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Connecting two batteries to one phone through the case

My Samsung Galaxy S5 is a little old and I would really like to augment the aging battery by connecting my old battery in parallel with my even older battery. I could just buy another new battery but that will only get me a relatively small improvement and this solution uses what I have already. I think one way to do this might be to drill holes in the back for a couple of wires to connect to the terminals of the battery to the two things in the back of the phone. I don't know the identity of all those electrical contacts but I do know that the wireless charging pad connects to the lower two so maybe I can use those? I plan to glue the external battery to the back of the case. It's going to look like a piece of junk but I'm okay with that.

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The main problem I foresee is that the case I'm using is the Otterbox Commuter wallet thing which has a sliding tray to store bank/ID cards and as a result I'm going to need the wires to be able to move which is eventually going to break them, I think. They're going to be quite vulnerable.
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Of course I don't care that this will compromise the waterproofing and the warranty expired a long time ago. There is no acceptable solution that involves the USB port because connection to USB is already flaky as it is and I don't want to make that worse.
 
Paralleling two batteries of dissimilar chemistries/ages/capacities/wear/state of charge is not recommended, but, you can do whatever you want with your stuff.
Bringing a wired connector out of the housing to use larger capacity cells can work, if the phone does not requiere sensing terminals on the cells... or wire those terminals too.
Attaching the 'canteen' is another story.

Or, glue this to its back and wire it to a charging plug
----> https://www.aliexpress.com/item/Sol...lgo_pvid=91d049b3-10bf-4080-aa88-fa84e68bdbac

----> https://www.aliexpress.com/item/Hig...lgo_pvid=91d049b3-10bf-4080-aa88-fa84e68bdbac

Total cost and hassle is more than a new cell for your phone.
 
Thanks for your response. Given that my phone stays in my pocket, a solar panel is not an applicable solution for me.

What is the problem with dissimilar age batteries being connected in parallel? I thought balancing issues only applied to batteries in series?

What is a "canteen" in this context?
 

davenn

Moderator
What is the problem with dissimilar age batteries being connected in parallel? I thought balancing issues only applied to batteries in series?

the good battery is still going to work harder than the poor one

so are you wanting the phone to be able to control charging etc for both batteries
This is not likely to work properly as the circuitry in the phone is designed for a single battery
 
Also, given that, as you say, your phone stays in your pocket, a sudden fire would probably also be unwelcome.
The extra battery, a new pair of pants, and medical care is going cost more than a new phone.
 
the good battery is still going to work harder than the poor one

I don't see how that's a problem. The good battery is doing all the work right now so anything less than that is clearly not an issue.

Also, given that, as you say, your phone stays in your pocket, a sudden fire would probably also be unwelcome.
The extra battery, a new pair of pants, and medical care is going cost more than a new phone.

I live in a country with socialised medical care but it's irrelevant because batteries don't explode for no good reason and I don't believe that what I've proposed is a good reason for a battery to explode.
 
interesting that you quoted that part of my comment, rather than the much more important one regarding charging ;)

Why mention the thing that makes no sense though?

Regarding charging, I don't see a problem either. The current is going to be limited by the supply and each battery will get less than it would if there was a single battery.
 
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