Battery meter

**romul** · 01-30-2006, 05:26 PM

Hey, is it possible to have a battery charge meter for car batteries? Noob question iknow, did a brief search..

Thanks in advance

**bad-at-this** · 01-30-2006, 05:34 PM

you would need hardware to read the voltage. Once you get that you would have to have a way to send the reading to computer (probably easy on a serial port).

-Bad

**meddler** · 01-30-2006, 06:37 PM

you could use a phidgets kit. It is USB and has 8 analogue inputs that could be use to measure voltage and current. Have a look here.

**RawsonDR** · 01-30-2006, 08:53 PM

But how can the internal voltage of a battery be tested when the alternator is putting out a fixed voltage across it's terminals?

**meddler** · 01-30-2006, 09:01 PM

you can't. If it is being charged that is the voltage the battery is at. The only way you can measure the standing voltage of the battery is when it is not connected.
Why would you want to measure just the internal voltage of battery itself? Wouldn't you rather know that you charging system is putting out the right voltage and charging the battery?

**fisherjo** · 06-16-2006, 10:52 PM

How does a laptop read the battery power? I'm such a n00b, this is my first post.
I was just wondering if you ran two batteries with a dual isolator, could the carputer tell the percentage of battery level and thus the time remaining and also tell that it is being charged by the alternator when the car is running. This could allow you to tell your computer to shut off into hibernation before the battery runs out. Just a thought. Joel

**muldrick** · 06-17-2006, 12:37 PM

It can read batt. juice (and many other things) through the OBD2 connector. Refer to the OBD section on the forums.
You should have your PC go into hyb. right away after the car is shut off. (Why keep it running?)
If you use a DC-DC PSU you can set it for certain "shut-down" (or hyb) times.
Check out the FAQ's too.

**fisherjo** · 06-18-2006, 08:19 AM

Thanks so much. The reason i thought of for the hibernation thing, is that many people say that they accidentally leave their carputers on and therefore drain batteries. This way you could shut it off with enough power to still crank.

**Uriel** · 06-20-2006, 05:23 AM

Originally Posted by fisherjo

Thanks so much. The reason i thought of for the hibernation thing, is that many people say that they accidentally leave their carputers on and therefore drain batteries. This way you could shut it off with enough power to still crank.

You can let windows shut down your computer after a few hours, use the power settings on the control panel, mine shuts down after 3 hours. In this way you never have problems when accidentally leaving the carputer on.