Follow along with the video below to see how to install our site as a web app on your home screen.
Note: This feature may not be available in some browsers.
i want to check true mAh of a battery just cant think of any devices that could do that. only thing i can think of is to video record charging or discharging and do a by hand integral of the whole thing? haha but thats painful there has to be a simpler way
What is your purpose? If you measure a non-rechargeable cell by the above method then the cell is dead at the end of the measurement; so that's a waste. The next cell you pick up won't necessarily have the same mAh as the first, even if it's the same brand and nominal capacity.for my purposes its not worth it.
What is your purpose? If you measure a non-rechargeable cell by the above method then the cell is dead at the end of the measurement; so that's a waste. The next cell you pick up won't necessarily have the same mAh as the first, even if it's the same brand and nominal capacity.
Hi again,
Well another technique is to use a constant current (active) load, where the current drain is always the same regardless of the battery voltage. This way you only have to make a few measurements over time and do a little math to figure out the rating. The active load would be made using an op amp and transistor rather than just a resistor. Not to hard to do though if you are interested.
For example, say we set the constant current load to 100ma. That means no matter when we look at it it will always be drawing 100ma. And lets say that when we turn it on, the voltage is 4.10 volts. We come back two hours later and the voltage is 4.05 volts, so we know we have gotten 0.1 times 2 which is 0.2 ampere hours out of it already. We come back 8 more hours later, and it is at 4.00 volts. As long as it is not under 3 volts we dont have to do anything really. We come back 5 hours later (a total of 15 hours now) and it is at 3.2 volts. We know we're getting closer to 3.0 volts now so we come back more often. We come back another 2 hours later and it's at 3.01 volts. We decide that is low enough, so we disconnect the load.
Now since it took 17 hours to complete this experiment with a 0.1 ampere load, that means the battery had exhibited a capacity of 17 times 0.1 which is 1.7 ampere hours. That's the capacity when we discharge at 100ma down to 3.0 volts.
So you can see how much simpler this is now. We only have to catch it when it reaches 3.0 volts (or whatever target voltage we choose that wont hurt the battery).
of course that would be grea but with a variable voltage how can we ensure a constant current draw throughout??
of course that would be grea but with a variable voltage how can we ensure a constant current draw throughout??