Battery voltage rebound effect?

I have some extra lithium ion ICR, IMR, and INR batteries in various sizes that I'm discharging in order to store at the recommended 40% of capacity. I'm noticing it's common for me to get a 40% reading, and then checking a while later I'll get a rebound to 60%, or a rebound from 20% to 40%. I'm measuring them with a ZTS MBT-1 Pulse Load Battery Tester which measures capacity in intervals of 10, 20, 40, 60, 80, & 100%. I know batteries do recover somewhat after discharge but this much of a gain surprised me. I realize I should probably be using my voltmeter but it crapped out so I'm using the ZTS unit, but part of the problem may be the fixed intervals of increments of 20 rather than 10 except on the low end.

The ZTS unit can be seen here:

http://www.amazon.com/dp/B000FQG1XE/?tag=cpf0b6-20

Hello Magellan,

Did you have a question...?

Proper procedure would be to do your discharge, let the cells rest for 30 minutes, then measure to see if you are at the value you want.

A rebound in voltage is normal when you remove the load.

Tom

I was only waiting 15 minutes which I knew wasn't long enough.

I was a bit surprised that the "recovery effect" was of this magnitude in a small battery. We've all seen this in typical lead acid car batteries which might weigh 50 pounds or more but in comparison a 18650 or 18500 is tiny.