18650's and their quirks

[BrianG]

How are you measuring IR? The best way IMO is to measure voltage unloaded, then measure again at X load, then take the voltage difference divided by the load current. Do that over the course of the discharge cycle to get a graph of IR. I think you'll find the IR for the poor performing cells is higher than the others.

When cells are in parallel, you are getting some conflicting results because a good cell is somewhat compensating for the not-so-good cells, and the not-so-good cells are surely affecting the performance of the relatively good cells. Basically, parallel cells masks each cell's true performance. Which incidentally, is one reason I don't like any kind of 2p+ setup.

[J57ltr]

It's a predetermined time in the discharge cycle, it actually unloads measures the Delta/Time and makes the calculation.

I was going to use the Eagle tree but was having problems getting the charger to work properly, it keeps telling me that there is no load. I am going to check the connections again I think I have a bad Dean's.

Also when I say the cells in parallel I am meaning as I pulled them so they should be about as matched as they are going to get.

I skipped a few days while I was out of town and am going to get started messing with them again tonight after I get this 4 wheeler unloaded.

Jeff

[J57ltr]

Ok so I got home and charged a single cell back up it took about 65 mah.

About an hour later I set it to discharge it at .2 amps 4.9 hours ago and it's still at 3.600V and it's at 1200mah. The IR is 189 milliohms.

One thing I have noticed is that at different discharge rates the IR changes.

Jeff