I'm contemplating getting a Sony battery's PCB flex soldered to a Samsung S8+ battery. This due to new official genuine products proving impossible to find for a 2014 device now, especially with a battery manufacture date within two years. Also there's no reputable third party manufacturers either.

Photo of S8+ battery. It's a significant upgrade in power to make it worthwhile while fitting decently, otherwise any other model may work. Successor Sony batteries have a different arrangement of the PCB flex which is why a transplant modification is going to be necessary either way. This XDA forums thread demonstrating removing the PCB flex from an older genuine Sony onto a third party battery helped inspire me.

The specific question is about the S8+ battery being 3.85V Nominal, 4.4V Charge. Whereas the Sony i'm coming from is 3.8V, 4.35V. Will that be a problem for the PCB or phone in general to accept? Is the only difference that the PCB/motherboard will be limited to charging the new battery to 4.35V?

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    \$\begingroup\$ 1) Please read the guidelines of the forum before posting, don't cross post, It angers the Internets. 2) Post a specific question 3) This isn't a repair forum, so you need to edit your question and make it design related or it will be closed \$\endgroup\$ – Voltage Spike Aug 29 '17 at 2:40
  • \$\begingroup\$ Sorry, edit fixed. \$\endgroup\$ – Infy_AsiX Aug 29 '17 at 3:14

As I understand, you want to retrofit the new Samsung S8+ battery into some older Sony device. It should be no problem, as long as you manage to connect plus and minus terminals correctly to the older Sony pads without shorting anything, and make these pads to connect reliably.

The difference 4.35V (Sony charger) versus 4.4V (Samsung charger) will give you somewhat less capacity, but more charge-discharge life.

The only problem I see is that the Samsung battery has some third terminal wire, which is usually associated with thermal sensor. If not connected to proper charger circuitry, the battery might have a chance to overheat and explode, so there will be some safety issue. The other issue, how do you envision to fit this long battery into the squarish compartment of old Sony phone? Duct tape?

  • \$\begingroup\$ Yes, I see thanks. Good point, I forgot to consider how it's thermal sensors are setup. I incidentally saw recently in this youtube that the S8's battery temperature sensor seems to be mounted separately externally. \$\endgroup\$ – Infy_AsiX Aug 29 '17 at 3:45
  • \$\begingroup\$ The phone i'm retrofitting to is a Z3 Compact. It houses the battery length ways behind the motherboard. The battery space measures with a little spare space for the S8+ battery surprisingly. Using an external case without the back panel will allow enough width to not squash the battery. I've tested the Z3C battery running attached while outside of the body to find the temp does not drop as cool as the actual battery surface temp. Plus when it's cool and goes back into a warm body the sensor temp drops immediately. So the sensor is in the phone body somewhere. \$\endgroup\$ – Infy_AsiX Aug 29 '17 at 4:20
  • \$\begingroup\$ Nevermind that. I tested more thoroughly with an ice pack and hot water container. The temp sensor is indeed in the Z3C battery. My safest bet would be to get a suitable Sony successor I suppose. How does the temp sensor inside the battery pass the data? I'm looking at a broken spare I have here and the only connection from the battery to the PCB is the + - tabs? \$\endgroup\$ – Infy_AsiX Aug 29 '17 at 5:40
  • \$\begingroup\$ @Infy_AsiX, usually it is a simple termistor of NTC type, 10k or 36k, or else, connected to ground. The charger inside the device senses the resitor value, and turns off if the level isn't right. At least this is how Texas Instruments chips (formerly Benchmarq) operate. You can fool the charger by having some constant resistor. \$\endgroup\$ – Ale..chenski Aug 29 '17 at 6:20

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