Announcement

Collapse
No announcement yet.

Dual-battery setup with a smaller battery?

Collapse
X
  • Filter
  • Time
  • Show
Clear All
new posts

  • Dual-battery setup with a smaller battery?

    I've done the searching and reading on dual-battery setups, I think I understand the need for an isolator and a few of the various options for setup. Here's something I didn't see.

    I've got a M1-ATX, so I don't have issue surviving crank or any of that. I want a second battery simply to handle the S3 powerstate overnight or for a few days. I don't need to play my PC with the engine off for hours on end, I just want a battery to handle the small drain required of the S3 (suspend to ram) state.

    Does this have to be a huge battery? I'm hoping I can use something smaller (but still sealed as it'll be in the car). Can someone help me with a schematic? I don't really care if my carpc runs off the main battery or secondary battery while the engine is running (or key in accessory) but I'd like it to run off of the secondary when the key is off. I think I this means I'll switch the input of the M1-ATX from the primary electrical system to my small backup battery when I take the key out.

    Has anyone done this? Is this more trouble than it's worth?
    My worklog.
    Status: VM GTI sold, got out of the CarPC tinkering hobby, but I still think about getting back in.

  • #2
    Once you hook up the carpc to the second battery it will always run off that battery. That's what the isolator does. It isolates the two batteries while still charging them.

    Comment


    • #3
      Originally posted by undisputed
      Once you hook up the carpc to the second battery it will always run off that battery. That's what the isolator does. It isolates the two batteries while still charging them.
      Ok, so it'll always run off of the second battery. That's fine as long as this smaller battery can handle the load. Is there any issue with having a smaller (considerably less amp hours) than a regular car battery (or a normal deep cycle) in this setup? I've got a new-ish car and a low powered system (90W M1-ATX runs everything), so I'm pretty sure the alternator isn't taxed.

      Can anyone recommend a smaller 12V approriate for this? As I said before, I'll be mounting in the car so it needs to be sealed. By going smaller, I'm hoping to save space and cost.
      My worklog.
      Status: VM GTI sold, got out of the CarPC tinkering hobby, but I still think about getting back in.

      Comment


      • #4
        Originally posted by undisputed
        Once you hook up the carpc to the second battery it will always run off that battery. That's what the isolator does. It isolates the two batteries while still charging them.
        No, this is not true. If the battery is being charged then the charging system will be powering the computer.

        Rob.

        Comment


        • #5
          Originally posted by gommino
          No, this is not true. If the battery is being charged then the charging system will be powering the computer.

          Rob.
          Yes but the computer is always connected to the second battery...

          I would just do a relay that is closed when the IGN in on that way the battery will get a charge but when IGN is off it wont see the other battery, that way you dont need to deal with isolators...
          1990 Jeep Cherokee
          2000 VW Golf TDI 4dr
          2005 VW GTI MKIV - SOLD

          Comment


          • #6
            Plain and simple- The more amp hours you have the longer you can run it that way. The only way you will know what size you need is to come up with your requirement. Example - I wish for the PC to be able to be suspended for one week with out me ever starting the engine. Then what you have to do is measure the draw of your car pc in amps, and then you can decide on the apropriate number of amp hours.

            Comment


            • #7
              Originally posted by agentloveless
              Plain and simple- The more amp hours you have the longer you can run it that way.
              That's what I was hoping for. That's great news.
              Well, I was hoping for one more thing....recomendations on "smaller" 12V sealed batteries. I have no idea what brands I'm looking for.
              My worklog.
              Status: VM GTI sold, got out of the CarPC tinkering hobby, but I still think about getting back in.

              Comment


              • #8
                Do you have a batteries plus around you? i would just get any sealed one they have...
                1990 Jeep Cherokee
                2000 VW Golf TDI 4dr
                2005 VW GTI MKIV - SOLD

                Comment


                • #9
                  Thanks for the Batteries Plus idea, I'll try them. Here's some followup questions:
                  I've done a little bit with solar panel charging a battery and running some wireless gear. In that instance we used a big deep cycle gel battery. We also but a charge controller in the middle of the solar panel, the battery, and the load. The charge controller aparently did voltage regulation as well as keep the battery in good condition by pulse charging or some other such thing. It also cut the load if battery voltage dropped to low to prevent a complete discharge.

                  Why don't automobile charging systems use charge controllers like this? Would a dual battery setup benifit from one on just the second battery? The charge controller was supposed to manage the battery charging better so you the battery lasted longer and you didn't have to worry so much about how it was discharged/charged.
                  My worklog.
                  Status: VM GTI sold, got out of the CarPC tinkering hobby, but I still think about getting back in.

                  Comment


                  • #10
                    if you cut the charge from the battery using a relay or aswitch then it would be running from the battery direct

                    Comment


                    • #11
                      never mind man i gotta learn how to read ahead

                      Comment


                      • #12
                        kbyrd,

                        Have you looked into this more? I'm thinking I'd like to add a second battery and run in standby when the car is off, all of the time.

                        I have an Opus, so cranking isn't an issue with me either.

                        This seems like the best way to hook it up:

                        http://mp3car.com/vbulletin/showpost...9&postcount=12

                        Just curious if you maybe tried this out, or if anyone had any other input.
                        '03 Intensa Blue Pearl Lexus IS300

                        Specs: Xenarc 700TS, Opus 150W PSU, CarCPU Case, 2.0 GHz Celeron D, DFI PS-35-BL, SB Audigy2 NX, Centrafuse 1.4

                        Progress: Car PC up and running!
                        To Do: Navigation, WiFi, AM/FM Radio, DVD

                        Comment


                        • #13
                          I've got this tank circuit and battery:
                          http://carpc.kyferez.com/Products/products.php?id=10
                          http://carpc.kyferez.com/Products/products.php?id=13

                          They also have a slightly bigger battery. Only lasts a few hours
                          but is sufficient for my needs and works great.

                          -arebelspy
                          See my trades here! My For Sale/Trade Thread. Email joe at eipse.com
                          Originally posted by xdjxklusivex
                          i think every thread is now a whoreing thread

                          Comment


                          • #14
                            azzuro: I haven't looked at this any more, I did compute my draw in S3, about 180mA. On my current (OEM main cranking) battery, that's many days if I'm willing to drain it. I installed a kill switch so I can cut all power if I leave the care a few days. But, constant drain isn't good for these starter batteries. So, I've been thinking of replacing my main batter with an Optima Yellow Top (or anything that will start the car but be more tolerant of a 180mA constant drain)

                            arebelspy: The smallest one there is 7AH (usually over 20 hours). For my draw, that's 7AH/0.18A = 38.8 hours. So I could leave my computer in standby for a little more than a day. That's not much, I'd like it to survive the weekend. For the 12AH battery, it's 12/.018 = 66H, a little over two days. That's more what I'm looking for. You said you have this tank circuit, are you using it to survive crank or to do what I'm asking (power the PC when car is off, but be recharged when the car is on?) How does the tank circuit do that? Finally, are these deep cycle batteries? How will they handle being discharged 80% every weekend?
                            My worklog.
                            Status: VM GTI sold, got out of the CarPC tinkering hobby, but I still think about getting back in.

                            Comment


                            • #15
                              Originally posted by kbyrd
                              arebelspy: 1The smallest one there is 7AH (usually over 20 hours). For my draw, that's 7AH/0.18A = 38.8 hours. So I could leave my computer in standby for a little more than a day. That's not much, I'd like it to survive the weekend. For the 12AH battery, it's 12/.018 = 66H, a little over two days. That's more what I'm looking for. 2You said you have this tank circuit, are you using it to survive crank or to do what I'm asking (power the PC when car is off, but be recharged when the car is on?) 3How does the tank circuit do that? 4Finally, are these deep cycle batteries? How will they handle being discharged 80% every weekend?
                              Labeled your thing with numbers to make a reply easier (you can reply to mine with the same numbers for simplicity's sake):

                              1) The 7AH one is the one I have. Sounds like the 12AH one would work for your needs, assuming you measured the draw correctly and such.. Out of curiosity do you know how many AH an average car battery is, or where to find specific info on a certain car model's battery?

                              2) I'm doing both, actually. I have the carputer hibernate so normally when I start my car the car starts with it and doesn't need to survive crank, but I have a switch in the front I can flip so the carputer stays on (or turns on if off) when the car is off. In that case the battery is powering the carputer when the car is off, and then when I start the car (assuming I don't flip the switch to hibernate again and exit the car) I use it to survive crank. I obviously don't standby like you're planning, but I have used it to power the carputer when the car is off, then charge up when the car is on.

                              3) Uhh, I have no idea. I attached the wires, and it does it.. ask a more electrical person if you really want the details if it matters

                              It was seriously plug and play.. I had the wires running straight to my PSU, instead attached them to this then the PSU, took me around 5-10 minutes max to set up and it worked first try. the easiest thing in my whole carputer insteall, literally.

                              4) Again, not sure. I'm not planning on deep cycling mine much, just for use to survive crank or when I go to the gas station I flip the switch to keep the comp on, gas up my car, and start the car again so the battery 1) kept the comp on while car was off for music, saved boot time, etc and 2) let it survive crank. Email the people at the site I linked to, they should know if deep cycling them is okay.

                              -arebelspy
                              See my trades here! My For Sale/Trade Thread. Email joe at eipse.com
                              Originally posted by xdjxklusivex
                              i think every thread is now a whoreing thread

                              Comment

                              Working...
                              X