Replacing Normal Batteries With 18650 Rechargeable Batteries

This may be a long instructable but hopefully there will be a lot useful stuff.
I recomend that you have an interest in soldering or electrical tinkering as you may need a little patience in the beginning.

Warning changing the battery type and voltage can destroy your equipment
and will void any warranty / guarantee claims - you do these modifications at your own risk.I take no responsible for damage or repair to your electrical / electronic goods or fires/ shocks or personal injury - this instructable is purely a guideline for those with basic electronics / battery knowledge wishing to start building and using their own rechargeable battery cells and packs.

1. multimeter - to check voltages, find circuits on battery compartments.
2. Solder and soldering iron.
3. Deans connectors male and female- can be found at RC hobby store or buy bulk online ali/ebay.
4. Different gauges of wire - or you can recycle a broken or cut extension cord.
5. Heat shrink wire protection and lighter.
6. Cloth automotive electrical tape - online ali/ebay.
7. 18650 li-ion battery cells - recovered from old battery pack or online ali/ebay.
8. Good quality battery charger - RC car hobby shops have good options.
9. Anti fire battery charging box/bag - online ali/ebay. I have had no incidents but still use one.
10. Dremel/drill to make wire opening in battery compartments and grind prepare batteries for solder.
11. Star shaped keys for battery pack screws if you are trying to recover batteries.
12. Pliers / wire cutters/ wire strippers.

Recovering Lithium-Ion Batteries By NickB6 in Circuits https://www.instructables.com/Recovering-Lithium-...

Sourcing Batteries.
When you rummaging only collect li-ion packs - often what happens is 1 or 2 cells fail and can't be charged and the whole pack is thrown out. If you are recovering batteries from a power tool pack they may have special star head screws or little covers hiding these screws - you can get the covers off with a small flat screwdriver. As you are disassembling the packs be careful not to short out batteries by touching or accidentally connecting the batteries with metal or the leftover joining plates. I remove the plates with a small long-nose plier and grabbing one side and rolling across the top like an old fashioned can opener. The electrical weld plates can sometimes be left if they suit your battery design. Prep the batteries for solder - I use a dremel to give the positive and negative terminals a light grind ready for solder. You can also use an electric welding technique using 12v car battery - check youtube for that and there are some references in the welding section of this instructable.

Salvaging Rechargeables for Projects By electronics for everyone https://www.instructables.com/Salvaging-Rechargea...

Recently I recovered some old electric bike battery packs - these are a major source of 18650 batteries - I recovered 40 cells in each pack. If you find them at the dump as I did most of the batteries will read as dead, so they will need to be revived just do a search on reviving 18650 battery.

Warning changing the battery type and voltage can destroy your equipment
and will void any warranty / guarantee claims - you do these modifications at your own risk. I am in no way responsible for damage or repair to your electrical / electronic goods or fires/ shocks or personal injury - this instructable is purely a guideline for those with basic electronics / battery knowledge wishing to start building and using their own rechargeable battery cells and packs.

How many 18650 cells do I need?

Avoid going way over the required circuit needs - many circuits have some electrical flexibilty but overloading circuits will lead to failure.

18650 Li-ion cells rated 3.7v (4.0v to 4.3v when fully charged) so I basically try to stay within 10% if possible of requested voltage.

2 x aa battery rated 1.5v (1.6v new, total 3.2v to 3.4v) so your if you want to replace that circuit rated at 3v you can get away with 1 single 18650 battery 3.7v.

3 x aa battery = 4.5v (total 4.8v to 5.1v)circuit can also be replaced by a single 18650 battery = 3.7v (4v charged).

9V battery is made of 6 x 1.5v batteries can be replaced by 2 x 18650 in series = 7.4v (8v charged).

4 aa battery = 6v circuit can also be replaced by by 2 x 18650 in series = 7.4v (8v charged).

Note D cell batteries tend to handle bigger tasks For example a 4 D cell circuit will be 6v but you may consider 2 packs of 7.4V ( 2 x 18650 in series) in parallel. This gives total 4 x 18650 cells batteries but an output of 7.4V

Deans Plugs.
These are available online and serve as cheap and very flexible connection elements for batteries and equipment. They can have large gauge wires soldered to them and keep positive and negative terminals well defined. I imagine the plug as a T the positive is always the horizontal stroke of the T and the negative is always the vertical stroke (as if heading down to earth) as long as you remember to maintain that protocol you should have no problem when soldering. Your battery packs should always use the female version of the deans plug connected to the array of cells

9v Cell replacement option 1.

For this you will need an old dead 9v battery - we are recovering the + and - cap then adding the male deans plug to to wire to make a 9v plug to deans connector. Make sure you have the right polarity for the 9v end ( +ve small male and negative female) as this will be to connect to the internal 9v terminal of the appliance.

9v Cell replacement option 2.

You can cut the 9v connection plug and either join wire to extend it out of the cavity. Add a male deans plug to the wires. Sometimes extending or running the wire out of the battery compartment is necessary as the 18650 batteries may not fit in the compartment.

Adjust Appliance connection and Battery storage.
Sometimes the batteries don't fit inside your electronics - in this case I run a cable out of the battery housing (doing a small opening with a dremel ) and either make a bracket or attach the battery with an elastic after drilling 2 holes in the battery door cover. Use you multimeter to find the positive end and negative end of the battery compartment - battery compartments use the installed batteries to complete the battery circuit, this is why we need to find the final + and final negative contact of the bay. You can also work it out by using aligator clips and a battery and working your way around until the appliance turns on. You can then solder a wire on the positive and a wire on the negative end and install a male deans plug ready to hook to your new 18650 battery pack.

Up until now I have always soldered my packs recovering the tin strips from recovered battery packs. One trick is to lightly grind your recovered battery ends with dremel or even scratch them up with a sharp stanley knife. This will help your solder stick to the battery. Also tin your wires first and try to tin the battery terminal and solder the wire straight after, this will reduce heat stress on the battery. For the battery leads I use old appliance multi strand electrical wire which I get from old appliances, extensiopn cords etc. This wire can also be used to make the bridge solder on your batteries.

I use hot glue to put the cells together/ protect terminals and cloth automotive electrical tape to give them a a little more protection. Once you have lots of packs its a good idea to label the voltage output depending if you hooked them up in series or parallel.

Below are some resources that go a little further on the welding and soldering.

Make a 18650 Battery Without a Spot Welder By CanadianWinters https://www.instructables.com/Make-a-18650-Batter...

DIY Battery Spot Welder! By Nematic! https://www.instructables.com/DIY-Battery-Spot-We...

DIY Spot Welder From Microwave - Now With OLED Display! By JackDavies https://www.instructables.com/DIY-Spot-Welder-Fro...

You will need to keep an eye on your li-ion installed appliances and the moment you start to detect a loss in performance its time to charge the battery. It is important to maintain and not let your li-ion batteries go below their minimum charge level as your charger may not be able to charge them at all, or make them unsafe to charge. I recommend a good RC Car battery charger to maintain the batteries - a worthwhile investment as they can also charge lead batteries, 12v motorcycle and car batteries as well as nicad, Nimh batteries. I usually have a few spare battery packs on hand to switch out the batteries every few months like on the automatic rubbish bin in the kitchen which is a little power hungry (previously equiped with 4 x D type batteries). Other appliances like weather/temp/humidity clocks last years on the more resilient 18650 batteries.

When charging the batteries it is also a good idea to store them and charge them in a fireproof battery bag these are also available online or at the RC hobby shop.