How to Test if Battery is Actually Rated Capacity?

[Used_Cars]

I'm looking for a high capacity batteries on places like eBay and AliBaba and I sometimes feel like they are selling batteries that are actually less than the rating on the label, example it might say 1300 mAh, but it's actually 900.

How can you test to make certain that a battery actually delivers the rated amount of power?

[budm]

Re: How to Test if Battery is Actually Rated Capacity?

http://batteryuniversity.com/learn/a...asure_capacity
Lots of info on that site.

http://www.rechargebatteryguide.com/...f-your-battery

Not verified:
http://electronics.stackexchange.com...um-ion-battery
https://www.quora.com/How-can-we-mea...-ah-accurately

You will have to do the experiment to verify the claim of above measurement methods.

[Used_Cars]

Re: How to Test if Battery is Actually Rated Capacity?

They don't have an off-the-shelf battery tester? Or a method of setting up a load and monitor the battery's discharge?

I was thinking something along the lines of setting up a simple circuit. Battery, light bulb, etc... and simply seeing low long the bulb will stay lit. or whatever.

I know basic electronics from years ago. Assume you could use math to figure out the total power output if you know how long the battery lasts, and what the wattage of the bulb is. Also I wonder if there's a fast way to get an accurate reading, or what the relationship is between the load and time and battery output, etc...

[Used_Cars]

Re: How to Test if Battery is Actually Rated Capacity?

Also, lets say I had a small, 9 volt radio. What instrument would I use to put in serial with the battery power to measure how much current the radio is drawing? I assume a multimeter, but this is more complex to me than simple volts or ohms.

[rhomanski]

Re: How to Test if Battery is Actually Rated Capacity?

If the amps are small enough you can just put in an ammeter but it has to be real small. Otherwise you have to put in a shunt and hook the ammeter to it.

[Used_Cars]

Re: How to Test if Battery is Actually Rated Capacity?

If the amps are small enough you can just put in an ammeter but it has to be real small. Otherwise you have to put in a shunt and hook the ammeter to it.

What does that mean? What's a shunt? How small is "small"? How many amps, etc...? Why does it have to be small? The whole concept of "smallness" her escapes me?

Is an ammeter on a standard multimeter, or is that a separate piece of equipment?

[rhomanski]

Re: How to Test if Battery is Actually Rated Capacity?

If the load your testing is only a few milliamps you can put a meter in the circuit. More than that, and you will overload the meter and must use a shunt. The shunt lets the majority of the current bypass the meter.

Some multimeters can be put in series with something and measure the current itself but only to it's rating. Some multimeters have a loop you put around a wire and senses the magnetic field to calculate the current flowing.

[budm]

Re: How to Test if Battery is Actually Rated Capacity?

Also, lets say I had a small, 9 volt radio. What instrument would I use to put in serial with the battery power to measure how much current the radio is drawing? I assume a multimeter, but this is more complex to me than simple volts or ohms.

Do you still have the user manual for your DMM?
I.E.:
https://cdn.badcaps-static.com/pdfs/...723182ce22.pdf
Using very low value shunt resistoras suggested is the good idea, if you are going to use your your meter in series with the load, I would suggesting using the shortest and bigger wire gauge for your test leads.

[momaka]

Re: How to Test if Battery is Actually Rated Capacity?

I'm looking for a high capacity batteries on places like eBay and AliBaba and I sometimes feel like they are selling batteries that are actually less than the rating on the label, example it might say 1300 mAh, but it's actually 900.

That's because they likely are.

Almost all cheap batteries on eBay are junk (I say almost, just in case some random person happens to sell unused Enerloops).

I was thinking something along the lines of setting up a simple circuit. Battery, light bulb, etc... and simply seeing low long the bulb will stay lit. or whatever.

That will work. It's a rather simple way, but it will work. Maybe also put a multimeter across the battery terminals as well to check the voltage. When it gets to some threshold level, say 1.1V for example, you an consider the battery depleted.

Also, lets say I had a small, 9 volt radio. What instrument would I use to put in serial with the battery power to measure how much current the radio is drawing? I assume a multimeter, but this is more complex to me than simple volts or ohms.

See this (particularly, watch the video from 3:30 forward):
https://www.youtube.com/watch?v=bF3OyQ3HwfU

If your radio is powered by a typical 9V battery (i.e. IEC 6F22), then you can use a multimeter in series with the battery and radio to measure current.

If the amps are small enough you can just put in an ammeter but it has to be real small. Otherwise you have to put in a shunt and hook the ammeter to it.

Most digital multimeters nowadays can measure up to 10 Amps. Even the really cheap 830-based ones will handle up to 3 Amps continuous (but don't attempt more, because they tend to have crappy leads that can melt at currents higher than that).

[kc8adu]

Re: How to Test if Battery is Actually Rated Capacity?

i use my old triton.
another one thats inexpensive is a REAL imax b6.
the fakes have lousy accuacy.
ebay and truthful labeling of batteries are mutually exclusive.

[Used_Cars]

Re: How to Test if Battery is Actually Rated Capacity?

The batteries are for a GPS tracking device and I assume the draw would be comparable to a cell phone. The batteries are 3.7 volt, and the battery that comes standard is 900 mAh. Typical operation time might be 4 to 5 days and I'd like to make it more like 40 or 50, by building an external battery pack with high capacity batteries in parallel.

At first I thought to purchase expensive "cell phone" style batteries, the highest capacity I could find, but have discovered I actually get LESS operation time than I do with the lower-rated batteries that come with the unit.

And then I discovered that 3.7 volt output was common and that there are a lot of "AA" sized batteries that had that output. And THEN I watched a YouTube video of a guy changing-out the rechargeable batteries of a DeWalt battery-powered screwguy and discovered that when you crack open the plastic, all that's in there are a bunch of "C" cell batteries all soldered together. Home Depot wants $90 for a replacement DeWalt battery.

So now I have batteries on the brain. I want to solder a bunch of AA 3.7 volt batteries together into one massive 3.7 volt battery pack. Well okay lets say 6 batteries together. 8 at the most. Soldered in parallel, they should output 3.7 volts, right? Wrap them in electrical tape or find some kind of rubber "dip" for them, modify a micro-USB cable and make it into a pigtail to provide power to the unit.

Easy peasy, right?

Anyways, that's what I'm trying to do. Take 6 or 8 AA batteries and make a GPS tracker operate for as long as possible. Since it seems some people are very familiar with the technical characteristics of rechargeable batteries, what specific recommendations for 3.7 volt batteries should I be considering?

[budm]

Re: How to Test if Battery is Actually Rated Capacity?

You are talking about Li-ion batteries, so how are you going to charge them? Safety and protection?
BTW, if you look at the DeWalt battery pack, you will see the circuit board in the pack.

[Used_Cars]

Re: How to Test if Battery is Actually Rated Capacity?

You are talking about Li-ion batteries, so how are you going to charge them? Safety and protection?
BTW, if you look at the DeWalt battery pack, you will see the circuit board in the pack.

Right. After I posted that I went and did some reading and learned that the Li-ion batteries need some kind of protection circuit which is curious to me because why not put the protection circuit on the charger instead?

Anyways I don't want to reinvent the wheel, so if there is an off-the-shelf solution I'm interested. I need something on the order of 10,000 mAh at 3.7 volts, so instead of 4 days operational time, I get 40 days of operational time. How that happens isn't all that big of a deal.

And I'm curious about these protection circuits for Li-ion batteries and how complex they are. Is this something I could build? Couple of caps, a diode and some resistors, or what? And what function do they serve? I suppose I could get a junk cordless drill battery and take it apart and look.

[budm]

Re: How to Test if Battery is Actually Rated Capacity?

"Right. After I posted that I went and did some reading and learned that the Li-ion batteries need some kind of protection circuit which is curious to me because why not put the protection circuit on the charger instead?" What happen if the load shorted out? What is going to cutoff the batteries when they are discharged below the limit?

http://batteryuniversity.com/learn/a...ttery_chargers

http://batteryuniversity.com/learn/a..._ion_batteries

http://batteryuniversity.com/learn/a...dern_batteries

http://batteryuniversity.com/learn/a...thium_ion_safe

MAKITA LI-ION batt pack:
http://www.instructables.com/id/Maki...attery-Repair/

[Used_Cars]

Re: How to Test if Battery is Actually Rated Capacity?

What happen if the load shorted out? What is going to cutoff the batteries when they are discharged below the limit?

Got it. I read only a bit and only remembered the part where the Li-Ion batteries need to be charged below a certain rate. I get your point, thanks. There are other techical hazards regarding Li-Ion batteries besides just charging them too fast. I'll keep researching and learning. Looking for an off-the-shelf solution, if possible. Electronics isn't my true passion; it's a means to an end for me, particularly on this project.

Also, while I'm thinking of it, I did some reading and found an article that seemed to say that the physical construction of the battery has a lot to do with how much power it can store? That cylindrical batteries have larger capacity per unit of mass (weight) than do square or rectangular batteries?

If true, then this would explain the differences in capacity between the cell-phone style batteries I've been looking at and the AA sized cylinders I've been looking at on eBay.

Also, if someone has a recommended source for accurately rated AA rechargeable batteries, I'd appreciate it. The person that said eBay and accurately rated batteries was spot on, I think, and while I don't know what I AM going to do, I've already made the decision that I'm not sourcing my batteries from eBay for this reason.

[Used_Cars]

Re: How to Test if Battery is Actually Rated Capacity?

Also another battery question:

As I read, I get the impression that batteries output a set voltage. What I read seems to assume that all batteries "X" output "Y" voltage. I would think that they are all analog and that they can be "set" to deliver whatever voltage is required, but apparantly this is not true?

Do various batteries all output the same voltage? If so, why?

[budm]

Re: How to Test if Battery is Actually Rated Capacity?

http://batteryuniversity.com/learn/a..._with_voltages

http://batteryuniversity.com/learn/a...dary_batteries

http://batteryuniversity.com/learn/a...charge_methods

http://batteryuniversity.com/learn/a...attery_runtime

http://batteryuniversity.com/learn/a...ng_lithium_ion

Just about anything you want to learn are on that site, you just have to search for them.

[momaka]

Re: How to Test if Battery is Actually Rated Capacity?

There are other techical hazards regarding Li-Ion batteries besides just charging them too fast.

Not just charging, but also discharging.

Basically...
- you don't want to discharge a Li-Ion batteries too fast.
- you don't want to discharge a Li-Ion batteries below a certain minimum level.
- you don't want to overcharge Li-Ion batteries
- you don't want to recharge Li-Ion batteries too fast
- you don't want to overheat Li-Ion batteries (which all of the above items can cause)

A good protection circuit will take care of all that - it will cut out the battery from the circuit if it detects that is overheating or goes above/below its max/min voltage.

The reason Lithium batteries need protection is because they can easily become a fire hazard and sometimes explosive hazard, if they are used in tight battery compartments (such as those cheap UltraFire or other "name-your-fire" flashlights that are an imitation of SureFire flashlights).
Like this:
http://www.candlepowerforums.com/vb/...sthand-account)

Also, if someone has a recommended source for accurately rated AA rechargeable batteries, I'd appreciate it.

If you don't mind going to Ni-MH (which has lower capacity than Li-Ion), Eneloops are wonderful. You can get them at any large electronics store usually. They are not cheap, but well worth the money. I can't recommend of any online place to get them, as I'm not sure what is fake and what isn't. But just beware - if it's too cheap and sounds too good to be true, stay away.

[FlyNN]

Re: How to Test if Battery is Actually Rated Capacity?

I know I'm late to the party on this one but I'm new here. I see you didn't get the answer I was looking for; Opus BT-C3100. This charger will do AA/AAA, besides others and give you how much charge it has taken. I've got one and I weeded out a lot of crap batteries in my stash.

[Gabriel]

Re: How to Test if Battery is Actually Rated Capacity?

I bought a Re:load 2 and a ZB2L3 v2.1, I have around 30 1200mAh used Htc batteries and I wanted to test a few and keep some of them.

Seems pretty accurate, tested two of them and one battery was 1200mAh and the other one was 1174mAh.