Go Solar, Or Go Home

Last modified on July 27th, 2009

I’m up at Cultus Lake now, doing some weird cross between camping and working. I honestly wasn’t too sure if I’d get 3G up here, and had planned to head back into town during the days. But given how I have four bars on my phone, and that 3G is working great, I might just work from up here.

Solar Laptop

To that end, I went back home a while ago and picked up my 15W solar panel and my 75Ah deep cycle battery. Right now my laptop appears to be drawing about 25W, which is fairly awesome considering I’m charging it and also working on it at the same time. At 120V, that means it’s currently drawing roughly 0.2 amps (200 milliamps). I’m currently using an inverter attached to the deep cycle battery, and since power must be roughly conserved across it, that means the battery must be putting out roughly 2 amps at around 12V. Since its capacity is 75Ah, that means it should be able to power my laptop in this configuration for appoximately 75/2 hours, or 37.5 hours.

When the solar panel is in full sun though, it puts out around 15W at 12V. The delta between the two is about 10W, which means that the battery is still putting out a difference of about 0.8 amps. At 75Ah, that means it will roughly last for around 93 hours, as long as the solar panel is in full sun.

Either way, I think it’ll be enough to last me for three days up here. Which means I can work from the comfort of my picnic table here. This is the first time I’ve used my solar panel like this, but it’s been something I’ve always wanted to try. I’ll put a few more photos up later, once it cools off a bit and I’m motivated enough to whip my camera out.

5 responses to “Go Solar, Or Go Home”

  1. Duncan says:

    Sounds like fun! Now u need a plug in cooler to chill the beer!

  2. That is pretty good power consuption. Thinking I may come up and say Hi tomorrow what site are you in.

  3. cloudface says:

    Hey Duane,
    Know this is an old post but it relates directly to something I need to know so thought I might just comment just in case..

    I’ve got two 40Amp/hour deep cycle, a 10W solar panel and a 300W inverter and want to use them to run my HP laptop for some DJing in the park.

    The laptops power pack says 19V, 4.7A, 90W max.

    I’ve tried out the set-up once and managed to charge my laptop battery to over 70% in about an hour and a half while playing music at full volume and fiddling with other programs starting at about 3:30pm in the afternoon.

    I thought it was all fine and good to go but talking to my computer head uncle (read: talks about Unix, has at least 10 PCs) the other day he told me the solar panel would spike the power and over volt the laptops power pack or something and burn it out or wreck the laptop even.

    From reading your post it seems like he might be completely wrong but I thought I’d just check as you seem to know what you’re talking about.

    Any advice you have would be much appreciated.

    PS. I live in Australia so our devices usually run at 230-240v and I’m not planing to run speakers out of the laptop (using a car battery and car amp for that)

  4. Duane Storey says:

    Well, I’m no expert or anything, so don’t take my word as gospel. Technically the inverter is powering your laptop, so as long as the voltage/current from that is pretty stable you should be fine. Normally when you hook a solar panel up to a battery, there’s a chance that the solar panel could over charge the battery. That is, if it’s still sunny outside and the battery is full, the solar panel will still be trying to shove amperage into it. For 10 watts, that’s probably not a huge deal, but as you add more wattage to the array, you really need to use a solar charge controller (which connects between the solar array and the battery) to stop that from happening. Basically when the battery is full, the charge controller will disconnect the array from the battery to stop that from happening.

  5. cloudface says:

    Thanks heaps for the response Duane!
    I got myself a copy of NCH for the lappy-which for some reason won’t tell me the volts (maybe a Windows 7 capability problem) but at least it’ll tell me if my CPU/HD is overheating-and I can grab one of those AC power meter devices maybe to double check myself if need be but as I’ve also Googled a bunch of solar powered laptop chargers I think my uncle may have got it wrong or been a bit OTT.
    I mentioned to my mother about what he said vs your example and she said something about “Aaahhh-you know uncle Pete he’s always a bit too overly cautious with computer things”..
    Experience works just as well as “being an expert” for some things and you not going “yeah, I did end up frying my laptop” is helpful enough..
    The deep cycles have gauges and fuses on them and the inverter has a fuse as well so I’m fairly certain I’m going to end up being 5 types of protected in the end.

    Thanks again.

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