interesting observation about cordless phone

[viorel00]

I have a Panasonic DECT cordless phone (2 handsets) which uses AAA batteries (Panasonic NIMH, 550 mAh min).

I usually charge these in the handsets, and when they say "Charge completed", it shows up 3 lines in the display and the battery lasts about 1 week.

On Dec 28, I tested both sets of batteries (2 in each handset) in my MAHA C-9000 charger, and they measured about 550-600 mAh each. I charged them up in the MAHA and put them in the handsets and both showed ONLY 1 LINE. What? anyway, they've been in handsets since Dec 29, and they still show only 1 line. But that is now 12 days and I don't think they ever lasted this long before.

so a fully charged cell (set of cells) from MAHA registers as almost Empty in both handsets, yet they last longer than if they were charged in the handset.

I guess the handset has some sort of mini-computers that says "hey, I got a cell, but I never charged this cell, so I think it must be almost empty".

What I'd like to do is when the cells run empty indeed, then I will re-charge them in the handset until it shows FULL (charge completed) and then I will discharge them in the MAHA to see how many mAh I get.

Anyway, more of an interesting observation rather than a question, but if you have any insights about what is going on, or you have seen a similar case, please share.

 

[davegLED]

Now I'm no expert but I'm sure the phone doesn't know it hasn't charged the cells. It must have a voltage monitor that a uC uses to indicate how full the battery is.

My guess would have been that initially the cell was over the range of the voltage monitor giving a spurious result on the bar meter. Why this is still reading 1 bar when the voltage must have dropped into a range it normally measures is past me.

 

[jsong]

I observed similar with taking out the battery and putting it right back.

 

[Lite_me]

I guess the handset has some sort of mini-computers that says "hey, I got a cell, but I never charged this cell, so I think it must be almost empty".

I believe you hit it with this quote above..

I think I have the same Panasonic phones and I have deduced that this is how they're programed.

When I got mine new, I charged the batteries on my LaCrosse BC900 wanting to ..do it right. After the charge and putting them back into the phones, the phones still wanted to charge for the 6-8 hrs it calls for in the instructions. I probably did the cells a disservice by... trying to do it right.

And they will, re-charge, if you briefly remove the cells even tho they are fully charged as jsong states above. This again demonstrates that this is how they're programed.

 

[davegLED]

Presumably it just has a timed charge then - removing the battery from the handset resets the timer and the phone can only assume it is a new and flat battery.

 

[Eugene]

Ours has what looks like three AAA's wrapped up in a pack, NiMH. But the phones appear to be simple trickle chargers, they are only a couple years old and the battery will discharge in a day if left off the charger. I was thinking of buying a couple AAA holders and pull out the contacts and see if I can't mount them in the phones to hold individual batteries so I can replace them easier.

 

[viorel00]

Ours has what looks like three AAA's wrapped up in a pack, NiMH. But the phones appear to be simple trickle chargers, they are only a couple years old and the battery will discharge in a day if left off the charger. I was thinking of buying a couple AAA holders and pull out the contacts and see if I can't mount them in the phones to hold individual batteries so I can replace them easier.

Eugene,

The 5.8 GHz or 2.4 GHz phones consume the batteries much faster. These DECT 6.0 Phones (which in fact operate at 1.9 Ghz, similar to GSM cell phones) are much more efficient and this is why the batteries last that long.

Since I posted the first message last night, in one of the handsets the battery died (I got those beeps, "Weak Battery") and now it is charging. The other handset, which I have not used that much, is probably probably going to beep soon.

You could try new batteries in your handset, but they're not going to last this long anyway, unless it is a DECT phone. I always look for handsets with AA or AAA cells, I don't like those shrink-wrap packs.

 

[Lite_me]

viorel00,

Sounds like we have the same Panasonic DECT 6.0 phones. I have 4 handsets. Each handset uses 2 AAA NiMh batteries.


After your post, I decided to 'refresh' the batteries in my 4 handsets. I've had the phones for 6-8 months now I believe. I've checked the battery voltage state of 2 of the handsets and all 4 batteries read 1.40v when removed. (these are AAA Panasonic NiMh 630mAh batteries) I did a discharge on 1 set (all I had room for at the time) on my MAHA C9000 @ 500ma and one registered 550 & the other 561mAh available capacity. Resting voltage was 1.20v for both after discharge. This looks pretty good to me but they're still pretty new.

I'll now put the batteries back in the handsets to recharge. I just did one, and the display read, "Please charge for 7hrs", or something like that. It showed 1 bar.

These are pretty nice phones. The best Ive ever had, and I've had many. I especially like the number blocking ability and the verbal caller ID announcement. If I'm not within reach of a phone and I'm screening my calls, I'll just wait to hear the announcement of who's calling before I decide to answer it. :devil:

 

[Mr Happy]

I have a Uniden 5.8 GHz cordless phone that is coming up to about 6 years old now. It takes a shrink-wrapped NiMH pack of approximately 3xAAA and 800 mAh (the original pack was 3x10500, but replacement packs tend to have 3x10450).

I leave the phones on the cradle 24 hours a day, and when the battery pack is new I find I can get over one and a half hours of conversation in speaker phone mode on a charge. After about 5 years, the original batteries degraded to the point that they would only last about 50 minutes. I replaced them, and now I again get from 1 1/2 to 2 hours of conversation from a charge.

I find this performance and battery lifetime quite reasonable, so I would favorably consider buying Uniden again.

 

[StandardBattery]

Hmmm, I don't have anything to add about this specific phone, but about 4 years ago I bought 3 VTECH phones and my main purchase decision was AA Battery, but security was one too. Each phone takes 2 AA batteries. I was not sure about the batteries supplied, 1400mAh generic green wrap (so they could be good), so I replaced 1 set of batteries with some old 1200mAh Energizer Accu cells that had been sitting for a couple years.

I do love these phones after 4+ years they are all still running great. One gets much more use than the others, last year that one was having reduced talk time (base-line was 4-5 hrs straight talk time when new). I took the batteries and charged and discharged, and charged them again in the BC-700. Put them back in the phone. No problems... getting 4 hours continous talk time again. When not in use all phones sit in their base, which appears to apply constant trickle charge, but I'm just guessing. What ever they have done it has not hurt the cells and I get great performance from them.

I've experienced this with other phones where the cells last longer and hold more energy if they are left in the cradles when not in use. Often I hear people say this is a bad idea, but years of phones has convinced me this is the best way to get the longest life from the cells.

The phones are a bit big by today's standards, but AA rechargeable rule!

Very happy with my AA powered phones.