BONAI Rechargeable D Batteries 10000mAh Pre-Charged Low Self Discharge, Ni-MH D Cell Recharge up to 1200x Times - 4 Pack

First, the bad news...My initial experience was not positive. Six of the eight BONAI D batteries I purchased would not charge. After about 10 seconds, the BONAI charger displayed an error message. I really wasn't sure whether the problem was the batteries or the charger. Now the good news... BONAI customer support is superb! I communicated with them several times via email as they attempted to solve the problem. They responded promptly (within several hours during the work week...and very early Monday morning when I emailed over the weekend.) Pretty quickly the tech determined that the batteries were bad and sent me eight new ones. They arrived on the second business day. The replacement batteries charged without issue. Having said that, buyers should know that it takes a very long time to charge these batteries. Here is what the support tech wrote me in one of the emails: "The higher the battery capacity, the longer the charging time. The capacity of this battery is 10,000 mAh. When charging one battery, the charging current is 2,000 mAh, and it can be fully charged in about 11 hours. When charging 4 batteries at the same time, the current of a single slot is 500 mAh, so , It takes about 22 hours to fully charge 4 D batteries with a capacity of 10000 mAh at the same time." So, a little patience and planning is required with these batteries. When fully charged, my new BONAI batteries showed 1.33 volts on my meter. After running a small portable fan for five hours, the batteries measured 1.25 volts. I'm ignorant on this technology but that seems like pretty good performance to me. Bottom line... the BONAI product seems high quality...and the customer support is even better.

I kinda figure that when you order large quantities of rechargeable batteries, there may be one or two that just don't take a charge, but in this case, I only ordered 4 D batteries and after 24 hours 2 of them still would not take a charge. I tried taking them out, let it sit for 10 minutes and then start again, that got two charged. But the other 2 just were not charging. I don't like to leave negative reviews, but I know there are others out there that look at these reviews to help make their decision. I know I do. so I am leaving this review. I am hoping that the manufacturer or seller may reach out to me to try and fix this. Other wise I am sending them back, and I will look at other brands. Update 10/07/2018: When the company saw my post they contacted me almost immediately, they offered refunds and replacements. Although I'd sent the others back, my aa/aaa, they offered to replace those as well but that had already been settled. They sent a brand new set of 4D batteries and they charged beautifully, haven't had the chance to use them yet, but they charged up, so I have to assume they'll work. Their customer service was outstanding!!!!!!!! I wish now, I'd just waited, let them contact me, and everything could've worked out. I'm really impressed, and customer service these days is a trait allot of companies lack.

These seem to work OK, they charged at any rate. They are heavy batteries, not AA in D cell casing. I hooked up a VOM meter set to the 10 amp scale and was only able to get a reading of 2.5 amps or 2500 milliamps. I was expecting 10 amps on a dead short. Is the capacity really 10 000 maHr? I don't have any high tech. equipment to test that for sure. I purchased these instead of bigger name brand batteries rated at only 2500 milliamp hr, not sure I got what I was expecting.

Update: The battery company reached out to me after I posted my earlier review. They said that they stand behind their product and sent replacement batteries to me. Received the replacements today and all batteries are good and hold a charge. I think they went above and beyond to correct this situation and for that I am revising my rating to 5 stars. ——————————————————- one of the four batteries that I received had no charge when received and I was not able to charge it. It is too much trouble to return it. I will find another battery for my needs.

We got these to put in our new Jasco Enbrighten LED lantern which on alkaline batteries last 20-350 hrs depending on brightness. 3 fully charged Bonai rechargeables lasted 10 hrs on the highest setting before dropping to the dimmest setting and lasted ~175 hrs on the lowest setting. This equates to about 50% of what alkalines last which is fine esp considering the internal Li-Ion battery in the lantern lasts 75 hrs on the lowest setting so 3 rechargeable D batteries extend the lantern to a total of 250 hrs. These are large 10000 mAh batteries and came precharged. Be prepared to wait the first time you charge them - it took ~18 hrs to charge three D batteries in a Bonai charger we purchased and then after the first cycle, it took less than 12 hrs (finished overnight). Customer service responded quickly and also let us know if you are only charging one D battery, it can take only 10 hrs. We wanted to see how well these batteries fare in our regular flashlights. This is *not* specific to Bonai: rechargeables (in general) have lower voltages than regular batteries. These batteries charge to ~1.4V (which is above the 1.2V spec) (for comparison, if you bought any of the popular 1.5V alkaline batteries, they often arrive at 1.6V+) This is important because we had both 3 and 2 D-cell flashlights and couldn’t tell the difference for our 3 D-cell flashlight (a Maglite, can’t speak to how long it lasts as we did not stress test it) and when we put 2 of these batteries in a 2 D-cell flashlight, it was noticeably dimmer. Overall, given we got these on Prime Day for the same price of alkaline batteries (because we bought the charger in the same order) - so even if we just charge them 2-5x over their lifetime, they will have paid for themselves over disposables. If you’re going to buy these full price, you are probably better off putting them in devices that have more consistent battery drain like a boombox or something (where you would charge them more frequently)

Very happy with these batteries.