ESticks -- a standardized quick-swap battery proposal

You’ve probably noticed that with many of our portable devices, especially phones and tablets, a large fraction of the size and weight are the battery. Battery technology keeps improving, and costs go down, and there are dreams of fancy new chemistries and even ultracapacitors, but this has become a dominant issue.

Every device seems to have a different battery. Industrial designers work very hard on the design of their devices, and they don’t want to be constrained by having to standardize the battery space. In many devices, they are even giving up the replaceable battery in the interests of good design. The existing standard battery sizes, such as the AA, AAA and even the AAAA and other less common sizes are just not suitable for a lot of our devices, and while cylindrical form factors make the most sense for many cell designs they don’t fit well in the design of small devices.

So what’s holding back a new generation of standardization in batteries? Is it the factors named above, the fact that tech is changing rapidly, or something else?

I would propose a small, thin modular battery that I would call the EStick, for energy stick. The smaller EStick sizes would be thin enough for cell phones. The goal would be to have more than one b-stick, or at least more than one battery in a typical device. Because of the packaging and connections, that would mean a modest reduction in battery capacity — normally a horrible idea — but some of the advantages might make it worth it.

Quick swap

There are several reasons to have multiple sticks or batteries in a device. In particular, you want the ability to quickly and easily swap at least one stick while the device is still operating, though it might switch to a lower power mode during the swap. The stick slot would have a spring loaded snap, as is common in many devices like cameras, though there may be desire for a door in addition.

Swapping presents the issue that not all the cells are at the same charge level and voltage. This is generally a bad thing, but modern voltage control electronics has reached the level where this should be possible with smaller and smaller electronics. It is possible with some devices to simply use one stick at a time, as long as that provides enough current. This uses up the battery lifetime faster, and means less capacity, but is simpler.

The quick hot swap offers the potential for indefinite battery life. In particular, it means that very small devices, such as wearable computers (watches, glasses and the like) could run a long time. They might run only 3-4 hours on a single stick, but a user could keep a supply of sticks in a pocket or bag to get arbitrary lifetime. Tiny devices that nobody would ever use because “that would only last 2 hours” could become practical.

While 2 or more sticks would be best for swap, a single stick and an internal battery or capacitor, combined with a sleep mode that can survive for 20-30 seconds without a battery could be OK.

Public infrastructure

With standardization, an infrastructure would grow up around ESticks. You would be able to buy new ESticks anywhere, like corner shops, possibly even disposable the way alkaline AAA batteries are. You might also find multi-stick EStick fast-chargers in all sorts of places — hotels, conference facilities, waiting areas, transit, etc. Indeed, you might not even recharge your batteries in your device if it’s really easy to charge the ESticks. Particularly if it’s very fast — the public chargers might be designed with cooling and high current.

There is also the potential for trade. ESticks would have chips in them, and if these can be trusted to accurately report the age of other attributes of the battery, one could have a system where stores give you a full EStick for your empty one, adjusting for the age of the stick given. (Admittedly this might give rise to fraudulent sticks.) Vending machines could handle the process.

As noted the sticks would have chips in them, which would handle not just charge counting and age and identification (some privacy issues here) but negotiation on power in smarter sticks. A popular “stick” would be one that is actually an AC adapter, particularly for devices like cameras that don’t have external power inputs.

On many devices, the stick port might even be (if it doesn’t need a door covering it) a suitable docking port with enough size to physically hold the device as well as power it and communicate data. Yes, the EStick port should have some wires able to do high speed data just for this.

Security

All of this has security and privacy issues. One useful feature would be the ability to give a stick a digital key. If you put a stick into a public charger (that declared itself as public,) the stick would then go into a mode where it can only go back into a device it’s been in before. As a result, casual theft of sticks from public chargers would be fruitless.

If there’s a data connection in the stick, again we must be on the lookout for malicious ESticks and assure they can’t now fake out or take over our devices. The use of an encrypted tunnel could ensure that only your own dock can say it’s a dock.

Market

Sticks would not be expensive. On the other hand, for some that’s a bug, not a feature, as many device vendors like that their devices take only proprietary batteries and that you must buy them, at high cost, from the original vendor. With the EStick approach, devices would eventually not even come with ESticks or chargers, expecting you to already have them or get them elsewhere.

Sizes

While we would want to keep the sizes to a minimum, there would still be some variations in size needed. You don’t want all sticks to be able to power a watch or eyeglass, and you don’t want to have to put 10 sticks into a phone or 50 into a laptop. Sticks could be designed so it’s possible to combine multiple sticks in a holder of one of the larger sizes. Chargers could also be designed with adjustable slots to take all sizes of stick. A typical charger should take multiple sticks and people would have several to charge each night. Devices that must run at night (like phones) would continue to need external power such as micro-USB.

Some devices might elect to have their own internal battery and have just one stick slot. In this case, the internal battery would never be drained so much that you can’t hot-swap — and indeed the stick might use some of its power to restore charge into a drained internal battery for the next hot-swap.

Not all devices need hot-swap. Still cameras and other fast-boot devices without a lot of state are fine with cold-swap. Slow-boot devices like tablets and phones prefer hot-swap or warm-swap. Devices like video cameras which want to shoot continuously need hot swap.

When ultracapacitors arrivek, an EStick approach could be great. Aside from letting all the old devices use the new sticks, fast-charging an ultracap needs a high-power connection which the device itself may not have. However, a charger with access to the whole stick and special charging electrodes could charge it in seconds. A person with two such sticks could swap them, run for however many hours they provide and recharge the stick that’s out whenever a fast-charge station is encountered.

So, how many form factors would we need? We can’t do worse than now. We have 5 different kinds of Canon camera we sometimes carry, for example, and they have 4 different batteries and chargers. (There are some chargers that offer multiple charging plates but none with all of them as yet.)

In addition, vendors would also make EStick based units which have a micro-USB or other charging connector on them, to mount your phone or other device in to power and charge it, even if it does not have internal sticks. People already sell these, but they are proprietary.

EStick Data

Brad,

Yet another well thought out idea.

I do have just one question. What is the point of the EStick with a data port?

Thanks,
Randy

Data port

I have a general philosophy that we should always combine power with data now that the electronics to do that are cheap. That no power cable should not offer data, and no data cable not offer power, as much as can reasonably be done. That it should be bidirectional (so either device can be the one to offer power.)

So when I considered that a battery stick could be your AC adapter and thus your dock, I felt it should offer data so it can be a complete dock. The main question is security. Your dock must be trusted, because it’s going to be able to pretend to be your mouse, keyboard and network. You don’t want to be surprised by a battery/adapter becoming a dock, especially if you might insert a random battery handed to you by an untrusted party.

SD ff,

Having had a part in manufacturing a device or two, I'd say that the design of cheap gadgets is well served by the current supply chain. It is disappointing.

When trying desperately to shrink a device external size, it is really handy to be able to dictate the size of the battery at the last minute to the optimal volume.
Battery manufacturers can supply a novel size quickly.

The bigger it is, the cheaper materials can meet the same lifespan, or it can just run longer.

Power electronics for devices are often among the costly parts, and they depend on the battery sensitively. They lose 20% of the power so if they can be avoided, you get significantly better life span. And it is easy to order a battery with the voltage you want from the factory.

You need to know the battery chemistry in great detail to manage its charging and discharging and lifespan. Ideally every battery should have an API that explains to the device the economics of its operation in various ways. So if you are making a cheap game player for kids, you might spec that a charge/discharge cycle be conducted for less than $0.10 of wear and tear on the battery. So the battery knows how much it cost, how many cycles are in it, and therefore knows when to tell the device that it is "empty" or "full".

Smarts in the battery

Yes, my proposal does indeed expect the batteries to have smarts for disclosing their power characteristics and capabilities, or being told what to do if they say they can be told.

As I said, this is a sacrifice from the ability to do an entirely custom battery. Custom batteries are doable for high-volume devices, but the sticks would be great for lesser volume because you would not even have to include a battery with your device, at least eventually.

I don’t see quite as much variation in voltage going on. First of all the voltage varies a lot during the life of many chemistries, so the device has to handle the range. And the L-Ion cell voltage of 3.6v is very popular because it also can be charged easily using the 5v of USB. Is there really that much tuning of the battery voltage going on?

Also worth noting that if you are ready to take the losses of a boost converter you can get a lot more life out of a single charge — at the cost of getting fewer cycles by draining it so much. That’s a choice designers would make.

It is my expectation that indeed a stick might get you only 80% of the life of the custom battery, though, but this would be worth it because keeping a spare stick in your bag gives you 160% or 240% of the lifetime easily. This is good when the lifetime is just too short.

There are still a lot of form factors — watches and tiny wearables, phones, digital cameras (in tiny, medium and SLR sizes,) tablets and laptops to name a few. Still would mean a lot fewer battery types even if you had 40 stick sizes and voltages.

Externalities of the current supply chain

"The design of cheap gadgets is well served by the current supply chain" only because we let the manufacturers and merchants optimize profits by selling more volume at the detriment of cost to consumers and the environment. The real cost is not that extra few cents of wear and tear. It is the over-consumption of batteries and the designed obsolence of the devices that become useless too early if the battery is not user-serviceable or if the specific battery form factor becomes unavailable.

Consumers would be better served with a standard, but don't expect market forces to introduce one. Before USB chargers, cellphone shipped with incompatible chargers. The European Union (EU) got enough of the waste and forced standard USB charging on devices sold on its territory. But the EU has now bureaucratic troubles of its own and so there is nobody who wields sufficient power to champion consumers interest.

How about a slot for a cheap

How about a slot for a cheap Bic lighter, with a fuel cell in the device? Distribution channels are already there, and it is tough to beat the power to weight ratio of hydrocarbons at the moment.

Butane

Yup, there have been various efforts to do fuel cells or super tiny turbines. Fuel cells are challenging because a fuel cell to process butane has to be really, really hot. So for now it’s not too common.

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