Electronics > Projects, Designs, and Technical Stuff

Harbor Freight Multimeter Add-on

<< < (4/6) > >>

Gyro:

--- Quote from: Wimberleytech on June 22, 2019, 02:27:01 pm ---
--- Quote from: Gyro on June 22, 2019, 12:16:28 pm ---Yes, just to be clear, I was commenting on the poor meter battery test functionality, not your 3D printed add-on.

Adding (switchable) load resistors, with appropriate loads for the two types of battery to your add-on would make a great deal of sense, using the voltage range instead.

Voltage under load is the natural measure of battery health. A battery labelled 9V should read in the vicinity of 9V, likewise a 1.5V marked AA cell.

Appropriate test current for an AA cell would probably be in the 200mA region.

--- End quote ---

See my post with the Linden attachment

--- End quote ---

Sure, there are all sort of load profiles and the useable battery capacity will vary with each one. Actually, rather than the Linden attachment, you're better going to the battery manufacturer websites particularly Duracell and Energizer and downloading the technical datasheets. There you will find quoted capacities and discharge curves for all sorts of conditions, constant current, constant resistance etc. together with the sort of effect storage and pulse loads have. Very informative when you're designing something that uses them and establishing realistic battery life.

Certainly testing the battery voltage under some sort of dummy load gives some sort of idea, as it reflects the internal resistance, which tends to increase as the battery ages.  Hopefully we can agree that a 'one size fits all' approach doesn't really work and that maybe Harbor Freight's implementation of sticking a 370R resistor in series with the battery, regardless of voltage, and displaying the resulting current is probably the worst possible implementation.

P.S. That's where an external add-on, with integrated push-button loads would come into its own.

Wimberleytech:

--- Quote ---Hopefully we can agree that a 'one size fits all' approach doesn't really work and that maybe Harbor Freight's implementation of sticking a 370R resistor in series with the battery, regardless of voltage, and displaying the resulting current is probably the worst possible implementation.

--- End quote ---
It is a big world...we don't have to necessarily agree--might be boring if we did.


--- Quote ---
P.S. That's where an external add-on, with integrated push-button loads would come into its own.

--- End quote ---

Yes, indeed...this would be a nice feature and it is something I am pondering.

Maybe this is the proper test to perform, no? 

Gyro:
Haha, maybe. I think I'd put that one slightly ahead.  :P

I've seen cheap meters with individual  1.5V and 9V battery test positions. Maybe they do a better job of reading voltage under load. Of course that still doesn't differential between an AAA and a D cell.

I remember many years ago, back when I was a teenager, I used to work Saturdays in the photographic department of a big store. We had a battery tester supplied by (I think) Ever Ready. It had a 3 zone moving coil meter - bad, ok, good, switch positions for all the various battery sizes HP2, SP2, SP11, HP11, HP7, PP3 etc. and a whole bunch of load resistors inside. This was in Zinc-Carbon days, 'copper tops' were only just beginning to surface.

Wimberleytech:
Well, I redesigned the battery tester so that it now looks pretty  :clap:

I printed wiring channels at the bottom of the battery holder.

I also shrunk the X dimension so that it does not hang over the edge.  I am done with this now!

tooki:
That looks great!

Navigation

[0] Message Index

[#] Next page

[*] Previous page

There was an error while thanking
Thanking...
Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod