Want to know if a battery is dead? See if it BOUNCES: Engineer claims simple trick reveals if a cell has lost its charge
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Forget swapping batteries countless times, or pressing buttons at either end to work out when all the juice has gone, there's a much simpler trick - bouncing them, one engineer has claimed.
When you drop a dead, or bad, alkaline battery on a solid surface it bounces, while a good battery falls over, electrical engineer Lee Hite explains.
In a video, Mr Hite began by addressing the two main theories put forward as to why batteries bounce when they no longer work.
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When you bounce a dead, or bad, alkaline battery on a solid surface it bounces, while a good battery falls over (pictured). Electrical engineer Lee Hite has created a video to test two theories - outgassing and the anti-bounce theory - to explain why this phenomenon occurs
The first is known as outgassing, which is a release of gas from the electrolyte.
This causes an increase in containment pressure and an increase in spring constant, all adding to the extra bounce in the bad battery.
A spring constant is used in Hooke's Law to determine the force a spring exerts on an object, and measures how stiff and strong the spring-like mechanism is.
The second theory is known as the anti-bounce theory.
This states that the gel-like substance in a good battery moves down as it hits the surface, causing the forces to equalise, meaning it stays flush with the floor.
To test the outgassing theory, Mr Hite dropped an object on the battery, rather than dropping the battery itself.
As Mr Hite explained: 'If in fact we have an increase in spring constant [caused by outgassing], we should see the different between a good battery and a bad battery by dropping a weight on the battery - and one should bounce higher than the other.'
To test outgassing, Mr Hite dropped a weight on the battery. If there was a build up of pressure, a weight should bounce higher on one than the other. He also drilled holes in the batteries to release this pressure. There was not a 'convincing' difference in the first test, and the bad battery still bounced in the second
During tests, there was not a 'convincing' difference between the bounce of the brass weight, so Mr Hite discounted this theory.
To confirm this conclusion, he also drilled a hole into the top and bottom of the batteries, to relieve any gas pressure, but the bad battery still bounced.
In terms of the anti-bounce theory, Mr Hite used hammers to demonstrate.
A regular hammer will bounce when hit against a surface, but an anti-bounce hammer is fitted with a cylinder full of buckshot.
As the hammer hits the surface, the buckshot lags behind the movement, and when the hammer hits the base, the buckshot catches up with it, pushing it down again.
This equalises the force.
In terms of the anti-bounce theory, Mr Hite used hammers to demonstrate. A regular hammer will bounce when hit against a surface, but an anti-bounce hammer (pictured) is fitted with buckshot. As the hammer hits the surface, the buckshot lags behind, and when the hammer hits the base, the buckshot catches up with it
Mr Hite then cut the batteries open to see how the electrolyte in a good and bad battery differs. In a good battery, it has a gel-like substance (left), while in a bad battery it is solid (right). Mr Hite believes the gel in a good battery works in a similar way to the buckshot in the anti-bounce hammer and causes a downward force
Mr Hite then cut the batteries open to see how the electrolyte in a good and bad battery differs. In a good battery, it has a gel-like substance, while in a bad battery it is solid.
Mr Hite believes that the gel in a good battery works in a similar way to the buckshot in the anti-bounce hammer.
As the battery hits the surface, the gel catches up and creates a downward force to counteract the upward trajectory.
'A non-rechargeable alkaline battery begins life using zinc powder mixed into a gel containing a potassium hydroxide electrolyte separated from a paste of manganese dioxide powder mixed with carbon powder using a porous membrane,' explained Mr Hite.
'To minimise hydrogen outgassing an extra measure of manganese dioxide is added.
'As the battery discharges manganese dioxide powder changes to manganese oxide causing the powdered granules to bond both chemically and physically.
'This packed-sand consistency reduces the anti-bounce effect exhibited by the gel mixture when the battery was fully charged.'
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