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LiPo fire. A cautionary tale.

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  • dpa_io
    The nBot robot was rebuilt as Version 5 in the winter of 2011, using 4000 mAh Lithium Polymer batteries. These batteries are much lighter than the NiMH pack
    Message 1 of 7 , Sep 15, 2013
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      The nBot robot was rebuilt as Version 5 in the winter of 2011, using 4000 mAh Lithium Polymer batteries.  These batteries are much lighter than the NiMH pack previously used, and  provided about 5 hours of run time, about twice the NiMH.

      However, just like the famous LiPo batteries in the Boeing Dreamliner,  these batteries destroyed themselves in a violent act of self-immolation in the Winter of 2012, destroying much of the robot in the process:

      <http://geology.heroy.smu.edu/dpa-www/robo/nbot/fire/nbot_fire_01.jpg>

      Evidently an internal short in the batteries was to blame. 

      In any event, the robot has now been rebuilt as Rev 6.0, using 2.4 mAH NiMH batteries.   It took about 5 months total, mechnical and electronics.  Here are some pics of the rebuilt robot:

      <http://www.geology.smu.edu/dpa-www/robo/nbot/nbot6.html>

      I pretty much have to fly LiPo batteries on my R/C helicopters, because of the energy density.  But Never Again on a hand built robot.  Word to the wise. 

      YMMV.

      happy roboting,
      dpa
    • Mark Kenworthy
      You might want to look at LFP (LiFePO4) batteries. Mark From: SeattleRobotics@yahoogroups.com [mailto:SeattleRobotics@yahoogroups.com] On Behalf Of
      Message 2 of 7 , Sep 15, 2013
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        You might want to look at LFP (LiFePO4) batteries.

         

        Mark

         

        From: SeattleRobotics@yahoogroups.com [mailto:SeattleRobotics@yahoogroups.com] On Behalf Of davida@...
        Sent: Sunday, September 15, 2013 10:01 AM
        To: SeattleRobotics@yahoogroups.com
        Subject: [SeattleRobotics] LiPo fire. A cautionary tale.

         

         

        The nBot robot was rebuilt as Version 5 in the winter of 2011, using 4000 mAh Lithium Polymer batteries.  These batteries are much lighter than the NiMH pack previously used, and  provided about 5 hours of run time, about twice the NiMH.

        However, just like the famous LiPo batteries in the Boeing Dreamliner,  these batteries destroyed themselves in a violent act of self-immolation in the Winter of 2012, destroying much of the robot in the process:

        <http://geology.heroy.smu.edu/dpa-www/robo/nbot/fire/nbot_fire_01.jpg>

        Evidently an internal short in the batteries was to blame. 

        In any event, the robot has now been rebuilt as Rev 6.0, using 2.4 mAH NiMH batteries.   It took about 5 months total, mechnical and electronics.  Here are some pics of the rebuilt robot:

        <http://www.geology.smu.edu/dpa-www/robo/nbot/nbot6.html>

        I pretty much have to fly LiPo batteries on my R/C helicopters, because of the energy density.  But Never Again on a hand built robot.  Word to the wise. 

        YMMV.

        happy roboting,
        dpa

      • dpa_io
        Thanks Mark. Just read the LiFePO4 wiki page, looks good. I found these, which are about what nBot needs:
        Message 3 of 7 , Sep 15, 2013
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          Thanks Mark.  Just read the LiFePO4 wiki page, looks good.  I found these, which are about what nBot needs:


          <http://www.batteryspace.com/lifepo418650battery256v2500mah64wh18arate2rx8withpcb.aspx>


          That's 2.5 amp hours with 862 grams (weight matters on a balancing robot!), about 150 bucks.  The 20 cell NiMH pack currently in use is 2.4 amp hours with 566 grams, about $100.  So not sure there would be much  advantage to making the change at this point.  Always on the lookout, though.  Thanks for the input.


          dpa




          --- In SeattleRobotics@yahoogroups.com, <seattlerobotics@yahoogroups.com> wrote:

          You might want to look at LFP (LiFePO4) batteries.

           

          Mark

           

          From: SeattleRobotics@yahoogroups.com [mailto:SeattleRobotics@yahoogroups.com] On Behalf Of davida@...
          Sent: Sunday, September 15, 2013 10:01 AM
          To: SeattleRobotics@yahoogroups.com
          Subject: [SeattleRobotics] LiPo fire. A cautionary tale.

           

           

          The nBot robot was rebuilt as Version 5 in the winter of 2011, using 4000 mAh Lithium Polymer batteries.  These batteries are much lighter than the NiMH pack previously used, and  provided about 5 hours of run time, about twice the NiMH.

          However, just like the famous LiPo batteries in the Boeing Dreamliner,  these batteries destroyed themselves in a violent act of self-immolation in the Winter of 2012, destroying much of the robot in the process:

          <http://geology.heroy.smu.edu/dpa-www/robo/nbot/fire/nbot_fire_01.jpg>

          Evidently an internal short in the batteries was to blame. 

          In any event, the robot has now been rebuilt as Rev 6.0, using 2.4 mAH NiMH batteries.   It took about 5 months total, mechnical and electronics.  Here are some pics of the rebuilt robot:

          <http://www.geology.smu.edu/dpa-www/robo/nbot/nbot6.html>

          I pretty much have to fly LiPo batteries on my R/C helicopters, because of the energy density.  But Never Again on a hand built robot.  Word to the wise. 

          YMMV.

          happy roboting,
          dpa

        • Pat Tressel
          Whoa, sorry to hear about the fire, and thanks for the heads up! ... I ll second the LiFe suggestion -- we use those on our hopefully-soon-to-be-autonomous
          Message 4 of 7 , Sep 15, 2013
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            Whoa, sorry to hear about the fire, and thanks for the heads up!

            You might want to look at LFP (LiFePO4) batteries.

            I'll second the LiFe suggestion -- we use those on our hopefully-soon-to-be-autonomous recumbent trike.  The passenger or payload sits directly over the battery pack, and the battery pack is maybe 6 in off the ground, so at risk of getting bumped or even punctured (we need to enclose it better...).  We've been assured that LiFe are a safe option.

            Here's an update on the "laptop battery fire video":
            Yeesh.

            -- Pat
          • Randy Carter
            How were you charging the batteries? The biggest fire problem with lithium batteries is improper charging. They all exhibit this problem whether they are
            Message 5 of 7 , Sep 16, 2013
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              How were you charging the batteries? The biggest fire problem with lithium batteries is improper charging. They all exhibit this problem whether they are lithium cobalt (like laptop, cell phone, Boeing batteries) or lithium polymer or lithium iron phosphate.

              Lithium batteries hate to be overcharged. You can not trickle/float charge lithium batteries any way. You have to have a battery management system that detects a full charged state and cuts off all charging current. So the practice of putting a power source on them and letting them trickle charge forever is bad.

              Lead acid (PbA), nickle metal hydride (NiHM), and nickle cadmium (NiCd) have self discharge mechanisms so the trickle current has some place to go (usually waste heat). Lithium's self discharge is practically non existent. So they continue to charge as long as the charging voltage is still present even with next to no current flow.

              ----------------------------------------------------
              "What the detractors and critics of electric vehicles
              have been saying for years, is true. The electric
              vehicle is not for everybody, given the limited range
              it can only meet the needs of 90% of the population."

              Ed Begley Jr.
              ----------------------------------------------------

              ---------- Original Message ----------
              From: <davida@...>
              To: <SeattleRobotics@yahoogroups.com>
              Subject: [SeattleRobotics] LiPo fire. A cautionary tale.
              Date: 15 Sep 2013 10:00:58 -0700

              The nBot robot was rebuilt as Version 5 in the winter of 2011, using 4000 mAh Lithium Polymer batteries. These batteries are much lighter than the NiMH pack previously used, and provided about 5 hours of run time, about twice the NiMH.

              However, just like the famous LiPo batteries in the Boeing Dreamliner, these batteries destroyed themselves in a violent act of self-immolation in the Winter of 2012, destroying much of the robot in the process:

              <http://geology.heroy.smu.edu/dpa-www/robo/nbot/fire/nbot_fire_01.jpg>

              Evidently an internal short in the batteries was to blame.

              In any event, the robot has now been rebuilt as Rev 6.0, using 2.4 mAH NiMH batteries. It took about 5 months total, mechnical and electronics. Here are some pics of the rebuilt robot:

              <http://www.geology.smu.edu/dpa-www/robo/nbot/nbot6.html>

              I pretty much have to fly LiPo batteries on my R/C helicopters, because of the energy density. But Never Again on a hand built robot. Word to the wise.

              YMMV.

              happy roboting,
              dpa
            • dpa_io
              Hi Randy, Exactly right. I ve worked with LiPos for many years in my R/C heli pursuits. I used the same Hyperion charger for the nBot LiPos:
              Message 6 of 7 , Sep 16, 2013
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                Hi Randy,


                Exactly right.


                I've worked with LiPos for many years in my R/C heli pursuits.  I used the same Hyperion charger for the nBot LiPos:


                <http://www.geology.smu.edu/dpa-www/robo/nbot/nbot5/nbot5-02.jpg>


                I watch the discharge curves carefully and always store the batteries in "storagte mode charge."  These were new batteries, about 6 months old, and had not been abused.  I had a similar violent LiPo fire on my Trex-700 abut two years ago, burned up at $2000 helicopter.  That was a case of a faulty ESC, and the company replaced all the electronics (including the IMU!) and the heli I rebuilt from parts from the LHS.  Harder to do that with a custom hand made robot.


                The very fact that such care much be taken with LiPos to keep them from violently combining with oxygen suggests that they are perhaps not ready for prime time.  My car, where the robot self-immolated, still has the faint odor of flaming robot... robot flambeau.


                best

                dpa





                --- In SeattleRobotics@yahoogroups.com, <seattlerobotics@yahoogroups.com> wrote:

                How were you charging the batteries? The biggest fire problem with lithium batteries is improper charging. They all exhibit this problem whether they are lithium cobalt (like laptop, cell phone, Boeing batteries) or lithium polymer or lithium iron phosphate.

                Lithium batteries hate to be overcharged. You can not trickle/float charge lithium batteries any way. You have to have a battery management system that detects a full charged state and cuts off all charging current. So the practice of putting a power source on them and letting them trickle charge forever is bad.

                Lead acid (PbA), nickle metal hydride (NiHM), and nickle cadmium (NiCd) have self discharge mechanisms so the trickle current has some place to go (usually waste heat). Lithium's self discharge is practically non existent. So they continue to charge as long as the charging voltage is still present even with next to no current flow.

                ----------------------------------------------------
                "What the detractors and critics of electric vehicles
                have been saying for years, is true. The electric
                vehicle is not for everybody, given the limited range
                it can only meet the needs of 90% of the population."

                Ed Begley Jr.
                ----------------------------------------------------

                ---------- Original Message ----------
                From: <davida@...>
                To: <SeattleRobotics@yahoogroups.com>
                Subject: [SeattleRobotics] LiPo fire. A cautionary tale.
                Date: 15 Sep 2013 10:00:58 -0700

                The nBot robot was rebuilt as Version 5 in the winter of 2011, using 4000 mAh Lithium Polymer batteries. These batteries are much lighter than the NiMH pack previously used, and provided about 5 hours of run time, about twice the NiMH.

                However, just like the famous LiPo batteries in the Boeing Dreamliner, these batteries destroyed themselves in a violent act of self-immolation in the Winter of 2012, destroying much of the robot in the process:

                <http://geology.heroy.smu.edu/dpa-www/robo/nbot/fire/nbot_fire_01.jpg>

                Evidently an internal short in the batteries was to blame.

                In any event, the robot has now been rebuilt as Rev 6.0, using 2.4 mAH NiMH batteries. It took about 5 months total, mechnical and electronics. Here are some pics of the rebuilt robot:

                <http://www.geology.smu.edu/dpa-www/robo/nbot/nbot6.html>

                I pretty much have to fly LiPo batteries on my R/C helicopters, because of the energy density. But Never Again on a hand built robot. Word to the wise.

                YMMV.

                happy roboting,
                dpa
              • dpa_io
                Thanks Pat. Definitely looks promising. I like this line from the LFP wiki: It is commonly accepted that LiFePO4 battery does not decompose at high
                Message 7 of 7 , Sep 16, 2013
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                   Thanks Pat.  Definitely looks promising.  I like this line from the LFP wiki:


                  " It is commonly accepted that LiFePO4 battery does not decompose at high temperatures.The difference between LFP and the LiPo battery cells commonly used in the aeromodeling hobby is particularly notable."


                  Recumbent trike sounds cool.  Any pics?

                  Thanks for the link.

                  dpa



                  --- In SeattleRobotics@yahoogroups.com, <seattlerobotics@yahoogroups.com> wrote:

                  Whoa, sorry to hear about the fire, and thanks for the heads up!

                  You might want to look at LFP (LiFePO4) batteries.

                  I'll second the LiFe suggestion -- we use those on our hopefully-soon-to-be-autonomous recumbent trike.  The passenger or payload sits directly over the battery pack, and the battery pack is maybe 6 in off the ground, so at risk of getting bumped or even punctured (we need to enclose it better...).  We've been assured that LiFe are a safe option.

                  Here's an update on the "laptop battery fire video":
                  Yeesh.

                  -- Pat
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