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Car battery voltage indicator using digital segment displays?

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Mishael

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hi all i am back! the guy always asking stupid questions, well i have another one
i work at a camp over the summer and my boss and i have a golf cart that performs everything from people transportation to ambulance escort, from a tool shed to a portable emergency PA system and doing all that takes some massive current draw on our little 70 amp hour 12 VDC. i have analog voltage monitors but i want to build something myself that looks nice. i really want a digital display that has XX.X or if it isnt much harder, XX.XX display. any help is greatly appreciated!

i know i could just go use the internet to find something but this i trust and i dont want to go blindly into something that doesnt work and i dont understand
 
Perhaps the best method is using a PIC chip but you need to be able to program the chip unless someone here will do it.
as for circuit-http://digital-diy.com/home/swordfish/58-swordfish-tutorial-adc-output-to-lcd.html
for ease of building etc with no guess work on what voltage the battery is why not just use a simple battery monitor circuit that has 3 LEDs (green, yellow, red)
have a schematic somewhere. will post when I locate
 
thats nice but something more accurate is what i was looking for. id like a numerical value as opposed to visual cues as to when my battery is going dead ALTHOUGH i have a few good uses for that design too. what do i need to program a PIC chip?
 
If you only want a digital voltmeter readout, this small **broken link removed**is waterproof and looks to be rugged. It's available with either 0.1V or 0.01V resolution. You just connect its two terminals to the battery to display the voltage.
 
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thats exactly what i would like but...i have a funding shortage and i would like to build it myself for the experience. it is a bit on the pricey side
 
Harbor Freight sells digital voltmeters for $6...$4 on sale. You can't beat the price, even if you do build it yourself! Maybe put a plastic cover on it and away you go**broken link removed**
 
Harbor Freight sells digital voltmeters for $6...$4 on sale. You can't beat the price, even if you do build it yourself! Maybe put a plastic cover on it and away you go**broken link removed**
The problem is, those voltmeters generally require a floating power supply (a separate battery) to operate. They can not be powered off the same source they are measuring.

For something cheaper you might try one of these from Futurlec. I just got one to monitor the battery voltage on my motorcycle. It says it requires a separate supply but it works fine to measure the battery voltage when powered from the same voltage as long as the voltage is above about 7V. Since it's rated for 12V power, I recommend putting a ≈200Ω resistor in series with the power input to reduce the voltage (the unit draws about 15mA on average) since the battery voltage when charging can go over 14V. Run the battery voltage directly to the measurement input to bypass the voltage drop so you get an accurate measurement.

You likely would not be able to build one as cheaply as that.
 
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