Review on Lenovo ThinkPad T480/T470/P51S/P52S Battery Replacement (01AV427 SB10K97584, 4X50M08812 01AV492, 01AV428 10.8V 72Wh 6600MAh 6-Cell) by Patrick Hamilton

I have an existing Lenovo Thinkpad T580 that I bought in the spring of 2018. The dual battery system represented One reason why I purchased a Thinkpad. After three years, the external battery on my thinkpad degraded. I wanted to buy a new external battery. Or so I thought.I bought this battery on January of 2021. After approximately one month and two weeks, the battery would not last beyond 4 hours. The extended battery works as intended for one month. Thankfully, I bought the battery on Ebay. The amazon representative refunded my purchase after I called them. For your reference, I bought from the seller jiazijia.Edit: the seller has reached out to me. The seller offered me a free replacement. I will update with further details if the battery exhibits any defects.Edit2: I received the replacement battery. After plugging the battery into my thinkpad, the battery works. However, after the battery became completely discharged, I cannot charge either the new battery or the inner battery in my thinkpad T580. The replacement battery has firmware issues. I plugged my old external battery into my thinkpad T580. Both batteries charged as intended.As a result, I appreciate the seller's efforts to compensate me. However, I feel that most of the seller's replacement batteries are old stock. Please do not buy this battery and think that the large replacement battery will be better than the existing battery. I will change my rating of this product back to two stars.As a side note, I have purchased the extended battery from several different sellers and different e-commerce sites. Based on my purchases, I believed most of the T61++ external batteries suffered defects and /or old stock. Hmm. I wondered why there are many T61++ batteries for sale from third party sellers.Edit No. 3: The seller contacted me regarding the new battery. I told him or her regarding the defect. The seller sent another battery to me. After receiving two defective batteries, I received a battery that worked. Hooray! The third battery I received worked as intended. On my computer, the screen showed 10 hours of battery life (which is the battery life combined with the laptop's internal battery). Thus, the battery worked.However, I believe the seller has some faults. Obviously, the seller is buying bulk batteries from the original manufacturer for sale. Even though I am happy that I received a working battery, I would be happier had I received a working battery on the first order from the seller. As a result, I will revise the review to four stars.