Problem with Battery power...

[dsanthosh67]

Hi,

I have a wifi module which is operated at 2.8VDC, Operation wise its works fine but am facing a problem while using different power. I have a regulator MCP1826 which is used to convert 2.8VDC from 4V when battery voltage is at fully charged condition. For power supply when i connected 5V adaptor through MCP1826 regulator wifi gets Turn On normally, but when i connect battery wifi not able to Turn On.Kindly give some suggestion to solve the issue.

5V adaptor have 1000mA rating, 3.7V battery have 1200mA.

 

[Audioguru]

A Lithium rechargeable battery cell is 4.20V when fully charged. I think the battery or its charger needs to be replaced.
A Lithium battery cell can be damaged if it has been discharged to a voltage less than 3V or has been stored fully charged longer than 6 months.

 

[KamW]

From first look it should work until Vin > 3.2V (Vout + Vdropout max) First of all check if you have voltages - there could be overcurrent or overtemperature shutdown. Check PWRGD pin state. Assune you haven't SHDN float.
The most common problem it is voltage drop on bat connections while high current flow

 

[dsanthosh67]

I am using lithium ion battery(Ultra fire TR 14500 1200mAh/3.7V), total device consumes only less than 30mA.
Now battery have the full charge capacity of 3.9V even though device not able to wake up.Is there any alternate solution for this kind of battery?.

 

[KamW]

in theory everything is fine. in practice there are parasite elements. Assume you have long wires, dirt contact etc. and there is serial resistance.
For calculation assume 1 ohm, with standby current it is 30mV volt drop, while in transmission stage (for instance initialisation) with 1A current it is 1V drop. It takes a few ms, but it is enough to not to initialise chip with your battery, while work fine with 5V.
Solution. thicker and shorten wires, clean contacts and use capacitor near module

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if you would like to test, try to add additional battery in series to increase voltage. For instance NiMh one. Be careful; voltage above 6V could destroy chip.

 

[Audioguru]

There are more FAKE Ultrafire batteries than any other brand. https://www.youtube.com/watch?v=eOshOXcSkDA
Use a Name-Brand battery (Panasonic/Sanyo) and do not buy it from ebay.
A Lithium battery that is only 3.9V is about half charged. It is fully charged when its voltage is 4.20V and its charging current has dropped low.

 

[dsanthosh67]

When i increase the voltage nearly 8V by series of two batteries(3.7V 1200mAh), Now the device gets starts working normal but i have one more query. Its maximum voltage is (4+4)=8V and its minimum voltage is (3+3)=6V so i decided a cut off voltage of (3.25+3.25)=6.5V but here 2 batteries not evenly discharge, One battery discharged to its minimum voltage 3.1V and another battery discharged partially around 3.7V.
How to handle this problem two batteries to get even discharge?.

 

[Audioguru]

Maybe your lithium battery is a fake one.
Maybe your battery has been damaged by being discharged too low (3.2V) or has been stored fully charged for longer than 6 months. Your product must disconnect the battery when its voltage drops to 3.2V.
Maybe your charger is no good or is not made to charge a lithium battery cell to 4.2V then shuts off when the charging current drops to a low amount.

Two lithium cells should be charged in a "balanced" charger to 8.4V which might destroy your product. Most Name Brand lithium battery cells with the same label have almost the same capacity for a fairly even discharge but they should be balance charged.

 

[dsanthosh67]

Could you suggest me any Branded Lithium ion battery with 3.7V at more than 1000mAH. Is it correct way to calculate the battery life"Battery Life in hours= ((Battery capacity in mAH*0.7)/ (Load current in mA))".
Based on this calculation my battery works only 3hrs but in theoretical ((1200*0.7)/(150)) = 5.6hrs.

 

[KlausST]

Hi,

from your post#4:

total device consumes only less than 30mA.

Now you calaculate with 150mA.. this is five fold..


Klaus

 

[Audioguru]

Could you suggest me any Branded Lithium ion battery with 3.7V at more than 1000mAH.

There are many good battery manufacturers. There are also many Chinese and other nations manufacturers who make fake ones.
Panasonic make good batteries but some are copied by manufacturers who make fake ones so do not buy from ebay, buy from a real battery distributor.
**broken link removed**

The new battery will be destroyed if it is discharged below about 3.2V.

 

[KamW]

For LiIon bateries internal resistance is about 20 mohm (poor battery, asume 50 mohm), so if you get 1A there wll be 50mV drop!!! You are still much above 3.2V.
For two batteries in series you lose a lot of power for voltage cut off - your 3 hour it is very good result.
To check if it is battery problem connect your circuit to power supply of 3.7 V and I am sure you get the same results.

Or maybe try to use DCDC converer?

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Or you could connect a few mF capacitor near MCP pins and it should start to work. Size of ypur capacitor depends on how bad is your circuit. You could decrease cap and test if it work