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Boosted Rev Custom Battery 3D Parts and build instructions (free!)

 I've been making custom parts for the defunct Boosted Rev for some time now. One part that I continuously get questions about is the battery. Considering many people end up with dead batteries, I put together two 3d-printable designs that allow for people to put together their own batteries with minimal effort.

I made 2 designs:

  • 370Wh battery, 12S3P 18650 cells. Original capacity, small size. Extra space for large/smart BMS.
  • 1000Wh battery, 12S5P 21700 cells. Huge capacity but very large. Requires a small BMS to fit the VESC.
1kWh extended battery, packaged and ready




Both designs are best printed in a water resistant, flexibel material, like PETG or ABS. If you wrap up the battery correctly in shrink wrap, the battery may be rendered waterproof using extra silicone or waterproofing tape.

Needed:
  • PETG, ABS or other watertight, flexible filament (it's important the filament is flexible, don't print in hard resin)
  • 180mm or 200mm battery shrink wrap (available on Amazon or battery shops)
  • 6mm² (10AWG) black and red cable
  • 12S (min) 25A - 50A BMS with balancing wired (some 13S BMS can be used too if two balancing wires are connected to the same cells, to make a 'single' cell). For the 1kWh battery, a small BMS is required!! (due to space restrictions)
  • XT90 female connector
  • Some default black and red wires for charging (1mm² or 18 AWG) (use larger diameter for fast chargers above > 2A) 
  • Wire shrink wrap
  • Silicone stay-flexible glue (non-corrosive!!)
  • M3 self threading screws
  • Superglue (suitable for your filament material)
  • Spot welder
The cells needed are, respectively:
  • 36 pieces 18650 3000mA li-ion 20A 3.7V cells for the 370Wh battery
  • 60 pieces 21700 5000mA li-ion 10A 3.7V cells for the 1kWh battery
You best order some extra cells in the instance some cells are damaged while making the battery.

Warning/disclaimer: Putting a lithium ion pack together is dangerous. Cells may explode, vent or catch fire if handled incorrectly. Shorts are often fatal to the cells and may cause fire. The battery may explode, vent or catch fire when charged incorrectly or when using a faulty BMS.


Parts I used are:
For the 370Wh battery:
Print the models in PETG, ABS or another flexible, waterproof material. It is especially important for the 1kWh battery that the parts if flexible, as the cells will have to bend a little inside the Boosted Rev frame.

Some models require printing with supports or a brim, depending on your printer. However, all models are designed with minimal support in mind.

370Wh battery: no additional work is needed after printing.
1kWh battery: Glue the bottom, middle and top pieces respectively together, using the embossed numbers as guideline, starting at 6, counting down.

370Wh Battery Instructions

370Wh battery, built

Once the pieces are printed, spot weld all 30 cells in pairs of two times 3cells (welding the plus side to minus) so that you end up with 6 sets of welded cells.

About balancing wires: It's up to you how to solder the balancing wires of your BMS (since every BMS has slightly different cables). The 3d parts contain spaces to lay your balancing wires in (including extra space on the top of the cells for small soldering). Be sure to guide your balancing wires out of the 3d parts through the front while constructing your battery.


Apply silicone glue to the bottom right side. Weld two sets you've just made together, making sure that:
  • A positive terminal will end up at the front
  • A negative terminal at the rear
  • The bends in the welding strips are at the outside of the mould
(Refer to images)

Spot weld two sets together, making sure that the strip bend is at the outside.


4 series are welded together (welds in red), with the bend of the welding strip at the outside of the pack


Apply glue to the left side of the mould and repeat, but the other side round. Negative terminal at the front, positive at the back. Once again make sure the welds are at the outside of the mould.

Apply glue to the left side and make sure the negative terminal is at the front and positive at the rear.

Bends of the welding strips should be at the outside of the mold.



Apply glue to the top of the cells and put the center piece in place

Weld the rear terminals respectively, making sure not to create a short between left and right side

Apply glue to the top piece and place a set of cells in the left mould, positive terminal at the rear. Weld the positive terminals.


Do the same for the left side, and weld both sets together at the front. (NOT THE BACK!)

At the back, weld the rear terminals respectively. Make sure not to create a short between left and right side.

Put the top piece in place (without glue). Screw in place with 2 M3 screws.

Screw the back plate on using 6 M3 screws.

Weld 2 strips at the respective front plus and minus terminals, leaving appr. 5 cm at each side. Be careful not to short these terminals.

Screw the front plate over the terminals. Bend the terminal strips in the respective spaces for plus and minus. Wires may be soldered to these terminals; Additionally you may use another method to attatch wires to the terminals. Glue in place.


Adding the BMS

The BMS is a vital part of the battery. It protects the cells against overvoltage, undervoltage, overcurrent and thermal problems.
By now, you'll have guided your balancing wires out of the holes that are present at the front. Depending on your BMS, there are different ways on how to hook it up. Follow the user manual of the BMS.

The BMS may be mounted on top of the front piece of your battery. Space is provided for a rather large BMS if needed. Don't forget to mount the thermal sensor of the BMS close to the cells.

DO NOT bypass the BMS for discharge! It is a popular method of delegating the handling of the discharge to the VESC but this is considered very bad practice, because:
  • In case the VESC fails, your battery is not protected
  • If the terminals of the battery itself short, the VESC won't protect the battery
  • If the VESC is misconfigured, it won't protect the cells from undervoltage
  • The VESC does not protect the cells in case of cell overheating
It is very easy to misconfigure the VESC to not protect the battery in it's entirety. Please DO NOT bypass the BMS.

Your BMS will always be placed in series with your battery. Solder the XT90 connector to the BMS terminals (most often 1 wire to one terminal on the battery, the other on the BMS, depending on your model). I use 10 AWG (6mm²) large wires to hook up the XT90 connector to. This connector will hook up to the VESC. You may additionally solder parallel smaller wires leaving your battery pack for charging up (also hooked up to the BMS, don't bypass). You may then solder these smaller wires to the charging port at the front of the Boosted Rev. (do not use these smaller wires for discharge, only charging with a charger. Check that these wires can handle the current from your charger. Typically 2A - 5A)

First Charge

When your built is done, it will be time to charge up the battery for the first time. This is often a critical step, take precautions. If you made a mistake or any component is faulty, it may be that some cells vent, explode or catch fire.

Safety first! For the first charge, place your battery in a safe (most likely) outside area, so that if it were to catch fire, no harm is done. I typically use a voltmeter and ampere meter to monitor the charge.

Your battery should charge to its maximum voltage and then cut off any additional current once this maximum value is reached. The current measures shouldn't exceed the charger's constant current (default Boosted Rev charger charges at around 2.4A).

The max voltage value for the battery is 50.4V. Depending on your model, the BMS may cut off current at a value slightly below it, to save up cell life.

If the battery draws significantly more current than your charger or battery is rated for, gets abnormally hot or the voltage rises above the max. value more than a couple of volts, DISCONNECT THE CHARGER!

Do note that measuring in parallel across the battery charging will read a voltage value slightly higher than the value of the battery itself. Disconnect the charger for a moment to get an accurate battery reading.

The battery reading may NEVER exceed 50.4V! Even exceeding by a few mV can get dangerous. The BMS will be in charge of managing this.

Finishing Up

Hopefully your first charge went well and the battery is now ready to be packaged.

Shrink wrap your battery carefully to make it (semi) waterproof. Additionally you may use waterproofing tape and/or non-corrosive silicone to glue your battery pack. Be careful no wires or other elements may tear the wrap apart.

1kWh Battery Instructions

Coming up


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