Determine mAh

Sure. Put the rated load on it and measure the time until the voltage drops. ...Jim Thompson

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Is the 7.7 Wh on the battery Watts/hr ?

How would the rated load be applied ?

I have a Sunwa YX-360TR but it does not have that feature.

Thanks.

I doubt if there is an accurate non-destructive method.

You can however measure the charge transfer, Q in a number of ways. integrating I*t=Q

2) Use a tiny shunt resistor and scope the current pulse ( harder)

You can also measure the quality of the battery by it's ESR which rises with with reduced capacity and rapidly near end of life. If you are looking for statistical data, it may be a good metric for SOC using historical data.

It's 7.7 Watt*hours... generally, but not strictly, 7.7Watts for 1 hour, or 1 Watt for 7.7 hours

Resistive load. The battery pack should mention that the Watt-hour rating is based on X amount of Ampere's as the load.

Lose the google ;-) ...Jim Thompson

Yes.

No, it's 7.7 watts * hours. One watt for 7.7 hours or 7.7 watts for 1 hour. In reality, your battery is something else. Reality matters.

If you want to test the batter to the manufacturer's specifications, than you test the way the manufacturer specifies.

What feature?

"miso" = moron

One the cell voltage drops below 1.1V it then drops rapidly to 1.0V or 0.9V.

Digital cameras auto shut off at about 1.1V per cell anyhow - and INCREASE the current draw as the terminal voltage falls.

A 10W resistor of 6.8 ohms will do fine.

Monitor the actual current and plot it against time every 10 minutes.

Use the simple average.

... Phil

I did it once using the camera as a load. The camera had a 'slide show' mode that continuously displayed pictures on the memory card. I think the camera drew about 600mA and the show lasted about 2 hours, so the battery capacity was around 1200mAH.

-Bill

has a 1900 mAh rating instead of a 1000 mAh ? Thanks.

You would think the 1900 would last a lot longer. If you have both varieti es, just time them in actual use.

The mAh rating is a guide, but becomes much more meaningful when you know t he discharge, recharge and temperate curves for the battery chemistry. You could rig up a discharge test while monitoring cell voltage, amperage and temperature and then test/compare each battery.

For a lead-acid battery, Google Peukert's Law. It won't hold perfectly true for a different battery chemistry, but it may give you some rough ideas about how to approach the problem. If both batte ries are the same basic chemistry, (Li-ion, for example) I'm wondering out loud whether you could just weigh each battery - and assume the energy-to-w eight ratios for both camera batteries are at least in the same ballpark.

Keep your day job.

y has a 1900 mAh rating instead of a 1000 mAh ?

ties, just time them in actual use.

the discharge, recharge and temperate curves for the battery chemistry. Y ou could rig up a discharge test while monitoring cell voltage, amperage an d temperature and then test/compare each battery.

y give you some rough ideas about how to approach the problem. If both bat teries are the same basic chemistry, (Li-ion, for example) I'm wondering ou t loud whether you could just weigh each battery - and assume the energy-to

-weight ratios for both camera batteries are at least in the same ballpark.

Thanks for the positive responses.

My question was because someone is selling Vivitar batteries at 1900 Mah.

Vivitar's own site has no such battery. Only a 1000 Mah battery.

I can see another company making a higher capacity battery, but why is Vivi tar's name on it? :-)

That's because 9 is next to 0 on the qwerty and it's a typo in the ad. They probably mean 1000mAH .

It's amazing the amount of useless posturing you get from such a simple question.

Why not start with the problem you're trying to solve?

The answer to the question you asked is that you read the label or the spec that you're sure matches the instance of battery that you have. If the RATING is not on the label, there's not much you can do to determine the RATING.

If you want to determine the ACTUAL capacity of the battery you're holding in your hand, you just load it with the test current you want and discharge it to the terminal voltage you want and see how long it takes.

But the devil is in the details. If 7.4V is the voltage RATING it's probably a two-cell lithium. If 7.4V is the MEASURED voltage, could be anything. While the battery technology doesn't really matter when you multiply the current and time, it might affect the test parameters.

I've done considerable automated battery testing. I've got a box full of laptop batteries that still have most of their RATED capacity when tested at low current, but won't boot the laptop at all. mAh is not always the problem. High ESR is often the issue for high-current applications.

What are you going to do with the answer? Acquiring info that doesn't change your future is wasted effort.

Which gets us right back to determining the problem you're trying to solve that will make your future better.

That makes a lot of sense. Sometimes they put in higher capacity batteries as chemistry progresses, but a pack the same physical size probably wouldn't have a nearly 2x improvement. A typo is much more likely.

What's the matter? Is your cellmate not routing you? Is that why you are so cranky?

He might be a little bit on the low side at 6.8R, but it is probably close to a realistic simulated load for a video camera. Most of these batteries will easily handle 1C discharge rates without much noticeable loss of capacity 5-10% and only modest heating.

Manufacturers specs are done on the most flattering discharge profile and what matters to the OP is how it behaves under a realistic load.

The only caveat for doing a battery test is monitor it and stop the test when the terminal voltage falls below number of cells volts. Otherwise the weakest cell in the stack could be damaged by the others if you forget and leave it connected overnight for instance.

Right but the point is the camera manufacturer has already done the work of testing the camera performance using the specified battery capacity and ch emistry. All the user has to do is match up the battery specs. I found this circuit in about 100 milliseconds and it's not half bad for testing these little batteries (you might need better compensation on IC1A since the IRL3

ut every battery, regardless of technology, specs the capacity, C, at load current of 0.1C. He needs to load it with 1900 mAH/10=190 mA. For 7.4V te rminal voltage, which as Miso stated is realy 6x 1.2=7.2V, he needs 7.2V/

I've used Phil's technique for testing/ matching cells. From the practical standpoint, (unless you have an automated system and are doing this for a living), no one wants to take ten hours of data. One hour while I watch so me nature program on 'tube' is just fine... especially for a ~10% measureme nt. As you say it's also good to test with loads similar to the real use.

George H.