Little Monster - Battery


For the little monster, a 13600maH 12.6V pack needs to be built.  This is done using individual 18650 cells.

To keep a good weight distribution we need to install the battery at the front of the mower.  As space is limited a custom 18650 LiIon Battery holder is provided in the STL files.


18650 Batterries

Please use good quality Panasonic 18650B LiIon Cells.  Its worth investing in good quality batteries once.

These single cells can be purchased online (e.g. Ebay).  Dont be fooled by manufacturers claiming enourmous cell capacities.  3400mah is the standard cell capacity.  I always use Panasonic NCR18650B cells.


Cell Setup and Connections

1. Solder connection spots on the positive (+ve) and negative (-ve) side of all the 18650 cells.   The +ve side will solder easily, the -ve side needs extra time to get hot as the -ve is the complete case of the battery.

2. Press the cells into the custom battery holder as shown here.  The battery holder is in the STL Pack.  You may need to remove 10mm of the green packaging on the negative side so the cell fits in.  Tap them in home gently with a rubber hammer if needed.


2. Now connect the cells on the top and bottom side as shown here.  You can use electrical wire 1.5 - 2mm thick




3. Now join the seperate packs together (purple wire) and add a longer wire to go to the battery protection board (BMS).



4. Connect the wires to the BMS in the positons labelled,  Connect a battery lead with an EC5 connecter to the P+



5. Using a multimeter you should measure the foloowing DC voltages

  • Between B- and B1 3.2V - 4.2V
  • Between B- and B2 6.4V - 8.4V 
  • Between B- and B+ 9.6V - 12.6V
If all this is correct you should measure:
  • Between P- and P + 9.6V - 12.6V

(If the first 3 voltages are correct and the last voltage is not correct it could mean a faulty BMS board)


6. If everything measure correct the battery is ready to be charged and installed.