10 LED Battery Monitor Circuit

The article shows a simple method of using the IC LM3915 for monitoring battery voltages right from 1.5V to 24V in 10 discrete steps using 10 LED indicators.

Using a LM3915 IC for the 10 Step Function


We have already learned a number of LM3915 projects such as vibration meter, 10 step battery charger circuit etc, yet one more circuit using the same chip is discussed below wherein it's configured as a 10 step battery voltage monitor circuit.

The circuit allows you to visualize precisely what voltage your battery has at any particular instance while it's being charged.

The LM3915 is basically a 10 stage dot/bar mode LED driver circuit which provides a sequential 10 step LED display corresponding to the varying voltage levels set at its signal input pinout#5.

This input can be set with any voltage level right from 1 to 35V for acquiring a correspondingly sequencing readout of the voltages fed on that pin.

In the proposed circuit of a 10 step battery charging indicator we assume the battery to be a 12V which is to be monitored, the circuit functioning may be understood as follows for the aforesaid condition:

The transistor at the right end is configured as an emitter follower replicating a  high current, constant voltage zener diode, fixed at 3V.

This is required so that the LEDs are restricted from drawing excessive current, unnecessarily making the IC warm.

The battery voltage is also fed to pin#5 via a voltage divider network made from a 10K resistor and a 10K preset.

The outputs of the IC are all connected with 10 individual LEds for producing the required 10 step indications. The color of the LEDs can be as per your preference.

How to Set up the above explained battery status indicator Circuit.



  1. It's pretty simple.

  2. Apply the full-charge voltage level across the point indicated "to battery positive" and ground.

  3. Now adjust the preset such that the last LED just illuminates at that voltage level.

  4. Done! Your circuit is all set now.

  5. For calibrating, simply divide the above mentioned full charge level with 10.

  6. For the present case, let's assume the full charge level to be 15V, then 15/10 = 1.5V, meaning each LED would stand for an increment of 1.5V. For example with the 8th LED just ON would indicate 1.5 x 7 = 10.5V, 8th LED = 12V, 9th LED = 13.5V and so on.

  7. Similarly, the circuit can be used with any battery and just needs to be set as per the above guidelines for achieving the proposed 10 step battery level monitoring.

Circuit Diagram


10 Step Battery Charger with Indicator Circuit

Need Help? Please send your queries through Comments for quick replies!




Comments

roderel masibay said…
sir Swagatam good day to you,sir can you make a design for power supply of a solinoid .

circuit description
1.12vdc/250mA.60'C temp.
2.when switched ON the 1st LED light ,when switched OFF,the 2nd LED light
3.sir circuit simple ,i have more 7812regulator thanks sir swagatam ....
roderel masibay said…
sir swagatam im roderel follow up information about my resquest 12vdc /250mA 60'C temp power supply of solenoid valv for controling air thanks sir
Swagatam said…
Hi Roderel,

The idea is quite simple, you can do it as explained below:

You can incorporate any standard transformer or smps 12V power supply design and connect the load via a SPDT switch.

The center pin of the spdt will go to the 12V(+), out of the other two pins the one which switches ON will go to the load.

The unused pin can be connected with one of the LEd anode for indicating switch off.

The switch ON LED can be connected acros the solenoid.

Both the LEds must have their own 1K resistors in series.

The cathodes of the LEDs, and the negative of the solenoid should be made common and connected with supply negative.
roderel masibay said…
thanks you sir swagatam very much
Umer Ilyas said…
what minimum current rating will this circuit support. will it be ok with 1200mAH battery.
Swagatam said…
It will work for all types of batteries within 30V.
Umer Ilyas said…
i have a problem i have build the circuit on veroboard, bread board, i have switched IC's LM 3915(doubting may be IC is defected). but it isn't working. the led's positive is always less than negative terminal connected to 1,10-18.
can you tell me what is wrong with my circuit. thanks
Swagatam said…
I could not understand what you meant by "led's positive is always less than negative terminal"

Varying the preset should make the LEDs illuminate corresponding to the set voltage level at pin5.

Set this voltage correctly as explained in the article.
Umer Ilyas said…
the preset has 3 terminals one in center and two side terminals. according to diagram the center terminal and one of the 2 side terminals are connected to ground. the other terminal is connected to pin 5. am i picking this right??

secondly i have a confusion that when we adjust the preset the LED that will glow at the desired voltage will be LED 1 or LED 10.
Swagatam said…
Yes you are right.

The 10th LED should illuminate at the desired full charge level.
Jinnamuru Xunte said…
how do the LED light, one by one OR as the Volt in gets higher the led glows as if a bar level indicator? or suggest me
Swagatam said…
yes with pin9 connected to supply the IC outputs sequence in bar mode.
Jinnamuru Xunte said…
this circuit is used to monitor a battery while charging, right?
can I use this circuit to monitor battery while discharging? or while the battery is being used?


And oh! you said that this circuit can visualize a battery's voltage, can I use this like a volt-meter exclusive only for 12v batteries?


and thanks for the suggestions! thanks for the help! you help me and everyone a lot!!
Swagatam said…
Yes, everything that you have asked is possible using the above circuit.
Jinnamuru Xunte said…
For Your Info. jinnamuru xunte and achilles hector are the same person.
Jinnamuru Xunte said…
what do you mean with this ...

"Now adjust the preset such that the last LED just illuminates at that voltage level."?

is it

ONLY the 10th led will light?

OR

all of the LED will light.
Swagatam said…
All the LEDs, up till the last one
Anthony said…
I have a cooler-warmer device which works on DC, the AC is usually converted to DC and now the power pack is bad and I could get an exact replacement. The power pack is rated 12v 5A. Plss help me with a schematic that's not bulky due to limited space in the device. Thanks
chris said…
Good day, Pls sir.... I need a circuit to step up a 12v 500mA to 12v 5A. I know you are so busy, but I need it. Thanks a lot
Swagatam said…
It would be a lot complicated to built a 12V/5amp smps, so i would suggest that you procure the unit readymade from the market.
Swagatam said…
Good day Chris, you can boost voltage but never current, not even by a mA...so your requirement isn't feasible.
Jinnamuru Xunte said…
if use your circuit like

"Simplest Automatic Emergency Light Circuit Using IC555"

where will i connect this battery voltage monitor?
Swagatam said…
across the battery terminals (+) (-)
Jinnamuru Xunte said…
can i connect this "How to Build a Simple Hi Efficiency LED Torch Circuit at Home" at the output?
Swagatam said…
you are confusing me...
Jinnamuru Xunte said…
ohhhhh!!!! im sorry i sent the wrong comment...:-)
Umer Ilyas said…
it is not 10 step max voltage is indicated by 10th led and minimum by 6th led
suresh kumbhar said…
sir,this circuit use inverter!
shawon kazim said…
Hello sir if i use LM3914 instead of LM3915 is there any problem in this circuit ?
Swagatam said…
either will work, both are almost similar
Alaa Jennoud said…
good day to you sir, i'm trying to use your circuit to monitor 12v lead-Acid battery while discharging.
I've build your circuit in "Circuit Wizard 2 SE" and uploaded it.
The thing I want is to make 10th LED illuminate at 13.2v "Fully charged",was able to by adjusting the 10k variable resistor, but the thing that I couldn't do is to make the 1st LED to illuminate at a desired voltage, lets say 11.5v.
In short, 10th LED at 13.2v and 1st at 11.5v .
Thank you sir very much in advance & sorry for bad English.
Circuit can be viewed at :
s9.postimg.org/bfvx1qt4f/image.jpg
Circuit file built in "Circuit Wizard 2 SE" link :
https://mega.co.nz/#!jhhT3S4b!VYxtapGyoo12r--1Ebdgc80Bj1_b3zrirp4c7kwz9UA
Swagatam said…
Good day Alaa,
you can try replacing the BC547 zener with a 10k preset and adjust it to get 3V at 13.2V input. Now adjust the IC preset to illuminate the last LED at this 3.6V.

Make sure the link from pin9 junction of the IC is now connected with the emitter of the BC547 and not to the battery, but the 10K from the BC547 should stay connected with the battery positive.
All leds get illuminated in dot mode ,10th and 9th led's brightness is less compare to 1st and 2nd led and i have removed transistor zener,and 10k resistor from bc547,is that a problem
Swagatam said…
the circuit should be built exactly as shown in the diagram..... you should adjust the 10k preset as instructed in the article for setting up the circuit.
hui said…
dear sir... what does it mean "Now adjust the IC preset to illuminate the last LED at this 3.6V" ..?? the last led is the minimum LED about 11.5v voltage source input??
Swagatam said…
hui, I can't remember exactly what I interpreted.. I think I meant to say that the 13.2V could be compressed to 3.6V across the IC preset, .... so that now the charging phase could be equally divided across all the LEDs

however still this will not fulfill Mr. Alaa's requirement...I may have to think hard to solve the issue
jacky said…
how to increase the brightness of leds as they lit very dimly . By decreasing the 10k,brightness increases, but transistor gets heated up.
Swagatam said…
remove the transistor, resistor and the zener stage and replace it with a 7805 IC.
jacky said…
Thanks,can i replace bc547 with any other medium power transistor.
Swagatam said…
it'll give the same results
Satya Yudhis said…
Dear sir, I think I can use this circuit to charge 3.7v li-ion battery by replacing some components. The problem is that I don't know what should be replaced and the value of the new components.. Can you please tell me? Thank you..
Swagatam said…
Dear Satya, you don't have to replace anything, just remove the transistor zener resistor stage entirely and connect the positive to the LED top rail....and the negative to all the points which marked as "ground", and also make sure that the 10K resistor from pin5 is also connected to the positive line
Satya Yudhis said…
Thank you, sir.. And what about the input voltage? Does it still need 22v? Can I use 5vdc instead?
Swagatam said…
No that's not required, 5V will do.... but I cannot see 22V mentioned anywhere in the article.
Satya Yudhis said…
It's on the diagram.. lol..
By the way, I made a modified diagram for my goal. Did I do it right? Here's the link.
https://drive.google.com/open?id=0B5tbDoK993tYd182SnNzWlBfVkE

Once again, Thank you, good sir!
Swagatam said…
that's perfect, you can go ahead with it

apply 4.2V and adjust the 10k preset such that the 10th LED just lights up.
Swagatam said…
.....by the way there's no 22V in the diagram as well...may be you are confused with the 2.2uF symbol, it's the capacitor symbol not a supply input :)
please click the diagram to enlarge
Satya Yudhis said…
Perfect! I'm going to build this circuit.. And yes, I just realized that it's a capacitor symbol.. Thank you so much, sir.. You are very helpful..
Swagatam said…
you are welcome!
Satya Yudhis said…
Sir, I've finally built the circuit using the diagram I provided before.. Everything works perfectly but one thing.. The LEDs won't work in bar mode.. It works in dot mode.. Do I need to add a 2.2uF capacitor? I built the circuit without one because I couldn't find 2.2uF 5v capacitor..
Swagatam said…
Satya, I think you might have missed the pin#9 connection with the positive line...do it and you will find the LEDs illuminating in the bar mode.
aobyrne said…
Hi sir. thanks a lot.

I have a 6V kid's electric car, i whant to do make this for it, because it dosent have. what i have to change?

thnaks
Swagatam said…
Ho aobyrne, you don't have to change anything in the circuit, you make sure to supply 7.2V to the circuit and the battery and adjust the preset such that at 7.2V all the LEDs are lit.
panji said…
Dear sir,
How use circuit with 24v battery??? Any component must replace or not?
Thanks
Swag said…
Panji, you can use the circuit with a 24V battery also without any changes in the circuit
panji said…
Thanks you sir. Ill try it.

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