Onewheel Pint Battery Upgrade - Extended Range

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Introduction: Onewheel Pint Battery Upgrade - Extended Range

About: http://www.youtube.com/c/AndrewWorkshop

The Onewheel Pint is one of the most unique personal electric vehicles but it's range is limited. It's big brother the Onewheel XR, has a much long range so in this Instructables I show you how I upgraded my Onewheel Pint to have over double the range.


VERY IMPORTANT: While I try to include as much information on how to do this, you should also do your own research and confirm what I am doing before proceeding to upgrade your Onewheel. We are dealing with high voltages and potential hazards with li-ion batteries. I take no responsibility if you damage your Onewheel, yourself or property as a result of attempting to do this. Apply some common sense.

With that out of the way lets get to it!

Step 1: Materials and Tools

Here are some of the items needed for this build:

Tools:

  • 3D Printer
  • Soldering Iron, solder, flux, helping hands
  • Torx screw drivers
  • #20 Pentalobe security bit https://amzn.to/2KvHwIB
  • Wire cutters, strippers

Step 2: The Battery/Power Supply

The power supply I used was a DeWalt Flexvolt battery. There are a few different options for the battery but most involve either making your lithium ion battery pack from 18650 cells or finding a battery used for electric lawnmowers or large power tools.

What I like about using an off the shelf battery like the DeWalt battery, is I can use it to power my power tools as well. The DeWalt Flexvolt battery is unique in that it can either power 20 volt power tools or 60 volt power tools.

Now the Flexvolt battery by default is 20 volts if you were to meter the connections. In order to get 60 volts from the battery, pins C1 and C3 need to be shorted/jumped and there are two physical slides that need to be pushed in on both sides of the battery, this then turns the battery from 20 volts to 60 volts if you were to meter the + and - connections on the battery.

Things to keep in mind is you can use any 60 volt li-ion battery as long as the battery chemistry is the same as the Onewheel pint (Lithium Nickel Manganese Cobalt Oxide (LiNiMnCoO2) — NMC) and the voltage matches, the amp hours (capacity) can be different e.g. 6Ah or 9Ah or higher.

The stock Onewheel Pint has a 148Wh internal battery where as the the Dewalt 9Ah Flexvolt battery is 180Wh (9Ah x 20v) or (3Ah x 60v). This should at least double the range of the Pint.

Some additional information that might be useful:

The pint's battery is a 15 cell (15s) li-ion battery pack. It comprises of fifteen 18650 li-ion cells, giving a nominal voltage of 3.7v x 15s = 55.6 volts or max voltage of 4.1v x 15s = 61.5 volts. (Nominal voltage for a single li-ion cell is 3.6-3.7 volts, the max voltage is 4.1 - 4.3 volts).

Note: You can't or shouldn't mix batteries with different voltages but you can connect batteries with the same voltage even if they have different capacities (Wh, Ah, etc). The voltage will remain the same between the two different packs. Think of capacity like water, they will equalize, that is why you never want to connect the two packs together unless the voltages are the same or there will be a rush of current from the higher voltage pack to the lower voltage pack.

Step 3: 3D Printing the Battery Mount

Now the easiest thing to do is to run a wire from the Onewheel Pint and put the battery in a backpack. I don't like that idea because now I'm physically tethered to the Onewheel Pint.

My solution was to make a mount for the DeWalt battery and have the proper connections to grab power from the battery. You don't have to make a 3D printed battery holder (if you don't have a 3D Printer) another option is to just connect some blade connectors into the DeWalt battery to grab power from it.

I found a DeWalt battery mount from Thingiverse and modified it in Tinkercad to meet my needs, I had to add two rails so they would engage the Flexvolt battery to switch it from 20 volts to 60 volts and also added a "jumper" connector so pins C1 and C3 can be shorted. Once both of those conditions are activated the Flexvolt battery goes from 20 volts to 60 volts.

Solder wires to some electrical blade connectors and heat the blade connectors and run them into the DeWalt battery mount that was 3D printed, the PLA will melt a little allowing a nice tight fit. Do this for both the positive and negative leads. Then take a thin piece of flat metal about 30mm long x 4mm wide and bend into a U shape. Heat it and push it into the square hole, there will be two slots that the metal will slide through. Again the PLA will melt around the metal.

Glue in a square PLA plug to seal up the hole. For the electrical connections fill the wire holes with some 5 minute epoxy and let set.

I then modeled a fender mount that I can velcro to the stock Onewheel Pint fender. To that the DeWalt battery mount is glued to it, I used Weld-On 16 but epoxy or CA would work too.

Note: included are files for a prototype design where I use a toggle switch to help prevent sparking when connecting batteries together. I recommend using an XT90 connector to simplify the whole system (more on that later).

The files can be found here:

https://www.thingiverse.com/thing:4663350

Step 4: Disassemble the Onewheel Pint

To disassemble the Onewheel Pint, just start by removing the torx screws from the fender, footpads, rails, bumpers, bottom/floatplate. The fender and foot pads are the first to come off then slide the bumpers off, it might take a bit of force to get them off. Or you can remove the larger torx bolts that hold the rails to the motor/wheel unit, to help loosen things up. For the front foot pad there is a connector that will need to be unscrewed.

Go slow and the Onewheel comes apart in a logical manner. Keep track of where each screw goes.

Eventually you will be left with one rail that is attached to the control box and battery box. The battery box is in the rear of the Onewheel.

Using a pentalobe #20 security bit (5 sided with a hole), remove all the screws to the battery box cover. Remove the battery box cover and carefully remove the gasket as well.

I recommend watching my video to see the all steps on how to upgrade the Pint:

Step 5: Tapping Into the Battery

I tried a few different methods to tie into the Onewheel Pint electrical system. There is very little room inside the battery box. At first I was going to make an XT60 connector wiring harness to plug into the pint's battery management system (BMS). Some people have had success doing that, I found it too hard so what I ended up doing was just splicing into the pint's battery leads directly.

What I did:

  1. Remove the plastic cover over the battery management system (BMS).
  2. Unplug the Pint's 15s battery pack.
  3. Remove some of the silicone insulation around the positive lead.
  4. Soldered a 14 gauge silicone wire to the exposed wire.
  5. Wrapped the connection with rubber sealing tape (high quality thick electrical tape).
  6. Repeat on the negative lead.
  7. Measure and cut to the lengths needed by running one of the wires on the bottom of the battery box and one on top. I left mine staggered so there was less chance of them coming into contact with each other.
  8. Solder on some female 3.5mm bullet connectors to each wire, cover with heat shrink.
  9. Drill a hole in the battery box, opposite of the battery connector/BMS.
  10. Solder bullet connectors to two 14 gauge silicone wires (positive and negative) cover with heat shrink.
  11. Run the wires with connectors into the battery box in the hole that was drilled.
  12. Connect the battery to the external wires and reseat the battery into the battery box (one wire will be on top and one on bottom)
  13. Reinstall the plastic cover over the BMS.
  14. Reseat the gasket and install battery box cover.
  15. Apply some silicone to the hole with the wires to make it weatherproof.

Be careful not to let the ends of the exposed wires cross as it's 60 volts of electricity. I'd recommend wrapping them with some electrical tape until they are needed.

Step 6: Reassemble the Onewheel Pint

To reassemble the Onewheel Pint is very simple, just go reverse order from disassembly. Start by putting together the rails with the hub/wheel, slide the bumpers back on. I used blue thread locker on all the bolt threads, the Onewheel gets lots of vibration when riding so don't for get this step.

Take note where the wires from where we tapped into the Pint's battery and match it with the Pint's fender. Drill a hole in the Pint's fender and feed the wires through. Might be a good idea to add a grommet or at a minimum file and sand the edges of the hole smooth. Run the wires through the hole and install the fender.

Step 7: Final Assembly

The upgrade is almost complete. The final bit of soldering is to solder on a female XT90 connector to the two lead wires. Taking care to make sure the positive and negative leads are in the correct spots. As mentioned earlier, my first designs used a switch to prevent sparking when plugging in the two batteries but the XT90 connectors have a built in anti-spark feature. This really simplifies the whole system when dealing with high voltages.

To the fender battery mount, velcro was applied and to the fender of the Onewheel Pint. This make the mount removable when I don't need to use it. I haven't had any issues with the battery coming loose while riding, velcro is very strong!

Before making the connection between the two batteries make sure to fully charge them both. Slide the DeWalt Flexvolt battery into the mount. Meter both connections to make sure they are around the same voltage, a voltage difference of a few tenths of a volt is fine. If not, drain the power from the higher voltage battery until they match. (Plug the DeWalt battery in a power tool to do this or ride the Onewheel around).

For convivence I have a small battery meter that I can use to meter the batteries, you can find them on amazon but the one I have does need the LCD screen powered from a lower voltage battery.

Once the voltages are the same you the two batteries can be connected. That's it the battery upgrade complete and range has been extended! Float on!

IMPORTANT

You cannot use the pint's battery charger (charges at 63 volts at 1.3 amps) to charge the Flexvolt battery, the battery management system in the Flexvolt battery is rated for 20 volts (I think). So you have to use the DeWalt charger to charge the battery.

The app that is used to monitor mileage and the LED status bar on the Onewheel Pint will no longer be accurate (depending on the firmware). It is still basing the remaining range on the capacity of the internal 148Wh battery.

There are a few options to figure out your remaining range:

  1. One is to install a LED voltmeter to the system by tapping into wiring.
  2. The DeWalt battery has three LED indicators that shows the remaining capacity, not perfect but gives an idea.
  3. Use the app and go into settings and view the voltage remaining.

For reference:

  • 55 Volts is around the 1/2 way point of the battery being drained (turn around point).
  • 50 Volts is the around where the 20% of battery life is left.
  • 45 Volts is the estimated safe low voltage, you should stop riding immediately. 15s x 3v = 45 volts

You do not want to over drain a Li-Ion battery, it will damage the battery!!

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3 Comments

0
nils2u
nils2u

1 year ago

Wow - simply blown away!
Have you registered a Patent yet? So well researched, great design, perfect implementation, excellent video....! Chapeau - I‘ve been thinking on how to do something like that with my Pint for some time, but never got close.
Have you sold the rights to OneWheel yet? Taking along a couple of extra standard battery packs to just switch when needed on a long trip, how great would that be?

0
AndrewW1977
AndrewW1977

Reply 1 year ago

Thanks, it's was a fun project to research and even better riding it! Just remember that you can't swap in a full pack when the pint battery is drained, or there will be a rush of current from the higher voltage to the lower voltage (discharged) pack. Of course if some how you wire in a switch to disconnect the pint's battery and just ride with Dewalt or external batteries that would work fine. To be able to swap batteries would be awesome, no more waiting for the pint to charge!

0
Adler Planetarium
Adler Planetarium

1 year ago

Good job on this project! Something to consider and ponder further: If the discharge rate of the pint battery is not equal to the discharge rate of the DeWalt, whichever has the largest discharge rate will deliver its charge to the secondary battery. This may the reason of why your DeWalt battery is still charged. Essentially, the pint might be charging the DeWalt, and once it fully discharges, then the DeWalt will take over and force some of its charge back to the battery. You might want to consider monitoring the current discharge of both batteries to really get down to what is happening in your system. CAUTION: If you keep running the batteries with such design, you may degrade both batteries.