Battery for 600x rebuilt by BatteryRefill exactly three years ago. Used only while traveling which takes place about twice a year. Balance of the time kept in the refrigerator at 40% charge.

This time, took it out, it charged to full. But when a recharge was needed, it only went to 20% or so. Trying another 600 had no effect.

Anything I can do about this?

Before I asked this question, I hit the literature on the subject which is voluminous. But I was unable to find a circumstance similar to mine, 100% and then down to 20% (and now less) at the next recharge. So I thought possibly something could be done about that.

Now it is acting 'normal' in that the subsequent recharges are getting less and less all below 20%, now down to below 15%.

So if I want portable power, looks like I will have to opt for a new battery.