Why is the (last legs?) LiPo battery in my device behaving this way?
March 18, 2023 3:31 AM   Subscribe

I have a 7 year old Sony Hi-res Walkman with a 3.7v 960mAh battery. Recently it ceased to function in its usual manner, and instead of a battery-filling-up symbol appearing on its screen when I connect it via USB to an external battery pack or computer, on its screen when I now only see a flashing low battery symbol. What could this be telling me about the state of the battery?

I should add that a week or two before this began, I noticed newly exposed wires at the part of the custom Sony USB cable where the cable extends out from the connector itself. (I had been playing the device with an external power pack connected most of the time...). I put some electrical tape around the spot and carried on as usual.

Figuring that my battery is dying and it's now time to replace it (it's soldered in, so changing it is not a piece of cake), I hunted around for a battery I bought on ebay for this unit last year, and took it into a cell phone repair place.

The repair guy brought out the player with the back still off after he'd put in the new battery to show me the result: The screen was now glowing, but there was no menu visible (as usually is the case soon after the device is powered on). Pressing different buttons did not alter this state of affairs. Also, the external battery pack no longer lights up when it is connected to the device, and the device no longer mounts on the pc.

As the device was of no use to me with just a glow, I asked him to just put the old battery back in. He did so, and the menu then appeared again along with the endlessly flashing low battery symbol. I left to think things over.

I then called an electronics store where I thought the staff might know more about these batteries than the cell phone repair guy, and indeed the person I spoke with did seem to be more knowledgeable, and speculated that that frayed cable I had taped up might be causing the charging issue, and suggested I order a replacement to see if the battery then charges properly . He suggested that the reason I saw a menu with my original and now constant "low battery", but only a luminous glow with my new one, is because the new battery has been sitting around for at least six months -- probably much longer -- and so the battery has gone into low energy mode, and needs to be charged a bit before being able to power up a device. The replacement cable I then ordered arrived yesterday.

When I attached the new USB cable from my Sony player to my external battery pack, it unfortunately did not begin charging (with lights on the battery pack flashing and remaining on when charging a device as is usually the case, but remained off) and that "low battery" symbol continued to flash without pause until the unit was powered down. So it looks like the issue was not USB cable, after all.

Now I need to decide what to do next, and this is where I need your counsel. Why is may battery flashing "low battery" at all times now, and not connecting with other devices. Is this typical behaviour of a LiPo battery on its last legs? Why didn't the new battery power up the device after it was plugged into a PC for a few minutes? How long might it have to be plugged in to fire up from "low energy mode"?
Do I have any hope of getting this thing running again?

BTW, this is 1000mAh battery, while the original SONY is rated 960mAh. The guy at the electronics shop didn't think that should cause any problems (although it probably was a bit bigger than the original and the tech guy did have a hard time fitting the wires into the very slim case after he was done). Should I pay the tech guy to solder in the new battery once again, this time leaving the device plugged into a battery pack until the battery springs to life? If it's too old, will it possibly not ever do so? Would I be better off ordering another 950mAh battery (closer to the original 960mAh, which don't seem to be in general production) and hope for the best? I don't want a more recent Sony model, or another brand. And I do not use or want a phone to play music on. If you have any idea what may be causing this issue , and what I might try to fix it, I would be grateful!
posted by tenderly to Technology (1 answer total)
I'm not much of an electronics expert, but here's a forum comment about replacing the battery of the Walkman NWZ ZX1:
For it to properly work, be recognized by the charging SW of the walkman and actually charge, you need to keep the Sony protection circuit in place. (hence not desolder the 3 colored wires attaching the battery to the board, but rather unsolder the battery from protection circuit.)
Not sure what exact model you have or whether it's similar, but this suggests that the issue might be that the Walkman is really looking for a Genuine Sony Protection Circuit- they managed to get the replacement battery to work by transplanting the circuit out of the Sony battery and into the new one.
posted by BungaDunga at 7:03 AM on March 18 [1 favorite]

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