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 Author Topic: Fuel Gauge for Lipo?  (Read 645 times) 0 Members and 1 Guest are viewing this topic.
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 « on: December 24, 2012, 11:54:44 am » Bigger Smaller Reset

anyone here used a Fuel Gauge for Lipo? can suggest me any?
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 « Reply #1 on: December 26, 2012, 02:04:22 pm » Bigger Smaller Reset

anyone?
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Measurement changes behavior
 « Reply #2 on: December 26, 2012, 02:16:30 pm » Bigger Smaller Reset

The concept of having a 'fuel gauge' indication for a Lipo depends on your expectation of accuracy and context. A Lipo single cell has a range of output voltages that vary pretty linearly from 4.2vdc at 100% of charge to 3.0 at what most consider a good 0% or empty charge. Discharging a lipo cell too low can permanently damage the cell so different people use different 'cut-off' voltage value. Now if you wanted a totally accurate fuel gauge measurement value you would not depend just on the cells terminal voltage but rather measure the actual mAH consumption of current consumed over time, which is a lot more complex then just measuring the terminal voltage of the cell. And of course if your specific lipo battery is made from a number of series wired single cells then the voltage values I gave above would be 2X or 3X, etc depending on the number of series cells your pack has.

So if your dealing with just a single cell then wiring the cells output terminal to an arduino analog input pin would allow you to measure the cell's terminal voltage and then based on that value calculate it's relative position between 0% and 100% terminal voltage. If your using a multiple cell lipo then you would need to use a two resistor voltage divider to safely measure the voltage on your arduino and the scale as required in your software.

Lefty
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 « Reply #3 on: December 26, 2012, 02:52:13 pm » Bigger Smaller Reset

Sparkfun sells a few.  Here's one:

https://www.sparkfun.com/products/10617
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Author of "Arduino for Teens". Available for Design & Build services. Now with Unlimited Eagle board sizes!
 « Reply #4 on: December 26, 2012, 03:00:16 pm » Bigger Smaller Reset

Try these Nishant, MAX17047, MAX17050
http://www.maximintegrated.com/datasheet/index.mvp/id/7181/t/al?ver=C&utm_expid=50713806-2&utm_referrer=http%3A%2F%2Fwww.maximintegrated.com%2Fpst%2Frun.mvp%3Fq%3Dlipo%20fuel%20gauge%26spell%3D1%26site%3D_products%26num%3D20%26access%3Dp

Both shown as In Production, may have to ask Maxim for a sample to get some tho.
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 « Reply #5 on: January 03, 2013, 10:29:25 am » Bigger Smaller Reset

Thanks Sir Robert ,actually I would need to see that whether one of these 2 are available on Digi/mouser/element 14 or not to buy them
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 « Reply #6 on: January 03, 2013, 10:32:23 am » Bigger Smaller Reset

Hi Again Sir The problem with these maxim parts is that they are available in atleast thousands!!!!! I want like 2-5.
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