please help me in Power Issue *_*

hi all ...

my problem is that i have small modem that come with 3.7 V battery, with 450 mah ... i change it to D battery with 3.6 V with 4000 mah ...

the problem now the modem not working ,... yes the LED in circuit work but the modem can not work ....... when i replace it with old 3.7 battery it work ....

how i can resolve this issue ... please help me out in this problem .....regards

Use the correct battery - presumably the 3.7V one is lithium?.

Yes , the 3.7 is Lith. .....but i need to use the D type battery becouse it much stronger in current 400mah ...

regards

A D battery cell is only 1.5V if it is alkaline and new and is about only 1.25V if it is a rechargeable Ni-Cad or Ni-MH cell. It is nowhere near the 3.7V of a Lithium rechargeble cell so your circuit doesn't work.

Lithium rechargeable cells are made in many different sizes that have different capacities. I got some 3.7V/2200mAh cells from a laptop battery that had a couple of bad cells, two more from a TV converter box and some more from a portable DVD player.

The charger circuit in your modem will also charge a larger Lithium battery cell but it will take longer.

I believe what you have may be like the attached image. It is not a D battery or D cell but three D Size batteries in a NiCAd battery pack. Each cell is 1.2 volts so three in series are 3.6 volts. This is not a good choice.

You would be better off using a larger battery of the same type as you have as in possibly parallel identical batteries.

Ron