Rick Beebe wrote:
On 04/17/2014 07:50 PM, Lee Hart wrote:
You don't *have* to monitor every cell to know if one is undervoltage.
If you want something very cheap and simple, try my Batt-Bridge. It
splits the pack into two halves, and compares the voltage of each half.
If they are different, some cell has just went dead, and is at a lower
voltage.
The Batt-Bridge normally lights an LED. But you can use the LED of an
optocoupler, and have the output of the optocoupler turn on a buzzer or
other more noticeable indicator.
The Batt-Bridge is described more fully at:
http://www.sunrise-ev.com/LeesEVs.htm#battbridge
Any ideas for an odd number of cells? Other than adding an additional
cell, of course.
See the circuit at http://www.sunrise-ev.com/LeesEVs.htm#battbridge
For a pack with an even number of cells or batteries, there is an exact
center-tap. So use two equal-value resistors for R1 and R2. They provide
a reference voltage of exactly half the total pack voltage.
For a pack with an odd number of cells or batteries, tap the pack as
close to the middle as possible. Then, choose R1 and R2 to have the same
ratio as the voltages on each side of your tap.
--
Any intelligent fool can make things bigger, more complex, and more
violent. It takes a touch of genius, and a lot of courage, to move
in the opposite direction. -- Albert Einstein
--
Lee Hart's EV projects are at http://www.sunrise-ev.com/LeesEVs.htm
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