Cordless telephone battery pack replacement question

[WildChild]

I have a cordless telephone with a 600 mAh NiCD battery pack that is starting to show signs of age after 1 1/2 year of use. The pack is made of 3 AA in serie with 2 wires connected to a small white plastic plug. Would it be a good idea to cut the wires, solder then on this holder:

http://www.thesourcecc.com/estore/P...atteryAccessories&product=2700412&swlang=true

and use 3AAA NiMH instead if it's not bigger than the 3AA battery pack? The batteries could then be easily be replaced in the future.

The charger of the phone is probably a dumb and slow continuous charger. I never left the telephone for more than 9h on the base for charging and I always charged when the pack was completely empty or almost empty (every 2-3 days). Now I have to charge almost every night.

 

[ACMarina]

Re: Cordless battery pack replacement question

Depends on the phone - some will work well with that kind of setup, and some won't. I've seen people retrofit AA NiMH into a NiCD phone and have serious meltdowns..

A standard battery pack here is about $15, and to pick up a pack of AAA NiMH is $20, so unless you've got extra batteries laying around I wouldn't think it's worth it. NiMH cordless batteries have a similar lifetime, from my experience..

 

[WildChild]

Re: Cordless battery pack replacement question

Meltdown?? Charger charges at too high current and the pack overheat? On eBay and with a Google search, NiMH packs are sold as replacement for the NiCD pack of my phone... I may want to try them for the longer runtime they may provide (1500 mAh instead of 600...).

 

[ACMarina]

Re: Cordless battery pack replacement question

I don't know what happened to the two that I've seen so far - I'm guessing the charger was a trickle charger, and it just kept going until the batteries overheated and popped..

 

[LuxLuthor]

I recently replaced 3 AAA's in a small white pack with 3 wire pin connector with NiMH, but used existing wires to remake battery pack and reshrinked. Only problem I forsee is those battery carriers have some resistance...but if it fits, try it.

 

[VidPro]

.

The charger of the phone is probably a dumb and slow continuous charger. I never left the telephone for more than 9h on the base for charging and I always charged when the pack was completely empty or almost empty (every 2-3 days). Now I have to charge almost every night.

yes they usually are dumb chargers.
i kinda doubt that any holder would fit the usual location for these wrapped tabbed packs, IF it does fit it would be a GREAT idea, but you add in 10mm x 5mm about over a tight pack size. with a holder you could pull the batteries once a year for cycleing maintance as seperated cells

Here we just make the AA packs instead with good batteries, and they fit , after shoehorning them in a bit a remade ni-cd pack with ni-mhy in it charges slower ( because of capacity), goes through less cycles , so it can last many years longer than the original cheap ni-cd packs. chances are you will never have to change it again, Although you should "cycle" them once a year or so, by leaving them off hook untill they run down. like to when it complains about low battery.

when you replace these stock ni-cd phone things with good ni-mhy batteries the Slow dumb charger takes 3X as long to charge them (when the capacity is 3X), and of course they run for 3 times as long also.

 

[VidPro]

Re: Cordless battery pack replacement question

I don't know what happened to the two that I've seen so far - I'm guessing the charger was a trickle charger, and it just kept going until the batteries overheated and popped..

now that you mention the disclaimer
what CAN happen, is that a ni-mhy cell in the pack during a discharge becomes completly discharged, and it doesnt "wake-up" when its put on the charger, because it needs a bigger hit of power to pull it off of the floor (0 volts) the lower rate ni-cd charger doesnt provide the current to snap the 0 volt battery back into charging again, so the charger charges only 2(3) batteries in the pack. That is ONE possible way to have trouble when you upgrade to higher capacity.
i have seen that occur on the 4x pack, but we just jolt it back off of 0V by slamming the pack with power, and its good to go again.

---1.0----1.0----0.0------ (discharged to this)

----1.4----1.4---0.0----- (tries to charge like this)

the ni-cds at thier lower capacity and more resilliant form than the ni-mhy handle reverse charge better, and are less likly to be stuck at 0, when hit with the charger made for them.

sometimes you can just put it on the charger 2-3 times and the capacitor on the charger will snap them back.
SOME chargers will notify you that its not "taking" the charge, some would just bake the 2(3) other batteries.

 

[WildChild]

yes they usually are dumb chargers.
i kinda doubt that any holder would fit the usual location for these wrapped tabbed packs, IF it does fit it would be a GREAT idea, but you add in 10mm x 5mm about over a tight pack size. with a a holder you could pull the batteries once a year for cycleing maintance as seperated cells

Here we just make the AA packs instead with good batteries, and they fit , after shoehorning them in a bit a remade ni-cd pack with ni-mhy in it charges slower ( because of capacity), goes through less cycles , so it can last many years longer than the original cheap ni-cd packs. chances are you will never have to change it again, Although you should "cycle" them once a year or so, by leaving them off hook untill they run down. like to when it complains about low battery.

when you replace these stock ni-cd phone things with good ni-mhy batteries the Slow dumb charger takes 3X as long to charge them (when the capacity is 3X), and of course they run for 3 times as long also.

Anyway, I almost always wait till the battery is empty (when the telephone doesn't power on anymore) before charging it. Cycling is not a problem!

 

[VidPro]

well just dont forget that its a series pack, being dumb charged, it aquiries its "balancing" by being overcharged well within spec, that brings each battery in the series set to fully charged.

discharging it all the way, which needs to be done ever once in a while, will incurr the usual reverse charge, depending on the minimum voltage the phone runs at.

so other than maintance cycling, it is better to have allowed the charger to fully charge it up, so they can all top off to full charge, and all become balanced the slow dumb way.

lets see if i can draw that too
CHARGING

------1893ma -----1905ma ---------1765ma------ (in capacity this is the unbalanced pack)

------1993ma -----2005ma----------1865ma----- (this is it getting neer fully charged)

------2015ma ---- 2005ma ---------2000ma----- (this is after it has dum charge topped off) (close enough)


now we DISCHARGE this unbalanced one

------1893ma -----1905ma ---------1765ma------ (start of discharge for unbalanced pack)

------863ma -----905ma ---------755ma------ (used up for a day or so)

------100ma -----150ma ---------0ma------ (by now its reading low battery)

then we DISCHARGE the one that topped off fully (balanced)

------2015ma ---- 2005ma ---------2000ma-----

------1010ma ----1001ma ---------990ma------

------50ma -----50ma--------0ma -------- (something about like that) nothings ever perfect

 

[WildChild]

I know! I finally decided to rebuild the pack using Sanyo 2500 mAh. They self-discharge within 2 weeks but I think the telephone will drain them faster. If they last 3-4 days, it will be OK for me! If it doesn't work... I'll put back the wires on the old NiCD pack. I also tested that the telephone charges at 75 mA which is much less than ~C/33 for 2500 mAh cells.

So if I make the calculation:

(2500mAh * 1.6 (for a full charge without balancing)) / 75mA = 53h20 minutes for a full charge!

So it seems I may get much more runtime but it will also take much time for a full charge. With the 600 mAh NiCD pack, it looks like it needs 12h for a full charge.

Did I made any mistake?

 

[VidPro]

close enough.
personally This week i would use enloops, even though i would choke on the price. they would stay in balance more , because they dont self discharge. so each would be closer in capacity to the other.

or use the low capcity ones they are using in hotwires, as tested by silverfox, there are some cheaper omnipotent 1600-1800 ones and they would handle reverse charge, and have less self discharge than high caps.

personally Last week (actually 3-4 years ago) i used energyser 2200s, and they are still working.

 

[WildChild]

close enough.
personally This week i would use enloops, even though i would choke on the price. they would stay in balance more , because they dont self discharge. so each would be closer in capacity to the other.

or use the low capcity ones they are using in hotwires, as tested by silverfox, there are some cheaper omnipotent 1600-1800 ones and they would handle reverse charge, and have less self discharge than high caps.

personally Last week (actually 3-4 years ago) i used energyser 2200s, and they are still working.

I'll see with them first... Since I have no other use for them. If I'm satisfied, I'll probably only use rebuilt pack of my own in the future!

 

[jzmtl]

Are you sure they are AA? Sometimes manufacturers use cells that's the same size but not actually 1.5v AA. And I would NOT use eneloop, so if the phone charger doesn't work with nimh and fry your battery pack, you are out less money. And there's no reason to use LSD battery for something that's being charged all the time.

 

[WildChild]

Double post removed...

 

[WildChild]

Are you sure they are AA? Sometimes manufacturers use cells that's the same size but not actually 1.5v AA. And I would NOT use eneloop, so if the phone charger doesn't work with nimh and fry your battery pack, you are out less money. And there's no reason to use LSD battery for something that's being charged all the time.

Yes, they are AA NiCD 600 mAh 1.2V flat-top cells.

After 2h of charging, the "new" NiMH cells are still cool and their voltage is slowly increasing. I'll leave them overnight and see tomorrow how they are.

 

[VidPro]

And I would NOT use eneloop, so if the phone charger doesn't work with nimh and fry your battery pack, you are out less money. And there's no reason to use LSD battery for something that's being charged all the time.

right there would be no use unless you leave it off the charger.
like mine can be off hook for 2 weeks to a month with the higher capacity cells, dependant of course on USE of the phone, talking on it takes much more power than its standby.

 

[BigusLightus]

I replaced the original nicad pack with this one several years ago and have never had a problem.

Sadly, the phone can only stay off the charging base for two weeks before shutting down completely. If I talk much I recharge it once a week. Sure would be nice to have one made from Eneloops. Do they come in flat tops?

Standard AA nicad in green for comparison.

 

[VidPro]

they didnt give you 2 extra milimeters to work with there BigusLightus?
i suppose "industrial" and pack making flat tops of LSD cells would be comming out even before consumer ones?

ok i just checked for you, you can NOT cut the nipple off of a sanyo enloop consumer AA to get the extra space :thinking:, the nipple has in it a rubber seal that seems to be the gas releace seal for the battery.
(it would ruin the cell).

 

[WildChild]

they didnt give you 2 extra milimeters to work with there BigusLightus?
i suppose "industrial" and pack making flat tops of LSD cells would be comming out even before consumer ones?

ok i just checked for you, you can NOT cut the nipple off of a sanyo enloop consumer AA to get the extra space :thinking:, the nipple has in it a rubber seal that seems to be the gas releace seal for the battery.
(it would ruin the cell).

In my telephone, I had to cut 2 plastic spacers that hold the pack in place to make space for the new pack that has button top cells in it. Those 2 spacers were about 1-2 mm long.

 

[jzmtl]

I replaced the original nicad pack with this one several years ago and have never had a problem.

Sadly, the phone can only stay off the charging base for two weeks before shutting down completely. If I talk much I recharge it once a week. Sure would be nice to have one made from Eneloops. Do they come in flat tops?

Wait, you don't put phone back in base after use? I always that's what people do, don't need to hunt for it everytime too.