Features June 2001 Issue

Small Batteries, Chargers, and How To Recharge on Board

You can recharge household batteries with your 12-volt system via an inverter. Here are tests of nine chargers and a brace of batteries.

Nobody paid much attention when it started with portable radios, but then along came cellular and cordless phones, cordless tools, video cameras, CD players, laptop computers, toys and games, and for us, the handheld VHF, GPS and plotter devices. Where we once just plugged equipment into wall sockets, we’re suddenly inundated with battery requirements and it’s a chore to keep up. D’s for this, C’s for that, AAAs for those and AAs for these. Or it might be a 9-volt or a custom battery for which the replacement must be found in a catalogue the size of the New York City phone directory. As the Radio Shack guys will tell you, the phone industries are the worst. They have a special battery for every unit ever created and no two are alike. 

Large general purpose chargers tested, clock-
wise from left: Ray-O-Vac 3 in 1 Power Station
PS3, Radio Shack #23-233, Millennium Rapid-
charger, Golden Power Model CKB-8A, Accucell
ACL2000, and in the center, the Ray-O-Vac Re-
newal Power Station.

Kudos to the marine industry. Years ago, we urged them to get away from the unique rechargeable battery pack and go with standard cells. (It makes economic sense not to have to supply a battery charger with each unit sold.) Almost everything now works with standard alkaline or re-chargeable nickel-cadmium batteries, or both. In addition, the semi-conductor industry has created devices that operate at voltages considerably lower than ever before, which means that handheld electronics can make better use of battery energy than ever before. Portability has become more practical and widespread than ever.

The Boat Owner’s Problem
You can stow away a large cache of single-use batteries, of course, but disposing of them is rough on the environment. It’s better to use re-chargeable batteries wherever possible.

But how? With a 12VDC lead-acid house battery as your only energy source, how can you keep small batteries charged? And, if you find a charger with a 12V cigarette-lighter plug, will it be an unrealistic drain on the ship’s electrical system?

The Tests
First, we scoured local stores and collected some universal battery chargers capable of charging just about any type of standard rechargeable battery. (We zeroed in on some chargers for AA only, since this is becoming the battery size of choice). Then we discharged and recharged a lot of batteries in a quest to find the most efficient brands of chargers.

Next, we studied the different battery technologies to see if one type had an edge on longevity over another. Using the clock-test method employed in our battery evaluations reported in the October 15, 1998, June 15, 1995 and October 15, 1995 issues (see sidebar, page 28), we compared the predicted life spans of various rechargeable nickel-cadmium (NiCad), nickel metal hydride (NiMH), and alkaline batteries.

Last, we used our different chargers to charge both the best and worst of the batteries to see if there were difference in efficiency or energy gain.

What You Need To Know
Battery types and performance attributes vary in some important ways. Regardless of manufacturer, the following are significant characteristics the user should know:

• Unless a product spec specifically advises differently, any of the NiCad, NiMH or rechargeable alkaline batteries will work. Only the operational longevity will differ.

• NiCad batteries still suffer from a memory problem. The battery will remember how far it was initially discharged before being recharged, and because the crystal structure on the electrodes has been altered, it will not accept a full charge. The “fix” for this problem is that usually (but, not always) the battery can be saved if it is completely discharged before being recharged again. The NiCad user must be prepared to further discharge his batteries after his equipment has stopped working.

• NiMH batteries were created to replace NiCad units in some applications, mostly because they don’t pollute the environment when trashed. NiCads are about 20% cadmium—a very poisonous heavy metal—and they must be disposed of properly. Because of their low internal resistance, however, NiCads are still best for short-duration, high-current applications such as cordless tools. NiMH batteries will perform in the same sockets but not as well.

NiMH batteries don’t have a memory problem. They can be recharged from any state of discharge and perform like new to full capacity.

• NiCads and NiMH batteries are both 1.2V when fully charged, while rechargeable alkalines are nominally 1.5V. Any charger specified to charge a NiCad will charge a NiMH as well. Alkaline batteries, however, must have a charger unique to their needs since they are charged to a higher voltage and require pulsing for an efficient charge. They should be periodically measured to avoid overcharging.

• NiCads and NiMH batteries both have a high self-discharge rate—about 1% per day—and should be freshly charged prior to use.. Fully charged alkalines have a very low self-discharge rate and can be stored for years prior to use.

• If the charging current for both NiCads and NiMH batteries is set so that it takes 12 or more hours to fully charge them, they will not be damaged by overcharging. Currents higher than this rate can overheat the batteries during extended charging, which may cause them to fail prematurely. (We proved this with NiCads manufactured in the 70s. They were inadvertently left in a back room wall socket charger for 10 years and then tossed into storage for another 10. We dragged them out for this study, recharged them, and they performed like new!)

• High-current rapid charging of NiCads and NiMH batteries of any size will shorten their life considerably and is not recommended.

• Rechargeable alkaline batteries must be fully recharged before storage for any length of time. A few days won’t matter, but leaving a dead battery in equipment for off-season storage is asking for trouble. As an experiment, we intentionally stored rechargeable Ray-O-Vac D cells for a year; four cells were fully charged and four were not. The four discharged cells soon swelled and cracked and issued a corrosive powder that would decimate a battery holder. The charged cells still work well.

What We Want
Not all battery chargers are alike…but they are close. The following is a list of the general characteristics we’d like to see in a charger to make it most useful on a boat.

• Ideally, make it a 12VDC plug-in unit capable of charging any and all types and sizes of batteries.

• Provide a reasonably quick charge time and make it turn off after it’s done. Eight hours is better than two days but super fast chargers (one or two hours) can and will shorten the life of our batteries.

• Provide a charging indicator so you’ll know when the cycle is complete.

• Be efficient and not over-tax the house battery.

• Be cost-effective.

Product Reviews
Despite all of the devices available for recharging small batteries, very few are marketed to the sailor wishing to use his house battery bank as the direct charging source. The Radio Shack catalogue lists a Travel Charger (#23-034) for charging AA and AAA NiCads and NiMH batteries from a 12VDC lighter outlet, but it is not yet available.

We found one other that charges only NiCads and NiMH cells of any size, and another that can charge NiCads, NiMH and alkaline rechargeables. Beyond that, all the rest are powered by plugging into a 110VAC wall socket.

This led us to test some chargers fed from an inexpensive inverter that converts 12VDC to 110VAC. These units, which are available everywhere in places like Wal-Mart, cost between $35 and $40 for the 140-watt model, which is the lowest power available. The design of these small inverters has been fixed for years and they are very much alike. They are extremely efficient. Our 140-watt Prestone burns just 1.2 watts unloaded. This makes an AC charger very feasible for the sailor with a house battery.

General Purpose Chargers:
Accucell MultiSystem Quick Recharger ACL 2000.
9-5/8"W x 5"D x 2-1/2"H. $99. We expected this unit to be the flagship of this report in spite of its $99 cost because it is the only 12VDC unit we found that will charge all sizes and technologies of batteries, including 9V. It will operate from 110VAC as well, or any solar panel capable of 1 ampere (or more) output at 12VDC to 16VDC. And, it will charge from two to eight AAAs, one to eight AAs and anynumber of one to four C’s or D’s, as well as one or two 9V cells.

A push-button switch allows you to select either NiCad/NiMh technology or alkaline. A red lamp indicates that charging is in process and a green lamp indicates that charging is complete. A blinking green light indicates an error; the unit has to be reset by pulling the plug and re-inserting it.

Because this charger won’t know which power source the user will plug into, it has a built-in oscillator of around 28Khz to create the pulses needed for charging alkalines. We watched it on an oscilloscope as it turned itself off every 1/3 second or so to measure the state of charge.

We discharged and recharged many alkalines manufactured by Ray-O-Vac and Accucell, plus we cycled NiCads and NiMH units. That was when the first problem surfaced.

As sophisticated as this unit is, it cannot distinguish between good and bad batteries as other chargers can. If one battery in the bunch is bad, the unit will keep charging all of them in an effort to make the bad battery respond.

To test for this, we were fortunate enough to get a faulty Ray-O-Vac alkaline D cell right out of a new package.

(In comparison, the Ray-O-Vac charger has a lamp for each cell that told us the battery wouldn’t accept a charge; the Accucell charger could not without singly testing each battery and waiting for a result.)

Problem #2 was that our unit seemed to occasionally forget what we hired it to do. When we loaded it with discharged batteries, it often wouldn’t start until we reset the internal processor by unplugging the power source. Then it would recharge the completely discharged batteries in just a few hours and we were quite pleased until, after a couple of months, it refused to work altogether.

We’ll be exercising the 1-year guarantee for a replacement unit to see if it fares any better. Because of its high cost and inability to flag a single faulty battery, however, we’re not enthusiastic about this model…despite its wide-ranging capability.

Ray-O-Vac 3-in-1 Power Station PS3. 3-1/2"W x 8-5/8"D x 2-3/8"H. $20. It’s hard to beat this versatile unit, which will charge any technology battery of any size except 9V cells. It will take from one to eight AAA or AA cells or one to four C or D cells. The only restrictions are that sizes and technologies can’t be inter-mixed. Amazingly, it will sense if alkalines are being charged and it will take them up to just over 1.5V before the lamp for each battery extinguishes.

Conversely, it charges a NiCad or NiMH battery to nearly 1.3V before the lamp turns off.

There are no switches for selecting the type of battery to charge.

Compared to the Accucell charger, this model takes about 8 hours to recharge a set of depleted D cells where the Accucell charger did it in 5. Further, this unit only works from 110VAC (it needs AC to generate the alkaline pulsing), but we were delighted with its efficiency using an inverter feed; the system consumption started out at 11.8 watts and dwindled to 7.5 watts as the batteries reached full charge. (For comparison, the typical anchor light is 10 to 12 watts).

We recommend it for use at home and with an inverter on a boat.

Golden Power Model CKB-8A-7C NiCad Charger. 8-1/4"W x 3-3/4"D x 2-1/4"H. $18.50. This 12VDC plug-in charger can handle either NiCads or NiMH cells in pairs. Two or four batteries of AAA, AA, C or D type can be charged as well as a pair of 9V cells. They can’t be mixed in a channel but they can be mixed in the charger. For example, two AAs can be charged with two D’s in separate channels where there is one charging indicator light per channel. The light tells you that charging is happening for the two installed cells.

The Golden Power utilizes the principle we pointed out in our home-made charger described in the sidebar. You don’t need to be too concerned with overcharging because you get to decide when it’s done. They spec it as a 7-hour charger but say it’ll take 7 to 8 hours to charge a set of batteries. You need to unplug it at that time because there is no automatic shut-off and the charging lights stay lit as long as the unit is plugged in.

House battery power consumption went from 7.46 watts to 5.75 watts as a set of four NiCad D cells reached full charge. Of the depleted cells we charged, they were fully charged after 8 hours.

For the attentive boat owner using just NiCads or NiMH cells, this unit is recommended.

Radio Shack Quick Charger #23-233. 9-1/4"W x 5"D x 3"H. $28. This 110VAC 5.5-hour NiCad charger allows you to charge one or two 9V cells and from two to six AAA, AA, C or D cells. It has three different compartments; the same size must be installed in a compartment. They don’t say so, but it’s also advisable to have the same count of batteries in each compartment. That is, if you’re charging 3 D cells in one compartment and want to charge AAs in another, put in three AAs.

To complete a charge, the unit has a timer that is push-button activated.After 5.5 hours, you’re done, whether the batteries are or not. We don’t see a problem with this since the charging currents are relatively high. However, you might have to add a cycle to some high-capacity cells.

There is a charging light for each channel that indicates charging is taking place. If the light fails to light upon start, it means one or more of the batteries is making poor contact and the contacts need to be cleaned (use a pencil erasaer). The unit then has to be unplugged and the cycle started anew.

The company says this charger is for NiCads only, but we found it charges NiMH cells equally well. The inverter feed tests we did showed the total power consumption to be about 18 watts when charging six depleted cells; this figure dwindled to around 13 watts at full charge. We recommend it.

Millennium Rapidcharger Power System. 7-1/4"W x 3-1/2"D x 2-3/4"H. $20. This is a 3-hour charger for NiCads in pairs from AAA, AA, C and D sizes, plus it can charge one or two 9V cells singly. There are two channels for a pair. A red light indicates charging is in progress; the light turns green when charging is complete. This charger has been on the market for some time and is still available through some outlets. It doesn’t specify NiMH batteries in its capabilities but we found it handles them quite well. The charger tells you when it’s done, and it only consumes about 16 watts from the house battery when used with an inverter. Recommended.

Ray-O-Vac Renewal Power Station. 7-1/4"W x 8-1/2"D x 2-1/8"H. $20. This unit also has been on the market for a few years and can be found at some retail outlets, although it has been made obsolete by the Ray-O-Vac 3-in-1 Power Station model described above. It can handle any combination of eight alkalines (only) of any size from AAA, AA, C and D in separate compartments.

A red light for each battery lights when charging is in progress and extinguishes when charging is complete. AAs and AAAs take up to 5 hours and C’s and D’s 10 to 12 hours.

This unit worked well with the inverter, but with a full complement of D batteries the system power consumption was more than 26 watts.

We don’t recommend it since it can only charge alkalines and the replacement model, Model PS3, is more versatile.

Unique Chargers
Also available are a host of compact chargers. Some plug directly into a wall socket while others have a power cord. Radio Shack alone has eight units priced between $8 and $35. Their only differences are the number of cells they hold and the time to full charge. The costlier chargers are microcomputer controlled so that the charger turns off when charging is complete. The cheaper units have a timer that guesses when time’s up.

Categorically, all of these units (except Radio Shack model #23-034, unavailable at this writing) operate from 110VAC and any one of them will draw considerably less power from the suggested inverter-fed system than the general purpose units reviewed above.

Two Radio Shack units (#23-335 and #23-419) offer a unique feature called “Battery Conditioner” which discharges NiCad batteries before the recharge cycle begins. Because this is a timed function, both units presume the batteries have been well discharged before installation and they then pull them down further. Unfortunately, there is no assurance the batteries have been discharged to absolute zero, which is the best point to begin re-charging NiCads. We found it easier—though a bit inconvenient—to either use a penlight flashlight or wrap our NiCads in tin foil for a while before charging. This assures they are first discharged to absolute zero.

Ray-O-Vac 3-in-1 Charger Model PS1. 3"W x 1-1/4"D x 4-3/4"H. $10. This compact wall plug-in unit is the little brother to the PS3 model reviewed above. It can charge any technology (NiCad, NiMH or alkaline) of one to four AAA or AA cells in any combination. A red light per cell indicates charging; the light goes out when charging is complete. And because it’s microcomputer controlled, the cell is full when it’s done. Our tests showed charging times varied between 5 and 10 hours depending on the capacity of the batteries. Maximum system power drain with the inverter was around 4 watts. This is our top-rated AA charger.

Energizer ACCU-Rechargeable Model 5H27. 2-5/8"W x 1-5/8"D x 4-1/4"H. $17.50. This compact wall plug-in unit is typical of what’s available on the market for charging NiCads and NiMH batteries. It can handle AAs or AAAs (in pairs only) or one or two 9V cells. A red LED glows when charging is underway and a 15-hour timer terminates the charge. Power drain on our system was just a few watts, and this model or any similar model from Radio Shack might be your choice if you need to charge 9V cells as well. Recommended.

Radio Shack Digital Camera Battery Charger #23-033. 2-1/4"W x 2-1/4"D x 4-5/8"H. $22. We reviewed this wall plug-in unit because it’s typical of what we’ve seen in photography shops. The charger purports to be unique for digital cameras, perhaps so it can be priced higher. In fact, it’s not special at all. It will charge two or four AA or AAA NiCad or NiMH cells and it has a switch for the user to select between the two. All this switch does is change the timer from 7 hours for NiCads to 13 hours for NiMH.

The instructions tell you that you might have to unplug the unit and plug it in again to start a new charging cycle if your batteries are heavy capacity.

We’d rather charge our batteries with a processor-controlled cycle. There’s nothing particularly unique about the cells used by digital cameras and this charger is not our favorite.

The sailor will find many different small battery chargers on the market that can do the job at home or on his boat. Most require 110VAC power so a small inverter will be necessary. Because the inverters are so efficient in this application, we don’t see an urgent need for 12VDC-powered chargers —although we’ll be interested to see Radio Shack’s upcoming TravelCharger.

We didn’t find any charger in our collection that had a clear energy-efficient edge over others. All fell within a very satisfactory range. We do recommend processor-controlled chargers as opposed to a timer. This way, you know your batteries are fully charged when the lamps go out.

We don’t recommend expensive specialty chargers that target a specific application. These are marketing ploys. And don’t believe battery manufacturers’ claims that their batteries perform best when charged in their own chargers. This is another ploy.

We’re delighted to see Accucell come to the market with a rechargeable alkaline better than Ray-O-Vac’s (see sidebar, “A Study of D and AA Rechargeable Batteries”) but we’d use a Ray-O-Vac charger to maintain it.

Some equipment requires alkalines and these rechargeable cells will likely yield a longer service period than our tests reflect because they may well operate under 1 volt.

We’re also glad to see Energizer produce a strong rechargeable NiMH battery that competed for best against the single-use alkalines.

The Radio Shack batteries tested, though rankedsecond, are acceptable as well.

Also With This Article
Click here to view "A Study of D and AA Rechargeable Batteries."
Click here to view "Charger Specifications."
Click here to view "A Word About Our Tests."


Contacts- Accucell-USA Inc., 24924 Independence Dr. #6301, Farmington Hills, MI 48335, www.accucell-usa.com. Ray-O-Vac Corp., Madison, WI; 800/237-7000; www.rayovac.com. Millennium Power Systems, PO Box 147116, Gainsville, FL 32614. Golden Power, Applied Power Corporation, 1210 Homann Dr. SE, Lacey, WA 98503; 360/438-2110. Radio Shack, Division of Tandy Corp., Fort Worth, TX 76102; 800/843-7422.

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