battery/voltage check

[CMoore]

Was just measuring three different batteries for the Canon 'A' series. It is a 6 volt battery.
These are batteries (same brand) that have been in and out of the camera a few times. My Digital Meter says:
1. 6.22
2. 6.18
3. 5.88
Regardless of how the camera meter might work, is it time to put #3 in the recycle box.?
Thank You

 

[AgX]

The idle-voltage of a battery is only a weak indicator of the state of a battery.
Use a battery tester instead.
But even these can fail (as they are designed for a certain load). I repeatedly experienced Lithium cells being indicated as fair, but rejected by a camera.

 

[CMoore]

OK, i did not think a camera put much of a load on a battery.
I can load my DMM. What should i use.......200-500-1k Ohms.?
Thank You

 

[tedr1]

Simple answer, dump #3. Complicated answer, measure in the camera with it switched on, it is impossible to know the current drained by the electronics so a load figure cannot be found.

 

[CMoore]

OK...I see.
I probably could rig something to measure the canon 6 Volt batteries. Not sure i am enough of an Engineer/Tech to figure a way to do it in cameras with the little button batteries.

 

[shutterfinger]

The old school rule of thumb when checking a circuit was if it had 10K ohms or more of resistance it was good, therefore put a 10K ohm resistor across the battery contacts while measuring the battery.
Battery 3 is gone and should be sent to the recycler, battery 2 is marginal at best and should go the same route as battery 3.
A 10K ohm resistor color code is brown black orange starting with the color closest to the end of the resistor.

 

[CMoore]

Oh Wow.....10k.....alright.
I guess it will be easy to see how a fresh battery measures with a 10k across it compared to the others.
Thank You

 

[shutterfinger]

Correction: the 6.18 battery is around half life. It may work fine depending on camera requirements.

 

[AgX]

Where do you base that on?
There are different types 6V batteries that the A-series cameras use (some use even 1.5V ones).
The 6V ones are: Silveroxide, Alkaline, Lithium. They all have different discharge curves.

 

[shutterfinger]

A ballpark/sports stadium rule of thumb from testing a lot of batteries. When a battery, regardless of type, reads its marked voltage its time to replace it.

 

[Ashfaque]

You need to measure the voltage under load (as AgX & others mentioned).

Anyway, not directly related, on the off chance that there are some battery aficionados amongst you check out Dave's excellent videos on various types of battery charging https://www.youtube.com/user/EEVblog/search?query=Battery+charging

 

[Steve Smith]

Does the camera have a battery check button?


Steve.

 

[John Koehrer]

Does the camera have a battery check button?
Steve.

Means pretty much nothing because it reads surface voltage not actual.

 

[AgX]

I rather expect it to work like those stand-alone battery testers. (But I would have to check circuit diagrams.)

 

[CMoore]

Regards the battery Check.....i am not qualified to say, and it probably varies from camera to camera, but.......a few techs have told me that a battery Check is just that, it checks to see if there is a Battery In The Camera.

 

[Steve Smith]

Means pretty much nothing because it reads surface voltage not actual.

When you press the check button on a camera, the load on the cell is the meter coil and a series resistor. When you use the meter, the load on the cell is the meter coil and the light sensor with some calibration resistance in series, the total of which will be similar to the check resistance at mid range.

So the check is relevant to the working load of the meter (which in any case is very low).


Steve.

 

[AgX]

But some cameras have working loads higher than the meter, as solenoids or motors.

 

[paul ron]

But some cameras have working loads higher than the meter, as solenoids or motors.

and thats where mAh means more than voltage.

if you are using a digital meter, the battery demands are much higher because of the display n its related circuit.

lightmeters are nothing more than whetstone bridges which merely determine the value of an unknown resistor, the variable resistor photo cell, exposed to light by balancing the load on both sides of the meter (galvenometer).

 

[AgX]

mA, not mAh

But the battey check nevertheless would be based on a voltage metering, just with a load in parallel.

 

[paul ron]

mili amp hours.

yes but a load test determines if the battery can deliver enough amperage to drive the device, not a direct measure of voltage but a loaded measure of voltage, which is different.

here is a good explanation of how measurements are taken and how batteries are rated.

http://www.allaboutcircuits.com/textbook/direct-current/chpt-11/battery-ratings/


.

 

[Joe VanCleave]

For checking batteries I like to use the inexpensive analog meters instead, rather than DVMs. Many of them also have a red/green good/bad scale for standard-sized 1.5v cells. They have a relatively low ohms/volt impedance, meaning they'll actually put some load on the dry cell under test.

~Joe

PS: These inexpensive analog meters also use D' Arsenval type meter movements, like many in-camera meter movements.

 

[CMoore]

^^^^^^^ Yeah, probably Something is better than Nothing. Some load is better than none at all.
With my DMM, i always just figured anything at or under the rated voltage is a goner.
I may have tossed out "good" batteries, but i doubt i ever keep many that do not run the meter close to spec.

 

[AgX]

For checking batteries I like to use the inexpensive analog meters instead, [because of their higher resistance]

As a side note: analog meters are also the way to go when metering the voltage of flash firing circuits, because of their higher resistance.