Do not freeze batteries, it won't help and there's a good chance you will destroy them.

If these are AA/AAA batteries, buy Eneloops because they basically don't self-discharge.

Make sure you have a proper delta-V charger that shuts off when the battery is full (the voltage actually drops a couple mV), not just a cheap timer-based charger. Anything else and you will be damaging cells through overcharging.