ReZap 7329 AA to C and D-Sized Battery Converters

I have a ton of AA/AAA rechargeables and almost no devices that take anything else, so when I recently got a couple of devices that needed D batteries, I decided to get two sets of these. Buying rechargeable C/D-sized batteries and the appropriate charger is a waste, unless you have devices that drain batteries fast enough to make it worth buying the "real" (and expensive) C/D-sized rechargeables, rather than the cheaper ones that are just basically...a AA rechargeable in a C/D-sized shell!The C spacers work fine; they're the same length as a AA battery, so there's no need for an extender, thus it's just a plastic clamshell. I imagine they might eventually break at the seam, but they'd still work just fine and safely even if that was the case.The D spacers are more finicky. As others have pointed out, the metal spacers have a tendency not to stay in place. Of the four D shells I received, one of them had warped plastic and a metal spacer that FLEW right out of the shell the first time I opened it. Even playing around with the plastic shell and bending the metal spacer, I couldn't get it to ever stay in place, and sticking it back in was a pain compared to the other three D shells due to how the plastic was warped.I ended up returning one set of these and keeping the other, since one of the devices I got it for won't be used much, so I just bought D-sized alkalines for it. I would buy these again if I did need more C or D-sized batteries in something where I was going through batteries more frequently, but not fast enough to bother with C/D rechargeables.In short, these spacers are cheap, work okay (though quality control is lacking), and seem to be the best option for the price. If you have a device that takes C or D batteries and doesn't drain a ton of power between uses, but does drain batteries fast enough for alkalines to be bad on both the environment and your wallet, then these are a decent option compared to actual rechargeable C/D batteries.8 Jun 2012 edit: I was looking at these again (while trying to find a new pair of D spacers), and noticed the price went up from $5 to almost $10! I would NOT buy another set at that price...at $5, they're okay, but not for $10.

At the time I ordered, the description on this item was lackluster at best.You receive 2 D-size adapters, and 2 C-size adapters in the package. Each one snaps over a standard AA battery, allowing use of your rechargeable AA's in devices that demand a C or D cell.Realize that you will be limited by power in a AA battery depending on the device that you are powering. These aren't magic, and there are no electronics associated with the adapters themselves. Their fit is solid, but I wouldn't say that these have extraordinary build quality. I am able to use rechargeable batteries in our baby swing, with no noticeable downside.These were cheaper and far easier to locate than the Sanyo Eneloop-branded adapters, but fill the same void.

When using the "C" shell on a AA battery, unfortunately the shell prevented the + end of the AA battery from sticking out far enough that it could make contact with the positive terminal in the device. This was because of the design of the battery compartment in the device. When I looked at the the converted AA against a regular C I could see that the positive terminal stuck out further on the C battery. By enlarging the hole at one end of the shell (with a craft knife) so that the AA battery could actually slide in via that end I got enough of the + terminal to stick out so that it worked.

The D-size cases work really well, better than other semi-transparent cases I have. The C-size case will work in a device that doesn't have a thick barrier in between batteries placed in series where the positve (+) "nub" has to reach the back of the negative (-) side. AA batteries are longer than C batteries, but, the C battery positive (+) connection "nub" is longer than the AA connection "nub", so the AA batteries might not reach in some situations. Also, since AA batteries are longer, you might need a device that has a spring or bending/springing metal where the batteries go so they can fit.

These converters do the job, but they're not the greatest you'll find, either. First, they only hold one battery unlike others that will use the extra room in the D-cell format to hold two AA's for longer life. Second, they snap together rather roughly and I can imagine them breaking eventually. Finally, they are a little bit larger than typical cells. They fit inside everything I've tried but it's a close fit.Overall, they're inexpensive enough and do accomplish their purpose, so they get 3 stars - just order more if they fail. But there are better ones out there.

These are nice spacers that completely encase the battery, unlike the Eneloop ones that that surround the battery with an open air case. Try aligning the battery contacts to the gadget contacts and you'll see how much of a pain in the butt it is to pop in with the Eneloops. These you can push right in and the contacts are wide enough that you don't have any misalignments the first go around. The biggest negative currently is that the plastic hinges break easily. Mine broke within the first five minutes of opening the package. Fortunately the case has a snug enough fit that it doesn't seem to entirely need the hinges to stay closed.

The C converters wouldn't work in a kid's toy that places the batteries side by side. The plastic casing prevented the positive node from making contact with the toy's metal contact plate. In a flashlight, where the batteries stacked on top of one another, these worked fine. It depends on what you're using them for.The D converters have metal spacers, which should prevent this kind of problem, but I see other people have trouble with those spacers staying in place.An interesting solution to buying C rechargeables, but not right for every use.