Rechargable batteries for DECT cordless phones - is there a problem with getting too high a mAhr rating?

[NY]

The bog standard rechargeable batteries (750 mAhr) in our DECT phones are starting to lose their ability to hold their charge: they indicate full charge but the phone cuts out with "low battery" within a few minutes of being taken off the charging base station, especially if used on speakerphone.

Is there a problem with replacing them with batteries that can hold more charge ie > 750 mAhr. I presume the phone will still charge them at its standard rate (though it may take longer to charge them).

I will go for branded (eg Duracell) rechargeable batteries.

I presume that if the original batteries are NiMH, I should go for that same technology.

[Graham.]

The cynic in me thinks Supermarkets place these "special" DECT batteries in the phone isle just so they can charge a premium.

Yes. Can you even buy NiCads on the High St?

[The Natural Philosopher]

As long as you keep the same technology you should be OK

Be very careful subsituting NiMh for NiCd.

It may overcharge and split

Never switch nickel to lithium

[The Natural Philosopher]

sort of.

Not high street but they are available,.

[Harry Bloomfield]

NY wrote on 07/02/2019 :

Go for the largest capacity you can find, but be wary that some sellers claim a larger capacity than actual. I just bought cheap ebay cells and they have been fine for the past couple of years.

Yes, the different type have differing charging requirements.

[nothanks]

Ours (Siemens c47) are always in their cradles when not being used but the original Chinese NiMH batteries are still OK after nearly 9 years. Maybe some phones have better charging control than others.

[Thomas Prufer]

No problem...

Correct. Some phones like to have the batteries charged once and then run down to zero-dead-nothing, as this calibrates the charge meter. Do it, because even if it doesn't do this, doing it won't harm anything...

Good choice.

Yup.

Thomas Prufer

[Pamela]

There is the option of low self-discharge NiMHs (such as Eneloops) which may not have been supplied with the phone. It might affect the calibration although that is rough and ready at the best of times.

[NY]

The BT 8500 set that we have replaces some Gigaset phones which had horrendous problems with failing to answer when you picked the phone off its rest and pressed the answer button if it failed to auto-answer, and with batteries dying with no warning. It was Gigaset support who first tried to tell me that my problems were due to fitting higher-capacity batteries to replace the ones that they had supplied (which sounds like fluent bollocks) and anyway it ignores the fact that the replacement batteries were only necessary because the supplied ones were unpredictable.

The BT handsets are fine as long as you don't turn on the speakerphone, then they drain quickly - I get about 30 mins before I get the dreaded bleep-bleep followed by cutting off within a few seconds: it is a race to turn off speakerphone and/or to find another handset. I wish there were more DECT phones with either bluetooth adaptors or a 3.5 mm jack, so you could use a headset rather than speakerphone when on a phone call while at a computer (I do a lot of telephone support for my parents' various computer problems and for a website that they manage, via Teamviewer).

[Dave Plowman (News]

Yes- easily checked if they are hot even after being left charging for ages.

[Brian Gaff]

Yes I've done this. You are lucky a few years ago they were tripple as in a little cage with a plug that were sealed and the replacements were nearly the cost of the phone. However I do feel that the way they charge shortens their lives. Brian

[Brian Gaff]

The other thing is to do away with the charger find a charger that does the batteries one at a time and keep two sets on the go, one in the phone and one in the charger. Brian

[The Natural Philosopher]

I doint think so.

Nickel chargers simply run a constant current through until they see a voltage DROP. Then tghe switch back to trickle.

Lithoum cahrgers charge to the correct voltage and stop

None measire the actual charge delivered. Unless like me you have a fancy model plane one.

[Dave W]

I acquired a Gigaset DECT phone on Freecycle, and the Chinese batteries exhibited the OP's problem. I replaced them with Duracell rechargeable "precharged" cells which are fine. They have twice the stated capacity of the originals.

However the battery charge symbol indicated empty when I installed them, and only showed full when the handset had been on charge. This makes me think the indicator only shows the calculated value, not the actual value. So when it shows empty perhaps it's only half empty, but I haven't tried to find out.

[John Rumm]

Yup, same chemistry, but higher capacity should be fine.

[Pamela]

Thomas said to use the same type of cell. Nothing to do with lithium.

[Thomas Prufer]

Try leaving the phone off the charger until it's completely empty, and only then recharge it.

It's in the directions for at least some Gigaset handsets as "first charge" instructions.

Thomas Prufer

[Thomas Prufer]

From several Gigaset manuals:

"Initial charging and discharging of the batteries "The correct charge status can only be displayed if the batteries are first fully charged and discharged. "Place the handset in the charger for 7 hours. "Then remove the the handset from the charger, (...) and do not put it on the charge runtil the batteries are fully discharged."

Thomas Prufer

[Bill Wright]

I changed mine ages ago for 1.2Ah AAs and they've been fine.

Bill

[bert]

Same here. I've only changed ours once and that was after a similar time period. I have however replaced one handset as the charger proved to be faulty. Got a replacement 2nd hand on ebay from Holland.