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Best Reliable Method to Test Battery Capacity

Best Reliable Method to Test Battery Capacity

Best Reliable Method to Test Battery Capacity

(OP)
I'm creating a product that requires a high-capacity, 3.7 volt battery. Ali Baba Express has lots of batteries for sale, but there's a cloud of suspicion on if those batteries actually operate at the capacity that is advertised. Since I plan on reselling these batteries, I need to make certain that they perform as advertised BEFORE customers complain.

I need a good, reliable way to verify that a full charged battery will actually output the power it's rated at. Is there some kind of practical "discharge test" I can do?

RE: Best Reliable Method to Test Battery Capacity

A "home-brew" process that I have used a few times is to test in three steps.

1. From each manufacturer, get a sample of about ten batteries. Put numbers on them so you don't mix them up.
Test idle voltage and working voltage, make notes. Let them work in the device you are producing. Make sure that the product is cycled on/off and put through typical cycles. Manual data recording or an automated method works equally well, but manual ties up workforce.

You can, of course, use a resistor to load the battery if there's a problem to get enough of the devices for the test.

Save all data for future reference.

2. Order the batteries that has the best price/performance ratio. Test a representative sample and record batch number(s) date and data. Test idle voltage and service voltage. Compare to reference data taken under 1. Contact manufacturer if there's a discrepancy. Some manufacturers do actually send you better first samples than they then deliver. A very old marketing trick that still is being practiced.

3. When everything runs smoothly: repeat until something changes.

I guess that there are procedures for this in diverse standards. But this one is simple and worked well for me when we did a similar thing.

Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

RE: Best Reliable Method to Test Battery Capacity

Random note... get your insurance in order. If one of those batteries explodes, you're in for a world of hurt financially.

Dan - Owner
http://www.Hi-TecDesigns.com

RE: Best Reliable Method to Test Battery Capacity

Many battery chargers have a built in discharge/tester feature that you may be able to leverage.

Z

RE: Best Reliable Method to Test Battery Capacity

I don't see that the discharge test need be too complicated - either you place a number of sample batteries in your device and time how long it survives, or you just apply a known resistor (with similar power draw to your device) and monitor voltage until it falls to whatever your device input threshold is. What's more pertinent is that batteries rarely meet their rated capacity - the rated capacity is generally given a highly favourable set of conditions. In particular, ambient temperature, current draw, battery age and initial charge status can all have a large effect. Getting the optimal initial charge is not always straightforward - you may find that the battery needs a couple of cycles before it really takes a full charge.

So keep those factors in mind when you're testing. I also recommend testing at least one reputable brand for comparison - you might find it just as hard to match the rated capacity with the reputable brand as with no-name batteries.

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