Should batteries be user replaceable?
Allen and I just had a discussion regarding user replaceable batteries in tablets. They have their advantages, but also some disadvantages compared to other options.
First of all, there are two reasons why you’d want a user replaceable battery; replace a end-of-life battery, and switch out a depleted battery. The former means that you’re planning on using your tablet for a longer period of time than what the battery is likely to survive, which is 500-1000 recharge cycles. If you charge your tablet once a day, then it should take at least a couple of years before that happens. At that point, your Android device has probably been outdated for 1-2 years, and even your iPad will probably not get updates anymore. Even if you really want to revive it, a battery that isn’t user replaceable can still be replaced, it will just cost you a bit more. Having a user replaceable battery also means a few design “issues”, namely that there has to be an accessible battery compartment- you can’t just throw a battery in there. In fact it requires a double compartment- a plastic casing around the battery, and a plastic compartment for the battery to go in. Even if this doesn’t take up a lot of space, it does add bulk compared to a unibody solution- everything else being equal. It also requires a removable battery lid, something that often falls off or gets lost if the tablet is being used by kids.
Still, it is (usually) cheaper to do it yourself- and you don’t have to send you tablet in to do so. As Allen pointed out, you can even get higher capacity batteries to put in there, or get cheaper OEM batteries- as long as you can get the correct battery at all 3 years down the road. That is not always so easy if you rely on brick and mortar stores, but it’s rarely an issue online.
The second reason you’d want a user replaceable battery is to have several batteries with you and swap them as they run out. That is especially useful for travelers, hikers etc who might be away from AC outlets for days or weeks at a time. However there are other solutions here as well, namely external battery packs. The HyperMac batteries are some of the biggest consumer models, going all the way to 22WH, roughly 9 times the battery capacity of the iPad.On top of being available in much larger capacities than proprietary batteries, they also work on pretty much any device, so you can use it with all your current gadgets and also bring it with you when you upgrade- rather than having to buy proprietary batteries all over again.
The downside of this system, as Allen said, is that you have to have a giant battery connected to your device. While that’s true, I think it all comes down to the default battery life of the device; with an iPad or similar tablet that can do 10-12 hours, chances are you don’t use it constantly, meaning you can let it charge from the battery while you’re not using it. If you’re out hiking or traveling, it might be just as easy to just charge your tablet, phone, camera etc off one giant HyperMac-type battery while you sleep as it is to carry a whole bunch of proprietary batteries for each device and turning the devices off to swap batteries right in the middle of whatever you’re doing. You might also end up bringing too few cell phone batteries and too many tablet batteries or vice versa, and you can’t magically transfer the power from one to the other- a problem you don’t have when they all charge from the same source.
Lastly, price is an issue. Even if you set aside the fact you might need to get a whole new set of spare batteries for each new device, the price/Wh is also very different. At $450 the 222Wh HyperMac battery might seem expensive (and be overkill for many, that’s why they have smaller ones, and there are dozens of such batteries out there), but it’s not if you do the math.If they iPad had replaceable batteries, each would have to cost $50 or less to match the HyperMac. Considering the iPad’s battery has more in common with a netbook battery than a smartphone battery, that’s an unlikely price. For smaller devices it’s even worse. A 1500mAh 3.7V li-ion battery (pretty typical capacity) is 5.5Wh. That means each battery will have to cost $11.5 or less to be as cheap. That’s possible with cheap Chinese batteries, but then again those come with a 50/50 chance your phone will blow up. You might be lucky enough to find cheap enough (and safe enough) batteries to beat the price, especially on lower capacity external batteries (which cost more per Wh) but this calculation didn’t even take into account that an external battery is more universal than a proprietary one. On the other hand, having 10 spare batteries won’t mean you have to “use up” 10 recharge cycles from your “quota” of 500-1000, unlike when charging from an external battery.
When it all comes down to it, both systems have their advantages and disadvantages. To quote Allen one final time, it all comes down to choice. I have external battery packs, and I have spare proprietary batteries. It all comes down to what fits your situation the best, and that is completely individual. It’s just important to be aware of the options so you don’t over emphasize user replaceable batteries thinking they’re the only option, or vice versa.