Flashlight adapter 3xAAA to 18650 & 18500

This adapter is for flash light pewered with 3 pcs of AAA batteries. 

These torches are cheap and quite common, but problematic and not economical to power. You need three batteries, but they sels in packs of four. If you replace primary batteries with NiMH, than you get next problem: the most cheap chargers can chare NiMH batteries only in pairs, ie kan charge two or four at a time. Obvously problem is to charge three batteries in a simple charger. 

I have replaced batteries in all my torches by Li-ion rechargable batteries of size 18650 (18 mm in diameter and 65 mm long). 

Li-ion batteries are very common. They keep lot of energy, are not too expensive and are simple to charge. 

Print this adapter, remove original battery holder for 3 AAA batteries. Install Li-ion battery together with this adapter into your flashlight. 

How to charge?

• I have ordered Li-ion charger board for a single cell, powered from USB port. Search on Aliexpress or Amazon for TP4056 or similar. This charger is incredibly cheap, but doing the job well. As my pictures show, I have soldered and glued this tiny PCB on a plastic battery holder (you can search and print your own) for 18650 cells. You have LED indication too, showing status of the charge. The battery holder shown on my pictures is not so practical. It is pain to remove a charged battery from it. Better suggestion is to print my 18650 Battery Magnetic Charge Holder and then solder it to the charger board, or
• use my magnetic holder and simply connect it to a bench Powe Supply (if you have). Adjust voltage to 4V (4.2V is max) and, for example 500mA. When battery voltage reaches the charge voltage, charge current will decrease. When the charge current drops below 50mA, the battery is charged.

How to get Li-ion batteries?

Buy at some reputable store. Do not buy UltraFire or similar on Aliexpress! This is completely garbage. Better solution is to disassemble an old laptop battery, but this is another story…

The another shorter adapter is for a bit shorter 18500 batteries, if you need.