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Re: I have lithium LiFePO4!

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  • Frans
    Don t I LOVE abbreviations!!!! BMS = Battery Management System (???) which in my humble opinion is a posh word for controller. Will the BMS effectively fool
    Message 1 of 13 , Feb 27, 2010
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      Don't I LOVE abbreviations!!!!

      BMS = Battery Management System (???) which in my humble opinion is a posh word for controller.

      Will the BMS effectively fool the Robomower electronics into thinking this is a Gel type lead battery fit for Deep Discharge. Or do you have to charge outside Robomow? In that case the docking feature becomes inoperabele, which is a big disadvantage IMHO.

      If you can not fit in 40Ah, why not 30Ah? Can you explain about "but the math says no"? - reminds me of Little Britain! What will be your typical charging time? From what I saw on RC cars and airplanes in the order of 10 minutes? That would somewhat do away the docking station issue, I think.

      Last but not least the cost an how long are they projected to last?
      Where did you buy them?

      Thanks,

      Frans the Stationmaster


      --- In RoboMower@yahoogroups.com, Danny Miller <dannym@...> wrote:
      >
      > Ha just got in some 20AH LiFePO4 cells to build a battery...
      > this should be fun.
      >
      > I need to design and build a decent BMS. This is no small task...
      > there's a lot of crappy BMS's out there, I wanna do one properly.
      >
      > Wow, there actually is a lot of extra volume here in the pack! Well, no
      > shortage of room for a BMS. I did look to see if I'd be able to double
      > up the cells and make a 40AH pack, but the math says no.
      >
      > Danny
      >
    • Frans
      Hello Danny, Thanks for reacting to my questions! Anyone considered using fuel cells? The only reference on the forum is this one:
      Message 2 of 13 , Mar 8 5:14 AM
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        Hello Danny,

        Thanks for reacting to my questions!

        Anyone considered using fuel cells? The only reference on the forum is this one:

        http://tech.groups.yahoo.com/group/RoboMower/message/14275

        There are fuel cells for mobil homes and the like, but they cost as much as a robomower, are too big and supply only 12 Volts, (the professional does 24 Volts, but it is Big Size!

        http://www.efoy.com/en/


        Also came across this one:

        http://www.engadget.com/2010/03/08/nokia-wants-patent-on-self-regenerating-phone-batteries-piezoel/

        Nice for your Nokia but I don't see it powering Robomowie.




        --- In RoboMower@yahoogroups.com, "Frans" <voorde@...> wrote:
        >
        > Don't I LOVE abbreviations!!!!
        >
        > BMS = Battery Management System (???) which in my humble opinion is a posh word for controller.
        >
        > Will the BMS effectively fool the Robomower electronics into thinking this is a Gel type lead battery fit for Deep Discharge. Or do you have to charge outside Robomow? In that case the docking feature becomes inoperabele, which is a big disadvantage IMHO.
        >
        > If you can not fit in 40Ah, why not 30Ah? Can you explain about "but the math says no"? - reminds me of Little Britain! What will be your typical charging time? From what I saw on RC cars and airplanes in the order of 10 minutes? That would somewhat do away the docking station issue, I think.
        >
        > Last but not least the cost an how long are they projected to last?
        > Where did you buy them?
        >
        > Thanks,
        >
        > Frans the Stationmaster
        >
        >
        > --- In RoboMower@yahoogroups.com, Danny Miller <dannym@> wrote:
        > >
        > > Ha just got in some 20AH LiFePO4 cells to build a battery...
        > > this should be fun.
        > >
        > > I need to design and build a decent BMS. This is no small task...
        > > there's a lot of crappy BMS's out there, I wanna do one properly.
        > >
        > > Wow, there actually is a lot of extra volume here in the pack! Well, no
        > > shortage of room for a BMS. I did look to see if I'd be able to double
        > > up the cells and make a 40AH pack, but the math says no.
        > >
        > > Danny
        > >
        >
      • Danny Miller
        A milestone in Robomower history! Monday, April 5, 2010- first Robomower running on lifepo4! I left it running for hours and hours and the pack still had
        Message 3 of 13 , Apr 6, 2010
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          A milestone in Robomower history!
          Monday, April 5, 2010- first Robomower running on lifepo4!

          I left it running for hours and hours and the pack still had plenty of
          charge. Cells down to 3.1v and the Robomower showed all but one bar on
          the batt meter and didn't slow at all. I can't run it all the way down
          without a BMS, and charging is still a rather "manual" process with the
          power supply.

          One cell appears to be underperforming, and it's not a balance problem
          with the charge state. Looks to be lower capacity than the others.
          Well, they were kinda sold to me cheap as "not necessarily good" cells.

          Danny

          richard gard wrote:
          > Danny,
          > Good luck. I have been hoping someone would try this soon. Please take some pictures and post if possible.
          > Richard in beautiful CT (with only 2" of snow)
          >
          > -----Original Message-----
          > From: Danny Miller <dannym@...>
          > Sent: Friday, February 26, 2010 11:48 PM
          > To: RoboMower@yahoogroups.com
          > Subject: [RoboMower] I have lithium LiFePO4!
          >
          >
          > Ha just got in some 20AH LiFePO4 cells to build a battery...
          > this should be fun.
          >
          > I need to design and build a decent BMS. This is no small task...
          > there's a lot of crappy BMS's out there, I wanna do one properly.
          >
          > Wow, there actually is a lot of extra volume here in the pack! Well, no
          > shortage of room for a BMS. I did look to see if I'd be able to double
          > up the cells and make a 40AH pack, but the math says no.
          >
          > Danny
          >
          >
          >
          > [Non-text portions of this message have been removed]
          >
          >
          >
          > ------------------------------------
          >
          > Yahoo! Groups Links
          >
          >
          >
          >
          >
        • Richard Gard
          I am interested to hear how/ and where you installed the BMS, how the charging is going, are you still happy with the LiFePO4?   ... From: Danny Miller
          Message 4 of 13 , Apr 9, 2010
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            I am interested to hear how/ and where you installed the BMS, how the charging is going, are you still happy with the LiFePO4?
             


            --- On Tue, 4/6/10, Danny Miller <dannym@...> wrote:


            From: Danny Miller <dannym@...>
            Subject: Re: [RoboMower] I have lithium LiFePO4!
            To: RoboMower@yahoogroups.com
            Date: Tuesday, April 6, 2010, 10:01 PM


             



            A milestone in Robomower history!
            Monday, April 5, 2010- first Robomower running on lifepo4!

            I left it running for hours and hours and the pack still had plenty of
            charge. Cells down to 3.1v and the Robomower showed all but one bar on
            the batt meter and didn't slow at all. I can't run it all the way down
            without a BMS, and charging is still a rather "manual" process with the
            power supply.

            One cell appears to be underperforming, and it's not a balance problem
            with the charge state. Looks to be lower capacity than the others.
            Well, they were kinda sold to me cheap as "not necessarily good" cells.

            Danny

            richard gard wrote:
            > Danny,
            > Good luck. I have been hoping someone would try this soon. Please take some pictures and post if possible.
            > Richard in beautiful CT (with only 2" of snow)
            >
            > -----Original Message-----
            > From: Danny Miller <dannym@austin. rr.com>
            > Sent: Friday, February 26, 2010 11:48 PM
            > To: RoboMower@yahoogrou ps.com
            > Subject: [RoboMower] I have lithium LiFePO4!
            >
            >
            > Ha just got in some 20AH LiFePO4 cells to build a battery...
            > this should be fun.
            >
            > I need to design and build a decent BMS. This is no small task...
            > there's a lot of crappy BMS's out there, I wanna do one properly.
            >
            > Wow, there actually is a lot of extra volume here in the pack! Well, no
            > shortage of room for a BMS. I did look to see if I'd be able to double
            > up the cells and make a 40AH pack, but the math says no.
            >
            > Danny
            >
            >
            >
            > [Non-text portions of this message have been removed]
            >
            >
            >
            > ------------ --------- --------- ------
            >
            > Yahoo! Groups Links
            >
            >
            >
            >
            >











            [Non-text portions of this message have been removed]
          • Danny Miller
            I m still designing a BMS. Right now I let it charge on a variable-voltage lab supply with the voltage a little low, check that none of the cell voltages are
            Message 5 of 13 , Apr 9, 2010
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              I'm still designing a BMS. Right now I let it charge on a
              variable-voltage lab supply with the voltage a little low, check that
              none of the cell voltages are >3.65v when it stops taking current, inch
              the voltage up a bit, check it again. Then come back with the supply
              set at 3.65v and bring up any low cells. Or, just "don't" and charge it
              up until most cells are ~3.65v. It's not a big deal to balance every
              charge, they're "mostly" balanced anyways and there's nothing wrong with
              using the pack with it only 90% charged.

              And stop it before it runs all the way down because it can bring the
              weakest cell below 2.5v before shutting off. But, even with the pack at
              90%, it's probably not gonna happen before the perimeter switch cuts off.

              So, highly "manual" until I get a BMS in. But, it's "working", and
              working well! The thing I dig is the mower doesn't slow down at all
              during this.

              There's plenty of room for a BMS. Something like 1/3rd the volume
              inside the pack is unused, although the heat the BMS can generate,
              inside a plastic case, is high on my list of "concerns".

              The thing is LIGHT... I can carry it with two fingers comfortably. I
              might be looking at a slight problem with reduced traction, but it still
              plows through tall grass most of the time. At least while in reverse.
              There's a problem with "forward" because the bumper's kinda shot and
              acting ultra-sensitive. There's a patch of tall grass here and it's
              tripping the bumper on the GRASS.

              Danny



              Richard Gard wrote:
              > I am interested to hear how/ and where you installed the BMS, how the charging is going, are you still happy with the LiFePO4?
              >
              >
              >
              > --- On Tue, 4/6/10, Danny Miller <dannym@...> wrote:
              >
              >
              > From: Danny Miller <dannym@...>
              > Subject: Re: [RoboMower] I have lithium LiFePO4!
              > To: RoboMower@yahoogroups.com
              > Date: Tuesday, April 6, 2010, 10:01 PM
              >
              >
              >
              >
              >
              >
              > A milestone in Robomower history!
              > Monday, April 5, 2010- first Robomower running on lifepo4!
              >
              > I left it running for hours and hours and the pack still had plenty of
              > charge. Cells down to 3.1v and the Robomower showed all but one bar on
              > the batt meter and didn't slow at all. I can't run it all the way down
              > without a BMS, and charging is still a rather "manual" process with the
              > power supply.
              >
              > One cell appears to be underperforming, and it's not a balance problem
              > with the charge state. Looks to be lower capacity than the others.
              > Well, they were kinda sold to me cheap as "not necessarily good" cells.
              >
              > Danny
              >
              > richard gard wrote:
              >
              >> Danny,
              >> Good luck. I have been hoping someone would try this soon. Please take some pictures and post if possible.
              >> Richard in beautiful CT (with only 2" of snow)
              >>
              >> -----Original Message-----
              >> From: Danny Miller <dannym@austin. rr.com>
              >> Sent: Friday, February 26, 2010 11:48 PM
              >> To: RoboMower@yahoogrou ps.com
              >> Subject: [RoboMower] I have lithium LiFePO4!
              >>
              >>
              >> Ha just got in some 20AH LiFePO4 cells to build a battery...
              >> this should be fun.
              >>
              >> I need to design and build a decent BMS. This is no small task...
              >> there's a lot of crappy BMS's out there, I wanna do one properly.
              >>
              >> Wow, there actually is a lot of extra volume here in the pack! Well, no
              >> shortage of room for a BMS. I did look to see if I'd be able to double
              >> up the cells and make a 40AH pack, but the math says no.
              >>
              >> Danny
              >>
              >>
              >>
              >> [Non-text portions of this message have been removed]
              >>
              >>
              >>
              >> ------------ --------- --------- ------
              >>
              >> Yahoo! Groups Links
              >>
              >>
              >>
              >>
              >>
              >>
              >
              >
              >
              >
              >
              >
              >
              >
              >
              >
              >
              > [Non-text portions of this message have been removed]
              >
              >
              >
              > ------------------------------------
              >
              > Yahoo! Groups Links
              >
              >
              >
              >
              >



              [Non-text portions of this message have been removed]
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