Battery holder for cellphone batteries

In this write up I will show a simple construction that I did to hold my cellphone battery for charging. The construction uses only few items which could be easily salvaged.

Why

The problem is that the cellphone batteries come in various sizes and to fit these batteries in a holder outside the phone is tricky.

This holder comes handy if you have a phone battery that you want to charge outside the phone especially if you are involved in servicing. One could solder the contacts of the battery but it is usually not advised to heat the Lithium battery contacts as they could explode. Also the soldering will leave a tinned surface which might not look good.

Disclaimer

Lithium rechargeable batteries are very dangerous if you are not handling them carefully. It could heat up or even explode if you reverse the polarity or short the contacts. I am not responsible for any damage, injuries, loss or anything caused directly or indirectly as a result of following these steps.

How

Here are the list of items you need,

1. 10cm long threaded screws and nut x 4 (or 2)
2. A base plate which I used an old PCB, 5x3cm
3. Another piece to keep in perpendicular with the base.
4. A prototype PCB 
5. Two spring contacts like pogo pins or custom made as we will see later.

Step 1: Long screw

Find long screw (2 or 4) that is suitable for your battery length.

If a long screw is not available, you can make one from smaller screws. I had to use 3 smaller screws to make for my required length. I chopped the head of 2 screws and joined them using solder as shown in the pictures below. 

You can use glue to hold them together and/or a heat shrink. 

With the custom made screws, the nut will likely stay on the top screw and wont go through the joint. So it is easier to build for a bigger battery and pad it from the bottom to fit smaller ones.

You can join the screws without chopping the head, but in that case you will have to check if the screw will go into the base plate after the construction or do it "in-place". See the base plate pictures below.

Chop off the head

Join for required length

Step 2: Base plate with screw holes

The size of the base plate will depend on the battery size, I used a 5cmx3cm old pcb. You can also see the screw tucked with some glue.

Base plate with 4 holes drilled

Step 3: Perpendicular plate with screws

The perpendicular piece is to support the battery from sliding over. It need to be only of a small size when compared to the height of the battery.

In the image I have shown an in-place screw joined with glue and supported with a heat shrink.

Base with perpendicular plate

Base and perpendicular with 2 screws diagonally placed

Step4: Prototype PCB for contacts

The prototype board is used  for placing the battery contacts. Having a general purpose board helps to adjust the placement of contacts especially as the contacts vary widely with batteries.
Drill 4 holes and align with the base.

Prototype board

Step 5: Spring contacts

• You need metal spring contacts to touch the battery terminals. 
• We can use the pogo pin contacts - spring contacts which are usually used for test beds. 
• I didn't have any so I decided to make my own version. 
• I got a metal  contact from an old aerial cable. 
• You also need a small spring and I salvaged it from an old mains plug which had automatic shutters. 
• Some other sources for springs are old toys, or pens.
• Just remember to get small diameter, so that it don't touch between the battery contacts.

A metal contact from old copper cable and a salvaged spring

Make both contacts

Step 6: Putting it together

• Get your battery and make sure to mark the polarity of the contacts. 
• Find the vero board through holes which aligns with the battery contacts and insert the sprint contacts.
• Again make sure about the polarity and let both leads of the contact go into the through hole so as to not rotate the contact.

Inserted contacts

Finished construction

Both contacts touching the battery, mind the polarity 

Conclusion

We went through the construction of a simple phone battery holder for charging. The exposed leads can be connected with a female header to a charging circuitry. The female header helps to readjust for the contacts for a different size battery. The contacts can be fed into a charging circuitry either custom constructed or ready made ebay charging circuits based on the TP4056. This is also extensively reviewed here, http://lygte-info.dk/review/Review%20Charger%20TP4056%20UK.html

Any constructive comments/suggestions are welcome.Thanks for reading through and hope this was helpful.