Hidden Power
Introduction: Hidden Power
Power may reside in a secret and therefore you may wish to keep it in a safe place and what better than a place of power storage, a battery.
This project will describe the process of converting a battery into a secret storage compartment with the added bonus that it can be inserted into a multi cell battery pack which will still function although with a reduced voltage.
Choose wisely an application that is not voltage critical and no one will be the wiser unless they dismantel the battery pack or measure the voltages.
Supplies
Materials
3D printer
PLA+ filament (Black)
22 SWG (~0.711 mm), tinned copper wire
Battery (AA type)
Multi purpose glue
Black Paint or Black marker and clear lacquer/paint
Epoxy filler
Adhesive Tape
Tools
Cura or similar splicer
Grinder
Drill bits 1 mm and 8 mm to 12 mm
Hand or low speed drill
Pliers
Cutters
Soldering Iron
Solder
Round profile needle file
Flat profile needle file
Sanding paper
Wire wool
Scalpel
Protective Glove
Eye Protection
Step 1: Preparation
Obtain an exhausted battery, in this case an AA type alkaline. (Other battery types could be used.)
If your unsure whether is exhausted, ideally test it under load to determine its condition.
For example it may not power your torch but has no trouble powering a TV remote.
In the absence of specific test equipment to verify its condition when its no longer capable of powering a Joule Thief or similar low power circuit we can consider it exhuasted.
We want an exhausted battery in order to prevent the occurance of a short circuit resulting in damage to the blade from an electrical discharge when the blade contacts the central negative pin and the positive outer case. Even these small batteries are capable of a large current of several amperes which can create a lot of heat.
Better still use a grinding wheel which is none conducted and exposes the end rather than cutting into the battery.
Further details for the type of battery used in this project can be found in the attached document.
(No affiliation or connection with the manufacturer of the product in this project, details provided for information only. Check with the manufacturer for the latest updates.)
Step 2: Removing the End Cap
With a scalpel carefully cut off the plastic cover that curls around the edge of the battery.
This will expose the edge of the end cap that is spot welded on the end.
With a flat blade screwdriver slip this under the edge of the end cap and carefully pry it off.
In the process the end cap may bend a little but if not too extremenly bent can be flatterned back into shape.
This will expose the vent and insulator ring.
Now with these removed the end can be ground off.
Step 3: Grinding
Wearing suitable gloves, eye protection and any other relavant precautions related to the equipment to be used and the process to be carried out.
Carefully proceed to grind off the negative end of the battery.
You will need to remove ~2 mm of the main body to expose the inner construction.
The central ring is the anode pin.
The white ring is the anode element.
The dark ring is the cathode element.
The next stage is to remove these elements from the body.
Step 4: Active Elements Removal
Wearing suitable gloves and eye protection.
Consult local regulations for the disposal of batteries to be used.
Wrap the battery with a cloth, bubble wrap, antislip material, cork wrap or other suitable material to protect the battery from being crushed when held in the vice or clamp and to prevent it slipping and marking the external surface.
First remove the anode pin with a cocktail stick, a pair of pliers or tweezers which should just slide out.
Next with a hand drill or electric drill on a slow speed, starting with an 8 mm drill bit remove the white anode paste.
The white paste is very soft and will come out easily.
Next proceed with a 9 mm drill bit to remove the dark brown cathode material, this is much more dense than the white paste and a little more difficult to remove.
Progressively, increase the drill bit to 10 mm, 11 mm and finally 12 mm which will remove all but a thin layer at the circumference of the cylinder.
This thin layer can be removed with flat blade screwdriver and/or scalpel blade.
The edges of the cylinder will be sharp as a result of the grinding process and will need to be smoothed with sanding paper or a round profile file.
Application of wire wool wrapped around a stick and pushed in the cavity should remove any remaining active material adhering to the insides. 713