Why is that the requirement? The extra layers of plastic to enable removable batteries cost close to zero dollars and don't have to cost more than a millimeter.
There’s also connectors that wouldn’t be there normally, those connectors also have to be large enough to support the current. Then there’s the plastic lined battery well, as well as the plastic battery case. It’s not as simple as throwing plastic around a battery and calling it a day.
> There’s also connectors that wouldn’t be there normally, those connectors also have to be large enough to support the current.
Supporting 5-10 amps requires very small pins. It's a tiny percentage of the battery size.
> Then there’s the plastic lined battery well, as well as the plastic battery case. It’s not as simple as throwing plastic around a battery and calling it a day.
Yes, those are the layers of plastic I was talking about.
I didn't say you could slap something together in half an hour, I said it would cost close to zero dollars when talking about the per-phone price.
> Why is that the requirement? The extra layers of plastic to enable removable batteries cost close to zero dollars and don't have to cost more than a millimeter.
That very last phrase you said a millimeter. None of this will fit in one millimeter, which was my counter.
The connector won't affect thickness, it will go at one end of the battery.
For the layers of plastic, the battery already has a wrapping, and the phone already has a back. You just have to reinforce the wrapping on the battery. How much thickness do you think that needs? It's definitely not five millimeters.
“ The extra layers of plastic to enable removable batteries cost close to zero dollars and don't have to cost more than a millimeter.”
“It’s two lines of code, how hard can it be?”
More seriously, the cost of designing a battery pack goes way beyond that, just like in software there’s a world of difference between an internal and an external interface. Adding ESD protection for instance can be a headache.
There's an enormous amount of design cost in a phone no matter what. Doing it differently from the start does not substantially increase the cost, and I'm not asking for a retrofit.
It's absolutely bonkers to suggest a 20-30% increase in total cost that would be driven by design costs; that's more than doubling the entire design budget!
I'm not talking about NRE costs, I'm talking about very real manufacturing costs that you are ignoring. Modern battery packs are one of these things that if you haven't designed one you tend to think they're simple, but have a lot of hidden complexity.
Just as an example, modern batteries require keeping track of a lot of parameters and metrics, and require keeping control of things like cell balancing. Making a battery removable means having to move all this into the pack, which then implies having exposed critical interfaces.
As an example check this device by Texas Instruments: BQ40Z50-R2. This gives you a lot of the functionality to the point that Apple keeps variants of them in current laptops, even if they're not removable anymore.
To make a software equivalent, imagine building an enterprise product that connects to a database, and then being asked to have this link exposed through public APIs. Now you need to consider delightful things like authentication, or being vulnerable to DDoS.
1. That just moves from phone to battery, doesn't it? That's not a cost increase for the bundle.
2. You don't need fancy things like cell balancing for a phone battery.
3. Even with this chip it's $4 BoM for small batches and significantly less in bulk. So that could be a 1% cost increase. So we have that, a thin plastic shell, and a tiny connector. How are we hitting 20-30% increases, hundreds of dollars?
1. Except now you need a new PCB, a new subassembly, new procedures...
2. You need a lot of fancy things, just not cell balancing. That “battery health indicator” all iphones have, guess where that’s from.
You can take it from someone who has built several devices with replaceable batteries, or we can just keep debating until I’ve fully explain to you how you actually build one of these.
The thing is, I don’t want to waste more time on this, you can do your research on your own, or just keep your preconceptions, whatever floats your boat.
> 1. Except now you need a new PCB, a new subassembly, new procedures...
Every phone needs new subassemblies and procedures. For the PCB, you end up with an extra one that's tiny true.
> 2. You need a lot of fancy things, just not cell balancing. That “battery health indicator” all iphones have, guess where that’s from.
Sure, okay.
> You can take it from someone who has built several devices with replaceable batteries, or we can just keep debating until I’ve fully explain to you how you actually build one of these.
> The thing is, I don’t want to waste more time on this, you can do your research on your own, or just keep your preconceptions, whatever floats your boat.
Where would I look?
I'm trying to follow your logic. But you mostly keep naming things phones already have. They already have all this engineering work. They already have the battery chip, it just changes location. And that chip is less than $3.
Could you please give me a couple sentence explanation of how you arrived at 20-30% for a phone that's designed from the start to have a removable battery? You keep nitpicking me for not understanding an argument that you never explained!
My understanding goes something like this: Posit a $600 phone of which $50 is the battery pouch. Remove battery pouch and chip from phone, replace with a connector, phone now costs $550? Add plastic shell and $3 chip and connector and tiny PCB onto the battery pouch. For the total price to rise 20%, doing that has to cost more than $100 and leave you with a battery that costs more than $150. How?
And phones didn't get massively cheaper when they stopped letting you remove batteries...
