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(Real) Intelligent NiMH Chargers?

Cliff posted more than 10 years ago | from the juicing-up-those-cells dept.

Technology 58

Anti_Climax asks: "I, like many Slashdot readers, have a lot of battery powered devices. With the large number of cells that are in use at a given time, I have taken to using NiMH rechargeables (Ten 2.0Ah Cells for $10 at the local Fry's Electronics). My current charger is a timed unit that was made when 1.3Ah was the norm. I have accepted the fact that if I want my cells charged properly and quickly, I will need to invest in an intelligent charger. With the dozens of manufacturers in the market right now, the Google results are promising but far too broad. What have been your personal experiences in this area? How many of the supposed Smart Chargers are anything but? Who's offering the best deal for my dollar? While I don't need my cells to charge in 15 minutes, I would like to find an inexpensive Intelligent charger that can charge 4 or more high capacity cells (in pairs or individually) in an hour or less."

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Kinda of a dupe (5, Informative)

xDCDx (635101) | more than 10 years ago | (#9536375)

This subject was covered a while ago in this ask slashdot [slashdot.org] . I remember because I bought my charger just after it being published.

My advice is that you just buy whichever one that *clearly* states that is microchip (that is deltaV) controled rather than stopped by timer. Mine is a Hama and it works well.

For the batteries, check this comparison [imaging-resource.com] . To sum it up, the more mAh the better, brands are usually not that important.

Wal-mart Duracell charger (3, Informative)

alienw (585907) | more than 10 years ago | (#9536401)

The Duracell charger that is sold at wal-mart for $23 (it comes with 4 batteries) is a good cheap one-hour CPU-controlled charger. It can do 4x AA or AAA size, NiCd or NiMH. I know it's DeltaV because if you take one battery out for 5 minutes while it's charging, and put it back, it will take exactly 5 minutes longer to charge than the others. I think it should work fine with high-capacity batteries.

A related topic ... (1)

jc42 (318812) | more than 10 years ago | (#9536717)

... is that it would be useful to find a good, compact case for carrying batteries. I often carry 2 or 4 spare charged AA batteries in a pocket, and on several occasions I've found myself with a pocket full of very hot batteries. They seem to be able to move themselves into a configuration that results in a discharge. Aside from the annoyance, this doesn't seem very safe.

I do have a couple of large bags that have a set of straps for batteries. But that means carrying a huge bag just to transport a few batteries. What would be nice would be a cheap plastic box just big enough to hold four AAs and protect their contacts. I've been on the lookout, but I haven't seen this for sale anywhere.

I wonder if there's a Tupperware container of the right size? ;-)

Re:A related topic ... (2, Informative)

Black Perl (12686) | more than 10 years ago | (#9536787)

You mean like this [inanycase.com] ?

Re:A related topic ... (1)

billcopc (196330) | more than 10 years ago | (#9536973)

Try carring two GBA battery packs, with those stupid little contact pads.. 2 years later my thigh is still dark pink from the boiling acid. It didn't help that I "ignored" the problem for a few minutes thinking it was just the midday sun. Yeah, 4 years of crack will do that to a nerve.

The worst is that now I have no battery pack for the GBA. Batteries suck.

Re:A related topic ... (2, Informative)

arnex (238036) | more than 10 years ago | (#9537294)

What would be nice would be a cheap plastic box just big enough to hold four AAs and protect their contacts. I've been on the lookout, but I haven't seen this for sale anywhere.

I have. It's called a Q-Tip travel pack. Go to your local drugstore and look for a $1 package of 30 Q-Tips in a plastic box with a flip up lid. Open box, discard Q-Tips, insert 6 AA batteries. They'll rattle around a little but it's as good a fit as you're going to find for the money.

Re:A related topic ... (0)

Anonymous Coward | more than 10 years ago | (#9540613)

Simplest answer for shifting batteries - use a rubberband to secure them :)

Just grab a rubber band, and loop it around one battery, and twist loop it around the second, etc.

takes almost no time, and it is a simple way to ensure they don't move in relation to eachother. You can then just stick 'em in a container if you want. (Or wrap 'em in a piece of cloth held by yet another rubber band!)

Rubber bands - all the use of string with none of the time of tying them!

Re:A related topic ... (0)

Anonymous Coward | more than 10 years ago | (#9540641)

compact case for carrying batteries

1. Buy a pack of ordinary batteries that comes in a plastic clamshell.
2. Carefully pry the cardbaord surround away and pry out the staple holding the clamshell together.
3. Remove the ordinary batteries and replace them with your rechargables.
4. Hold the pack closed using an appropriately-sized rubber band.

Re:A related topic ... (1)

Webmoth (75878) | more than 10 years ago | (#9550803)

I've found that a 8mm cassette case (the kind for Exabyte-style drives) is the perfect size for holding 8 AAs (need to put them in (-) ends together), but it's probably a good idea to throw a rubber band around it for safety.

Re:A related topic ... (1)

Gavin Miller (702821) | more than 10 years ago | (#9552737)

I have a little square plastic container with tabs inside to keep them inside that came with my digital camera... I imagine you could find something similar at a electronics store or in Ritz Camera etc.....

Re:no CPU involved (1)

Splork (13498) | more than 10 years ago | (#9537796)

a simple analog circuit to switch from high to low (trickle) charging current is all thats needed.

any charger that uses a timer is silly.

fyi, frys carries 2300mAh batteries now.

Re:no CPU involved (3, Informative)

alienw (585907) | more than 10 years ago | (#9539599)

It's not that simple. You can't just terminate the charge when the battery reaches a certain voltage. You have to monitor the battery voltage and detect when the voltage slope either becomes negative or decreases. Plus, you need things like cool-off periods, reverse protection, dead battery detection, and so on. A microcontroller makes things much simpler and cheaper than an analog circuit. Plus, it can charge multiple types of batteries.

Rayovac (2, Informative)

Syris (129850) | more than 10 years ago | (#9536605)

I have a Rayovac charger that I'm quite happy with. It's a 'smart' charger that'll charge NiMH batteries in about an hour individually, up to four at a time.

The model number is PS4. Info here. [rayovac.com]

I got mine at Walmart for under $30 with a couple batteries.

Re:Rayovac (1)

PD (9577) | more than 10 years ago | (#9538499)

I've got one of these. About 1 time in 5 it would never shut off, cooking the batteries. I finally got sick of it ruining my cells, and bought an inexpensive trickle charger (Maxell Ni-MH & Ni-Cd model P2000). It's never failed to shut off.
And I can easily live with the very long charge times.

Check out your local hobby shop (1)

stienman (51024) | more than 10 years ago | (#9536622)

I got a very nice intelligent charger from my local hobby shop. It'll do ni-cd and nimh, and has 10 user defined programs. I got it for speedy charging of bicycle headlight battery packs for a 24 hour race and a full-duplex wireless intercom system, but it works great for any pack up to 8 cells.

It stops on delta v or capacity - you program in that your packs are 2AH and it'll stop after delivering that much capacity if delta v doesn't stop it first. You can program the charging current and the delta v trigger. After the charge it complete it'll perform a trickle charge as long as the cells are connected so you know they won't self discharge and you don't have to worry about leaving them on for too long.

And it has reverse polarity and short circuit detection and protection.

I've been very pleased with it. It was about $50, though, but for such a useful charger it was well work it. You can certianly find less expensive models that will automatically charge the cells you have. I like the configurability, but I have lots of different packs in lots of different configurations.

-Adam

Re:Check out your local hobby shop (1)

Anti_Climax (447121) | more than 10 years ago | (#9536680)

Is it made for packs of cells or for individual cells? Mine aren't configured in packs of any number and I can't gaurantee that they are at the same level of discharge if I were to put them together for charging.

I think we may be speaking of different areas of battery tech.

Re:Check out your local hobby shop (3, Informative)

stienman (51024) | more than 10 years ago | (#9536984)

It charges according to current, there is no configuration for pack size. You can charge a single cell, or you can charge many cells.

You'll find that the vast majority of chargers put batteries in series for charging anyway. You'll have a hard time finding a charger that has four single cell chargers - it'll have one charger and either parallel four batteries into two sets of two series, or put all four in series. Either situation doesn't provide a great charge.

The trickle charge at the end of the full charge should equalize the individual cells in series.

So put them in parallel, set the capacity limit to the least discharged battery (ie, if one is still 3/4 full then set the limit to charge up to 500mAH) and then let it trickle charge for another few hours.

Either way, there is no consumer charger out there which will charge each cell individually - it doesn't make economic sense to sell high qaulity chargers because in the end the consumer isn't willing to pay 2-3 times the cost of a similar cheap charger - especially when you consider that they are buying rechargeables to save money.

Buy a good intelligent charger if you want your cells to last. If you want to be really anal about it, charge each cell individually. You won't find a cheap charger that will do that for you.

If we are talking about different areas of battery technology then it's probably because you don't understand battery technology. I can see why you're asking slashdot for battery charger recomendations - you don't understand battery charging so you hope to purchase a device that will do all the work for you. But then you state you have all these 'special needs.' Until you understand how batteries and packs work and how charging works then you won't be able to determine what a good charger is, or how to correctly use one if you happened to buy the right one for your needs. We can't help you any more than you can because you haven't really defined your needs.

For this reason I suspect you'll be best served by a simple intelligent charger such as one sold by radio shack, sam's club, or batteries plus. You don't have to understand how the cells work, how charging works, or anything more difficult than plug-n-chug.

If you want the batteries to get a full charge, if you want them to be conditioned so you can use the full capacity, if you want them to last through hundreds of charges, if you want them to be well matched, if you want them to charge quickly, and if you want to charge them without observation and not worry about leaving them on for 'too long' - learn more about how an intelligent charger works, and then buy a good intelligent charger. Those higher end models made for radio controlled cars are good for this because they follow one of the 'ideal' charging algorithm and are fairly configurable and feature complete.

But that's kind of like setting up a Linux firewall when what you really want is to buy a linksys router with built in sort of decent firewall. In the end you need to decide whether your time and energy in going over the learning curve is worth the benefit. If you aren't going to learn, then you'll not only find the linux solution more confusing, you also risk doing it wrong and making the situation worse than it is.

-Adam

Re:Check out your local hobby shop (1)

Anti_Climax (447121) | more than 10 years ago | (#9537599)

learn more about how an intelligent charger works, and then buy a good intelligent charger. Those higher end models made for radio controlled cars are good for this because they follow one of the 'ideal' charging algorithm and are fairly configurable and feature complete.

The whole purpose of this submission was to get other readers experiences with intelligent chargers, for my benefit as well as that of others. From your original post I got the (mistaken) impression that the charger you were recommending was solely for multi-cell packs for RC cars and the like.
My apologies.

Re:Check out your local hobby shop (2, Informative)

evilviper (135110) | more than 10 years ago | (#9540464)

You'll find that the vast majority of chargers put batteries in series for charging anyway.

Hmm... No, that's not true. In the past, most charged in parallel, but not serial. Today, most charge individually, and cheap ones charge only in sets of 2.

You'll have a hard time finding a charger that has four single cell chargers

No, not even slightly. I know my Energizer 1hr NiMH charges each of the 4 cells individually, and I suspect so to do the Duracell chargers. They aren't very expensive, and are found just about everywhere now. Besides this one, I know that most, if not all "smart" chargers these days handle batteries individually... Having twice the circuitry is really no big deal (ie Charging 4 individual, vs 2 in pairs).

Either way, there is no consumer charger out there which will charge each cell individually

No. There are lots, and they've been around for a long time.

Re:Check out your local hobby shop (0)

Anonymous Coward | more than 10 years ago | (#9552445)

Either way, there is no consumer charger out there which will charge each cell individually

You are a little out of date. For example, see the Energizer CH30MN smart charger [energizer.com] , which charges 4 AAs or 4 AAAs individually in 30 minutes. I saw some for sale at Best Buy a couple days ago. Even Wal-Mart sells Energizer 2300 mAh NiMHs (at rather low prices too).

I think Energizer and Wal-Mart fall under the definition of "consumer".

just use IC3 (1)

XO (250276) | more than 10 years ago | (#9536639)

For AA and AAA batteries, use IC3. The IC3 chargers will charge standard batteries in about 4 hours, and IC3 batteries in 15 minutes. The cost differential is virtually negligible.. really. A 4-bay IC3 charger, and a couple sets of IC3 batteries will run you about $60-80 depending on what you get.

If you need something that does other sizes, that's different.

C. Crane QuickCharger (2, Informative)

Katravax (21568) | more than 10 years ago | (#9536646)

This one is excellent and well-reviewed in a number of publications: http://www.ccrane.com/quick_charger.asp [ccrane.com] . I have had mine for a while now and can attest it's excellent. It handles from four AAA through 4 D-cells. It has a slow-start (which prevents the batteries from getting hot), and for NiCd, it even discharges the batteries to 1.0V before recharging them. The spring clip is VERY strong, which helps assure good contact (at least I assume that's why they're so strong). You can leave the batteries in it, too, and it will keep them topped off.

It's not cheap (US$40) but it's been well worth it to me. I use rechargeables for everything and in every size except 9V. I get my batteries from http://www.batteryspace.com/ [batteryspace.com] . I like the AA 2250 mAh (currently 24 for US$30); they seem to last forever in my digital camera. My 11-year old daughter goes through batteries like crazy for her CD player, radio, clocks, toys, and flashlights, and going all-rechargeable was one of the best moves I ever made. I do keep a spare set of alkaline D-cells for my radio in case of extended power outage, but haven't had to use them yet (My 8 9500 mAh D-cells, like the A-cells, seem to last forever.

The C. Crane charger says it only does NiCd and NiMH, but I also recharge "rechargeable Alkalines" http://www.rayovac.com/products/recharge/rec_alk.s html [rayovac.com] in it with no problems.

Don't use rechargeables for all needs (4, Informative)

Tux2000 (523259) | more than 10 years ago | (#9537944)

I use rechargeables for everything and in every size except 9V.

Rechargeables are not the best idea for low(est) power devices. A common TV remote control operates on two, sometimes three Alkaline cells for two or three years, sometimes even longer. Most, if not all, remote control chips are optimized for this operation mode. True, if you press a button on a remote, it draws a lot of power for the infrared LEDs. One ampere is not unusual. But it sends very short pulses (or else the LEDs would literally burn), and the real power does not come from the battery, but from an electrolyte capacitor contacted in parallel, via a very small resistor, to the battery. It is rapidly discharged by the LEDs, and then charged again by the battery. The battery just has to provide a very small current to recharge the capacitor after each pulse, and an even smaller, permanent current for the controller chip. Alkaline cells have a very low self-discharge factor, so they can work like this for years. The remote control continues to work even if the alkaline cell is nearly dead (1.3 V), but with a reduced range (because of the lower available energy due to the lower voltage) and with a noticeable recovery time. When the voltage is so low that the chip does not work properly, it starts to send nonsense to the TV (and may under certain circumstances crash the microprocessor inside the TV - nobody is perfect).

If you replace the alkaine cells with NiCD or NiMH, this lowers the available voltage by 0.3 volts per cell (NiCD=1.2 V, alkaline=1.5 V), thus reducing the available engergy for the LEDs, thus reducing the range of the remote control. Those rechargable cells discharge themselves, so you need to recharge them often. But at that time, you want to use your remote control as well, so you need two pairs of rechargeable cells, and you need a charger. Probably a good one, so it does not kill your cells while loading them. And after some time, your rechargeables are dead because they had nothing "to do". So you need two new pairs of cells, probably after two years. Just about after the same time that you would have bought the first new pair of alkalines (the first one is usually included).

Just calculate for yourself: Using rechargeables in remote control is nonsense. And if you are concerned about the environmental impact: At least here in Germany, there is a well-working return system for alkaline (and zinc carbon) cells (in fact, you have to return your used cells).

The same is also true for other low(est) power devices, like clocks and calculators with liquid crystal displays (LCDs), and most analog quartz clocks. Radio controlled analog clocks need a little bit more power and a "high" voltage for the receiver, so they can not drain alkaline cells as much as clocks without receiver and remote controls.

My "BRAUN" electical toothbrush uses a single NiCd cell which is permanently charged when it sits in its "docking station". After about one year of permanent "keep alive" charging, the cell is now nearly dead. It still can hold enough energy to work for five minutes, but when it is disconnected from the wall outlet for more than a few hours, it simply does not work and needs two days to recharge. The cell is sealed into the toothbrush, having a predetermined breaking point in the case to take out the cell for disposal, so I can not replace the cell without permanently damaging the toothbrush. A trick I've seen too late on TV: Do not permanently charge the toothbrush, discharge it while using, and connect it only to mains when it is empty. It will need round about a day to charge. This will avoid the memory effect.

About batteries and cells:

A cell consists of two electrodes (the positive anode and the negative cathode), the electrolyte, and a case. Depending on the materials used, a single cell has 1.2V (NiCd and NiMH), 1.4V (zinc air button cells), 1.5V (alkaline and zinc carbon), 1.55V (Silver / Quicksilver button cells), 2V (Pb=lead acid), 3V (Lithium), or 3.6V (LiIon). Other voltage are possible, but unusual. NiCD, NiMH, lead-acid, and LiIon are rechargable, alkalie cells can be tortured to recharge, with a big loss of capacity and only for a few recharge cycles. There are Lithium cells with 1.5V, and LiIon cells with 3.0V, both obviously with a different chemistry. And there are LiIon cells with 3.7V, but that may be just good marketing. ;-) Using zinc carbon cells is usually not recommended, they discharge themself very quickly and store only little energy. Their only advantage is that they are a little bit cheaper than alkaline cells.

A battery is a set of cells, often in a common case. In your car, you will find a lead-acid battery (for the starter) composed of six lead-acid cells, forming a 12V battery (with 13.8V when full charged and 14.4V during charging, i.e. when you drive). A 9V block used in many toys and some remote controls is a real battery, composed of six alkaline or zinc carbon cells, or three lithium cells. A rechargable "9V" block combines seven NiCd cells, resulting in not more than (*drum roll*) 8.4V. All those A, AA, AAA "batteries" are technical no batteries, they are single cells. Inside your PC, you may either find a single LiIon cell or two or three NiCD cells to supply the real time clock and the CMOS ram.

Tux2000

Re:Don't use rechargeables for all needs (1)

Veramocor (262800) | more than 10 years ago | (#9543984)

I did see one manufacture that had a NiMH 9.6V, I guess they added an extra cell.

Maha (3, Informative)

Gulthek (12570) | more than 10 years ago | (#9536710)

Get a Maha charger. Get either the C4012FS [mahaenergy.com] , the C204F [mahaenergy.com] , or the C204W [mahaenergy.com] .

All are good, the C401FS is their most intelligent charger and has a gentle charge time of 5 hours or a fast charge time of ~100 minutes. I own the C204F and it has been solid like a rock for two years. With the 204F you still have to recondition the batteries every 5 charges or so, the C401FS eliminates that need so I'd go with that if I were buying a new charger. Use the C204W if you want easy international power use.

Re:Maha (2, Informative)

linuxwrangler (582055) | more than 10 years ago | (#9537228)

I bought the MH-C401FS at a ham-radio swap mostly because I was buying new batteries since my old Kodak batteries were only good for a few shots in the digicam and the charger had a 12v as well as 120v supply.

I was very pleasantly surprised to find that the charger restored the Kodak batteries as well (up to ~100 shots instead of ~10).

I later saw this review of the charger:
http://www.imaging-resource.com/ACCS/C40 1FS/C401A. HTM

One nice thing is that each cell is independently charged. This is a very nice feature when you have things like the Motorola FRS radios that use 3 cells. Chargers that only charge pairs of batteries are a real pain. Avoid them.

Unfortunately I then bought a new camera that uses a proprietary lithium battery. :(

Oh well, I now have extra sets of cells for the GPS, MP3 player, camera flash, etc.

Re:Maha (1)

Craig Maloney (1104) | more than 10 years ago | (#9537364)

I second the recommendation for the Maha chargers. Other chargers I've used are toys in comparison with the MH-C401FS I have. Individual charging wells, intelligent charge... it doesn't get much better than this.

Maha Is good... (1)

pr0c (604875) | more than 10 years ago | (#9536872)

We've been using Maha Powerex batteries and have been very satisfied. I ordered 25 sets of something very similar to this MahaEnergy [mahaenergy.com] and it has worked fine. They are easily better than other batteries I've tried.

Why not more popular? (2, Interesting)

Veramocor (262800) | more than 10 years ago | (#9536997)

Why arent rechargable NiMH batteries more popular? These things should be flying off the shelf. The only application that they are not good for are products such as fire detectors where the NiMH self discharge would cause reliability problems.

Anyway they pay for themselves in less than 5 recharges (assuming 50 cents for non rechargable and 2.00 for a rechargable). Then you have at least another 100 charges left after that(they claim 500-1000). 100 charges * 50 cents = 50 bucks saved.

Charging time is not a factor anymore both druacell and energizer offer 1 hour and 30 min chargers. There is also a 15 min charger out there by Raynovac but you need to buy rayovac batteries (they include a chip).

The only barrier I see is high intial cost. I guess people only look at the short term.

Re:Why not more popular? (1)

travail_jgd (80602) | more than 10 years ago | (#9537752)

I agree with you. I've got almost everything that uses batteries on some form of rechargeable. These are just my observations and educated guesses...

* The term "rechargeable" gets associated with NiCad batteries for a lot of 'older' people. They immediately think low capacity, short shelf life, "memory effect", etc.

* Standard NiMH cells (AAA-D) can only output 1.2 volts. That causes problems in some devices; they may use the voltage to determine battery capacity. I had a Rio MP3 player that said the NiMH cell was only "half-charged", even though it lasted longer than a rechargeable alkaline cell. I have an LED flashlight that refuses to work with NiMHs, and another that is noticably dimmer when using NiMH cells. Other lights may be dimmer with NiMHs, due to the "reduced" voltage.

* The self-discharge rate increases with temperature. NiMHs left in a hot car in summer will drain faster than those in a cool house. Single-use lithium style batteries can hold their charge for 5-7 years.

* The NiMH C and D cells sold in most stores suck -- their capacity is about 2200 mAh. The latest AA NiMHs have capacities around 2100-2300 mAh.

* People are short-sighted and cheap. I bought a pack of six NiMHs the other day for about the same price as 48 alkalines. So I won't break even until the 9th charge. After that it's like having batteries "for free".

Re:Why not more popular? (1)

Veramocor (262800) | more than 10 years ago | (#9538426)


* The self-discharge rate increases with temperature. NiMHs left in a hot car in summer will drain faster than those in a cool house. Single-use lithium style batteries can hold their charge for 5-7 years.

I wonder if they can improve on this substanitially or if it is a chemistry limit.

Re:Why not more popular? (3, Insightful)

Dun Malg (230075) | more than 10 years ago | (#9539607)

* The self-discharge rate increases with temperature. NiMHs left in a hot car in summer will drain faster than those in a cool house. Single-use lithium style batteries can hold their charge for 5-7 years.

I wonder if they can improve on this substanitially or if it is a chemistry limit.

From what I've heard, it's mostly the chemistry. Just like you can't make a hydrogen tank that the hydrogen can't leak out of. You can minimize the leakage by making better seals and such, but when you get right down to it, hydrogen always gets out somewhere 'cause it's so darn small. You can improve batteries by fractional amounts through careful manufacturing, but in the end the chemistry of it is such that a certain base amount of current will always leak through and discharge.

Re:they'll never be advertised (2, Interesting)

Splork (13498) | more than 10 years ago | (#9537846)

rechargables aren't popular because the "big battery" companies (duracell and energizer) will *never* advertise them. why tell consumers to buy something once that they can reuse over and over again for 5-10 years when you could tell them to buy something cheaper that they'll have to keep coming back and buying more of every couple months?

this is the same reason the name brand rechargables are worthless low-power shit. they *want* rechargable batteries to seem bad. i -always- see people at the rechargable rack in the store pick and buy the name brands first, despite the power output being advertised. consumers are clueless. hell, they allowed bush to steal an election and fuck up the world; you think they'll bother to learn about batteries?

Re:they'll never be advertised (1)

Veramocor (262800) | more than 10 years ago | (#9538406)

well their C and D cells suck but the AA's are pretty good energizer has out a new 2200 mAh (as commented by the other poster)

In a free market economy then the Big players should lose out to newer small companies which offer the products people want.

Agreed I don't think people actually look to do an ROI or something on a battery. Its the same situation with compact florescent lightbulbs. 35% of the energy usage plus they last 5 times as long, yet they aren't popular.

Re:Why not more popular? (3, Informative)

evilviper (135110) | more than 10 years ago | (#9540074)

Why arent rechargable NiMH batteries more popular? These things should be flying off the shelf.

1. Voltage.
2. Discharge.

The voltage of rechargeable batteries is only 1.2V, which means you are undervolting anything you are using them in. They work fine in things like portable CD Players where they were designed for rechargables, the voltage is mostly irrelevant for all their electronics in the device, and they only use 2 batteries anyhow.

If we are talking about most other electronic devices, a 0.3v drop makes the batteries last a much shorter ammount of time. Or, in something like a flashlight, it makes the bulb dimer, like the batteries are nearly dead, even when they've just been fully charged. The more batteries you use in a device, the most serious the undervolting is... If you put around 4 batteries in a single device, the voltage is so low with rechargables, it's like one whole battery is missing. That means the device goes dead very quickly, and it may not be opperating well while it is able to work.

The second problem is discharge. Alkaline batteries hold their charge for years and years if they aren't used. NiCad and NiMH batteries don't. Most battery-powered devices are not ones that use up massive ammounts of power every day, they're more like flashlights, portable CD players, etc, where you want to leave the batteries in there for months before you actually want to use them. Waiting for them to charge when you need them is not an option, and constantly re-charging a rotating set of dozens of batteries is so cumbersome that it's not worth the effort.

Now, the second issue isn't one that's easy to solve, but the first one is. Somebody should smack around the battery manufacturers and ask why they aren't making higher voltage rechargable batteries. There is no technological reason why they can't make batteries as high voltage as Alkalines, but they just don't do it.

Re:Why not more popular? (1)

NemosomeN (670035) | more than 10 years ago | (#9541356)

Look up a standard reduction potential table. There ARE technological reasons.

Voltage = (Reduction potential of the cathode) - (reduction potential of the anode)

Rechargable batteries are limited to only those substances whose oxidizing agent adheres to the anode. (This sentence is error-laden, so sue me. I hate Chemistry.)

Re:Why not more popular? (1)

evilviper (135110) | more than 10 years ago | (#9541406)

It would be trivial to make two, half-height batteries, the same width as a AA battery. If they are both 0.75 volts, when put together, they will be 1.5 volts.

It's not a question of chemistry, just basic electronics knowledge, and common sense.

Re:Why not more popular? (1)

Insanity (26758) | more than 10 years ago | (#9541415)

The reason you can't do that is the same as the reason you can't make a 1.5V rechargable cell - there is no anode/cathode combination that makes 0.75 volts and can be recharged many times while providing high current when needed, reasonable self discharge rates, and a manageable memory effect. It's a matter of electrochemical effects, not a vast conspiracy or the widespread incompetence of battery companies.

Re:Why not more popular? (1)

evilviper (135110) | more than 10 years ago | (#9541440)

there is no anode/cathode combination that makes 0.75 volts

Have you heard of a resistor?

I'd be happy to hear why that couldn't work...

Re:Why not more popular? (1)

Mage Powers (607708) | more than 10 years ago | (#9544939)

V=IR
(Volts) = (Current)(Resistance)

basically as you change the current (I) you have to change the resistance or the voltage changes...

Re:Why not more popular? (1)

qbwiz (87077) | more than 10 years ago | (#9547865)

How about a diode with a constant voltage drop. Of course, doing anything like this would loose a lot of energy, so much that it likely wouldn't be worth it.

Re:Why not more popular? (1)

NemosomeN (670035) | more than 10 years ago | (#9548205)

I'm sure there are MANY combinations that yield .75 volts. It's a huge table, and deviations of up to .3 are common, as we've seen (Though problematic), showing a deviation of .15 should be managable. This, however, makes manufacture more expensive, since they still require the same dimensions of a standard one cell battery. Resistors would add to this as well. Rechargables are ALREADY much more costly that alkalines, adding resistors and separate cells wouldn't help that. And, a two cell battery the size of an AA would last half as long as a one cell battery the size of an AA.

Re:Why not more popular? (0)

Anonymous Coward | more than 10 years ago | (#9554768)

Because using a resistor in a battery would eat up some of the energy needlessly??

Re:Why not more popular? (1)

WormholeFiend (674934) | more than 10 years ago | (#9550927)

Each time I go out after sunset with my bicycle, a lot of people ask me how I power the two 12" green Cold Cathodes I attached to the front main bar and under the rear rack.

Two 8xAA battery holders filled with 1800mA NiMH AA batteries, one for each Cold Cathode. Each time I'm asked, I take the time to explain the value of NiMH.

Even though cold cathode specs say they need 12V, with freshly charged batteries (8x1.2V=9.6V), I've been able to power my cathodes at least 4 hours continuously.

It also makes me VERY visible on the road, and on very dark bikepaths, I illuminate a 6-7' radius!

Re:Why not more popular? (0)

Anonymous Coward | more than 10 years ago | (#9554751)

One drawback of NiMH vs NiCads is that they have a higher internal resistance. NiCads can put out quite a bit of current.

MH C204F - India (2)

proudlyindian (781206) | more than 10 years ago | (#9536999)

I stay in mumbai and i got a MH C204F from US and just recently from mumbai got Sanyo 2100mAh NiMH batteries ...
they charge in 4 hrs and thats pretty decent to normal chargers which take 16 hrs

I got the batt for 450 RS (9.5$) gr8 deal

If you need a serious charger, get one ... (2, Informative)

dougmc (70836) | more than 10 years ago | (#9537000)

The R/C community has some serious chargers that can pretty much charge anything out there.

My current favorite is the Great Planes Triton charger [towerhobbies.com] -- I like it so much that I've got two of them. It'll charge anything. If you need it to run off of 110v AC current, this page [marcee.org] will probably help set you up cheaply. You'll need to make a battery holder to hold the cells, but you could easily charge 10 at once, or possibly even charge them inside whatever you're using them in.

(And this [google.com] tells how to find the best price on it right now.)

I would like to find an inexpensive Intelligent charger that can charge 4 or more high capacity cells (in pairs or individually) in an hour or less.
Note that most NiMH cells will only tolerate being charged at up to 1 C -- so don't charge your 2 Ahr cells at more than 2 A if you want them to last (and one amp, 1/2 C, would be better.) I don't know what they do to the 15 minute cells to let them be charged at 4 C, but whatever it is, most NiMH cells do not have it. No charger, no matter how smart, is going to remove this limitation for you.

Of course, chargers like the Triton are probably overkill for what you need, especially at $130, but I certainly love mine ...

Re:If you need a serious charger, get one ... (1)

aluser (771756) | more than 10 years ago | (#9537688)

In the R/C jet community the Alpha 4 [att.net] is considered the end-all charger. It handles NiCad, NiMH, and wet/gell cells and can handle packs of from 1 to 30 or so NiCad or NiMH cells. Most importantly the packs *never* get hot, even on its fastest charge rates. At least when I got hold of my alpha a few years back, it was basically the only charger that could actually do this. It will also do a peak charge at C/10 rate, to really baby your packs. Unfortunately they're built by a basement operation and there is always a huge backlog of orders. You have to get a used one off ebay for probably more than new price, which is kind of steep to start with. The other downside is that it will only charge at up to 1 amp, which is slow on very large packs.

Re:If you need a serious charger, get one ... (1)

dougmc (70836) | more than 10 years ago | (#9538100)

In the R/C jet community the Alpha 4 is considered the end-all charger.
It's a popular charger, mostly because it can charge four packs seperately. The big downsides are that it's $300+ dollars, and you can't get one without getting lucky in a lottery, or paying even more on Ebay.
Most importantly the packs *never* get hot, even on its fastest charge rates.
That's because it's got one more big disadvantage -- it can only charge at one amp, *total*, added up between it's four outputs. That's why your packs don't get hot -- it can't charge them fast enough to make them hot. (But one amp could make a AA pack get warm.) There's nothing special about this charger (beyond this limitation) that keeps it from making packs hot -- any other peak charger, charging at a rate of 1 amp, will make a battery pack just as hot as this one charging at one amp.

One more disadvantage -- it can't do LiPoly cells. But I don't know how many jet people use them -- probably not too many. I don't understand why it doesn't do LiPoly cells yet -- a simple firmware upgrade should be all that's required, and since it's all custom made by them, you'd think that would be trivial for them to do. I guess they just don't want to make money -- they won't increase production to match demand, and they won't add simple to add features that would increase demand.

It will also do a peak charge at C/10 rate, to really baby your packs.
A minor nit -- at C/10, most packs don't really exhibit a peak at all. So it's probably just doing your standard charge (with no peak detection) at that rate -- which is fine, because a few hours of overcharging at C/10 is a good thing (it helps equalize the cells) rather than a bad thing. But you don't need the Litco charger for that -- any wal-wart can do this for far less money.

In any event, the Alpha 4 is a fine (but pricey and hard to get!) charger for keeping a fleet (it's overkill if you only have one or two planes) of glow or glider planes ready to fly, but it's totally inadequate for the needs of an electric flyer. It also can't even charge 2000 mAh AA cells at a 1 C rate, meaning that it probably wouldn't do the `Ask /.' guy much good.

Actually, the Triton is way more than the guy needs too. He could probably do very well with any peak charger that can charge 1-8 cells, and can probably find one for around $40. Something like this [towerhobbies.com] would probably be just fine for $50. And it has two charge ports too, which is a nice feature.

Re:If you need a serious charger, get one ... (1)

cms108 (96258) | more than 10 years ago | (#9537803)

i use the pro peak supernova...
http://www.ripmax.com/ProductFrames/ O-SUNG-RP250S. html

doesn't do all of the stuff that triton thing does.. like lithium cells... but it does up to 25 nicad or nimh cells and and 2v-12v pb.
and it costs a bit less.

The Great Battery Shootout (1)

WSSA (27914) | more than 10 years ago | (#9537208)

You should take a look at this [imaging-resource.com] . I followed the advice therein and bought a Maha charger and Powerex batteries and have been pleased with their performance (I have an Olympus E-10 which is notoriously hard on batteries, standard batteries, e.g. Duracell, die in the middle of taking the first picture with it!)

Chargers for mobile use..? (1)

Myself (57572) | more than 10 years ago | (#9537559)

I've heard there's a 12v car cord for the IC3 charger, which would be tempting if the thing weren't so expensive to begin with. As it turns out, running a regular desktop charger from an inverter isn't too horribly inefficient.

The problem is that some of the quick-chargers, like the one that came with my camera, do a fast-start and don't even bother measuring the cells until 5 minutes later. If their AC input is constantly cycling on and off, this destroys batteries. I'd probably do fine with a deltaV unit running off an inverter.

At the moment I've got enough AA's that I can charge them at home and only rarely need to charge them in the car anyway.

Re:Chargers for mobile use..? (1)

vlm (69642) | more than 10 years ago | (#9537712)

MAHA MH-C777 PLUS-II comes with a 12V car charger and was maybe $75 when I got it a few years ago. Works great for my purposes.

Re:Chargers for mobile use..? (1)

Divlje Jagode (710824) | more than 10 years ago | (#9542807)

This is not going to be much help, but... In Korea, I bought a Diplus ultra-fast ni-mh & ni-cd battery charger. Delta-V and all.

I got mine with 2 packs of 4 2300mAh batteries for about 30$ (sorry, I could be off, I don't usually use $).

I thought I'd mention it because mine came with a 12V wall-wart charger and a car adapter as see here [daum.net] .

mh-c777 -c777plus or -c777plusII (1)

Dun Malg (230075) | more than 10 years ago | (#9539374)

I have a Maha mh-c777plus [mahaenergy.com] universal charger.I've had good results with it charging NiMH batteries. It has a few flaws-- it pushes too much current for NiCd batteries in "Ni type" battery mode, the 24v power connector sparks when plugging it in, and the piezo "squeaker" it uses is as loud as a smoke alarm-- but nothing that couldn't be worked around*. It's designed with battery packs in mind rather than individual cells, so you need to pick up a couple battery [allelectronics.com] holders [allelectronics.com] to get enough cells together to satisfy the charger's minimum voltage requirement (3v, as I recall). If you're looking for just a straight AAA/AA cell charger/conditioner, Maha has other [mahaenergy.com] models.

* charge NiCd's in Li-ion mode, add a power switch to unit so you don't have to plug the 24v in "hot", and fill the hole on that damn piezo "siren" inside with epoxy-- it's still audible, but only if you're in the same room.

astroflight and triton chargers (1)

jotux (660112) | more than 10 years ago | (#9540596)

I've been using the astroflight 110D for a few years on my battlbot batteries(3 Ah NiCD and NiMH). Its worked great for me. Recentely I've gotten into small robots and am starting to use li poly batteries, so I went ahead and replaced it with the triton chargers...its worked great so far. You can get either one from robotcombat [robotcombat.com]

In the UK... (1)

cowbutt (21077) | more than 10 years ago | (#9541397)

this charger [maplin.co.uk] and these cells [maplin.co.uk] are pretty good VFM. The 12 pack of 2300mAh AA cells (L50AL) was 14.99GBP until recently.

--

Why not recharge your alkalines as well? (1, Interesting)

Anonymous Coward | more than 10 years ago | (#9554958)

http://www.rezap.com.au/

This Australian microcontroller-based charger will do conventional non-rechargeable alkalines, titanium, nicad, nimh, and rechargeable alkaline-manganese cells, in all sizes. I'm not associated with the company, but I do own one, and it really does work (apparently safely - despite the dire warnings on the side of non-rechargeable alkalines about charging).

You can supposedly get up to 15 cycles from a normal alkaline, 25 from a rechargeable one. It's quite slow at nimh and nicad, but alkalines recharge fairly fast and don't have self-discharge issues.

These guys are working on exporting these things to the US.
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