Reviving a Samsung Smartwatch battery

The Samsung Galaxy Gear SM-V700 smartwatch was launched September 2013, and it was Samsung’s 1st generation of smartwatches. It came with a 320 x 320 pixel display, 4GB of storage and a 1.9MP camera (which is something you don’t see on the Smartwatches available today!) It was an expensive accessory for your Samsung smartphone!

Camera located in the strap of the V700

This watch has a 315 mAh lithium battery , that would typically last a few days before it needed recharging. However, you will find a number of forum posts where owners are complaining that their watch would no longer power up after leaving it uncharged for a while. That was the case when I received this watch. It was dead and wouldn’t power on or charge.

To me this sounded like the typical problem where the voltage of a lithium cell has fallen below the threshold of the BMS (Battery Management System). The nominal voltage for a lithium cell is 3.6V and you would not want to let the cell run down any lower than 3V. If the cell is left to discharge further then its voltage will drop below this threshold and the BMS may no longer charge the cell. This is a safety feature of a BMS meant to prevent charging of a defective cell. Well there was only one way to find out if the cell was still any good in this watch. I had to remove the cell from the watch and test it!

Opening up this watch is tricky! The 4 screws that you see on the front of the watch are fake :-). They are cosmetic and for looks only. I found this out by trying to turn one of them. It just fell out and I could see it didn’t even have any threads. So I just glued it back in and flipped the watch over to look for the real screws holding it together. I found 4 more screws on the back. These came out as expected of real screws.

Remove the four screws with a T6 Torx bit or driver

I still had to pry the back cover off the watch to get it apart. Be careful because the 2 halves are going to be connected together with a flexible cable. Shown in the photo below is the main board located in the face of the watch and the battery located in the back cover. You can see the battery under the metal plate. I removed the metal cover and disconnected the battery from the flexible connector and the back case.

First time inside the SM700

This battery is in a silver pouch, and it’s a single cell, so I would expect it to have a voltage reading between 3 and 4.2V. However when I measured the voltage on the battery it was lower than 1V. I decided to try and revive this battery using a technique of used in the past with other lithium cells ( see my article on reviving a power tool battery:

Charging the V700’s battery battery with my SkyRC charger

In the photo above, I am using my SkyRC charger to first boost the cell voltage to roughly 3V and then fully charging and discharging the battery to make sure that it is still good. I was finding that the battery capacity had been depleted from its original 315mA down to about 200mA. This battery still had about 60% of its capacity. The capacity may even improve some more after a few more charge / discharge cycles. I reassemble the battery back into its case, carefully reconnected the flex cable and closed the watch up. When I tried to the power button I was greeted with the Samsung logo on the screen! You can see the first sign of life in the photo below.

First sign of life after reassembly

I was happy to see that the watch continued to boot up and when it was done I could check the battery status. As you can see below, it was at 100%. Excellent!

Battery status is 100%, watch is in its charging cradle

I put the watch back in its charging cradle, which has a USB port on it. I connected the watch/cradle to my computer via a USB cable. I ran the Samsung Kies utility and sure enough it connected to the watch. Using the utility I was able to check for software updates for the watch, and sure enough one was available. So I began the process to update the watch firmware.

Updating the watch firmware via my computer and Samsung Kies

Once the update was completed I power cycled the watch a few times. Everything seemed to be working and I was able to pair the watch with my Samsung Galaxy phone. Great! It was back in service!

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