How to Capacity Test Camera Batteries
Many cameras no longer have OEM batteries available. Even when they are, the markups are outrageous. Third party batteries can be 1/4 the price, but there are no assurances about actual capacity or longevity.
~$30 will cover the cost of equipment.
You can repeatedly check the capacity of batteries. You can verify if the capacities listed on third party batteries is true or not. It can also be used to spot fake batteries.
Easy Tests to Spot the Lowest Quality Batteries
The three easy ways to spot a low quality or fake batteries is to squeeze, spin, and weigh them.
If you can squeeze the case, it’s a problem. That room should be filled with lithium ion cells, not foam and air.
If a battery is starting to expand, that is a sign that it should be properly disposed of. If the battery can spin on a flat surface, that is a sign it is failing. Low quality third party brands can have this happen to them within months of purchase.
Use a known OEM battery as a reference for weight. Preferably a battery that came with the camera. Any purchased batteries should be close to that weight. If they are noticeably lighter, like 10g, that’s a sign that the battery is fake or low quality.
A Look Inside a Sony NP-FW50 Battery
Camera batteries are 1 or 2 cells, a battery protection board with contacts, and a plastic shell. The quality of the battery is determined by the quality of the cells used.
The cells have product numbers and manufacturer data sheets that contains specs. Often the capacity of a cell will be printed on it. My testing of NP-FW50 batteries confirms mislabeling.
It is impossible for a 7.4V battery to have a 1500 mAh capacity when the cells inside are 3.7V with a 900mAh capacity. Cells do not exist with the energy density to create a 1500 mAh battery with a Sony NP-FW50 form factor.
Fly by Night Third Party Brands
Amazon is such a large part of the market that third party brands base their entire strategy around it. They show up, break all of Amazon’s rules, gets a bunch of sales, and then get banned.
They manipulate reviews by buying fake reviews and paying for reviews via gift cards. This can go on for years.
Once they get caught, they dump the brand and start over again with the same practices. All it take is a different packaging and a new sticker on the battery.
That’s why you won’t find RAVpower for sale on Amazon anymore.
What the Four Battery Contacts anymore
4 pin connections (balance and temp?) T = Thermistor C = Charge Protection Circuit + = Positive terminal -= Negative terminal
An Inexpensive Testing Setup
The TEC-06 is an inexpensive battery capacity tester. It can be found on eBay or Amazon.
The TEC-06 needs a 1A (amp) via mini USB to work correctly. Many USB chargers do not provide enough power. The charger output should be labels, usually between the prongs.
It also does not come with a way to connect camera batteries to it.
Using a universal battery charger solves that problem. By unscrewing the case, you can easily remove the part that has the battery contacts and that holds the battery in place.
If you are not comfortable soldering, this can be a good option. You can simply cut the wires attached to the battery contacts, strip them, and then attach them to the TEC-06.
Another easy alternative is to use the battery holder from the chargers that are included with third party batteries. They often have a battery holder that clips into the charger.
The TEC-06 will discharge a battery until the cutoff voltage is reached. The energy will be turned into heat, which will be disipated by the fan and heatsink.
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Using the TEC-06 Battery Capacity Tester
Use a fully charged battery.
I choose a 500 mAh load as the rate to discharge a battery. That rate of discharge would drain the battery in a similar length of time as shooting video on a Sony A7.
The TEC-06 is controlled using an encoder dial. It is pressed down to allow a setting to be changed. Turning it will either increase or decrease the value for that setting.
Different settings can be viewed or changed by rotating the control dial.
The TEC-06 has 5 menu items and 4 settings.
- Discharged amp hours
- Battery Voltage
- Battery Cutoff voltage
- mA Draw
- Internal Resistance
When the device is first powered on, the display should be 0.000. The red LED closest to the display should be lit up. The line ends in (AH), meaning amp hours. We are interested in mAh, meaning milli amp hours, which are 1/1000th of an amp.
Discharged milli amp hours (mAh)
Pushing down on the encorder dial will start the capacity testing. It will take approximately 2-3 hours to discharge most batteries at the recommended settings below.
How many mAh will be shown on the screen while the test is ongoing. When the test is complete, the capacity will flash on the display.
Turning the dial clockwise one “bump” will go to the next menu item. The second LED will light up. In this case the battery I had attached had a voltage of 8.26V, meaning the battery was fully charged.
The voltage listed on the label shows 7.2V. That’s the nominal voltage of the battery. It’s just a quick way to summarize the expected performance and what will be the most common voltage during discharge.
Discharging the battery will cause the voltage to drop. Once it gets to a certain level, the battery will be considered completely discharged. Discharging it further will damage the battery. The damage can shortern the number of charge cycles the battery can go through or reduce the maximum charge it is capable of holding.
Using your camera, drain a battery until the camera shuts off. Take the battery out and place it into the battery holder for your TEC-06. You can then use it to see the current battery voltage. Take note of this voltage.
Another way is to use a multimeter on the battery.
The next turn to the right will bring you to the battery voltage cutoff setting. Here you want to set the voltage that you found from a drained battery.
My Panasonic GF7 powered off when the battery reached 6.4V.
The battery protection board also has a set voltage where it will prevent the battery from further discharging in order to prevent damage. This should be treated as a fail safe, especially with third party batteries. You don’t want to be the one to find out someone cheaped out.
The next line ending in (mA) is the option to set the load for the battery. I went with 500 mAh, as this would fully discharge one of the third party NP-FW50 batteries in a similar amount of time that the Sony A7 was able to record video for.
As an example let’s use a battery that has an actual capacity of 1000 mAh. Discharging the battery at a rate of 500 mAh, it would take 2 hours to drain the battery. 1000 / 500 = 2
Testing Internal Resistance
The final menu item ends in (mΩ), which represents milli ohms. The Ω is the capital omega symbol from the Greek alphabet.
This will only show a value if the TEC-06 is wired up with a second pair of thing wires into the correct screw down terminal. The resistance will change during the test.
Ohms measure electrical resistance. For batteries, higher is worse. Tracking this number over time can help identify a battery that is going bad before it actually goes bad.
For instance, if you are going traveling. It might not be possible to get a replacement battery. You don’t just want to have several batteries, you want to make sure they are in good condition.
Internal resistance can be used as a rough way to judge the remaining lifespan of a battery. As batteries go through charge cycles, they will slowly degrade.
By measuring this through soldering 2 additional wires to the battery tester, you can keep track of the internal resistance of your batteries. When the internal resistance start to go up, you’ll know it’s time to replace those batteries.
NP-W126S Battery Test Results
| Battery | mAh | IR | Weight |
|---|---|---|---|
| Gray Market NP-W126S | 1117 mAh | 229 mΩ | 48g |
| Counterfeit Japanese NP-W126S | 809 mAh | 329 mΩ | 38g |
| BM Premium | 1037 mAh | 266 mΩ | 48g |
| BM Premium | 1021 mAh | 388 mΩ | 48g |
| FirstPower | 955 mAh | 448 mΩ | 46g |
| FirstPower | 984 mAh | 390 mΩ | 48g |
April 10th, 2023 - One of the FIRSTPOWER batteries has started to expand. I can easily spin it on a flat surface. This is a sign the battery has gone bad. Further expansion of the pouch cell could cause the battery to get stuck in the camera.
Cameras that use NP-W126S batteries:
| X-H1 | X-T10 | X-A3 |
| X-Pro2 | X-T100 | X-A2 |
| X-Pro1 | X-E3 | X-A1 |
| X-T3 | X-E2S | X-A10 |
| X-T2 | X-E2 | X100F |
| X-T1 | X-E1 | FinePix HS50EXR |
| X-T30 | X-M1 | FinePix HS33EXR |
| X-T20 | X-A5 | FinePix HS30EXR |