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Re-chargable Batteries


Station27

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I was getting tired (and poor) always replacing AA batteries, so I thought I'd be clever and get some rechargable ones. I bought 6 and all seem to act the same. When I turn on my eTrex Vista, the screen goes white to black, then verticle bars, then static. If I press the button to change the screen e.g. MAP to NAVIGATE etc, the display goes back to normal and the GPS works. The battery display shows a fully charged Ni-cad. I tried changing the battery setup from alk to nic but it acts the same. The GPS turns on normaly with disposable batteries and actually does WORK with the rechargeable ones, it's just the turn on that's wierd. Any ideas???

 

TOM

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Alkaline batteries have a voltage of 1.5 V when fully charged. NiCd and NiMH batteries have a voltage closer to 1.2 V when fully charged. Probably your GPS unit uses a display driver that automatically compensates for voltage changes when the display is switched, but assumes a constant voltage otherwise, and that results in the effect you see.

 

Try replacing almost-worn-out alkaline batteries with the fully-charged NiMH or NiCd batteries, and I will bet you don't see the same effect.

Edited by fizzymagic
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There is a firmware update to resolve this problem. Check the garmin site. Im not sure if your model is affected (sure sounds like it) but I do remember seeing some newer firmware that addresses the problem you are describing. It is in fact a voltage issue just as the above poster stated. Hope this helps.

 

Geoff

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When I was buying my rechargable batteries, I asked the Radio Shack doood which were better, NiMH or NiCad and why. He said that the NiCad batteries should be drained completely or almost so before recharging. It seems they don't work as well if this is not done. The NiCads they had there would charge in 2 hours while the NiMH batteries took 4 hours, but didn't have to be completely used up before recharging. I went with the NiMH ones. Good for 300 charges!

 

Maybe this explains your problem? I'd ask the Radio Shack doood near you.

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Asking a Radio Shack doood a technical question about electronics is like asking me how to do cold nuclear fusion. It's a complete waste of time, because the answer you get may have no basis in reality.

 

CLOSE !!

 

NiCad batteries have what they call "memory".

 

If you discharge NiCads to 60% and then recharge 4 or 5 times the next time when you try to get more than 40% out of them they die on you -- memory. This is why you are supposed to dischage them fully.

 

NiMH batteries are a little more expensive. They typically have a higher power rating (that's the amper hour rating). 2200 MA means 2.2 amps for an hour or 100 MA for 22 hours [ you engineers out there please don't beat me up - I know it is not competely linear - close enough for this discussion ]. So the higher the capacity the longer they last for a given current draw by the gps (or whatever).

 

The main things about NiMH is that they do not exhibit the memory and have a higher capacity.

 

Std batteries have a voltage of 1.5 while the rechargables are only 1.2 volts.

 

I have a setting on my Magellan also - but the NiMH never show more than about 75-80% on the battery guage. But they last a long time.

 

You can get NiMH batteries pretty cheeply these days. They do require a special charger. Be careful with the so-called fast chargers. They can charge in about 30 min - you have to have batteries that will take the high charging currents. And they get HOT! Too hot for my taste and I have some 40 years experience in electronics.

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NiCad batteries have what they call "memory".

 

If you discharge NiCads to 60% and then recharge 4 or 5 times the next time when you try to get more than 40% out of them they die on you -- memory.  This is why you are supposed to dischage them fully. 

It's also worth mentioning that many electronic devices, GPSs included, Wont fully discharge a NiCad. Only something like a flashlight, or a discharger, will fully discharge them. Most electronic devices have voltage sensors, and turn off when the voltage drops below a preset threshold. This is often a higher voltage than what counts as "Discharged" for a NiCad (From memory a "discharged" nicad should be about 0.7 volts?) It's also bad for NiCads to be completly, utterly drained, as in left on overnight on a flashlight bulb - That'll reduce their lifespan as well.

 

Me, I Love my NiMHs... My GPS72 was chewing through alkalines in about 2 - 2.5 hours. Now I get about 6 hours, with backlight for some of it (Never timed how long backlight was on....)

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another note is that you dont want to overcharge the NiMH batteries. If you overcharge them they will out gas and you will loose capacity. That is why you should use a recomended charger.

 

On another note...I read an article that told you how to get the most out of your rechargables. When you buy new ones use them in pairs and charge them in pairs...that is mark them and then keep them together when you charge and use them, if you mix them the weaker of the two will bring down the stronger of the two...and then the weaker will become reversed charged once it goes dead which is a bad thing...

 

Alos sometimes a new NiMH battery is hard to charge. I have some I put in a small trickle type charger for a week and they never charged. I eventually had to put them in my larger charger and kept reseting them to charger for 3 days. Eventually they took a charge and they work great now.

 

here is the article...

Battery info

Edited by Rainwater
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A trick I learned about NiCads is to put them in a plastic bag & put them in a freezer for 24 hours if they develop a memory or won't charge at all. This totally drains them. Let them sit & adjust to room temp before charging them. I've only had one video camera battery that this didn't work on.

Worth a try.

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I use the nickel batteries, they are more money and must be used with the right charger.

They last very long on a charge, and I am very happy with them.

 

My etrex Legend has a setting for the battery types, in the setup menu somewhere.

Check for it.  Maybe that's all that's wrong?

He said in his post:

 

I tried changing the battery setup from alk to nic but it acts the same.

 

So I would guess that is not it.

 

I would say it's nothing with the batteries.

 

Make sure you do any software updates and if that does not fix it send it to Garmin.

 

Good luck,

 

Edited to add: I find the Energizer 2500 Mah AA's are awesome in my GPS

Edited by Milbank
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The rechargeable battery thing re-visited. This has been the topic of many discussions on this and other web sites for a long time. There is an on going question as to how to treat rechargeable. Many of the above post are right on, however some are not even close. My background with NiCd's and NiMh's comes from the RC hobby were we often use a battery pack made up of six sub C cells and costing up to and sometimes past $100. So we have kind of weeded out the myths.

 

First, if you have a choice always go with NiMh. The NiCd's are on the way out of the market, the nickel cadmium can not be recovered, and it is a huge polluter of our landfills. NiCd's do have a memory, they are not effected that much by cold (they have been used in polar expeditions) and discharging them to zero and even putting them on a dead short is helpful. I often store my old NiCd's on a dead short for a week at a time, let them "rest" off the dead short for a day then fully charge them. I have packs that are several years old and are still raceable. They should also only be cycled (charged,discharged) once per day, this has to do with internal heat of the cell.

 

NiMh's do not form a memory, they also are not effected to a great degree by cold, they will not be harmed by recharging them before they are totally depleted (memory), they don't seem to be effect adversely by deep cycles (that is running till totally discharged, then recharging). NiMh's also are not effected by internal heat as the NiCd's are, in fact many people charge their NiMh cells until they reach 130 degrees on the outside. This is a practices of those that wish to get the most out of the cells for a five minute race in which the draw can be as much a 90 amps (that's a bunch of amps from a small battery pack, and often are hotter after the race). NiMh's can be used as many time as needed in a day, within reason. They do not pollute the landfills.

 

Now on to something we have all been waiting for the Lithium Ion/Polymer. I hope that they are soon on the market, they have the best of both batteries, and so far none of the bad.

 

Hope this serves to help and not confuse.

 

Thumper :huh::huh:<_<

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Now on to something we have all been waiting for the Lithium Ion/Polymer. I hope that they are soon on the market, they have the best of both batteries, and so far none of the bad.

I called the help number for one of the big online battery sellers to ask why Li-Ion rechargeables aren't yet available in standard sizes (AAA, AA, C, D) - only in specific configurations for phones, laptops, etc.

 

The reply I got was that since these batteries have a very low internal resistance - lower even than NiCd (NiMH is less bad) - any short circuit could pose a real fire hazard. And apparently people who carry spare batteries in their pockets with keys, etc, get short circuits from time to time. So it seems there's a potential safety issue with Li-Ion cells.

 

Of course, it could also be that, like (allegedly) Detroit, they're making such big money with the current technology that they have no incentive to innovate <_<

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The short-circuit issue is a possible problem. Even with NiMH things can get very hot if

a key or other metal object causes a short. There were even some problems with eTrex models used with an early NiMH cell where a combination of an atypical spring contact in the eTrex and poor insulation design of the AA cell caused a short and things got hot enough to melt the eTrex battery compartment.

 

But the main issue with rechargeable Lithium ion chemistry is that the voltage is inherenetly around 3.6 as compared to 1.5 for alkaline and 1.2 for NiCd and NiMH (the non-rechargeable lithium [not ion] cells are about 1.6). That makes them unsuitable for a direct AA replacement.

 

One approach that is being used is to make the Lithium ion cell in the shape of two side-by-side AA cells and drop the voltage a bit to 3V. That type of cell is called the RCR-V3 and is being used in some digital cameras. It lets you use either a pair of AA cells or a single RCR-V3 in the same battery compartment.

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I've used rechargeable batteries since I started this game. And before that I was using rechargeables in my old Palm IIIxe.

 

I started out with Ray-o-vac rechargeable alkaline, but I've had these bust open in the charger. Grrrr. Makes for a nice mess to clean up.

 

Since switching to NiMH's I've never had trouble with one breaking. When I buy new ones, I wrap a piece of masking tape around the battery and write an identifying letter or number on each pair (A, B, C or 1, 2, 3, etc). This way the same batteries are always together. I'm not sure if that's helpful or not, but it was something I wanted to do.

 

I continue to buy more of them, but only because I've come to trust these batteries more and my kids have more electronic toys. I'm not sure if we have non-rechargeable batteries in anything at home any more.

 

Bret

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Asking a Radio Shack doood a technical question about electronics is like asking me how to do cold nuclear fusion. It's a complete waste of time, because the answer you get may have no basis in reality.

This is so true :DB) I needed a clip to hang a michraphone in my truck for one of ham radios. This is what happened

 

Me: I need a clip to hang a michraphne in my truck for a two way radio (I knew dood would not know what a ham radio was)

 

Dood: You mean a cell phone

 

Me: No a michraphone

 

Dood: (dood stands there looking bewildered)

 

Me: You know like a micraphone for a CB radio

 

Dood: What's a CB radio (They do sell CBs at radio shack)

 

Me: Forget about it (I walked out at this point)

 

I sent an e-mail to radio shack and told them they should take Radio out of their name.

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I've posted this in another thread. Here's a place I like for ordering NiMHs;

http://batteryspace.com/index.asp?PageActi...TS&Category=285

 

I just ordered another 48AAs today to split with some friends, and a combo pack for my buddy who didnt have a charger.

 

I have been using cells from these guys for a couple of years, and have been very satisfied using them in my digital SLR, flashlights, 2-way radios, remotes, etc.

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sTeamTraen: I am not sure about the voltage issue being the reason for not having them on the market yet, after all they could just make the cell with less guts in it. I have heard that they are having problems with the cell being able to develope/discharge enough amps to run many of the items that AA's are used in. That is the reason that NiCd's and NiMh's are used in high amp situations rather than Alkaline cells. Alkalines dont put out (develope/discharge) a lot of amps at a given time.

 

Thumper :DB)B)

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sTeamTraen: I am not sure about the voltage issue being the reason for not having them on the market yet, after all they could just make the cell with less guts in it. I have heard that they are having problems with the cell being able to develope/discharge enough amps to run many of the items that AA's are used in. That is the reason that NiCd's and NiMh's are used in high amp situations rather than Alkaline cells. Alkalines dont put out (develope/discharge) a lot of amps at a given time.

 

Thumper B)B):D

The physics is a bit more complex than that. Any chemical reaction which produces electricity has a characteristic voltage, which is typically on the order of magnitude of 1 volt or so; it depends on how much effort is needed to pull whichever electron off the atom in question, but most such reactions are in the same ballpark. 3.6V for Li-Ion is high, but potentially means you can get more oomph in the same space.

 

You can get round this in the positive sense by running several cells in series; for example, a 9V PP3 alkaline battery has 6 small cells and a 9V PP3 NiCd accumulator has 8. But you can't reduce the voltage much.

 

For Li-Ion cells, I hadn't realised this figure was as high as Peter pointed out, but there isn't much that can be done without additional circuitry. And building in a voltage regulator whacks the price up again.

 

The main obstacle to high current drain is probably the internal resistance of the battery. However, if that's true, it would mean that if Li-Ion batteries are highly vulnerable to shorts, they should also be able to sustain high current. But I suspect Peter is our man here :D

 

Incidentally, the increasing requirement for current in cars means that their batteries are starting to appear in 42V rather than 12V. But again, there are multiple cells in there (I think each cell is 2V).

 

Nick

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The people who cite low internal resistance as the reason for not having LiIon rechargeables are right. I can't speak about the voltages, as I don't really know.

 

I work for UL, and I test battery chargers and sometimes, batteries. There are certain batteries (usually LiIon) that have to have a fuse built into them to pass our tests. Otherwise a short circuit is very hazardous.

 

It seems to me that they could make them in about any voltage configuration they wanted to, as long as it was a multiple of the base amount. I can't believe (without proof) that the base amount for LiIons is 3.6V. That seems kind of high.

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So, does anyone have any recommendations on good battery chargers??

I purchased my charger from Powerex

 

I like it because it has a slow and a fast charge mode. I usually use the slow mode because the charge seems to last longer.

 

I use Enegizer 2500 mAh batteries that you can get at SAMS club.

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Asking a Radio Shack doood a technical question about electronics is like asking me how to do cold nuclear fusion.  It's a complete waste of time, because the answer you get may have no basis in reality.

So true,

 

"You got questions, we got answers"

 

Yeah, what BS......

Oh they've got answers all right.. it's just that they are answering a different set of questions! ;) I've never been a big fan of rechargables. Wal-Mart's house brand alkaline AA batteries are cheap ($<2.50 Cdn) package, and that keeps my 76CS going for at least 14-16 hrs straight no probs. Much less hassle then chargers, remembering.....

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