TenergyCombo: 4 pcs Premium D Size Rechargeable Batteries High Capacity 10000mAh NiMH - UL Certified

I own 8 of these great rechargable batteries. They work very well and keep the charge a long time used in a baby mobile. The issue is, that the baby mobile draws a very low current and the batteries get exhaustive discharged and appear dead to the charger. After refreshing, the dead battery seems to be fine. 4 stars because of the high price.How to refresh a "dead" battery:I read on a discussion board, you place the "dead" and an equal sized battery in your charger. Take a paperclip and connect the plus(+)-poles of these two batteries. Wait 15 minutes and remove the paperclip. The "dead" battery keeps charging.Update 06/13/2016: The price is now reasonable. Changing to five stars. The best is, I have bought these batteries 4 years ago and we used them constantly for a crib white noise toy. Now after four years 3 of the eight show signs of fatigue and will not hold the charge much longer. Well worth the price. Go for it!

We have a baby swing that uses 4x D cells and I was tired of wasting money on regular alkaline batteries since a 8-pack of quality (Energizer/Duracell/Rayovac) is 8-11 dollars, by the 10th purchase we'd have the cost of the swing!For those who don't care or geek on batteries 10,000mAH (10AH) is a good bit juice for a battery of this size...The simple math is that if you had a device that needed 10AH, the battery would last (theory of operation) for 1 hour.Something that drained at 5AH, would last 2 hours and so on...With that in mind, a battery like this (or set of in series) would provider longer run times than their fellow alkaline cousin with a great benefit, reusable!There's always a catch though! NiMH cells run a native voltage of 1.2 vs. the 1.5 from alkaline... Most electronics were designed on math of 1.5v cells so 4x alkaline would be 6 volts, where NiMH only provide only 4.8...Depending on the device, this may or may not be a concern as some devices have regulation circuits that compensate for the lower voltage...The pitfall on the baby swing is it has a motor. Simple math again says if the motor was designed to rotate at a particular speed, it was also designed to receive a particular voltage... Most devices with motors don't put the extra circuity in to keep the motor regulated as it's a different type of regulator setup than powering say an LED flashlight or portable TV... So with just 4 cells installed, it wasn't enough to keep the swing(ing) even at highest setting since the motor just couldn't 'push' as hard regardless of cell storage capacity, the motor will only take so much per it's design...The fix you may wonder? More batteries! I snagged 2x more making 6 total cells at 1.2v = 7.2 volts.Yes, it's more than the unit was rated, BUT that's at no load! Adding the load drops the voltage to 6.5~6.4...I did have to add a 2 D-cell battery holder to the outside housing and using a piece of popsicle stick to intercept one of the cells to add the wiring to get the extra 2 cells in series, but 15 minutes later I was doing a mad scientist laugh!Now we literally get 3x the lifespan before having to recharge the cells!Previously one 4-pack of quality alkaline batteries was lasting about a week to 10 days... Now it's just a monthly task and my wallet thanks me!What's the ROI (Return on Investment)? 6x cells + 2-D cell holder + misc. supplies = about 40 dollars.. If a 8-pack of alkaline cells cost 10-dollars and we go through 2 packs a month, just 4 months and we're good!Lastly, the perk on rechargeable (of standard battery) is they can be used elsewhere once the swing retires from duty...Enjoy!

[Capacity:]Tenergy seems to have world wide the highest rated capacities for rechargeable NI-MH batteries.Looks like Tenergy has almost maxed out of whats technically possible.No other maker has these capacity range, hats off !!Even the best Japanese makers have max roughly only 60% capacity (5700 mah), again respect for this !!It's awesome how much capacity this rechargeable batteries have.[Weight:]Lets face it, batteries are heavy. Capacity limits and weight are probably their worst obstacles.Fortunately the extended capacity plays as advantage as you might come by with one battery pack where you usedtwo or more in the past. This comes in VERY handy when either every gram counts or stamina is everything.[Charging:]We all know that increased capacity not only gives you better mileage but also requires fewer (but long) charging cycles.Generally speaking high capacity is a good thing but long charging times might be a turn off when you are in hurry.In addition quick charging or charging to often (to early) might decrease life cycle of the battery (read: damage it). So itmakes sense that you also invest in an "intelligent" charger, that checks the battery status, de-charges it controlled andrecharges it gently. This way your investment is protected.[Usage:]So far I have used those batteries and haven't realized any significant drop of capacity.Its to early to tell the long term quality of the product, however so far everything isindicating a good quality product.I will update this section in regular intervals to indicate any capacity changes.---[Summary and target user:]---I am conservative. For the technology and capacity alone I would easily give 5 or even 6 Stars. I understand that 10.000mahis a capacity that is almost unheard off and more likely bikes or even small car batteries have it.For the average user even 50$ + charger cost is a deep price to pay, so its not a deal for occasional uses.HOWEVER, for power sucking heavy usage this is a steal, especially if you MUST HAVE the extended stamina.5 Stars for heavy users4 Stars for average users ((Reason is initial cost)Enjoy the ride !!