> Anyone here charge their wearable with solar panels of some kind? Are you aiming for actually running the wearable off solar cells, or just using them instead of a "wall wart" charger? > I was thinking of getting a solar backpack [1], but then realized it > only puts out 7.2V and I'm guessing since it's not designed to charge > laptops that it won't run an AC inverter either. I think your main trouble here might be finding an inverter that runs on 7.2V. With the battery pack charged, you have 2.2AH available, which is not bad. My current wearable is designed to use 7.2V, so it could run off that. The thing is, since you would be drawing from the battery faster than you would be recharging it, the solar cells might not help much. I'm going to make a few assumptions here: You have or can get a 7.2 -> 120V inverter Your inverter, laptop supply, and laptop all together take 2A, constantly You are laying on your face at high noon in an open field on a sunny day (to point the cells at the sun) If that is the case, in about an hour and ten minutes, your laptop and power chain have eaten 2AH, and the battery is nearly flat. In that time, the solar cells have provided 400mAH [4], which is sufficient to keep the laptop/inverter running for another 10 minutes or so. Of course, during that 10 minutes, you'll pick up a bit more charge, but it won't be much. Someone who remembers more calculus than me can do the math in a continuous way, and get a better answer, but I think that's an illustrative approximation. If your laptop or other hardware is more efficient, or you get a bigger battery, then you get more run time, at the expense of charge time. 7.2V rechargeables are sold at hobby shops to run remote control toys. > So then I looked at the "XPower Pocket Powerpack 100" [2]. The battery > is designed to work with the included pocket inverter; however, there > appears to be no way to charge the battery from a solar panel. Am I > wrong? That thing looks pretty cool. The line "The Powerpack has a nickel metal hydride (NiMH) battery you can recharge using household electricity or 12 V DC power from a vehicle DC outlet" makes it sound like if you can supply 12V at some reasonable current, you may be able to charge it off solar cells. Whether you can wear a sufficient solar cell is another question entirely. > So now I'm thinking there just has to be a battery pack that can be > charged from a DC source (ie the solar panel) and strong enough to > power an inverter, even if it takes a very long time to fully charge. > > I took a brief look at the Solio [3], it provides 12V output not just > 7.2. But it can only output 8 watts so not much use trying it with an > inverter I don't think. 8W at 12V means 0.667A. Unless you have a very efficient laptop, that may not be enough power. If you don't mind long charge times, then using solar energy becomes a lot easier. You can get a big solar array, and charge one set of batteries at home while you use another set out in the world. The main downfall of modern photovoltaics is the power to size ratio is poor, but if you don't have to carry it, that's not a problem. In my opinion, this may be the way to go for solar until the energy density gets higher. If you can get a battery that matches the power requirements of your laptop, you can use it in place of an inverter/laptop power supply chain [5]. That will get you a bit more time, as the inverter and laptop supply are not 100% efficient. Don't use lead-acid batteries like that guy did, they are enormously heavy. I get away with using 7.2V toy car cells because I built my own power regulation board. They are still by far the heaviest part of my wearable Also, don't let me discourage you. It may well be that there are solar products that will fit the bill, or something you can make. Abe > [1] http://www.voltaicsystems.com/bag_pouch.shtml > > [2] http://www.donrowe.com/inverters/xpower_100_pocket_pp.html > > [3] http://www.solio.com > [4] http://www.voltaicsystems.com/solarpanels.shtml [5] http://www.qotile.net/blog/wp/?p=347 _______________________________________________ Wear-Hard mailing listhttp://www.haven.org/mailman/listinfo/wear-hard
From Wear-Hard Mailing list Archive (WH)
Maintained by R. Paul McCarty
Archive created with babymail