# Method to measure maximum energy stored in battery

Thread Starter

#### Grim_hitsu

Joined Nov 10, 2016
5
Hi guys, I'm trying to measure the maximum energy stored in a battery but I'm not allowed to use any stopwatch or timer. Is there any other method to measure it?

#### joeyd999

Joined Jun 6, 2011
4,434
Hi guys, I'm trying to measure the maximum energy stored in a battery but I'm not allowed to use any stopwatch or timer. Is there any other method to measure it?
E=MC^2. Weigh it!

#### AlbertHall

Joined Jun 4, 2014
10,564
Take a very well insulated (against heat loss I mean) container full of water and connect the battery to a resistor in the water. Then you measure the temperature of the water at the start and then watch the temperature rise. When it stops warming up, the difference in temperature and the specific heat of water will give you the total energy delivered to the water.

#### crutschow

Joined Mar 14, 2008
25,670
Sounds like homework.

#### Dr.killjoy

Joined Apr 28, 2013
1,196
For me I could just guess and be pretty close as most battery are pretty close in value..
Or cheat and measure the battery and type ,then search google for similar battery..

Thread Starter

#### Grim_hitsu

Joined Nov 10, 2016
5
Take a very well insulated (against heat loss I mean) container full of water and connect the battery to a resistor in the water. Then you measure the temperature of the water at the start and then watch the temperature rise. When it stops warming up, the difference in temperature and the specific heat of water will give you the total energy delivered to the water.
Thank you so much for this brilliant idea, can I know what value of resistor would be suitable for this experiment?

#### #12

Joined Nov 30, 2010
18,210
can I know what value of resistor would be suitable for this experiment?
Can we know the voltage and amps-hours alleged to be in the battery?
For that matter, you can calculate energy by knowing the voltage and amp-hours in the battery.
The question remaining is, do you want to do the math while allowing for the decrease of voltage during discharge? Do you want to estimate for a new battery you might buy? Do you want to measure the reality of one battery in whatever condition it is in today?

#### dannyf

Joined Sep 13, 2015
2,197
measure the current (+ voltage optionally) until the battery is fully charged. the area under the current vs. time plot is the capacity of the battery, in mah.

#### AlbertHall

Joined Jun 4, 2014
10,564
measure the current (+ voltage optionally) until the battery is fully charged. the area under the current vs. time plot is the capacity of the battery, in mah.
But we're not allowed to measure time.

#### dannyf

Joined Sep 13, 2015
2,197
we're not allowed to measure time.
It didn't say that, at least explicitly. It only prohibits stopwatch or timer .

Thread Starter

#### Grim_hitsu

Joined Nov 10, 2016
5
It didn't say that, at least explicitly. It only prohibits stopwatch or timer .
How are you going to measure time if stopwatch and timer are not allowed?

Thread Starter

#### Grim_hitsu

Joined Nov 10, 2016
5
Can we know the voltage and amps-hours alleged to be in the battery?
For that matter, you can calculate energy by knowing the voltage and amp-hours in the battery.
The question remaining is, do you want to do the math while allowing for the decrease of voltage during discharge? Do you want to estimate for a new battery you might buy? Do you want to measure the reality of one battery in whatever condition it is in today?
The battery i'm using is an AA battery with voltage of 2V and 2600mAh. I'm planning to measure the maximum energy for 2 different kind of batteries which one of them would be a fully charge rechargeable battery and a newly bought non-rechargeable battery. The condition on the day of experiment wouldn't matter

#### debe

Joined Sep 21, 2010
1,200
This is what I use for checking battery capacity, from Ebay for \$6 free freight. You just set the voltage that you want the test to terminate. Then read off the Hhrs accumulated on the display. While its working it scrolls through current draw & Voltage & Ahr.

#### #12

Joined Nov 30, 2010
18,210
debe just showed you an excellent method. You can do pretty much the same thing by attaching a volt meter and watching the voltage until the battery is weak.
According to my old Radio Shack battery book:
An alkaline AA is rated as 1.5V and can power a 4 ohm load for 228 minutes as it fails to 0.8 volts.
A ni-cad AA is rated for 1.2V and has about 1/2 an amp-hour in it.
Some NiMH AA batteries are rated at 1.2V and contain 2.6 amp-hours.

So, it looks like about 4 ohms, 1 watt, and most of a day to test a couple of batteries.

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