Instruct: Classify Amazon reviews into positive or negative sentiment
Query: Overcharges 9V batteries - not recommended

I was really disappointed in this battery charger. The charger operates on timed charge for AA, AAA, C, and D cells rather than operating on the batteries actual state of charge. This can dramatically shorten the life of batteries that are not deeply discharged before recharging. The charger is almost unusable for 9V rechargable batteries, as there is not even a timer function that shuts off the charge voltage. This means that the 9V battery can be overcharged to the point of destruction if left on the charger too long. A really bad and cheap design, I wouldn't recommend it to others.