Solar Odyssey – Power

One of the challenges for the Solar Odyssey is that Ra is a solar powered boat. No sail, no diesel, just solar. This raises two primary issues: how do we power equipment without native 110v; and how much extra power do we need to generate to run production, above and beyond what’s needed by life on the boat and – most significantly – the motors? Neither have simple answers.

As much as possible I want to avoid the penalty and inefficiency of inverting power from the boat’s DC system up to 110V AC, particularly since every device we use internally is close to 12V DC. Now the boat’s native system – from the solar chargers to the batteries and motors – is 48V DC. Downconverting that to 12V DC is virtually lossless and the technology is well proven. Nothing new here.

But finding gear that has direct 12V (or other DC voltage) is difficult. The laptops are relatively easy. The input is 14-18V DC and, despite a lot of research elsewhere, it turns out that Hypermac has a great solution: pair their Magic Box adapter with their (included free) Hypermac Pure DC Car Charger and there’s the perfect solution for all our laptops. For the Mac Mini has a step by step on what to do. I’m comfortable enough (and time constraints mandated) that I can perform the operation myself, but took advantage of the Mini DC conversion Kit item in the store.

My most significant current issue is that we have a great partner working with us on modifying their drives for direct 12V but they’re constrained by their boss being out of the country and can’t commit. Given that drives run off 12V natively, that shouldn’t be too big an issue. So, there’s an open sponsorship slot (for the assistance) or I’ll buy and mod raids myself.

The Nady radio mic receiver combo has an external 15V DC power supply, which just happens to be right in the range of the output from the Hypermac Pure DC Car Charger. Another problem solved.

All iPhones, iPads and similar devices will be preferential charged via USB. 12V to USB adapters are very common and I use a two outlet version in my car to charge the iPhone. Easy.

MOTU 8pre has a built-in power supply and neither manual nor anything I can find online reveals the actual power need internally, nor even the power load at 110V – making it hard to estimate how much 12V power we’ll need for a typical production day. So that remains an unknown at the moment. The power rating will have to be on the back of the device, at least at 110V, but I’ll bet internally it’s not far from 12V DC (although it may have a more complex power need within the device, it’s hard to know).

As much as we’re avoiding paper – using iPad apps for clearances and metadata entry, etc – it will be necessary to print postage labels, etc, and scan in receipts and other documents. For printing we chose the HP OfficeJet Mobile 100 – it may even get through the journey on one charge! I suspect we’ll be able to charge via DC direct, but otherwise it could be charged from a 110V AC circuit at planned (power advantageous) moments.

Scanning duties will be handled by the bus-powered NeatReceipts scanner. If you like it, buy from Amazon, I didn’t have a good time with their ordering system. This should allow us to go as paperless as we can.

What I haven’t been able to find direct 12V equivalents are, as mentioned, the 8pre but also some of the battery chargers. In some cases I’ve been able to find alternate chargers (thanks Steve) and in others the amount of power they draw is so small that it may not be worth the effort.

The other big challenge has been calculating the total amount of power we need for production. It’s quite difficult to get the 12V equivalent current from the 110V stats. Sent me back to my high school days when I was totally on top of current conversion between voltages. Seems it was still residing in the back of my mind. Given the difference between average and peak load, I’ve asked for the peak hoping the difference between peak, and average will cover the things I didn’t account for!

Roughly half the power we need will go to production. Or putting it another way, without doing the production on board we could have twice the power available for propulsion, lighting, etc.


6 replies on “Solar Odyssey – Power”

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  1. Have you considered solar charging for your own equipment or at least some of it?

    Many an expedition have charged their cameras this way and have also used disposable expedition batteries.

    1. Yes, considered trying to charge each device independently but we would have to take surface area from the bigger, more efficient solar panels for the boat. It quickly became obvious that adding more master solar panels was the job. Plus, there really aren’t individual chargers with enough capacity to run our gear 8-10 hours a day.

      We rejected disposable batteries completely as being environmentally inconsistent with our message.

  2. A rewatching of Apollo 13 may be in order. Those folks really had power budget issues.

    1. They did indeed. And my cell phone has more computing power than NASA at the time! Apollo 13’s pin board computer had 32K of RAM??

  3. I’ve already been able to eliminate paper charts in my cockpit with the use of the iPad (the device people laughed about when they heard the name)
    I tend to leave all of my drives running, since I always thought that things in motion remain in motion. That concept might be flawed.

    1. In general I prefer to keep drives running, but in this haiku the risk of a start-up failure in the six months on two towers is relatively low, balanced against approximately twice the running time and power need. (It may turn out they’re running more than expected simply because editorial takes more time each day than allocated.)

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