EEVblog #774 - Low Battery Discharge Testing Part 1

Dave shows how to do discharge testing on AAA and AA alkaline batteries, for the specific purpose of investigating how much energy is left under the industry standard 0.8V cutout voltage.
This is an explanation of the test setup, verification, and a sample plot of some data before the long term testing.
The setup consists of the BK Precision 8500 electronic load, the Keysight 34470A 7.5 digit meter, and the Rigol DP832 for testing.
Duracell AAA battery datasheet:

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[MhDaMaster]

Hopefully now people understand why the graphs cut off there hopefully.

I really appreciate that you go THIS far to make it easy to understand for everyone not only engineers that are familiar with the terms and topics. This alone is a fairly demanding task that not even all teachers want to go through so for that you have my respect Dave. Keep up the good work.

[enginerdy]

The binary command format is much better because you can write a generic command processor that passes the data on to specific handler functions. Add in the checksum and you get a much more reliable data link.

[superdau]

Serial string commands are a PITA to decode. Changing field length, commands to mistype, sometimes protocols that are case-sensitive, values returned in weird E-notation or non-system decimal point. And as soon as you handle something like status codes you have to deal with a list of arbitrary numbers anyway.

[OHEFI]

This small and simple stuff is just what I am searching for, hats up for Dave!

[PriorUniform]

I think you should design a test and logging rig. Something arduino compatible. Then test a bunch of manufacturers, lots, chemistries, etc. Keep "big battery" honest.

I really love the video series where you take a set of specs, start with simple circuits, discuss/expand. Then end up with a fully functional product. Like the power supply series.

[slidefuse]

As a software engineer I appreciate the hex-based communication interface!!! Less bandwidth, more data!

[Eletronicafg]

Well, I think that this serial protocol isn't so difficult to implement. Just a couple of hex commands.

[vincentrobinette]

If the ambient temperature changes, it will greatly affect the characteristics of the battery under test, much more, than the test equipment. At very low power levels, the differences won't be nearly as much, than if you were testing at much higher power levels. Beautiful test rig!

[ciprianwinerElectronicManiac]

Who said that the rule of attraction doesn't work. I was just trying to figure out how to calculate remaining energy in mWh or mAh and long be hold, a follow up video on battery capacity testing, there can never be enough info about that. Thanks for sharing. Keep up the good work Dave. Cheers :)

[canadianavenger]

At the point of "failure" look at the voltages reported by the 3 devices. You'll see as the source decreases, the disparity between them increases. [Verifies that the error is in the wires]

[fredlllll]

rs232 and serial strings?? are you nuts? if you want to get as much data over it as possible you have to use binary. and its not that hard if you have the specification for it. also strings are horrible to parse.

i just implemented a library for a little display that uses serial communication for its commands. wasnt that hard. even though the specification is in bad english.

(if ya have the spec, i might take a look at that thing :P)

[bertblankenstein]

I use AA (Duracell coppertop) in my GPS. When the batteries are low and done, they are typically at 1.25V unloaded. So that is not too bad. I also noticed that at -20C the batteries last maybe 50% as long as opposed to+20C, and they do not recover when brought back inside (ie I do not get that other 50% back when the batteries are warmed up). I keep the GPS in my pocket during winter hikes but it still gets pretty cold.

[TheHunChem]

21:08 Okay, after the bench meter fixing fun, I think either your equipment or the workshop itself, but something is posessed for sure :D

[glctv]

Dave, what if you used a Batteriser? I heard it gives you 800% battery life! ;)

[murmaider]

There are some red dot sights for rifles that use a single button cell and have a life of 10 years. You're actually supposed to turn it on and it should glow for 10 years.

[johnborchers]

The BK precision meter is using a PID algorithm for constant power output. PID terms are tricky to optimize for all conditions. Not enough derivative term and you get oscillation as is shown by this meter's response. Of course there's no energy here which is why the companies don't show <0.8V on the curves. Dave is right here, it's bugger all. If it was good you could guarantee the company marketing datasheet would show it.

[chuck-]

Maybe the large voltage drop below 0.8 volts is due to the internal resistance of the battery not allowing the current to flow below that voltage level. That may be the reason for the oscillation, as the internal chemistry changes due to lack of electric charge. The alkali material becomes more corroded (corrosive) as the battery looses charge. That's why alkaline batteries burst and corrode when they are old, destroying PCBs.

[FooBar]

Dave, why constant power mode, couldn't you use constant current, and also just log the voltage?

[frankbuss]

What HP benchmeter did you mean at 5:19? It's Keysight. If they change their name some more time, I need to make a list to remember that it is HP :-)

[pcfreak]

Great video! But I can't seem to find part 2. Where can I find the continuation of this? 🙂