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Convert 52V Luna battery pack to work on 24V electric mower?

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    Convert 52V Luna battery pack to work on 24V electric mower?

    Hi guys. I bought a 52V 18650 pack from Luna Cycle back in 2015 for a new ebike kit. I've not put a ton of miles on the bike since then and now have a pair of 12V SLA batteries that have gone back to power a electric mower like this one:

    https://www.peoplepoweredmachines.com/epic/index.htm

    I was thinking it'd be great if I could at least temporarily rig the 52V back with some sort of step down transformer (to 24 or 30V) to run the mower. I don't know a ton about this so I thought I'd check in here to see if it's likely I could do this without a ton of risk to either the 18650 pack or the mower.

    Also, there's not much point if I have to spend almost as much as the new SLA batteries would cost on the equipment to convert.

    I'll figure out some way to make a mechanical connection between the battery pack and the mower but am wondering about transformers and general feasibility.

    I'm thinking something like this:

    https://www.ebay.com/itm/Tobsun-360W...r/223766680001

    but of course it needs to handle the full 52V DC input, which I'm not sure that one does.

    #2
    If 20 amps are enough, use this:
    https://www.ebay.com/itm/48V-to-24V1...MAAOSwaP5cd0Ga
    Input range 30-60vdc output 24vdc 20A max. I use the 12v output version to step down my packs for lights and accessories on my bike. Just add whatever connectors on the input and output wires and your done.
    Last edited by Defjr333; 1 week ago.

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      #3
      I have an old electric trolling motor that I would like to use standalone in a small boat. It is 12V and draws up to 17.5A. However, I don't have a stand alone 12V deep cycle battery anymore. Is there a step down converter recommended that would allow me to use my Luna 52V packs? Obviously I don't want to spend a lot of money..., so cheap, but still works, is better.

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        #4
        The one I listed in above post converts 30-60vdc to 24vdc up to 20A. The same ebay seller has them in the same input range(30-60v) and 12vdc output 3A, 5A, 10A and 20A as well. I use the 12v model on my ebike to step down my dual 12.5ah 52v packs for my lights, turn signals, music, alarm system, horn, and more. Work great, no issues.

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          #5
          I just found this one, and ordered the 13.8V 20A version. Should be plenty of power for my trolling motor.
          https://www.aliexpress.com/item/3230...65fd4c4deKgLoQ
          Might take a month or more to arrive, but that's OK, as long it works.

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            #6
            Dumb question, but I thought I'd ask... since I'm not sure what the total power draw is on this mower (and don't see an easy way of figuring it out), I was wondering how much risk I'd be taking just trying to hook my 52V battery directly up to the terminals that used to take the two 12V batteries (I assume wired in series for 24V)?

            What are the chances the motor itself won't like the high voltage (and, I suppose, more importantly, the electronics between the battery and the motor)?

            I know electronics can handle a range of voltage around their nominal voltage, but I'm hesitant to try this on a mower that's probably worth at least a couple hundred bucks (it was about $500 brand new, including the batteries which are now shot, but the mower itself probably has a lot of life left ... new batteries are at least $80-90 shipped).

            The original batteries are 12V SLAs at about 20Ah each.

            Also, if I choose not to risk that and do want to still try to save a bit (and salvage some more use out of my Luna battery pack which I'm sadly not getting much use out of on the ebike) and go with transformer approach, what tips does anyone have on how to estimate how much peak power my transformer needs to be able to produce?

            I think I used to get about 1 hour of mowing out of those two batteries before they'd be discharged enough that the unit would shut down (though I don't know what voltage they would be at that point).

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              #7
              Originally posted by tgice View Post
              Dumb question, but I thought I'd ask... since I'm not sure what the total power draw is on this mower (and don't see an easy way of figuring it out), I was wondering how much risk I'd be taking just trying to hook my 52V battery directly up to the terminals that used to take the two 12V batteries (I assume wired in series for 24V)?

              What are the chances the motor itself won't like the high voltage (and, I suppose, more importantly, the electronics between the battery and the motor)?

              I know electronics can handle a range of voltage around their nominal voltage, but I'm hesitant to try this on a mower that's probably worth at least a couple hundred bucks (it was about $500 brand new, including the batteries which are now shot, but the mower itself probably has a lot of life left ... new batteries are at least $80-90 shipped).

              The original batteries are 12V SLAs at about 20Ah each.

              Also, if I choose not to risk that and do want to still try to save a bit (and salvage some more use out of my Luna battery pack which I'm sadly not getting much use out of on the ebike) and go with transformer approach, what tips does anyone have on how to estimate how much peak power my transformer needs to be able to produce?

              I think I used to get about 1 hour of mowing out of those two batteries before they'd be discharged enough that the unit would shut down (though I don't know what voltage they would be at that point).
              Don't try that! It'll blow up for sure. If it doesn't blow up the controller (best case and highly likely) and it is able to actually run, then the blade would dramatically exceed it's speed rating. And chop off your feet as it explodes....

              Please don't.
              Fabrication is fun! Build something today. Show someone. Let them help. Inspire and share. Spread the desire.

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                #8
                Originally posted by JPLabs View Post

                Don't try that! It'll blow up for sure. If it doesn't blow up the controller (best case and highly likely) and it is able to actually run, then the blade would dramatically exceed it's speed rating. And chop off your feet as it explodes....

                Please don't.
                Hah. Thanks for the advice. I guess I won't do that. My dad's not alive anymore to talk me out of such foolish experiments.

                I'm considering buying either a single 720W 48V to 24V transformer for about $50 like this:

                https://www.amazon.com/Cllena-Voltag.../dp/B07JK7ZM8D

                or wiring two of these in parallel for more total power if it seems I need it:

                https://www.amazon.com/KNACRO-36V-48.../dp/B07JH8MWDR

                they're only $27 a piece. I understand if I parallel two rated at 480W it should be equivalent to a single one rated at 960W.

                Since I have no idea how much power I need for this mower, I figure 960 would be safer than 720.
                Last edited by tgice; 1 week ago.

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