The Naked Scientists Forum

Author Topic: How can the amount of charge remaining in a battery be measured?  (Read 45300 times)

ukmicky

• Neilep Level Member
• Posts: 3011
How can the amount of charge remaining in a battery be measured?
« on: 30/04/2006 19:27:44 »
Moving on from the other battery topic

Is there an easy way to tell using everyday household items how much life is left in a battery.

The reason being is because I've got a wireless keyboard and mouse and when things slow up and the keyboard fails to respond the people of my house always assume the batteries have gone and replace them with new ones, whereas usually the batteries are fine and all that is required is a computer restart to rectify the problem.

so Ive now got a draw with 35 AA bateries, some half used ,some almost dead and 12 new ones because someone emptied a new box in their

So is there anyway using everyday house hold items  i can put together a device to accurately tell me how much life is actually left in each individual battery.

Bearing in mind that a dead battery as far as a keyboard or mouse is concerned may not be dead enough for a small test lamp and may still light it up.

Michael

Michael
« Last Edit: 22/09/2008 23:47:45 by chris »

Atomic-S

• Hero Member
• Posts: 919
• Thanked: 17 times
Re: How can the amount of charge remaining in a battery be measured?
« Reply #1 on: 08/05/2006 06:49:45 »
Well, how much current does a mouse require?

another_someone

• Guest
Re: How can the amount of charge remaining in a battery be measured?
« Reply #2 on: 08/05/2006 14:54:43 »
quote:
Originally posted by ukmicky
Is there an easy way to tell using everyday household items how much life is left in a battery.

The reason being is because I've got a wireless keyboard and mouse and when things slow up and the keyboard fails to respond the people of my house always assume the batteries have gone and replace them with new ones, whereas usually the batteries are fine and all that is required is a computer restart to rectify the problem.

so Ive now got a draw with 35 AA bateries, some half used ,some almost dead and 12 new ones because someone emptied a new box in their

So is there anyway using everyday house hold items  i can put together a device to accurately tell me how much life is actually left in each individual battery.

Bearing in mind that a dead battery as far as a keyboard or mouse is concerned may not be dead enough for a small test lamp and may still light it up.

Depends on what you regard as an everyday household item – multimeter are fairly common devices, and easily attainable, and the only way you can really judge how much energy a battery still contains (other than to consume it) is to check the output voltage of the battery.

Ofcourse, depending on the battery technology, some batteries may gradually decrease their voltage as they use up their energy, and the measure of voltage is a good indicator of battery life; whereas other battery technologies (Lithium Ion technology is one) will have a fairly constant voltage right up to then end, and then rapidly plummet, and so by the time you see any significant change in voltage the battery is already effectively at the very end of its life.

George
« Last Edit: 08/05/2006 14:56:40 by another_someone »

Pumblechook

• Hero Member
• Posts: 569
Re: How can the amount of charge remaining in a battery be measured?
« Reply #3 on: 22/09/2008 09:41:06 »
Some multimeters have a battery test facility for 1.5 or 9 volts batteries.  The multimeter draws a current form the battery while it measures the voltage.  This gives a better idea of the state of the batteries..  1.5 - 1.6 V.. New battery..  1.3 - 1.4 ...Some life left..  1.2 - 1.3 Nearly used up. Leave the tester on for 30 secs and see if the volts drop off.  Tricky to be exact because batteries vary in behaviour depending on their chemical construction and the ambient temperature.

techmind

• Hero Member
• Posts: 934
• Un-obfuscated
Re: How can the amount of charge remaining in a battery be measured?
« Reply #4 on: 22/09/2008 21:26:34 »
Moving on from the other battery topic

Is there an easy way to tell using everyday household items how much life is left in a battery.

The reason being is because I've got a wireless keyboard and mouse and when things slow up and the keyboard fails to respond the people of my house always assume the batteries have gone and replace them with new ones, whereas usually the batteries are fine and all that is required is a computer restart to rectify the problem.

so Ive now got a draw with 35 AA bateries, some half used ,some almost dead and 12 new ones because someone emptied a new box in their

So is there anyway using everyday house hold items  i can put together a device to accurately tell me how much life is actually left in each individual battery.

Bearing in mind that a dead battery as far as a keyboard or mouse is concerned may not be dead enough for a small test lamp and may still light it up.

Michael

Michael

If these are regular alkaline AA or AAA's, try the batteries in a single-cell torch (or buy a 1.3-1.5V torch bulb and use a bit of wire to make the circuit):
- bulb lights tells you the battery has plenty of life
- bulb is dim, battery is on its way out, but might power low-drain things for a bit longer
- bulb doesn't light. Battery is definitely fit only for the bin.

Get a multimeter (I don't recommend cheap tools, but Maplin have some cheap stuff - £6.45 perhaps), and you'll find other uses for it anyway. For Duracells, unused expect over 1.5V unloaded, maybe 1.55ish. Well-used Duracells will show around 1.1-1.2V unloaded (end-of-life for a torch, small radio or other mid-drain appliance). A Duracell reading under 1.0V unloaded should be heading directly for the bin. Other brands have slightly different characteristics. It is also my experience that very low drain devices (eg digital clocks, where the battery lasts several years) may still show a fairly high open-circuit voltage by the time their internal-impedance has risen to the point of the battery being past-useful.

turnipsock

• Hero Member
• Posts: 586
• Beekeeper to the unsuspecting
Re: How can the amount of charge remaining in a battery be measured?
« Reply #5 on: 22/09/2008 22:34:01 »
You can get a battery checker from Maplins.

Why not just get rechargables like the rest of the world?

neilep

• Withdrawnmist
• Naked Science Forum GOD!
• Posts: 20597
• Thanked: 8 times
Re: How can the amount of charge remaining in a battery be measured?
« Reply #6 on: 22/09/2008 23:29:21 »
Well Michael ?

What did ewe do ? seeing as it's 2 and half years since ewe asked !...or do ewe now have two drawers full of batteries ? :-)

The Naked Scientists Forum

Re: How can the amount of charge remaining in a battery be measured?
« Reply #6 on: 22/09/2008 23:29:21 »