EneloopPanasonic BQ-BS1E8SA D Size Battery Adapters for Use with Ni-MH Rechargeable AA Battery Cells, 8 Pack

I used this adapter for my Exercise bike which only accepts D batteries. I used it with Energizer Lithium AA batteries inserted in this adapter and it works with my device (the exercise bike). I purchased this item because it has the large negative terminal that a regular D battery has and does not use the AA battery's negative base as an adapter.

I like the engineering and design of these battery adapters. I use them in my lanterns that require size D batteries. AA size batteries are so much more convenient to manage for recharging. I think the D adapters are good but I would steer clear of the C adapters. There seems to be a lot of issues with the AA to C adapters.

UPDATE 07.01.2022. Having 3 or 4 of these adapters in a row in a MagLite I observe some dent in the negative pole (back on the metal) where the other positive pole is resting against. It could be as well just me as one time the heavy 4 D cell MagLites spring wasnt sitting all in and it must have given more pressure on these adapters than normal bending the metal a bit. But then again the front part of the MagLite is springloaded as well, so... But these are built sturdy and so damage is unlikely. Yes these measure 61 mm from the +pole to the end of the -pole plastic cap that is the same overall dimensions from outside as an D cell battery has according to its specs. These are made of ABS plastic and that can be attacked slightly by Vaseline. So I recommend NOT to apply Vaseline (or petroleum jelly) to the metal parts of the adapters in order to prevent rust. I normally tend to grease slightly metal contacts with Vaseline as that is recommended by MagLite for their flashlights. ABS plastic can be weakened and swell slightly on from spilled over Vaseline so do not do that.UPDATE 22.12.2021. The D cell adapters of this latest gen I got of these Eneloop adapters measure exactly the same as an D cell battery would. That is 61.5 mm. I measured it with an caliper. The complaints other reviewers have about bad fitting when stacked most likely is a problem with older generations of these adapters. The latest gen at least has fixed that problem since the adapter itsels is now of an very different design, much improved design, and measures exactly the same dimensions from end to end as an D battery would. The latest generation have an vastly improved design over previous generations of these adapters. At least the D cell versions. It may be the C cell adapters sport still this design flaw since the C adapter design is still the same as the flawed D cell design of previous generations used to be.The D cell adapters have no engineering flaw nor design flaw anymore and are the best adapters in the market today.Main review:Excellent. Best idea ever. Awesome.This new design of the Adapter works well in an 3 D cell Maglite. The huge negative contact face is just awesome. Works well and makes the light lighter. I have these in use already for a few years.Seldom I give such an 100% positive Review. I can not find any negative or flaw on these D cell Eneloop adapters.Awesome. 5 stars.This newest design is perfect since it changes the tiny negative contact to an huge area one which is big enough for the huge spring of the MagLites. Eneloop had a previous design which was flawed but since has upgraded the design. This is prefect and solidly built. I use it in all my D cell appliances like radios and flashlights. It saves you different sizes of rechargeable NiMH batteries so you can stick just to size AA mostly and for some appliaces AAA (control remotes, etc.)Dont go for other brands. You cant go wrong with this Panasonic Eneloop brand. Perfect engineering. These are built sturdy as they are reinforced with plastic ribs from the inside. That gives for a big stability. I grease the metal contact parts (positive and negative) with Vaseline which is actually recommended by MagLite.Using these with AA Eneloop NiMH gives you about 16 hours of run time instead of the 80 hours claimed when using alkaline D cell batteries with an 3 D cell LED MagLite with an 168 Lumen LED bulb.Dont hesitate. Buy these.

So many of the smaller battery powered devices I have seem to not be 'designed' to support the 1.2v level batteries anymore, but insist on something closer to 1.5v or they throw a low battery warning very soon after a battery swap.As a result, I had quit using my AA rechargeable NiMH batteries and was switching to the Lithium rechargeables with 1.5v output as I could afford them.But I saw these adapters and they looked like they had high enough quality they would last for a while. So decided to use these with all my 1.2v AA rechargeables as most of MY use of D cells was flashlights and they don't generally nag at you about battery level as the bulb not illuminating well is the universal sign it is time to swap out the D cells.I always put off buying any D Cells (alkaline) as I use them so infrequently and they cost so much per battery. And I didn't want to buy a desktop charger for D cells as I would hardly ever use it.When I saw the (looks like) higher quality AA to D adapters I decided it was a way to 'recycle' my old tech 1.2v AA rechargeables I had been thinking of throwing out.Yes, they won't last as LONG as D Cells (Alkaline or NiXX) - but if you are like me, you leave the flashlight switched on way too often and run the cells down before the next use anyway.So not an optimal solution to spend too much money on 'creating' - but if you have a medium to large size pile of older rechargeable AA batteries this may be a low cost way to put them back into the 'things I actually like to use group' of stuff you own.A way to 'recycle' the old 1.2v tech to get a few more years out of it. I had 32 of the old NiMH AA's and with the 8 pack of D Cell adapters I have 'plenty' of (wimpy but usable) D cells ready to go (for a day of use maybe) whenever I need them.

The adapters worked in some of my flashlights and not in others due to the way the external positive tip is formed within the plastic surrounding it. Some of my flashlights have an indentation where the typical D-size battery's positive end nicely cradles. The AA to D-size adapter's external positive end has a little bit too much plastic surrounding that metal connection point, keeping the contact points between the flashlight and the adapter from connecting. As others have suggested, I put a 3/4" square of double-folded aluminum foil on that end of each battery going into the flashlight and all was well. I suppose it might be possible to file down the plastic edges surrounding the adapter's positive end to fix it but then there may be sturctural risk involved. I'm mostly happy with the product and may buy more for non-issue flashlights etc :-).(***Eneloop batteries are great and I've been using dozens of them for over ten years with no failures or noticeable charge capacity degradation over hundreds of cycles!***)