Rayovac (PS3) Universal Smart Battery Charger

[IMPORTANT NOTICE on Jan 1, 2010]:I've been informed (thanks to Domenico Perrella) that the item being shipped now is the 'PS3D', which is an inferior product compared to the 'PS3' described in my original review. If you have ordered the PS3 but received the PS3D instead, return it to Amazon for a full refund - on the ground that the product description does not match the product received.[Original Review follows]I already have at least half a dozen smart chargers in the house, including top-of-the-line models such as the La Crosse BC-900 and Maha C9000, but I still wanted this Rayovac Universal Battery Charger (PS3) for the following reasons:1. It can accept C, D, and 9V batteries in additional to the standard AA and AAA cells.2. It can handle rechargeable alkaline cells in addition to the standard NiMH or NiCd cells.3. It has the potential to recharge up to 8 AA or AAA cells at once.So far, I'm very satisfied with this charger. Of course it is bulky and heavy. But that's to be expected for an unit that can accept four D-cells at the same time. For home use the size and weight is not an issue at all.I'm happy to report that this charger is a lot smarter than I previously imagined. Unlike a typical dumb charger in this price range (for example: the Energizer CHFCV Overnight Family Charger), the PS3 has four independent charging channels. That means I am free to charge different cell in any channel. Each channel comes with a status indicator LED, which goes out once the cell is fully charged. But most of all, this charger is smart enough to recognize the difference between NiMH cells and alkaline cell, and can pick the correct charging method accordingly.When an unknown cell is inserted into the PS3, the charger first starts off with a trickle current (800mA peak current at 10% duty cycle, or an average current of 80mA). Based on the voltage profile of this cell, the PS3 can determine whether this is an alkaline cell, or a NiMH cell. After two minutes, the duty cycle is increased to 60%, so the average current is now around 480mA. For a NiMH cell, charging will continue until a negative dV/dt is detected, in which case it switches back to trickle current again. But for an alkaline cell, charging current will gradually decrease with higher terminal voltage until it reached 1.65V.The Rayovac PS3 is designed to recharge the Rayovac 'Renewal' brand of rechargeable alkaline cells (which are now discontinued). The user manual warned against charging ordinary disposable alkaline cells, but I experimented with it anyway. So far, I have observed very good results with recharging Duracell alkaline AA cells [see warning below]. Of course, the capacity of a recharged alkaline cell is lower than that of a fresh cell, and it drops with each subsequent cycle. But since I can squeeze another half a dozen cycles out of an exhausted alkaline cell at no additional cost, I really should not complain.Back to the charger itself, I do have a complaint about its claim of "recharge up to 8 AA or AAA batteries". It turns out that each of the four charging channels can accept one to two AA or AAA cells, but the two cells are electrically connected in parallel. So in case somebody accidentally placed two cells of different battery chemistries (NiCd, NiMH, or alkaline) in the same channel, the one with lower voltage will discharge the other one. The charger may also get confused and fail to terminate correctly in such case. It is safer and faster to charge only one AA or AAA cells in each channel.[WARNINGS:]1. Do NOT try to recharge alkaline cells that are completely exhausted (terminal voltage below 1V). It will not work.2. Do NOT try to recharge Energizer alkaline cells. Four Energizer AA cells I tested completely dropped dead after just two discharge/charge cycles. Two D-cells started leaking electrolyte a few days after charging. Luckily they were left outside and not being used.[Update on Jan 26, 2009]Out of maybe one dozen Duracell AA alkaline cells I have recharged, two started leaking electrolyte a few weeks later. I must now officially advise AGAINST recharging disposable alkaline cells: do it at your own risk!

This charger was purchased to help my church use NiMH 9-volt batteries in place of the disposable alkalines that had powered two microphone body-packs. (As a "green church," we are committed to reducing our impact on earth's resources wherever possible. We researched the various options and found that the nickel metal hydride chemistry has less impact than other types of batteries, and also offers desirable electrical characteristics for this type of application.)Rayovac Rechargeable NiMH Battery, 9-Volt Size, 1-Count Package (Pack of 3)The charger is well-built and solid. The power cord does not have a "wall wort" transformer on the plug, but rather a simple, detachable line cord. The compartments under the sturdy plastic cover can accommodate a variety of different battery types. It was blister-packed, and easily set up.The limitation is this: for a 9-volt battery, the charger has only a single set of terminals. Although it can take up to eight cells for smaller batteries, it can handle just one 9-volt unit at a time. This should not be surprising, as most other cells output 1.5 volts nominal.In practice, this is not a problem. A red LED indicator illuminates when a cell is attached. The charger's controls monitor the battery charge condition, and step down to a trickle mode when charging is complete. The LED extinguishes as well. A complete charge of an exhausted cell takes about five to seven hours to complete. For the three 9-volt cells we have in rotation (two in use and one in reserve), I can store all three easily in the charger body.This is a well-designed product, even with the one-cell limitation for 9-volt batteries, and it is already saving us money while it reduces our waste footprint.

It works, it is heavy so it seems good, but it takes a pretty long time to charge batteries. You can probably get away with a few hours for AA batteries but for anything larger than that, overnight is needed. I had a set of brand new AA batteries (did not come charged) so I charged them for the first time and I had to leave it overnight in that situation, too.For those of you buying the charger because you want to use rechargeable C or D batteries- did you know that the basic kind you'd buy at Walmart or Radio Shack have no more power than a AA battery? Look at the specs- you'll be surprised, I was. Essentially, these basic C and D's are nothing more than AA's in a larger sleeve!! (This is NOT true for the top of the line rechargeable C's and D's you can buy online at battery warehouses, and I don't think this is true for non-rechargeable, alkaline batteries). I had no idea until recently- otherwise, I wouldn't have even bought this charger. How you get around this is you can buy "adapters"/"converters" that are simple sleeves you slip your AA batteries into. Then, wa-la- you have C and D batteries, at a much lower cost (C and D rechargeables cost a LOT more than AA rechargeables). Search the web for a place to buy the converters- they are not carried in basic stores (or Radio Shack- the guy there didn't even know what I was talking about).