Help please.

[yafch]

Hello friends.

Two days ago i found that NI-MH battery pack in my wireless desk phone were not recharging any more. I checked it to confirm and found the pack was worn out.It won't recharge any more.It was 3.6v 1500mAH NI-MH.(3 1.2V batteries in series inside the pack)
I purchased the new genuine battery pack,(really costly one it was). every thing went fine new pack recharged and phone worked as it was working before.

I hacked the old battery pack and took out the wiring along with two components inside.(see image 1 for original wiring diagram).

Just for fun i decided to make the battery pack myself. So i put new 1.2V 4800mAH NI-MH batteries (see image 2 ) togather according to original diagram and followed the original wiring schematic which i took care to draw in paint while opening the original battery pack.

I took care to not make any mistake and i am sure i made no mistake. But it did not work.
After 12 hours of recharging the phone goes to shut down in a couple of minutes with my home made battery pack. but the battery pack shows it is recharged and can drive the 4 white led light as long as i want while phone did not turn on untill i attached the charger. the charger is 12v 500mA.

what is the wrong with it?

 

[kchriste]

Are those 4800mah AA batteries? Sounds too good to be true.

 

[yafch]

Yes the packaging and two batteries in the package says so.
The backside of packaging says, rechargeable NH-AA-B2E. AA 1.2V 4800mAh. 4600mAh UP! HAUSSE! 4800mAh.More energy with 4800mAh!
distributed by SONY
Made in JAPAN.

 

[Sceadwian]

That's twice the capacity of even the highest high capacity NI-MH's I've ever seen. You can't just magically make the chemistry twice as effective. Whatever you have seems like it would have to be a scam or fake battery set. The only reason it wouldn't work in your phone is it's not producing a decent amount of current where as a few white LED's hardly use any. Sounds like crappy rip off cells.

 

[kchriste]

The backside of packaging says, rechargeable NH-AA-B2E. AA 1.2V 4800mAh

Hmmmm, the Sony site shows the NH-AA-B2E as being rated at 2500mah:
NH-AA-B2E : Rechargeable Batteries : Battery : Sony Asia Pacific
So yours must be knockoffs and their quality is suspect as Sceadwian pointed out.

 

[yafch]

Ok. Now i think that you guys are right. i went back to dealer and he showed me a pack of four batteries same brand same type. This Battery pack says "rechargeable NH-AA-B4E. AA 1.2v type 3800mAh. 3200mAh UP! HAUSSE! 3800mAh.

The guy at the shop told me the pack was from six months old stock.
So long story short. In a time of six months the battery capacity for the same size increased from 3200mAh to 4800mAh. That,s seems to be impossible with chemistry of battery as pointed out by Mr.sceadwian.

i am going to buy other brand and try my luck. But i think i have to ask one more question.As you can see in the diagram attached with first post there is a component attached to center green wire and negative of third battery. This looks like same size and appearance as common 4148 diode but there is no polarity mark on it. can you make a guess of what it is?
If i would not attach green wire to phone, it won't detect the battery.

THANKS A LOT for your help.

 

[audioguru]

My cordless phones have a cheap Chinese old fashioned and toxic Ni-Cad battery that lasts about one year.
A replacement battery costs more than the phone so I buy a new phone each year that comes with a new battery.

People have complained about those phoney Sony battery cells here before. They might be cheap carbon-zinc cells.

 

[kchriste]

As you can see in the diagram attached with first post there is a component attached to center green wire and negative of third battery. This looks like same size and appearance as common 4148 diode but there is no polarity mark on it. can you make a guess of what it is?

It could actually be a diode. A diode can be used as a temperature sensor when forward biased by a small current. If your meter has a diode check function you could verify this by measuring it in both directions. One direction should read open (OL on some meters) and the other between 0.5 - 0.8. If it reads the same in both directions, it is a thermistor which is also used to read temperature. It is more likely to be a diode going by your description.

 

[Sceadwian]

I think they have some higher capacity NiMHs being developed currently with some novel internal cell construction methods which is supposed to allow more electrolyte, they might break 3000ma and the self discharge rate is supposed to be significantly lower as well, but these cells aren't available for purchase yet that I'm aware of. 2800mah is the highest I've ever seen, and standard ones are 1800-2400 or so. Definitly search around for a real supplier. You don't necessarily need top of the line cells but you don't need to get ripped off either. High capacity cells aren't necesarily the best choice either, if I'm not mistake part of how they're higher capacity is the anode/cathodes are thinner to allow for more electrolyte which means they may have a lower number of charger rates compared to standard cells.

 

[yafch]

Just finished another battery pack. This time with a capacity of 1500mAh chinese origin cells. installed the new pack in phone, lets see what happens now.

The diode like thing is yet to be identified, Multimeter in diode check mode with beeper on gives no reading in both direction no beeping.That means it is NOT a diode. It is not a thermistor.If it would be a thermistor it could be identified in resistor check mode.
Anyway lets see what happens with the new pack in the phone.

 

[yafch]

Now after leaving the phone recharging the new battery pack for few hours i removed the charger. Oh god same thing happened again.The battery died in a couple of minutes.

I think there might be some thing with the phone that prevents it from recharging the non genuine battery packs.While it still works fine with new genuine battery pack.

I am going to leave it with genuine battery pack and use my batteries for some other application.After all i am much more thankful to all of you for your kind help and suggestions.