Makita Battery Adapter (barrel jack)

prusaprinters

WarningLithium batteries are very dangerous if mistreated, especially tool batteries like these that are capable of delivering several hundred watts of power in an instant. If you short them out, or get the polarity wrong, they can explode or catch fire. Make this at your own risk.The model without the voltmeter is safer to make, as it does not have any wires close to each other.Note I'm not 100% sure of this, but from what I've read, the older (non star marked) batteries do not have under discharge protection in the battery. If this is true, you need to keep a close eye on the voltage so it doesn't drop too low. If it does, it will be marked dead by the BMS, and will no longer take a charge. It's also bad for the cells. If you can clarify this, post it in the comments.Edit: As far as Makita batteries go (star and non-star marked). I've been able to discharge them all the way down to 10V (2V per cell) without them cutting off. This is far below usual cutoff voltage, which would be around 15V (3V per cell). It looks like Makita batteries do NOT have over-discharge protection, unless it's extremely low (below 2V per cell).This is a simple adapter for 18v Makita lithium tool batteries. It's designed to use 5.5x2.1 or 5.5x2.5mm metal barrel jack connectors.It will fit older and newer (marked with a star) batteries, as well as off-brand types like japcell.The fusion 360 file is available, so If you need a different connector you can modify my model. The timeline is a little strange on this one so it's probably better to build on top of the model, rather then editing something early in the timeline.You will need some copper strips that will connect to the battery. Wires are soldered on to these strips. I used strips 10mm wide and 0.95mm thick. I got them from a UK eBay store called copper-solutions.This store seems be be gone. Another way get get strips is to buy 1mm thick copper or nickel plates that can be cut into strips using metal-cutting shears, or a Dremel.This adapter was made to be used with my 70w floodlight, but you can use it for other things as well.Print instructionsThere are two models you can print. One has space for a voltmeter, and one is without.The model you will be printing is slightly different then in the pictures. The wires on the copper strips has to be soldered before putting them in the adapter. That was not possible on the prototypes, so the plastic melted a bit. The strips are then glued in place.To find the connector, you can search eBay for:5.5 metal female connectorThe models do not need any supports.