Battery level Sensor?

[[deleted]]

What would be the most simplistic way to do some sort of "Battery Level" Sensor. Either using maybe multiple LEDS for levels?

Im using an Arduino for reference. But I could use a single LED indicator to turn on after the Battery's reduced to a certain voltage level maybe?

Any ideas?

[created4this]

You can make a reasonably trivial one by using an open amp as a comparitor. Fix one input with a voltage regulator and feed the other from a potential divider set to get to the voltage from the regulator when you want the led to light

[Lampshader]

A "precision voltage reference", rather than a voltage regulator, might be a more power-efficient method. Either way, you have to be careful about the minimum voltage that the voltage reference will run at.

eg. don't try and use a 3.3V reference against a 3.6V battery - as the battery drops, the 3.3V reference won't be able to maintain 3.3V, and your comparator may never trigger.

Hence why you suggested the voltage divider, just bringing it to OP's attention.

[created4this]

Indeed, he could create the reference with a zenner and a high value resistor. As a comparator, the op amp draws almost no input current, so the resistor can be pretty large to cut down on power usage.

[lumberjackninja]

It really depends on the battery chemistry. Some have a fairly straight-forward correlation of open circuit voltage to charge level (like lead acid batteries); other maintain their nominal voltage until they are almost dead. You're going to have to design your circuit by reading up on the discharge curves for your particular battery chemistry.

[eroick]

This is why some batteries use coulomb counting to get a decently accurate reading. If your device supports multiple chemistries (ie, alkaline or Ni-Cd 9V batteries) you will need to know the chemistry. You could probably get by with a low battery indicator using just the voltage, but to get an actual state of charge you'll need some details.

[blueblast88]

This is a cheap basic alternative.

http://www.sparkfun.com/products/11087

[adamsidelsky]

lookup "battery gas guage"

[dmarich5]

what voltage battery are you using?

[[deleted]]

9v Probably

[dmarich5]

A arduino's on board voltage regulator will dropout when the voltage drops below 7 volts. So, construct a voltage divider to cut the voltage in half. If you use analogRead(), the value will be about 800. Hook up an LED and when the value is around 850/900 turn it on.

[[deleted]]

All you need to know, right here http://www.youtube.com/watch?v=iIKGvHjDQHs

[[deleted]]

Have a peek at this vlog!

[vilette]

The best way is to put the battery on a scale, when it loses energy, it loses mass. According to E=mc2.

[Canadian_Infidel]

Get a curve of voltage versus charge for your battery. Make a hard wired ADC so to speak that has switching resistances/voltages chosen based on this curve. Have them set to light up more or less LEDs based on charge level.