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  • Real time monitoring of battery level? Hardware + software

    Just wondering if anyone has implimented something like this? Im basically hoping there might be a fairly straight forward way of monitoring the battery level while the carpc is in use? To give an idea of how many hours left and what % is remaining. Perhaps a piece of hardware + software that could be embedded within CF?

    I have an auxiliary battery (isolated from the main battery) which powers my system but this could be handy for single battery systems as well. haha..I thought it would be a nice date idea to take the GF out and watch a movie in the backseat but it would be kinda dorky to have to pull out a multimeter every so often to check battery levels =)

  • #2
    I do know that some of the nicer UPS battery backups came with battery monitoring software (via serial port). You could easily replace the small battery with something that has more Amp hours (same voltage), and I bet the software would still work.

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    • #3
      I use an Arduino to monitor my battery level, but for more of a user friendly solution, have you looked at the Fusion Brain? I believe it has a CF plugin, and you should be able to buy a module that will allow you to read battery voltage.
      "stop with the REINSTALLS, what do you think we got some lame-o installer!!!" - mitchjs
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      • #4
        there is gauge that just indicate the voltage of the battery
        English is not my first language so if I say something weird just say it to me and i try to be clearer :) :)

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        • #5
          back on one of my work-road trips, i bought a bunch of cig. lighter adapter digital readouts.

          i hacked one up, and velcroed it to the corner of my windshield(high tech, i know )-- so i always know how low it really is...
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          carpc undecided

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          • #6
            Originally posted by soundman98 View Post
            back on one of my work-road trips, i bought a bunch of cig. lighter adapter digital readouts.

            i hacked one up, and velcroed it to the corner of my windshield(high tech, i know )-- so i always know how low it really is...
            That's in the true spirit of cobbled and hacked together carpc's... what this hobby used to really be about
            "stop with the REINSTALLS, what do you think we got some lame-o installer!!!" - mitchjs
            RevFE
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            • #7
              What power supply do you use for the carpc? many of them offer ways to monitor battery voltage....same thing if you have an ODBII reader.
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              • #8
                PS - this is meant for nobb. On posting I realised it might be construed as mocking previous replies. Far from it! (Or is my paranoia too close?)

                It's called a voltmeter.
                In rough terms, every 0.1V drop from its fully-charged voltage is a 10% drop in remaining capacity. (It's usually more like 0.12V/10%).

                That is probably the best you will do.
                To figure out the actual capacity remaining is not possible, and even the best methods still require lots of intelligence (regular battery discharge tests etc).
                [ If you have ever seen a "battery predicter" in operation, you'll know what I mean. If you think "tme remaining" predicters for file copies & downloads are bad (where size an bandwidth is supposedly known) - battery predictors are worse - especially when its "5 minutes remaining" display suddenly does blank. Even UPS systems intend systems take their graceful exit ASAP (maybe after a 1-2 minute delay) rather than wait based on assumed reserve time. ]


                FYI - The general rule of thumb is not to discharge below 70% for normal (cycling or cranking etc) batteries, and not below 50% for deep-cycle batteries.

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                • #9
                  Look into a product from Xantrex called the XBM or I believe they have replaced it with the Link Pro or Link Lite. This is a meter for the RV and Boat world and specifically is designed to monitor secondary batteries. It will monitor State of charge (% of capacity left), Battery Temp (optional sensor), Battery Voltage, Current, Amp-hours, and a calculation of time to go. http://www.xantrex.com/web/id/274/p/1/pt/7/product.asp.

                  They also make a communication add on that allows you to hook it to your computer. I have written a program to read the data.

                  Click image for larger version

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                  If running a secondary battery you should have a isolator or separator between the two batteries. I believe the Link pro monitors one battery fully and can monitor the voltage on a secondary battery.

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                  • #10
                    Originally posted by SGAsgard View Post
                    there is gauge that just indicate the voltage of the battery
                    I remember when this gauge where standard equipment of all cars!

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                    • #11
                      Yea I wish they would put a voltmeter on cars these days!

                      Looks like reading voltage directly is the way to go. Im fairly familiar with lead acids to know that 12.8V is fully charged and 12.0V is fully discharged. However, those voltages are unloaded. The higher the current drawn, the lower the loaded voltage will be even at the same capacity level. Or is there a good rule of thumb for this?

                      I rather not have to drill out holes and such for a physical gauge. Would be nicer to just have this integrated in my carpc case and hooked up to an internal USB header then have the voltage readings displayed on screen. The Fusion Brain looks like it's exactly what Im looking for. Voltage, current, and even temperature sensors!

                      edit: Wow this is so cool. "car voltage meter"...basically what soundman98 was talking about above. Im looking for a more integrated solution (and also my cig power is hooked up to the main electrical system, not the auxiliary) but this might be handy for some people.
                      http://cgi.ebay.ca/New-Red-DIGITAL-L...item3f02098aab

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                      • #12
                        What power supply do you have in the car pc? As another user mentioned, these often have voltmeters built in that you can access through their driver software.
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                        • #13
                          M2-ATX. Definitely does not have any power monitoring features.

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                          • #14
                            Originally posted by Crinos View Post
                            I remember when this gauge where standard equipment of all cars!
                            I didn't find it that common, but I remember when ammeters were common. Nowadays I do my best to talk people out of them - they are both useless and dangerous (though remote shunt types are merely useless).


                            As to typical battery voltage vs %age capacity...
                            (from sidewinder.com.au/page168).

                            Although that shows a 1.2V range from 0% to 100% (0.12V per 10% capacity), I use a 0.1V per 10% rule. Not only is that easier, but it's conservative and tends to compensate for various conditions & variables.


                            Under load, I use the 0.1V/10% rule. IE - at (near) no load, read the voltage; the add the load - that voltage is you starting voltage. EG - if 12.7V unloaded is 100% and under load it drops to 12.5V, then 12.5V is the loaded 100% voltage. (I find my car batteries are 12.7V fully charged, but 12.6-12.8V is a typical variation.


                            PS - definitely an inter-battery isolator. I recommend circuit breakers rather than (the essential!) fuses at each end, and a relay controlled by the alternator/regulator's charge lamp circuit (which is the best isolator you can have for typical applications).

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                            • #15
                              Originally posted by nobb View Post
                              Yea I wish they would put a voltmeter on cars these days!

                              Looks like reading voltage directly is the way to go. Im fairly familiar with lead acids to know that 12.8V is fully charged and 12.0V is fully discharged. However, those voltages are unloaded. The higher the current drawn, the lower the loaded voltage will be even at the same capacity level. Or is there a good rule of thumb for this?

                              I rather not have to drill out holes and such for a physical gauge. Would be nicer to just have this integrated in my carpc case and hooked up to an internal USB header then have the voltage readings displayed on screen. The Fusion Brain looks like it's exactly what Im looking for. Voltage, current, and even temperature sensors!

                              edit: Wow this is so cool. "car voltage meter"...basically what soundman98 was talking about above. Im looking for a more integrated solution (and also my cig power is hooked up to the main electrical system, not the auxiliary) but this might be handy for some people.
                              http://cgi.ebay.ca/New-Red-DIGITAL-L...item3f02098aab
                              Yup the FB will do it, it actually is just a voltage measuring device. All the sensors convert data to voltage.

                              And you would be surprised how many cars have voltage meters built in, you just don't know it. For instance, on all Prius models you can enter a diagnostic screen with the OEM display and one of the boxes is a 12v battery check that shows the live 12v battery voltage on the display. Lots of cars have this ability, but not usually "user" accessible unless you know what you are doing.
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