Announcement

Collapse
No announcement yet.

LiFePO4 battery packs for Bafang mid-mount?

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

    LiFePO4 battery packs for Bafang mid-mount?

    I'm planning on retiring to a sailboat.

    I've been musing about putting together a folding bike with electric assist, for transportation around whatever town I'm moored at.

    I haven't settled in details, yet, but front-the now would be the Montague Paratrooper or Navigator, with a Bafang 750W mid-mount motor. (I could go with the M-E1, but I want something I build myself so I have something I can repair myself.)

    The problem with the designs I've seen is that they use Li-Ion battery packs, and sailors don't trust Lithium other than Lithium Iron Phosphate. LiFePO4 isn't quite as energy dense as the alternatives, but it allows for more charge cycles and it can't spontaneously combust.

    Having your car spontaneously catch fire is a problem. Standing on the side of the road watching it burn is unpleasant. But if your boat catches fire you don't have the option of getting out to watch it burn.

    There's no reason I can see why a Bafang wouldn't work with a properly-sized LiFePO4 battery pack. Volts are volts, amps are amps. But I've not seen any 48V LiFePO4 packs suitable for mounting to a bike frame.

    Are there any?

    #2
    People have used them and a bafang mid you can adjust low-voltage cutoff will support them just fine

    Very few folks use them for the reasons you mention, they are much heavier and larger for the same energy

    I'd think the best arrangement would be 16s (16 groups of cells in series) for a maximum voltage of 58.4V and since they are often sold as 12V lead-acid replacements in a 4s configuration 4 of those in series should also work well

    There was a fellow that went for them recently on a front hub trike where it had a lot of space and weight wasn't a concern - I think he was more interested in lower cost than anything however... My recollection is he did the 4x 12V lead-acid replacements - it was pretty large and heavy though, much more so than the conventional electric bike batteries so a lot will come down to the amount of energy (range) you are going to comfortable with and whether you can source what's appropriate once you've determined that...

    Comment


      #3
      I'm wondering if using Li-Ion is such a risk.

      I mean, yes I can see the worry about a house bank on a boat catching fire, but a portable battery? Can't you just throw it overboard?

      Comment


        #4
        Hard to say

        Risk management is generally a "personal" thing - everyone has their own sensitivites

        A decent electric bike battery from a reputable manufacturer wouldn't stop me on a boat but that's my own thing... I'd still be very sensitive to them - boat fires on open water is not a happy thing at all...

        Comment


          #5
          Originally posted by AZguy View Post
          Hard to say

          Risk management is generally a "personal" thing - everyone has their own sensitivites

          A decent electric bike battery from a reputable manufacturer wouldn't stop me on a boat but that's my own thing... I'd still be very sensitive to them - boat fires on open water is not a happy thing at all...
          I'm going to have a number of small Li-Ion batteries on the boat, phones, tablets, laptops, etc., regardless.

          And I'm going to have large banks for house and propulsion.

          If a phone catches fire I can toss it.

          The propulsion batteries will be solidly mounted below decks and weigh two hundred pounds each. I'm not going to be able to toss them.

          The bike will be larger even then the laptop battery, but it's still something I can toss, so Li-Ion should be acceptable.

          The one precaution I might take is to remove the battery from the bike, when I'm packing the bike away into an inaccessible corner for a long passage, and keep the battery someplace I can keep an eye on it.

          Comment


          • AZguy
            AZguy commented
            Editing a comment
            I have far more batteries than bikes and so most aren't on bikes and unless I'm riding the bike within a day or two it's not likely to be kept with a battery mounted

            OTOH I know folks that likely have never removed their battery from the bike - everybody's different!
        Working...
        X