I checked two batteries, both were completely dead. The first battery I put into repair mode worked really well for a few days. It took about 16 hours to complete the passage. The battery works like new. Second battery. I changed the mode back to normal, took a night to fully charge with great results. I would give this product five stars, it does what it promises. It is small and handy to have on hand. I've attached a short video and some progress photos. I highly recommend this item. Many Thanks.