cordless phone batts?

[vivid]

I am visiting my mum and she has asked me to look at a few things for her, including her cordless phones. One will no hold a charge. I have been looking for a replacement and the batt has two sets of numbers on it. When I search one it give me OEM batts, the other gives me what look like compatible batt. The batt is a wrapped 3 AA package with a two wire connection.

The oem batt is NiCd and the compatible batts are Nimh. I thought NiMH and NiCd used different charging types and were therefore not compatible, could someone confirm this for me? Oh the NiMH are 1/2 the price of the OEMs.

 

[PerttiK]

Check the voltage and current of the charger.
I would think nimh's are ok.

 

[Mr Happy]

It's generally unsafe to replace a NiCd battery pack with NiMH where the original equipment was designed to use NiCd. The phone may have a trickle charge that will ruin NiMH in short order.

Your safest option is to replace like with like.

When I replaced a cordless phone pack recently, I was very unhappy with a "compatible" 3rd party pack I purchased (in this case both original and replacement were NiMH). The replacement pack died within weeks. I ended up buying some high quality AAA cells and constructing a replacement pack myself with a soldering iron and lots of care (you must not overheat the NiMH cells when you solder to them).

But if you can find the OEM replacement packs I would stump up the money and go for those. They will be at least twice as good as the cheaper 3rd party ones in most cases.

Another option I just did with my mother was to replace the phones with a new set. The new phones we bought were sleeker and more compact, had a much longer talk and standby time and had more features.

 

[ltiu]

I bought my mum a totally new cordless set when her old cordless set's batts won't hold a charge long. New cordless models take regular AAA NiMH (cheaper).

I replaced the OEM NiMH batts that came with with cordless with high capacity 1000 mAh AAA NiMH and no issues with talk times.

 

[vivid]

Mr Happy,

thanks, I had the same kind of situation when I use "compatible" batts before, but that was before I knew about this forum and some limited knowledge on batt types.

Itiu,
I was thinking just the same. With a costco coupon I could get 5 new cordless phone package for not much more than the three OEM batt.

 

[Nubo]

If the OEM battery is NiCD, I'd stick with NiCD. They are much more tolerant of the type of life lived by a cordless phone battery. I.e., constant-charge and being run to exhaustion. In order to use NiMH effectively, the phone would need smarter charging and a battery cutoff that did not fully drain the battery. If they did not spec NiMH originally, then they probably did not include these features.

Good news is you can probably find loose replacement NiCD cells with significantly better capacity than the originals and rebuild the pack with them.

 

[ltiu]

If the OEM battery is NiCD, I'd stick with NiCD. They are much more tolerant of the type of life lived by a cordless phone battery. I.e., constant-charge ...

Interesting. I never thought about this. Maybe some cordless do this - constantly charge.

But my cordless came with NiMH and it has says "Charging" or "Fully Charged" on the console. I assume once it says fully charged, it stops charging.

 

[Mr Happy]

But my cordless came with NiMH and it has says "Charging" or "Fully Charged" on the console. I assume once it says fully charged, it stops charging.

Yes, Panasonic phones do that. The user manual also says it does no harm to leave the handset on the cradle all the time.

On the other hand, it is known that NiMH cells benefit from being cycled regularly. They tend to develop higher internal resistance if they are kept in a fully charged state for a long time.

So the best plan would be to remove the phones from the charging cradle when they are charged and then leave them off the cradle until they reach a low battery state before putting them back on charge. Unfortunately my mother was very resistant to doing that: the phones are "tidy" when they are sitting on the cradle, and they are "untidy" when they are lying round about. My mother is big on tidy, so those phone batteries are unlikely to get much cycling... :shrug:

 

[Vesper]

I priced new batteries for my 5-6 year old phones (3) recently and figured I was crazy to not just go to costco and buy a new set of 3 and base for less than $20 more than just the price of the replacement batteries. Yup, disposable society.

 

[Niconical]

What are y'all doing making sure your Mothers have extended talktime on their phones? Don't they talk enough already? :laughing:

Years ago I got my mother her first cellphone, which was fine.

Then I showed her how to text. big mistake!

 

[Linger]

I've got an LG (costco) with 3aa shrink-wrapped nicd, they're good for ~10min now. So I'm watching this thread for suggestions.

re: older mother's and cell phones, txt.

I actually prefer now that my mother uses txt. For example, she'll write to say she's going out for a walk to the damn and ask I check in with her in 2h to ensure she wasn't attacked by beavers or squirrels or whatever else haunts the Ontario wilderness. Keeps a short text to what would otherwise be a rambling conversation about the health of the forest, the road, the creek,...
At any rate, I too participate as an adult male providing technical support and repair for my mother.

 

[ltiu]

On the other hand, it is known that NiMH cells benefit from being cycled regularly.

Yes, I let my mom talk through it for a while. That works :thumbsup:

 

[WDG]

I priced new batteries for my 5-6 year old phones (3) recently and figured I was crazy to not just go to costco and buy a new set of 3 and base for less than $20 more than just the price of the replacement batteries. Yup, disposable society.

I recently put new battery packs in our three-handset system. Will never buy phones that take these custom packs again. Our next phones will take loose NiMh cells, for exactly that reason. Plus, I'll be able to give them periodic attention in the MH-C9000, so I would expect they'll last longer than the expensive packs.

 

[fivemega]

https://www.candlepowerforums.com/posts/2968793&postcount=12

 

[InHisName]

I recently put new battery packs in our three-handset system. Will never buy phones that take these custom packs again. Our next phones will take loose NiMh cells, for exactly that reason. Plus, I'll be able to give them periodic attention in the MH-C9000, so I would expect they'll last longer than the expensive packs.

That is where I am at presently. I have set of 4 cordless DECT phones. The orig. [NiMH] batteries lasted 2.5 years, 3 to a phone, plugged loose into the phone. They all went HIGH in 6 month span when each phone accidently left off cradle overnight and died. They failed to recharge, and also failed C9000. So in spirit of research, fun, and excitement, I started the HIGH & C9000 thread. It has been very educational. I am loosing the enthusiasum to rejuvenate these and just buy some more to 'sacrafice' to the unknown phone base charger god.

I did try to mix the better cell with a NexCell EnergyON AAA but in two months those new cells deteriorated WAY more than their brothers in onther uses. Sooooo, streatching marginals with new ones was a disaster. Kinda like putting an almost spoiled apple into bushel of new ones.

Now I am going to try new Ray-O-Vac4.0 and hope they survive 2+ years. At 5.49/4 with postage it's not too terrible of experiment.

 

[Mr Happy]

They all went HIGH in 6 month span when each phone accidently left off cradle overnight and died.

This is somewhat the opposite of normal expectations. It is leaving phones on the cradle that is more likely to harm the batteries, not leaving phones off. Most phones, especially modern ones, should have several days of standby time when off the cradle. To obtain the maximum life from the batteries you should leave the phone off the cradle until it shows the low battery warning, put it on the cradle until it is fully charged, and then take it off once more.

As I write this I am conscious that I don't actually do this with my own phones as I usually wish them to be fully charged at all times, but nevertheless my batteries would last better if I did.

 

[InHisName]

This is somewhat the opposite of normal expectations. It is leaving phones on the cradle that is more likely to harm the batteries, not leaving phones off. Most phones, especially modern ones, should have several days of standby time when off the cradle.

I fail at monitoring the batt indicator closely enough. These phones show 'half' used for about 20 minutes after several days when batts were new, then phone went blank. It did recharge. Soooo, I kept them on charger when not in use.

After 2.5 years the life span is not several days but counted in hours. Probably near an hour talk time. I always switched to another phone in 5-10 minutes. So an accidental non cradle left one dead and NOT able to recharge when put back. That is why I wasn't aware that things were getting much worse over the 2.5 years. I might be able to salvage 4 cells to hold a charge with cradle and nurse them along for a couple of months while I search for more bargains to 'sacrafice' to the cradle god. I just received 4 Ray-O-Vac4.0 and am testing the break-in. First came to 760MAH. 3 more to go.

 

[Aquanaut]

I just came across this thread and thought you would like to know my experience. I found an AA NiMh 2000 mah battery with tabs that is designed for cordless phones and similar applications. I have replaced five battery packs (3 AAs each) in Panasonic cordless sets and leave them in the cradle charging continuously. Off the charger, the batteries last a few days. These packs have been in use for several years and are still doing fine. They have C/10 overcharge and reverse polarity protection and can be trickle charged. :twothumbs The original batteries were NiCds.

Here is where I bought them:

http://www.thomasdistributing.com/s...html?SP_id=&osCsid=a98rm8a91donrsllit8gi3gna7

 

[WildChild]

I replaced a dead NiCD pack with homemade NiMH pack twice in my cordless phone. The original NiCD pack lasted 1 year. I was always cycling them completely before charge and it was lasting 3 days at the beginning and 1 day on a charge at the end.

I checked tested the charging current to be 70 mA. My first NiMH pack lasted 2 years, made with Duracell 2650 mAh cells. It takes around 50h to charge them and 3 weeks to discharge them. Much better! They tend to develop a high internal resistance very fast but with the low charge current it's not a problem. The cells wouldn't charge anymore in a quick charger so I thought it would be a nice way of stretching their life. Two years with those is great IMHO. Now on my 2nd NiMH pack and still going strong after 1 year.

 

[InHisName]

It's been a few months now. I googled for 'BT-446' battery and found many being offered for sale via eBay. I bought one and found the connector kept popping out. So I cut a strip of paper-plastic from some waste and used for shim. No more battery running down fast anymore. I just removed from phone and battery pack was just slightly warmer than room temp.

I tried the old one and it still takes a charge. Maybe it wasn't the battery after all, just a loosing up socket for the battery plug ? I may have a spare battery soon.

I got the phones free with my sunrocket account in '05. Batts been on charge ever since. 3 out of 4 battery packs still going strong. :twothumbs