How would you make a 5 led battery charge indicator circuit?

[SA Dev]

Hi,

I was reading at http://tinyurl.com/33b2z that 12V SLA type batteries are
considered empty at 11.4V and charged at 12.9V.

With 5 LED's how would you design a circuit to show a graph indicating
charge?

Something like :

11.4V-11.69V 1 led lit
11.7V-11.99V 2 leds lit
12.0V-12.29V 3 leds lit
12.3V-12.59V 4 leds lit
12.6V-? 5 leds lit

What would be the easiest and cheapest circuit to do this?

Thanks,

SA Dev

 

[Joerg]

Reference, resistor ladder, five comparators (or opamps used as such), five
LEDs. That's how I would do it if it had to be low cost. Even if it didn't
have to be.

Regards, Joerg

 

[SA Dev]

Hi,

Reference, resistor ladder, five comparators (or opamps used as such), five
LEDs. That's how I would do it if it had to be low cost. Even if it didn't
have to be.

Can someone post a LTSpice example for me?

Thanks,

SA Dev

 

[GPG]

Reference, resistor ladder, five comparators (or opamps used as such), five
LEDs. That's how I would do it if it had to be low cost. Even if it didn't
have to be.

Regards, Joerg

= LM3914??

 

[SA Dev]

Hi GPG,

= LM3914??

I looked at the specs - how do you tell it to have 0 bars when the voltage
is 11.4 or lower and 10 bars when the voltage is 12.9 or above? Does the
spec say the sensed voltage can't be higher than 12V? Can you post a
LTSpice example?

Thanks,

SA Dev

 

[Joerg]

Just look at its data sheet, 2nd application. There is no need to simulate
this kind of circuit.

Regards, Joerg

 

[B Ghostrider]

give this link a try http://www.uoguelph.ca/~antoon/circ/batmon12.htm.
I have used this circulr to monitor the voltage of a 12 volt gel cell
I use as a power supply for a vhs camcorder. Works good. If you are
inerested i can go back in my notes and tell you what changes I made
to the circut.

 

[Rolavine]

Subject: Re: How would you make a 5 led battery charge indicator circuit?

From: B Ghostrider [email protected]
Date: 4/28/2004 12:44 AM Pacific Daylight Time
Message-id: <[email protected]>

give this link a try http://www.uoguelph.ca/~antoon/circ/batmon12.htm.
I have used this circulr to monitor the voltage of a 12 volt gel cell
I use as a power supply for a vhs camcorder. Works good. If you are
inerested i can go back in my notes and tell you what changes I made
to the circut.

If you didn't want to use a processor you should be able to use a dot bar
display driver like an LM3914, using only 5 of it's LED outputs. This chip
allows you to scale the internal reference voltage with a simple pot and if
memory serves. works at your voltages.


Good luck

 

[Rolavine]

Lol, I responded before I checked out the circuit at the link Barry provided.
It uses the same chip I suggested.

http://www.uoguelph.ca/~antoon/circ/batmon12.htm

Rocky

 

[SA Dev]

Hi B and Rocky,

give this link a try http://www.uoguelph.ca/~antoon/circ/batmon12.htm.
I have used this circulr to monitor the voltage of a 12 volt gel cell
I use as a power supply for a vhs camcorder. Works good. If you are
inerested i can go back in my notes and tell you what changes I made
to the circut.

Yes guys, that was *exactly* what I was looking for--many thanks!!

SA Dev

 

[GPG]

This will be easier and have lower drift. Refer to the "expanded scale
meter" in the application notes;


.--------o Pin7
.|.
Battery | |
| | | 470
.-. '-'
| | 10K |
| | |
'-' .-.
|------ Pin5 200 | |<-------o Pin6
| | |
.-. '-'
| | |
| | 10K |
'-' .-.
| | |
| | |680
=== '-'
GND |---------oPin8 & 4
|
.-.
| |5K6
| |
'-'
|
|
.-.
| |<-------o
1K | | |
'-' ===
| GND
created by Andy´s ASCII-Circuit v1.24.140803 Beta www.tech-chat.de
To set up input low led voltage and adjust 1K.
Input high led voltage and adjust 200
The resistor chain will give about 10mA led current. If you run the
leds from the battery directly use dot mode to limit dissipation

 

[B Ghostrider]

glad to hear that. Here a littke thing I did with the circurit. I
replaced the 4K7 ohm resistoir with a 5K pc mount pot. with this you
can control the brightness of the leds. Another thing. for some reason
LED 1 is drimmly lit all the time. onther then that its a nice little
addition to the battery pack

 

[GPG]

glad to hear that. Here a littke thing I did with the circurit. I

replaced the 4K7 ohm resistoir with a 5K pc mount pot. with this you
can control the brightness of the leds. Another thing. for some reason
LED 1 is drimmly lit all the time. onther then that its a nice little
addition to the battery pack

The circuit you gave a link to has an input range of ~72mV, it could be noise
partly lighting led 1. (7.2 mV/step)
The values I posted give a range of ~.75V for the voltage range reqd.

 

[B Ghostrider]

I mean a 50k pot not a 5k pot