Rechargeable Lithium D Batteries with USB 2 in 1 Charging Cable,1.5V LR20 Battery D Size Replacement for Flashlight,Toys,Gas Stoves (2 Pack)......

I had never seen these before, and I wasn't sure what to expect. Well, after using them for several weeks, I can report that they are a fantastic product! I go through a lot of batteries. I have one of my favorite flashlights, a 2 D cell one that I keep by the back door for using when I take the dog outside in the dark. I felt like I was replacing the batteries in that flashlight every few weeks, and half the time it was dim and ineffective. When I got these batteries, I charged them up. It seems a little strange to charge batteries via USB-C cable, since I'm used to charging rechargeables in a battery holder device of some sort. But these I just plugged in using the provided dongle directly into a USB charger. They have their own battery management system built into the battery itself, so you charge them up and can tell when they're done by the green LED light on the top of each battery. I put the fully charged batteries into the flashlight and, well, they work perfectly! I've been using them on the same charge for a few weeks now. One of the interesting things about them is how light they are. I strongly recommend these batteries. They are not cheap, but they will save money in the long run!

I use these batteries in an outdoor detection light. I've been using them for the last couple month and they hold a great charge and last a while when being used. I love that they are chargeable via USB-C. Another cool thing is that the box includes a USB-C cable that lets you charge both batteries off one cable. Overall these are handy and I plan to get another set, saves a ton of money

So, if you go through a lot of D batteries, these will solve that. They dont last as long as alkaline, but youre getting rechargeables. Kids still have toys made for D batteries and these work. Until they start making kids toys rechargeable, get some of these.

I dont have many devices that use D cell batteries any more, just an old Mag Light and the lights on my Weber grill. I dont want to stock large numbers of D cell batteries because theyre expensive, bulky, and tend to go bad before I get around to using them. So far these have been a great substitute for alkaline primary cells. Fast to charge, decent capacity, high quality construction, USB C charging with included 2 in 1 USB C cable. I got 4 of these with a Storacell to hold them. Problem solved.

While most devices today use either AA or AAA cells, we still have a few that take D cells. I thought Id give these rechargeable lithium cells a try instead of continuing to use disposable alkaline cells. These arrived almost fully charged because it didnt take long for them to top off using the split USB charger cable. I thought I had a poor contact when using my DVM to check their no-load voltage because the reading kept fluctuating between 1.50V and 1.68V. So I measured the battery on my scope with to confirm the variation was not a meter problem. Sure enough, the voltage was pulsing once a second in a sawtooth pattern between 1.5V and 1.7V. Then it dawned on me how they create the 1.5V. Lithium batteries are normally above 3V, and these must use a switching regulator to drop the voltage down to 1.5V. Since that regulator is always active even when the battery sits unused, that explains why the battery must be recharged every 6 months. Then I tested the battery under load to check its capacity. The battery specifies maximum load current is 1800mA. D-cells dont normally have a maximum load spec, but that must be the maximum current the switching regulator can deliver. So I tested with a 1.1 ohm load (including clip-lead resistance) to keep comfortably under the 1800mA rating. The voltage under load measured 1.432V. That is similar to what would be expected from a fresh alkaline D-cell under load. But while the voltage delivered by an alkaline cell would slowly drop, this lithium D-cell maintained that same 1.432V after 1 and 2 hours. It finally dropped out of regulation at 2 hours 35 minutes. But then the voltage dropped rapidly with only minutes of energy left. With a 1300mA load, that represents 4.8 watt hours. Since efficiency goes down with increasing current, I suspect these will indeed deliver the quoted 6 watt hours at the 430mA load current specified on the battery. It should be noted that a quality alkaline D cell can deliver 20 to 25 watt hours. So these will have to be recharged 4 times over the typical life of an alkaline cell. But for frequently used higher drain devices (under 1.8A max) where recharging is not an issue, these are an excellent choice. That voltage regulation under load is impressive.