Introduction: Battery State of Charge Meter

Picture of Battery State of Charge Meter

 Here's a simple project that indicates how much energy is remaining in your batteries.
It's a gauge for lead-acid batteries, It’s an LED bar graph voltmeter with a scale it starts at less then 11.5 volts up to 16 volts.
I have it hooked up to my solar battery bank so I can tell how much its charging when its sunny out to how much it has left when I’m using the batteries.
I also made the case that it sits in with my new 3d printer lol.
I will be posting the files if you would like to print your own case also will put case up on thing-a-verse
lets start with a parts list they should be very easy to find parts i had to only buy the leds since it takes 11 of them but get 12 and burn one for the led god for good luck lol.

Parts List
Integrated Circuits
U1- 7805, 5VDC, 1A. Voltage
U2- LM 3914N, LED Bar/Dot Driver

D1- 1N4002, 1 A. Silicon
D2- 1N5241B, 11VDC Zener
D3-Amber LED indicates 16.0 VDC
D4- Amber LED indicates 15.5 VDC
D5- Amber LED indicates 15.0 VDC
D6- Green LED indicates 14.5 VDC
D7- Green LED indicates 14.0 VDC
D8- Green LED indicates 13.5 VDC
D9- Green LED indicates 13.0 VDC
D10- Green LED indicates 12.5 VDC
D11- Green LED indicates 12.0 VDC
D12- Amber LED indicates 11.5 VDC
D13- Red LED indicates <11.5 VDC

R1- 390, 1/4W.
R2- 820, 1/2W.
R3- 1.4k, 1/4W.
trimmer potentiometerR4- 10k

Miscellaneous items
On/off switch your choice
A connection bus for the outside of your case if you use a case again your choice
Didn’t think I was going to make an instructable. so I didn’t make a step by step guide
If there is enough of an interest I will make one.
Have fun be safe


xained made it! (author)2015-07-19

Made it, thanks, it's nice and simpel !

Rainymadman (author)xained2016-04-25

Very cool
Sorry Ifir the late response lol

walang hiya (author)Rainymadman2016-05-04

can you pls indicate the zener diode that you use..does the zener diodes you used works in 48 VDC Solar battery Bank?ty

Rainymadman (author)walang hiya2016-05-04

I clearly added all info
1N5241B, 11VDC Zener
You'll need to get a larger one for your needs
I'm only familiar with 12 volt systems

walang hiya (author)Rainymadman2016-05-04

well i guess i just need to search about my 48 VDC system..anyways thanks for the help..keep me updated if you have some great ideas.THANKS!

hozr84 (author)2016-04-25

I'm a novice at this and would like to build it. Would you be able to make a guide?

Rainymadman (author)hozr842016-04-25

I'm not up to building a guide but I'll try and answer what ever question you have not sure how much of a novice you are but you need a breadboard to build and test this circuit before you commit it to a board so get all the items on the list first

walang hiya (author)Rainymadman2016-05-04

what specs of zener diode if im going to use in 48 volts?i really need help btw.. this device is great but i need to make it in up to 48VDC..tnx

rahuldj (author)2015-12-23

Hello, I am searching for simple battery charging indicator. I am using a 4 volts 1 amp lead acid battery and charging the same on 3 Watt solar panel. It charges fine with existing circuit but does not have indicator. I just need 3 indications 1. Battery low - to indicate charging should be started 2. Battery full - to indicate charging should stop 3. Charging on indicator, can some one help please

r2p2 (author)2013-10-16

Would it be possible to put a large resistor on the input to test for voltages up to about 300 volts DC?

r2p2 (author)2013-10-16

Would it be possible to put a large resistor on the input to test for voltages up to about 300 volts DC?

ToXiCATOM (author)2013-09-21

can u give us a picture of this when it is working PLZ!!!

Rainymadman (author)ToXiCATOM2013-10-10

I lost every thing when sandy (big as storm) flooded me out

Macattacku (author)2013-10-01

Huh. I wouldnt even have the amber lights there. Any thing over 14.5 should throw a switch and disconnect the solars from the battery because thats a serious over charge. If 15 volts lights up you have issues.

Rainymadman (author)Macattacku2013-10-10

That's why the lights are there or how else would u know you had an issue

Berniecheah (author)2013-10-10

Does it only work with batteries ranging from 12V onwards?? What if i were to use a 12V battery then? Will it automatically shift the range? Cool project by the way. From Malaysia :)

Rainymadman (author)Berniecheah2013-10-10

Hi berine
It's a meter that will tell you what the current state of charge is .
It starts at <11.5 volts goes as high as 16 volts.
On my list of parts it shows you what each light means
I hope this helps you if you need more info just ask
And let me know how you make out

ToXiCATOM (author)2013-09-21

men it is too hard to find LM3914N.but i found one on the internet but it is like 6.00$ men!!!

ToXiCATOM (author)2013-09-20

Thanks bro!!!

Smitho (author)2013-08-18

Thank you for this project, I'm trying to make now. Greetings from Spain

Rainymadman (author)Smitho2013-09-19

Hey your welcome let me know how you make out

ToXiCATOM (author)2013-09-19

Thanks bro I'm making This Project.but I don't have the lm3914 and 7805 LOL.but don't worry i will get it and make this project.this is my first thing that i'm making from instructables.

Rainymadman (author)ToXiCATOM2013-09-19

Hey your welcome let me know how you make out

Vpatel24 (author)2013-07-31

Thanks for replying,
I have tried online, like looking for similar voltage indicator but its not exactly what I want thou =/
I should have said before but yeah so the reason why was because Im making a 'solar phone charger'. For my iPhone 5 and thats why i wanted to know if you knew how.
With this indicator whenever im charging the batteries in the circuit i can see if they are fully charged!

Thanks for your time!

Vpatel24 (author)2013-07-30

Hey there, is it possible to make a 0v-5.5v led inductor??

Rainymadman (author)Vpatel242013-07-30

Hi vpatel24
I'm sure there is I never had a need for it , what I know about electronics is very small been teaching myself and burning up a lot of resistors lol
If I can help you ill try my first response would be to do a search for it and see if its been made if you haven't done that already
If you give me more info on what you need it to do as in an application .
I needed a way to check on my charging so I made this

Brose549 (author)2012-06-12

I am interested in building an LED monitor like yours for the batteries in my EV project. I have 12 lead acid batteries. Can you give me any help how I might go about doing this. I know that there is probably a way without duplicating this circuit 12 times but not sure of how to go about building what I need. Any help would be greatly appreciated.

Rainymadman (author)Brose5492012-06-13

Well I have a bank of six battery's and only use one batts are hooked up I think it's called parallel positive to positive and negative to negative
So total output will be twelve volts so metter checks state of all batts not on a one on one bassis
So when there being charged I can see the charge voltage and when there not being charged I can see there standing voltage or how long it takes to drain them
If I can help you with anything I'll try

Dr.Bill (author)2012-02-09

Are the LED's bussed together on the positive side ?

Rainymadman (author)Dr.Bill2012-02-09

LEDs anodes are all connected

Rainymadman (author)Dr.Bill2012-02-09

Hey for the LEDs the cathodes connect to the chip except the red led
And the diode D1 cathode to the chip and diode d2 cathode to positive
That should fix you up the schematic is online

Dr.Bill (author)2012-02-09

Never mind I got it but I still need the polarity of the Zener

Dr.Bill (author)2012-02-09

How about the cathode on the zener, which way does it face ? The picture is not so good to see the band. There is light reflecting off the part.

Dr.Bill (author)2012-01-29

This is just enough Instructable to get the job done. 5.0 Stars.

Rainymadman (author)Dr.Bill2012-01-29

Each led is 0.5 volts . The meter reads up to 16volts but you shouldn't be charging them that hi lol
I have a 150watt solar system setup with a four battery bank works well

Dr.Bill (author)Rainymadman2012-02-04

I have 10/ 20watt panels to be connected to a 4 battery bank.
This looks like a very simple circuit, can you explain how it works to me ? Spicifically the need for a Trimmer.
I imagne you have to monitor the voltage personally while the bank is charging so as to not over charge ?

Rainymadman (author)Dr.Bill2012-02-05

Hey drbill the trimmer is to control the led briteness that's all so if it's setup outside you can turn up the briteness or if indoors turn it down since they do use power the dimmer the better and I put a switch since if I'm not around no need to waste current..
I don't have to monitor the charging at all but with this I can with just a glance. My charge controller works well. The circuit is very simple I hope I answered your question it's early and I'm off to work lol

Dr.Bill (author)Rainymadman2012-02-09

Thank You. You have answered my question in full.
I am in the process of putting this 'Ible' together.
5 stars

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