Tenergy 9V Battery Rechargeable 250mAh 4 Pack NiMH Square Battery with 2 Bay 9V Battery Charger for Smoke Alarm/Detector

Customers find the battery charger works well, particularly in metal detectors, and appreciate its quick 2-hour recharge time for two batteries. They consider it worth the cost, with one noting that AA and AAA sizes pay for themselves quickly, and find it easy to use and convenient. The battery life receives mixed feedback - while some say they hold their charge for months, others report they don't hold a charge at all. The size also gets mixed reviews, with some finding it compact while others say it's too big for their needs.