Capacity Testing 5 Third Party Sony NP-FW50 Batteries

A pocket full of OEM Sony NP-FW50 batteries gets expensive.

Third party brands make ridiculous claims about the capacity of their batteries. Capacity testing them is the only way to find out what you’re getting.

The official battery charger is the Sony BC-TRW.

Neewer batteries are comparable to Sony’s for 1/4 the price.

RAVPower would have been a good choice, but they got banned from Amazon. PowerExtra, Wasabi Power, and the cheapest I could find on eBay were not close to their labeled capacities.

36 cameras use NP-FW50 Batteries

It’s crazy how many Sony Alpha cameras use NP-FW50 batteries.

Source: Sony NP-FW50 Accessories Compatibility Information

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The Best Third-Party NP-FW50 Battery Is…

Neewer are the best batteries from my testing. They don’t meet the labeled capacity, but they are higher than the labeled 1020mAh of genuine Sony batteries.

I expect a official Sony NP-FW50 lithium-ion rechargeable battery will last through more charge cycles.

RAVPower was banned from Amazon due to “incentivized” reviews. That’s too bad because they tested well.

• Test Capacity is an average of 5 discharge cycles at a 500mAh draw rate.
• The Voltage reading was taken 4 hours after batteries were fully charged in the Neewer charger.

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Battery Chargers

The Sony BC-TRW is the official battery charger.

RAVPower & Neewer Dual USB Battery Chargers

The Neewer batteries I purchased from Amazon came with a dual USB charger. It looks identical to the charger that is bundled with RAVPower batteries.

What’s nice is that a power bank can be used to charge batteries.

After seeing that it worked, I took it apart. There’s not much inside. The case is either glued or plastic welded together. I would not recommend disassembling the charger.

If you need a USB NP-FW50 charger, this one charges batteries. I am going to continue to use it. If you want an adapter that plugs into an outlet, get a DigiPower TC-U450.

Impossible Capacity Claims

How to capacity test camera batteries.

The cells in the Wasabi Power Sony NP-FW50 batteries are labeled as having an 880mAh capacity. This also lines up with the test results. That’s 70% of the labeled capacity.

The 1300mAh on the label is not true.

Taking a look inside shows the cells having a 900mAh capacity. That’s not the 1500mAh on the label.

This is why weighing batteries can be an easy way to spot poor quality.

I was not surprised that these were the worst quality. They were the least expensive batteries available on eBay.

What’s Inside a Camera Battery?

No identifying information can be seen on the cell.

RAVPower and Neewer have the same tested capacity, weight, and case. They can even be purchased with the same style charger.

Opening the RAVPower and Neewer batteries did not reveal any information on the cells used. Internally, the battery protection boards appear to be the same.

TEC-06 Battery Capacity Tester

The TEC-06 is a USB powered battery capacity tester. A test load can be placed on a battery. The measured capacity is displayed on the screen when the battery is fully drained.

Energy stored in the battery is turned in to heat. The heat sink and fan are there to dissipate that heat.

Testing Methodology

Battery contacts I made to test the batteries.

• Batteries were charged with the Neewer USB charger.
• 6 volts was used as the cutoff voltage.
• A 500mA load was placed on the batteries.
• Nickle strips were soldered to wires to connect to the batteries.
• The TEC-06 has firmware V6.06.

Two Li-Ion cells are wired in series to make the batteries. I do not have a data sheet for any of the batteries. I picked the most common cut off voltage, 3V, for Li-Ion cells with a nominal voltage of 3.7V.

Cells in a series have their voltages added together. 3.7V + 3.7V = 7.4V.

When the cell reaches 3V, it is considered fully drained. Discharging the cell past 3V can shorten the life of the cell. The cells are in series, so 6V was used as the cutoff for the batteries.

My Sony A7 gets about 2 hours of life out of a battery. A 500mA load was used because it would drain the cells in approximately 2 hours.

500mA x 2 hours = 1000mAh

Testing Self Discharge

Batteries will slowly discharge over time. This is an issue with high drain rechargeable Ni-MH batteries. There was almost no change in charge of the Sony FW-NP50 batteries over the course of a week. Self-discharge is not a problem you have to worry about.

Here is the process I used to test the batteries:

1. All batteries with fully charged on the Neewer charger.
2. Batteries sat for ~4 hours before the initial voltage was taken with the TEC-06.
3. A week later the battery voltages were checked again with the TEC-06.

At the end of the week, all of the batteries read 0.02V lower. This is a negligible amount. You would not notice the difference in charge from a battery that sat for a week. All of the batteries started as showing a 100% charge in my Sony A7.