Rechargeable AAA batteries for DECT phones

[NY]

There was a discussion in this group a while ago about the best type and brand of rechargeable batteries for DECT phone handsets. I believe Eneloop was recommended as a good brand. Is there anything else - capacity, technology - that I need to look for? The current batteries are Philips HR03 RTU NiMH 1000 mAhr, which I bought in replacement for the ones that were originally supplied with the BT8500 DECT handsets. All the handsets have started suffering at the same time from batteries not holding their charge and running out very quickly with no warning.

I believe that larger capacity is not always best with batteries in DECT phones, and that some makes/technologies are better for devices which are kept permanently on charge except when they are being used, otherwise the batteries will discharge because they are constantly connected to the base station.

[Nick Odell]

I guess it may depend on how you use the phones.

The ones I used to use at work were taken out of the base station, carried around the building all day then put back on the cradle at night. A set of 350mAh Pound Shop NiMH jobbies were good enough and it didn't break the bank when we had to replace them.

Nick

[Theo]

I think most cordless phones ship with 550mAh batteries, so that would be the capacity to aim for.

Theo

[Peter Johnson]

That's my experience now the phones are hardly ever removed from the base station/chargers the batteries lose their charging capacity in about a year. I've taken three handset out of use because of it and this message has prompted me to take the other handsets off their chargers for a few hours to run the batteries down a bit and hopefully prolong their life.

[Thomas Prufer]

Just get Eneloops specialy desgned for DECT phones, i.e.:

"eneloop AAA 750 mAh single blister 2 pieces for DECT phone" by Panasonic.

Thomas Prufer

[newshound]

Just checked, mine (BT badged) is several years old and still on the chinese originals.

[Pamela]

Continuous low-rate charging of NiMH cells is usually okay provided the rate is low enough not to trigger venting.

[Dave Plowman (News]

Lots of them seem to cook the batteries - by the temperature of the handset when you pick it up.

[NY]

As little as that? When I replaced the ones that were supplied with the phone (when they stopped holding their charge and ran out after a few minutes) I used 1000 mAhr to give longer talk time.

[The Natural Philosopher]

up to 2200mAh are available in AA format. If that is what they use

[Harry Bloomfield, Esq.]

BT8500 which accepts two AAA per phone.

[NY]

So is the consensus that the BT8500 will work with higher capacity batteries than the 500 mAhr ones that it is supplied with (*), and higher capacity Eneloops will be OK? I'm slightly puzzled: is Eneloop a brand name of Panasonic or is it a generic term (eg for technology used)? As I was looking for Panasonic Eneloop I discovered some Sanyo Eneloops. Are Panasonic and Sanyo effectively the same company?

What's the difference between white Eneloop and black Eneloop batteries?

(*) To give longer talk time.

[The Natural Philosopher]

ah AAA is a bit less then.

A quick search seems to indicate 1100mAh is about tops on NiMh

But 500-850 is probably less bleeding edge

[The Natural Philosopher]

Most chargers will be delta peak and designed not to stress smaller capacity batteries, so should work fine on larger capacity - just take longer to get to the delta peak and fall back to trickle charge.

Yes.

No

"On December 21, 2009, Panasonic completed a 400 billion yen ($4.5 billion) acquisition of a 50.2% stake in Sanyo, making Sanyo a subsidiary of Panasonic."

The former are racist

[Theo]

The hypothesis is as follows:

- higher capacity cells have a lower cycle life (they're more tightly coiled). Cordless phones which live on the cradle get one cycle per phone call, because they get topped back up when the handset is replaced. This is wearing on the batteries. A 'high capacity' cell might provide 300 cycles whereas a lower capacity cell might have 3000.

- the phone and its charging circuit is designed for ~500mAh batteries. Larger capacity cells may confuse it and lead to overcharging. (I'm not exactly sure of the mechanism for this given I wouldn't expect their charging to be out of the ordinary). Temperature rise at top of charge on a dumb charger might cause worse degradation for more tightly wound cells.

- few people really need extra talk time, given the batteries can do 18 hours (or whatever). Most people will replace the handset in the cradle between calls, from when it'll get topped up again.

- few people really need extra standby time - only if the handset spends a long time away from the cradle.

Basically bigger does not equal better.

Theo

[Brian Gaff (Sofa]

The issue is that they are in series and as soon as one cell goes down early the others reverse charge it making it far worse next time. I tend now to have several sets and charge them one at a time in a proper single cell at a time charger. The naff chargers given with these phones, in my opinion are designed to trash them. Brian

[Jeff Layman]

I doubt it. I have a Panasonic Dect phone which uses 2 x AAA (550mA) NiMH cells in series. It's 8 years old and shows no signs of battery failure. I was on a call for 45 minutes this morning and the battery symbol was still at 3/4 full. It's been used for over an hour several times in the last couple of years without problem.

The batteries do not appear to be Eneloops, but perhaps because they are Panasonic-branded batteries in a Panasonic phone they are more reliable than other brands.

[PeterC]

IRRC it's under 8 years since Panasonic took over Eneloop. I have Eneloop, Panasonic Eneloop and Panasonic, the Eneloop being the first that I bought. Fujitsu Pro and Panasonic (was Eneloop) Pro appear to be the same, even to the physical size (v. slightly smaller than Aldidl's and 7day shop's equivalent) and thus fit in my torches without jamming.

[Pancho]

I've not tried that strategy yet, but my Siemens Gigaset handsets cook their batteries and hence the batteries only last about a year. So maybe it is a good idea.

[Peter Johnson]

I don't see why they/ it should. I'm reporting my experience with Gigaset (formerly Siemens) phones so I'm not sure that your experience with Panasonic or what the Panasonic manual says is relevant. The best batteries in mine were those supplied with them. Them I got some 'never heard of brand' from Amazon with higher capacity that didn't last very long so I replaced them with Duracells but they didn't last very long either. Gone back to 'never heard of brand' from Amazon with orginal capacity. But I think the key issue is that the phones don't get used much compared to former times.