What electrical design reasons are there for making rechargeable batteries non-removable?

Question

There are lots of consumer devices that run on rechargeable batteries and have those batteries non-removable without disassembling a device. The most notable example is I guess an iPhone.

Making a battery non-removable has these advantages:

1. simpler case - no need for the door that would otherwise need to be strong enough to survive careless operations by the user

2. better case sealing

3. tighter packing of the battery into the case allows for more space for other components or smaller case

4. users are forced to use service shops that can generate money for the manufacturer through "authorization" programs

Yet none of these reasons seems to have any electrical design basis.

Are there electrical design reasons for making rechargeable batteries non-removable?

Answer 1

6) The battery management logic and possibly some of the circuitry can be simpler and more effective if the exact battery type, and therefore the battery characteristics, are known. This could include getting more capacity out of the battery because the algorithm doesn't have to work accross a variety of battery characteristics.

Answer 2

5) The user can't replace the battery with the wrong type (especially voltage), which may damage/destroy the device. This could well be reason number one.

Answer 3

7) Legal dept recommends what the company should do with it's warranty claims, risk management to massive recalls, service costs and service profits.

If a user can service it with 3rd party batteries that fail due to mismatched energy management profiles or quality, it is a huge financial risk at every level from marketting, advertising, sales, service.

Was the design technology driven? No It is always about Revenue. And the sales of batteries is just a small part of the cost equation. The cost of failure from 3rd party batteries if they ever failed for any reason due to the host charger or even just the "loss of face " from media slander has a cost implication. AS well could Apple rely on consumers to re-cycle their batteries safely? They also have salvageable content.

Answer 4

The spring-loaded contacts commonly used for user-replaceable batteries have much higher resistance than other options, especially once an oxidation layer forms.

Answer 5

Device design plays big part in this. Battery that is not removable is usually in very thin (less than millimeter) enclosure thus enabling thinner devices.

If same battery was to be made removable, they would need to add some rigidity to it and that usually means at least few millimeters increase in size.

Other reason is aesthetic one. Smooth lines seem to be favorable these days and, no matter how good your battery compartment is, external battery interrupts that smoothness.

Answer 6

Another reason I can thin of is to avoid the need for a backup battery or supercap for the RTCC or memory chips that should retain data.

Answer 7

I'm surprised nobody seems to have mentioned weather-proofing. Making a sealed case weather-proof (or waterproof) is fairly easy, but throw in a user-replaceable battery and associated battery door, and suddenly it becomes a lot more difficult to ensure that water cannot enter the part of the device where the electronics reside. Yes, it can be done (high-end cameras do it all the time), but is the buyer willing to pay the extra money for it?

Just one example of this: electric toothbrushes. Entry-level models can probably be manufactured for 10-20 dollars, if not less, and the better models likely don't cost much more in manufacturing. Now make the battery replaceable, add a battery door and the necessary adaptations to support these. The cost for this probably adds up to a fairly large fraction of that manufacturing cost, while delivering very little value to the customer.

Answer 8

If the design treats the battery properly, most consumers will throw the device away before the battery needs replacing. You may still have your 1st gen iPod, but do you actually use it? And most devices are fine until they sit unused in a drawer, killing the battery.