Inductive charging of dive computers

[RonR]

Everything is a tradeoff. Tradeoffs with inductive charging for a dive computer (compromised battery life, speed, need for additional hardware inside the DC) may not be worth it in a device that one expects to last many years. Just a few observations from the design side:

• Rechargeable Li-ion batteries are good for quite a while in a dive computer application, typically 500 or more charge-discharge cycles before capacity gradually starts to diminish. They have a long shelf life (>7 years) and don’t have the memory issues of earlier rechargeables. In the case of the Atomic Cobalt, each charge gives 30-50 hours of dive time, depending on screen brightness. We started selling Cobalts with Li-ion batteries in 2010, almost all are going on the original batteries, very few have needed replacement so far. I’ve seen plenty with1,000 dives in the log, large numbers with hundreds of dives. The failure mode is typically starting to get less diving time on a charge. I think Atomic charges $50 for a replacement battery when it becomes necessary. The battery can easily be changed by the end user. Sealed in batteries, like Liquivision or the old Uwatec, are not the norm today.
• Many dive computers sense water presence to activate (as opposed to just sensing pressure changes). There are some good reasons for a dive computer to detect the presence of water. That means there will already be some metal contacts through the housing. In our case it’s those pins that do double duty for charging and also a standard USB data link for dive logs and updating firmware.
  
• Absolutely agree with the comments about there being no need for expensive, proprietary cables. We use generic USB cables and chargers, and I think that's becoming more normal, along with bluetooth for log data. You are kind of stuck with some kind of plug or adapter to connect, since standard USB connectors can’t be made waterproof. But the adapter can be simple and inexpensive.
• Both removable-disposable and rechargeable batteries have pros and cons. Rechargeable because you don’t ever have to open the computer or carry spares, disposables because they are ubiquitous and energy dense and they don’t require charging circuitry to be built into the computer. This comes down to personal preference.
• Computers with emissive color screens and more feature rich programs will need more power than the older segment based displays. The old coin cells that lasted for years won’t power these products. Bigger batteries are part of the deal.

-Ron

 

[victorzamora]

Thanks for the long response. Between this and the posts from Shearwater, there's certainly some food for thought. However:

• Absolutely agree with the comments about there being no need for expensive, proprietary cables. We use generic USB cables and chargers, and I think that's becoming more normal, along with bluetooth for log data. You are kind of stuck with some kind of plug or adapter to connect, since standard USB connectors can’t be made waterproof. But the adapter can be simple and inexpensive.

It's great that PART of the "cable" is inexpensive and standard (looks like miniUSB to USB-type-A). However, you still need the charge/USB adapter to connect to the computer itself (unlike the Nitek Q that has a USB port behind a sealed cap). How much is that adapter if I were to request a spare? What would happen if, on a trip, I damaged it and needed to charge it?

Even if you did have a USB port behind a cap, like on the Nitek Q, USB ports tend to eventually go bad on things like phones and chargers. The USB port on the Atomic Aquatics Cobalt2 adapter will also eventually wear out: another reason for a backup/spare proprietary adapter.

 

[kelemvor]

What would happen if, on a trip, I damaged it and needed to charge it?

I'm guessing that was rhetorical, but just in case... I've had it happen with a dive light that had a proprietary connector. You've got three options. 1. Go without it or 2. Replace the whole unit at least for the duration of the trip. 3. Change from a dive trip to a bender and drink your face off. Since it was in Key Largo and it was a light not a dive computer it was fairly easy to go without.

Other than the cost of (some) proprietary connectors, it's a big reason not to purchase equipment that uses such connectors if you can avoid it. At least, that's my opinion.

 

[dmaziuk]

You need to consider the fallout: if it's a user-replaceable battery and the plug that packs it is only there for log download and firmware updates, is one thing. Some users won't even buy it as they keep paper log and never update the firmware. It's not quite the same as proprietary connector that gets damaged and your device stops performing its primary function.

 

[RonR]

...It's great that PART of the "cable" is inexpensive and standard (looks like miniUSB to USB-type-A). However, you still need the charge/USB adapter to connect to the computer itself (unlike the Nitek Q that has a USB port behind a sealed cap). How much is that adapter if I were to request a spare? What would happen if, on a trip, I damaged it and needed to charge it?

Even if you did have a USB port behind a cap, like on the Nitek Q, USB ports tend to eventually go bad on things like phones and chargers. The USB port on the Atomic Aquatics Cobalt2 adapter will also eventually wear out: another reason for a backup/spare proprietary adapter.

Valid points. The Cobalt adapter has two sides that operate independently, one for A/C charging and one for USB charging and data. Hopefully both would not break at once. But if someone were to drop your adapter overboard, then the hope would be that there is enough charge in the computer to finish your dives. We tried to make it so you could reasonably expect to do at least a week long liveaboard trip (40+ hours of diving use) on a single charge. It's not as if you need to charge the battery every day. But the adapter is a critical link if you do need to charge. I think an extra / spare is $50, as is a spare battery.

At the time the Cobalt was designed (more years ago than I like to think) virtually every dive computer that allowed downloads used some kind of proprietary serial cable that was an add on purchase of $100 or so. We wanted to include that capacity with the computer, and use standard USB rather than a serial conversion. Since then this approach has become more normal.

We considered a standard USB connector behind a port. The downside is another O-ring seal that needs to be opened every time you download or charge. For every opening there is some non-zero chance of flooding the electronics. And we still wanted water sensing, so were going to have external contacts in any case.So we opted to put the battery in a separate sealed compartment that doesn't need to be opened, and use the pins and adapter for both charging and data. As you say, USB connectors will wear out (or more likely be broken), though probably in a dive computer they don't see as much plugging and unplugging as in most consumer electronics. Putting them on an external adapter makes the fix easier.

All designs are compromises. We did our first computer with removable AA batteries, then opted to move to a Li-ion rechargeable. Both have pros and cons. Going on 8 years of production I'd make the same choice again, for our product and market. Batteries and charging just have not been big issues. To the OP's question regarding inductive charging, I'm just offering some insight into why we are still using wires to charge and why we think, at this point, that the tradeoffs for inductive charging may not be worth it. Future technology may change that.

Ron

 

[rhwestfall]

this cracks me up.... you compare this to Cell Phones? What is the expected life of a cell phone? Basically a throw away after two years. I'd like to hear the comments from the sidelines when that is the SOP for dive computers....

I'll be just fine continuing with a user accessible and replaceable cell....

 

[kelemvor]

this cracks me up.... you compare this to Cell Phones? What is the expected life of a cell phone? Basically a throw away after two years. I'd like to hear the comments from the sidelines when that is the SOP for dive computers....

I'll be just fine continuing with a user accessible and replaceable cell....

It's interesting, really - in my opinion. Cell phones cost more than most dive computers and have vastly superior hardware. Still, cell phones get replaced frequently (I do it every year) and dive computers do not. I think it comes down to R&D dollars for improvements. Comparatively, there isn't very much being spent on dive computer R&D. Therefore there's not a big drive to replace your DC for a long time.

I'm sure if dive computer manufacturers could count on their customers replacing their computer every year or two they'd put a little more into R&D.

Anyway, a good reason to compare them to cell phones when it comes to batteries is this. Cell phones have much greater power needs than a dive computer, and cell phone battery technology isn't exactly fast moving. Every cell phone I've seen in the past decade (maybe ever) still uses lithium batteries. Wireless charging features in cell phones are also not new, it came about in 2009. Other commercial electronics products with wireless charging were being sold in the 90's. Android phones got wireless charging in 2012, and Apple in 2017. Also, you can add wireless charging systems to just about any phone that doesn't natively support it as long as the phone has a replaceable battery.

To top it off, wireless charging seems (to me) like it was tailor made to be used in dive computers. A piece of electronics that goes underwater? One of the more common failures involves opening the thing to put batteries in? Wireless downloads already integrated into many products?

I have no doubt at all that eventually some company will produce a DC with wireless charging, it's just too obvious a feature to be left out forever. Even if it isn't the greatest thing since sliced bread, it will likely be enough of a selling point that people may turn to whatever model gets it first JUST because of that feature. Especially for divers who have lost a DC because it got wet inside...

 

[victorzamora]

Valid points. The Cobalt adapter has two sides that operate independently, one for A/C charging and one for USB charging and data. Hopefully both would not break at once. But if someone were to drop your adapter overboard, then the hope would be that there is enough charge in the computer to finish your dives. We tried to make it so you could reasonably expect to do at least a week long liveaboard trip (40+ hours of diving use) on a single charge. It's not as if you need to charge the battery every day. But the adapter is a critical link if you do need to charge. I think an extra / spare is $50, as is a spare battery.

At the time the Cobalt was designed (more years ago than I like to think) virtually every dive computer that allowed downloads used some kind of proprietary serial cable that was an add on purchase of $100 or so. We wanted to include that capacity with the computer, and use standard USB rather than a serial conversion. Since then this approach has become more normal.

We considered a standard USB connector behind a port. The downside is another O-ring seal that needs to be opened every time you download or charge. For every opening there is some non-zero chance of flooding the electronics. And we still wanted water sensing, so were going to have external contacts in any case.So we opted to put the battery in a separate sealed compartment that doesn't need to be opened, and use the pins and adapter for both charging and data. As you say, USB connectors will wear out (or more likely be broken), though probably in a dive computer they don't see as much plugging and unplugging as in most consumer electronics. Putting them on an external adapter makes the fix easier.

All designs are compromises. We did our first computer with removable AA batteries, then opted to move to a Li-ion rechargeable. Both have pros and cons. Going on 8 years of production I'd make the same choice again, for our product and market. Batteries and charging just have not been big issues. To the OP's question regarding inductive charging, I'm just offering some insight into why we are still using wires to charge and why we think, at this point, that the tradeoffs for inductive charging may not be worth it. Future technology may change that.

Ron

Well said, Ron. And at $50, the adapter (and battery) is a pretty reasonable cost. There's certainly lots of compromises to be made in ANY design process. I hope I didn't come off as criticizing the choices made for the Cobalt, I was simply using it as an example of Pros and Cons of different choices. There's certainly no "one right answer."

The idea of a Qi charger on a dive computer, which is the point of the thread, I think is a good one. It'll be interesting to see what else moves to BTLE+QiCharging for data/charging needs. Qi seems to be gaining lots of traction in the standardization department, even being included built-in to cars and available on public bar-tops.

 

[victorzamora]

I have no doubt at all that eventually some company will produce a DC with wireless charging, it's just too obvious a feature to be left out forever. Even if it isn't the greatest thing since sliced bread, it will likely be enough of a selling point that people may turn to whatever model gets it first JUST because of that feature. Especially for divers who have lost a DC because it got wet inside...

One thing is that phones get used daily and charged at least daily (in my experience). My dive computer gets used a few times monthly. Something I use to interact with so many and something I interact with so often (my phone) is something that gets replaced. My needs from it are much more than my needs from my dive computer. Dive computers need to last years and years to be feasible in the marketplace. That's one big delta between the two.

As for the above: Heinrichs-Weikamp has had Qi charging in their computers for at least a few months now. And with Apple finally getting with 2012 and including it in their phones, we might see Qi become the standard enough that PDC manufacturers start looking at it more closely.

 

[dmaziuk]

It's interesting, really - in my opinion. Cell phones cost more than most dive computers and have vastly superior hardware. Still, cell phones get replaced frequently (I do it every year) and dive computers do not. I think it comes down to R&D dollars for improvements.

Didn't you hear? -- Apple and Samsung deliberately cripple their last year's models to push users to upgrade while the carriers offer new phone every year absolutely free for only $100/month 24 months minimal contract term. It comes down to a scam. Parting fools from their money, plain and simple.

If dive computer manufacturers tried that we'd all be diving tables.