Tenergy10000mAh NiMH D Battery, Rechargeable High Capacity D Size Battery, High Drain D Cell Batteries for Flashlight, 8-Pack - UL Certified

EVERYONE NEEDS TO READ THIS who has troubles believing these batteries are bad (won’t change showing an error or null). I have many “SMART or INTELLIGENT” chargers (controlled by advanced auto sensing circuits) and IF the battery is drained below a certain point or depleted, sometimes these batteries show an error or simply are not recognized because the intelligence can’t detect a fully dead battery or below a certain voltage.IF YOU USE A CHARGER WITHOUT THE FULL AUTO SENSING “intelligent” CIRCUITRY, IT WILL CHARGE. I have placed these “supposedly malfunctioning” batteries in a MORE MANUAL CHARGER THAT IS NOT SO SMART (just auto-off) for 10–30 minutes (enough to infuse a certain charge or polarity, then place them back into you smart charger… bingo. THESY ARE RECOGNIZED & CHARGES 100% or the time. Or just leave them in there until charged.I have used this solution for many years and it works 100% of the time with battery errors / unrecognized with intelligent chargers, many hundreds of times. These older more manual chargers just begin charging when you place a battery in them, it doesn’t look for status, battery voltage or battery type at all, it just sends a charge, then shuts off when it reaches a certain voltage.Buy one of the “dumbest” or “least intelligent” UNIVERSAL chargers you can find and THIS WILL WORK WITH ALL batteries you thought were defective.I have 3 old model Rayovac PS3 Universal chargers and THESE WILL CHARGE ANY BATTERY THAT AN INTELLIGENT CHARGER HAS AN ISSUE RECOGNIZING (or will get it started). I have at least 7 newer smart chargers (especially those with bar meter displays) and THEY ALL have various issues one time or another with some depleted batteries, but not these older chargers.ISSUE OF NOT LASTING LONG:Also I have noticed that all my intelligent chargers tend not to fully charge a battery, as these less intelligent chargers will. Batteries charged in a modern intelligent charger just never seem to last as long. But when charged in a more manual non-sensing charger (ie. no bar / voltage display) just with auto off, they last so much longer because they are charged more fully. I have experienced this for many years. In fact, I can take ANY battery that is “fully charged” in a newer intelligent charger with a bar meter that claims to be fully charged, place it in the more manual universal charger; and it will continue charging for a few more hours (Cs or Ds), indicating that it isn’t really fully charged to capacity. This is also the case for AA’s as well, but obviously shorter extra charging times. If I recharge those batteries BEFORE getting too depleted, they are recognized, w/o the error indicator.You don’t have to believe me, but you will be a believer if you get your hands on an older or simple auto-off universal charger, it will be an awakening and you will be a believer then. (and don’t argue the merits of intelligent charging over simple chargers - that’s not the point here). THIS IS TO GET YOU PAST THE ERROR STAGE AND CONTINUE USING BATTERIES YOU THOUGHT WERE DEFECTIVE - AND RESURRECTS THE MONEY YOU THOUGHT YOU WASTED ON DEFECTS & ERRORS.

I was shocked to find out that the D-size rechargeable batteries sold by Energizer are really just AA cells in a bigger casing. What a rip-off. 2500 mAh just won't cut it for the types of applications that D-sized cells are used in.We have a baby swing that requires 4 D batteries. This swing makes our lives infinitely easier. It allows our daughter to fall asleep on a whim, which is amazing. I was buying alkaline D cells every 3 weeks to keep this thing powered, and it was getting expensive. I already had a charger that can handle D-sized cells, so I started looking for rechargeable Ds, and learned the awful truth about Energizers. With 2500 mAh cells, I'd be recharging batteries every 2-3 days!!! Not to mention that NiMh batteries have a much lower voltage than alkalines, so the swing (which doesn't have a voltage regulator) would be running much slower the whole time while pulling max output from the batteries.The solution was a combination of 2 things: these Tenergy 10,000 mAh D-sized cells, and a secondary battery holder for the swing to add 2 more batteries. The battery holder was very easy to put on, just cut one of the power wires on the swing and connect each end to the wires on the battery holder. I attached it to the swing using Velcro tape. Now the swing uses 6 D batteries. So instead of 6 volts alkaline (4x 1.5v), it now has 7.2 volts NiMh (6x 1.2v). Why the extra 1.2v, you ask? Easy, now I can run the swing at level 5 and get the same speed I used to get at level 6 (max). This prevents the batteries from getting warm and helps them last even longer. Still not as long as alkalines used to last, but long enough that charging the batteries isn't a chore. I'd say we get about 2 weeks out of a charge, vs the 3 weeks we used to get from alkalines.We bought a total of 12 Tenergy 10,000 mAh D-sized cells, one set for the swing and one set to keep charged as backups. A set of 6 takes about 10 hours to charge. We need the spare set because when these batteries lose their charge, they die very suddenly. It's not a gradual slow-down like it was with Alkalines, where I'd have a couple days' warning to let me know to buy fresh batteries. These things go from full speed to completely dead in less than 10 minutes.Now my 5-month old daughter can swing away and sleep without the incessant cost of alkaline D batteries! I have a feeling she'll be using it for many months to come.