Can someone suggest a 1.5V rechargeable battery tester circuit for me?

[tengyy]

Prefer use led to show the battery volume.. or something like empty, half, full LED indicator or use the LM3914

 

[D.A.(Tony)Stewart]

Best intelligent charge monitor will pulse battery with light load and heavy load and compute C, capacity based on load voltage and ESR.

For example using programmable current source ,pulse 1st 5 mA then 505 mA and use S&H to display ESR or delta V over delta I (0.5A) which is a function of C the Ah capacity of battery. Each battery chemistry has a different correlation between ESR and Ah storage, but is a linear indicator from 10 to 90%.

Another method is to measure light load voltage 5mV then S&H this value then use a current shunt to measure V/2 currents level or brief short circuit current ( 50 us). This current is also a function of ESR and charge state where initial voltage and short circuit current are indicators of SOC. scale must be selectable for different battery sizes as AAA and D size are inversely proportional size to ESR and thus proportional to Ah capacity.

Normally open circuit or Voc is not a good indication as float voltage drops 10% or so from a light load (5-20mA) due to chemistry and short circuit pulse is best indicator usng S&H during very short pulse to display on light bar.

If you can , design a nonlinear or log scale for wide range of battery capacities from 1/10C to 10C. The ESR may have a wide range in decades between different battery chemistry.

ESR affects charge discharge rates as well like 1/10C to >10C which all are limited due to self heating of ESR and resulting internal thermal rise. This is determined by max W/Ah of self heating that the mass of battery can dissipate. e.g. LiPo is 8W(from ESR) per Ah capacity and max sustainable current load without damage can be derived from this.

- also readand understand Peukert's Theorem which accounts for variations of Ah capacity with discharge rates.

 

[BradtheRad]

It would be easy if they made led's that only require 1V to light up.

Radio Shack sells battery testers. I have an old one that has a built-in voltmeter. It applies a 100 mA load to a 1.5V battery (which is the proper way to test for battery condition). It is simple to use.

To light an led from a 1.5V battery, you might try boosting the voltage with an IC. The 3909 is an 'led flasher' which operates down to 1V. I believe it has been replaced by a modern IC, or else its function can be duplicated with a charge-pump circuit.

 

[D.A.(Tony)Stewart]

I agree Brad, it is pointless to design an LED display for a 1.5V battery using 2V LEDs. It would end up costing more than a cheap DMM and a 10 Ohm resistor to measure current. which would indicate roughly Vbat= Voc - I*ESR. Both Open circuit voltage and Vbat under load are better testers than a complex custom design with LEDs.

 

[tengyy]

Battery Tester Project Using LM3914 IC
is this circuit can be function well?

https://www.electronics-project-design.com/batterytester.html

 

[Audioguru]

Battery Tester Project Using LM3914 IC
is this circuit can be function well?

https://www.electronics-project-design.com/batterytester.html

When the input pot resistance is turned down too low and the battery can supply plenty of current then the pot and/or the battery will blow up!

 

[tengyy]

Battery Tester Project Using LM3914 IC
is this circuit can be function well?

https://www.electronics-project-design.com/batterytester.html
When the input pot resistance is turned down too low and the battery can supply plenty of current then the pot and/or the battery will blow up!

Thank you for your answer, now my problem is don't know why the 18,17,16 pin LED will light up even no battery is testing.

 

[D.A.(Tony)Stewart]

It could be missing cap to suppress noise.

Otherwise an answer may come after you record and list all Voltage readings for pins 2 to thru 9. for different conditions.

 

[Audioguru]

Thank you for your answer, now my problem is don't know why the 18,17,16 pin LED will light up even no battery is testing.

I think the LED on pin 1 will also light with no battery on the input.
It is a stupid circuit, designed by somebody who does not understand the LM3914.

The LM3914 creates 1.25V between pin 7 and pin 8 just like an LM317 voltage regulator. The 1.25V across R1 causes a current of 1.25V/1k= 1.25mA. This 1.25mA also flows through the pot on the input of the circuit causing a voltage there that the LM3914 is showing.

I fixed the circuit for you:

 

[rajaram04]

I think the LED on pin 1 will also light with no battery on the input.
It is a stupid circuit, designed by somebody who does not understand the LM3914.

The LM3914 creates 1.25V between pin 7 and pin 8 just like an LM317 voltage regulator. The 1.25V across R1 causes a current of 1.25V/1k= 1.25mA. This 1.25mA also flows through the pot on the input of the circuit causing a voltage there that the LM3914 is showing.

I fixed the circuit for you:

yeah right sir we too discussed it once & it is really a wastage of time .