections to the cell. When I first did the test the cells made some funky fast clicking sounds. It was a crappy connection. Once connected better that went away. I think I could still do better.

                                   

Below is the graph where I charged at 40 amps. Too fast and too hot. 152 F.

Here is a link to the PDF Spec Sheet

A123 26650