How to check battery capacity

Simple way to test your disposable alkaline batteries to decide whether you should keep or throw away.

Some inaccuracies in the annotations:

For 1.6v: Subtract 1.1v from actual v and multiply by 200
For 9.6v: Subtract 6.6v from actual v and multiply by 33.33

If cell is 1.6v or 9.6v, assume fully charged.

[bobl]

You should rename this video to "voltage" as you are not actually testing the capacity. I was looking for a way to check the battery capacity (which is in milliamps). mA or mAh

[keithfreeman]

I use a flashlight bulb with a couple of wires soldered to it. This is used to test D cells down to AAA cells.
Depending on the brightness of the bulb tells me how much juice the cell has in it.
I admit that this isn't really as accurate as a meter but it works, and it is very, very cheap to make.
Yes, I do have a Multi-Meter.

[guillepk]

That's wrong. The curve is specified at a given drain current, while you're meassuring it without a load. You must connect a load drawing that specified current and *then* meassure the voltage. If you do that quickly, it won't make a dent on the battery's charge.

[JohnMSawyer]

As some commenters have already mentioned, sometimes a used battery's voltage will measure fairly high even when its capacity is mostly drained--they just become big resistors. So, my simple way to check remaining battery capacity is to use the current-measuring setting on a multimeter (I usually use a Fluke 77). I touch the leads briefly to the battery so I don't drain it very much, and see how much the digital display "deflects". I don't keep figures in my head for how much current a fully charged battery is able to deliver, but I go by rough memory, so that if I see little deflection, then I know the battery doesn't have much juice left.

[noweare]

As long as put a small load on the battery you can use the voltage to figure out if it's worth keeping or not.

[ZLau]

Always measure voltage under load! This is incorrect, even a dead battery can show voltages like 1.5V if it's been idle for a while.

[waynekendall]

I came here expecting to watch a video about checking battery capacity, not battery voltage.

[bitTorrenter]

So, 1.6V measures full. 1.1V measures the minimum useful voltage. The difference (x 100) gives the capacity. According to this method.

[arnoldtarbooz]

Old video - but I need to find the capacity of a Prius Lithium battery brick/cell. How do it do that?

[EWOverland]

Thanks for the video, but I dont understand the multiplying numbers to get the percentange

[VaughanMcCue]

I missed the rationale for 1.1 for 1.5 cells and 3.3 for 9 v cells. What formula do we use for button batteries and the small 12v used in car remote key fobs? AND what about lead-acid 6 and 2 volts. This was a great video and I got a real "kick" out of it and it brightened my day.

[theyjustwantyourmoney]

I have a whole bunch of so called dead cells in the house awaiting disposal, I'm glad this will give me a job of screening them all. thanks

[nnejiamaechi]

Good. What if it's a 12v lead or litum battery pack

[retrosteve]

Where would one get such a thing as the Electronic load with built in mah please?

[jaremaw]

You assume, that eg AA battery's internal resistance is the same for all types/manufactures. That's wrong.

[frv]

Why is not Wh (battery capacity?) calculated with max full charged voltage? For example if an electric kickbike's (Sealup Q8) battery (38km range on a good day) is rated as 48V21Ah (48x21=1008Wh) but it's full charge voltage is 54.6, so why not calculate it as 54.6V x 21Ah = 1147 Wh? I have a kickbike Q8 battery (Samsung cells purportedly) rated as 48v21ah but it soaks only 877Wh according to power outlet meter. Should it be soaking 1008Wh or 1147Wh, or is 877Wh correct? I also have another battery from (Aliexpress) Liitokala (tested 27km range) rated as 48V20Ah (48x20=960Wh or 54.6x20=1092Wh) but it soaks only 698Wh (it's more like 15 or 17Ah?). So am I scammed or it is normal? I complained to Aliexpress about it LiitoKala battery, that it should be at least 835Wh in it if it is 20Ah but they ask for more proof. I already proved with power outlet meter how much it soaks, it is 698Wh and showed my other battery soaks 877Wh (for comparison). Aliexpress supports vendors lying about real capacity of battery. Idk how I can prove to them that LiitoKala is not 20Ah battery (more like 16Ah). I also bought on Aliexpress a 48v24ah battery called Aimjin but it only charged to 53v (not 54.6v) and from empty to full only soaked 340Wh which indicates its capacity is 7Ah. It also became warm when I used it which indicates it is an old tired battery. But I paid for it near same price as for new battery. Scammed.

[tarstarkusz]

That discharge curve is under ideal very low load conditions. ONLY rechargeable batteries have anything like that flat curve. The complexities of primary cells is the reason they do not ever advertise the capacity of a primary cell.

[abjurian]

I was wondering at the beginning of this video you showed a load tester, Do you know where I can get one of those? Even a DIY kit would be nice. Thanks and thanks for the video.

[belowmars]

So how do you test battery capacity of a Zinc Chloride battery, or NIMH battery or lithium ion battery? Apply the same voltage upper and lower limits and calculate the percentage the same way?

[Beauchot]

This was the video I needed to see, thank you. Most people don't realize voltage doesn't tell you much about the charge level of a battery. Unless you do this math.