A Cordless Phone's Major Problem - Dealing w/ Batteries?

Brian James asks: "I am sick to death of cordless phone batteries going dead at the drop of a hat. And with frequent recharging they tend not to hold much of a charge. Replacement often equals the cost of a new phone altogether... so what's the point? Ultimately I wish cordless phone manufacturers would design a phone that used standard rechargeable batteries, preferably with 2 battery bays and a switch that allowed you to switch over to the fresh set when one set starts to go dead (of course, I don't see this happening any time soon). Is there any way to modify a cordless phone such that I can run the handset off of standard batteries? I don't care how 'cheap and dirty' it ends up, I just need to know I can pop in a fresh battery and call the guy back, without waiting 8 hours for it to charge up." A few cordless phone manufacturers do have a clue. Some phones allow you to charge an extra battery in the base while the other is being used by the phone, which works well (I have a Sony 900Mhz model that does this). It would be interesting to see if someone has done what the poster has asked, however if you'd like to recommend a cordless phone that keeps downtime to a minimum, I'm sure such would be appreciated.

Comments

In my expirence

[seann]

at Radioshack, I've dealt with people like you over and over again. They bring back their nickle Cadium based phones a few weeks later, and tell me it's dead. I then say "heres your new battery" and they buy it.

Now when the old couple comes in with the pre-1980's cordless phone, and I tell them the batter is 40-60$, I generaly ask if they want a new phone.

So I bring them over to the wall and show them the selection of phones with a lithium-ion batter in them, and I tell them about how if they keep charging their old battery (nickle cadium) it will damage the battery, but instead with these lithium-ion phone batterys, give them one good charge on your first use, then recharge them any time you wish!

The same thing is with my cell phone, the Sanyo SCP-4000. Not a spectacular phone, but the default lithium-ion battery that comes with it is a god send, I recharge it every night with no fear of the battery dying.

So in short I tell you, pick a cordless phone that has a lithium-ion battery in it, instead of a nickle cadium, or nickle metal hydrate (the latter is your next best alternative).

dyi

[elfkicker]

You can always make your own to save yourself a few bucks. Of course, it's probably more trouble than it worth. But, if you're the DYI type check out http://www.rccentral.com/guides.asp?ATCL_ID=51

That'll give you a little primer on what's involved. It's geared towards hobby RC cars, but you could adapt this for phones pretty easily.

I also make it a point to stay with NMH batteries when possible. They actually get batter after a little use, and no need to drain them completely before you charge them again.

You won't need a battery switch.

[eugene ts wong]

preferably with 2 battery bays and a switch that allowed you to switch over to the fresh set when one set starts to go dead

You won't need "two battery bays" and switch, because if you had that much room for batteries, then you could just connect your power cells in parallel and not have to switch between the 2.

It would be nice to have solar cells to help compliment the amount of power from the battery. I don't expect that you'll get much power out of the solar cells, but every bit helps.

i have never had a problem

[mozkill]

when my batteries get low and i need to talk to someone, i just plug it into the wall while i talk... it charges and i talk at the same time...

i have your basic motorola startac... its not like i am out of business when my batteries are dead... its not any more inconvenient than a normal telephone used to be... i just look at the batteries as being a luxury to have them at all... the important part is the ability to talk from anywhere.

Siemens Gigaset

[ivan256]

Not only are the siemens gigaset phones well featured, but they also take 3 standard NiCad rechargeable AA batteries. I haven't had them wear out yet, but at least I know it'll be cheap and easy to replace them when they go.

Re:Siemens Gigaset

[zsazsa]

I also have a Siemens Gigaset (An older model 2415, which I got CHEAP on closeout at Staples.) It came with two standard Panasonic 600mAh AA NiCad batteries. After looking at the manual, I saw that it could take NiMH batteries. Awesome! 2-3x More capacity and no more stupid memory effect!

I got a couple 1800mAh Powerex batteries from Thomas Distributing and the phone has worked great. After weeks of on-hook/off-hook type usage, it can go for a LONG time without charging with no memory effects.

With standard AA NiMHs, you can keep a spare set sitting in the charger if you need em.

It's a freakin' cool phone, too.

Ian

Solutions: 1) Don't charge so much. 2) Discharge.

[Futurepower(R)]

I'm surprised no one else has said this:

Nickel Cadmium cells have 2 unfortunate limitations: 1) They have a "memory effect". 2) Charging them all the time makes them old very quickly, and makes the memory effect much worse.

So, this is what you do: 1) Don't charge the batteries all the time. I have two ATT 900 MHz Cordless phones. (I bought one for $30 at Costco, and the other for $5 at a garage sale. These are not expensive phones.)

I charge the batteries for about 6 hours once a week. I regularly talk for 3 or 4 hours in one phone conversation, and I have never had problems with the battery going dead. I've never switched phones in the middle of a conversation, either.

If I have a conversation lasting more than 20 minutes, I charge the phone then, also, after the call.

This is how you tell if you should stop charging a NiCad battery: It becomes warm. That is because all of the charge energy goes into making heat after the battery is fully charged. Before the battery fully charged, some of the charge energy goes into charging the battery, of course.

Don't worry about overcharging a little. A few extra hours, even 10 extra hours, in one or two charges a month seems to make no difference. It is 24-hour, 7-days-a-week charging that causes the problems.

2) The memory effect can be completely cured by discharging the battery completely. To do this, buy a 510 ohm, 1/4 or 1/10 watt resistor (an electronic component) at Radio Shack or an electronics parts store or an electronics surplus store. Remove the battery. Just push the leads of the resistor into the contact sockets of the battery (where the contact pins normally go), and leave it for 12 hours. Once the battery is discharged, it will no longer have the "memory effect" and will be as good as new, or 95% as good as new. Then, recharge the battery until it is fully charged (when it becomes especially warm).

The memory effect works this way: It causes the battery to discharge rapidly, even though there is a small load. The memory effect causes the battery to have a "shallow discharge curve", they say.

Lithium Ion and Nickel Metal Hydride batteries do not have memory effect. However, they also get old faster if they are constantly charged.

This is reliable information. I was an electronics designer in past years, and I have talked to an RCA battery engineer about the exact parameters of NiCad memory effect.

Siemens Gigaset

[maggard]

The older 2nnn series and the new 4nnn series of the Siemens Gigasets all come with 3 AA NiCad batteries. These can be switched out for other batteries if you prefer. This was a big sales feature to us after years of dealing with non-standard battery packs.

I bought 3 4200 handsets and a 4215 basestation/answering machine a few months ago (first US shipment) and have loved them. We did replace the shipped batteries with Lithium ones but friends with the same phone didn't and they've never had problems either.

We constantly leave our phones floating around the house and they last for a few days before running down. In conversation I've never had one run down except once when it really was on it's last mAmps - it beeped to warn & I just walked over to another extension and switched to it.

Other nice features are a great shape for the hand (the older series was flat like old TV remotes and uncomfortable to hold after awhile), reasonable controls & menus, the ability synch phone books from handset to handset, can PA from room to room and also PA incoming messages being left on the answering machine.

One big win in our case was individual handsets can be set to dial a specified extension or outside number if the sound volume exceeds some number. We use that if we have guests coming in to visit when we're out of town. Their voices trigger the call to us and we can welcome them, give them a rundown of the house.

Oh, and the phones can be set to dial in response to a spoken name. Really it's the same as speed dial but is useful for the non-techie members of the household. It'll also announce out the name of a caller who is set up this way and recognized via Caller ID. We've 4 or 5 numbers set up for that and it's worked out well.

Only thing I could still wish for would be a USB link for doing that first entry of phone numbers.

NiCd Memory effect is a myth -- don't overcharge

[kgp]

There is no memory effect in NiCd batteries** the real problem is lousy charging systems overcharging the batteries. This heat the NiCds and causes to vent electrolyte.

Short form:

Long (and accurate) from ARRL:

http://www2.arrl.org/tis/info/pdf/119470.pdf

** At least not for ones on earth -- there is a real memory effect for slow charging and discharging NiCds in orbit. But unless you phone is in a satellite in orbit this won't be a issue .

Solution: Don't put the phone back in the cradle until it needs a charge.

ALWAY keep a regular (loop powered) phone in your local loop. You can always pick up with it when you battery is dead oer when power is out (and the base is dead).

And Radio Shack carries a lot of cordless phone batteries (I had the same problem with a VTech 900Mhx cordless -- now on its third battery).

Check out RAM Batteries

[frank249]

A Canadian company called Battery Technologies produces Rechargeable Alkaline Manganese (RAM) batteries. A technical description is here. Compared with NiCad batteries, the advantages of using RAM batteries include the following:

* Longer Operating Time
* Environmentaly Friendly(contains no hazardous toxic substances)
* Longer Shelf Life (minimal Self Discharge)
* Ready For Use when purchased
* No Memory Effect
* Lower Cost
* Better Cell Capacity

These batteries are currently available in four brands- PURE ENERGY(Canada), RENEWAL (manufactured in the United States by Rayovac Corporation), ALCAVA (manufactured in Korea by Young Poong) and GRANDCELL (manufactured in Malaysia by Grand Battery Technologies).