For the battery holder I ended up using
this one since it’s slotted. I tried a different one that was solid and with the batteries it was too tall for the space available.
The molex connector is a bit overpriced and includes both male and female connectors. For 18650 cells I bought
cells that were flat on both ends as comments on the holders claimed the button versions might not fit. And of course a
charger.
The connector is also available from DigiKey but you need to buy both the
connector and the
pins. You could use the connector off the old battery. The middle blue wire isn’t needed as it is used by the charger which you won’t be using to charge these cells.
View attachment 6479
Then just basically solder everything together, charge the batteries, insert them in the controller in series to get 7.4v and go. This is from my first attempt using some scrap wire I had. But it works just as he describes in his video. The pads underneath will need to be peeled off the controller in order for the door to fit. I replaced the screw with a
knurled thumb screw so it would be easier to get to the cells in order to remove them for charging.
Good luck and hopefully this helps.