Solar Laptop (not portable)

Sammaron
Sammaron Registered Users Posts: 15
I have been absent from this forum for a while now, and had this thread which really helped me out. However, I didn't want to drag back such an old thread, so I have started this one.

My plan has changed slightly since my original thread. I am trying to now put my laptop totally on solar power using an 18 watt Sunsei solar panel, and a 12volt, 12ah battery. The laptop draws about 30 - 50 watts (hovers around 30 once totally booted, upper 40's and 50's for the first 5 or ten minutes. I will use a 40 watt draw in my calculations.) At 120VAC, that is about .3 amps. Since i plan on using an inverter for my battery, I use 120VAC as the voltage. I am trying to calculate how long I could safely use my laptop (which, unfortunately, must be plugged in at all times :( ). I have been told that dropping a battery below 50% charge is bad, so I will take that into account in my calculations, meaning I can charge for 6ah worth of charge. According to my math, I could charge it safely for approx. 18 hours safely. That is more than enough. I got this number by multiplying .3333a x hours = 6ah, and 18 hours is 5.994 ah. Is this correct?

Now, to charge the battery, it would take about 4 days (144wh/36wh = 4 days. 144wh is the storage capacity of the battery, just in wh, and 36wh is the wh I'd get per day with a 50% efficiency on my panel. 9w * 4h of good sun = 36wh/day.) However, it should only take 2 days, because I will not drop the battery lower than 50% charge. Right?

I'm sorry if I'm coming of dumb, but I'm trying to get everything straight, and I finally think I may have, and just need to make sure.

One last question: My idea was to buy a 12 volt 12 amp hour lead acid battery. However, my panel provides a 15 VPMax, while I learned from my previous thread that that may not be enough for a lead acid battery efficiently. However, i see little alternative. Will i do harm to my products if the battery is charged at too low voltage?

Finally, assuring my battery is being treated well. I want to know how much juice my battery has. Is there a tool, or method to discovering this? It'd be nice to just have a little meter :) How do most people with small setups as mine keep tabs on this information? I'm working on a budget, so the cheaper the better.

If needed, information on the solar panel is as follows:


Solar Panel

* PV module performance, rating at: 1000w/m2, 25C
* lpmax: 1200 mA
* Maximum Power: 18 watts
* Minimum Power: 14 watts
* VPMax: 15 volts
* lsc: 1225 mA
* Max Sys V: 50volts
* Voc @ 0 C: 24 volts

Thanks for the help. I think i'm making progress :)

Comments

  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    Re: Solar Laptop (not portable)
    Sammaron wrote: »
    12 volt 12 amp hour lead acid battery

    Will i do harm to my products if the battery is charged at too low voltage?

    12V, 12AH is NOT a very big battery, and cycles to 50% will kill it MUCH sooner than a 48AH battery cycled to only 20%

    You do not have a charge controller factored into this. I think you are trying to to just recharge by time? That will work fine till you sleep in one day, and don't use the laptop enough, and the solar cooks the battery. A charge controller prevents that.

    Too low of voltage prevents a full charge

    Your SEALED "clone" battery, needs to be charged properly, at the Right Voltage, for the right period of time. This varys from AGM to GEL construction, so knowing the physical construction of the sealed battery is important.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Solar Laptop (not portable)

    By any chance is there a 12V "mobile adapter" available for your laptop? If so, it would simplify things considerably. If I understand right your currently (sorry about the pun) looking at an 18 Watt panel charging a 12V battery to run an inverter to power the laptop's AC adapter. If you could run the computer directly from 12V you could skip the expense and power loss of the inverter. In either case, as Mike said; without a charge controller you're asking for trouble. And that panel may prove insufficient, depending on how much light actually falls on it during the day. Using your 40 Watt average, the panel would have to be in full sun for 2.5 hours for every one hour of computing time. That's not a very good return.
  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    Re: Solar Laptop (not portable)

    There are universal car/plane adapters for lap tops,, 12vdc in, regulated dc out with the proper end for specific brands. I have one,, but it is not here so I can't give you a make/model. All in all a pretty good way to recharge a lap top either from the car directly or a car battery.

    Tony
  • RandomJoe
    RandomJoe Solar Expert Posts: 472 ✭✭✭
    Re: Solar Laptop (not portable)

    Your current calculations are off by a factor of 10. The laptop may be 120V, but the current that matters is the battery side, which is going to be roughly 10x higher (or 3.33A) at 12V. In addition, there will be a little more than that for losses induced in the inverter.

    3.3A draw from a 12AH battery is pretty stout, it isn't going to be very happy with that long term. Most of them seem to be "ideally" specced for something closer to C10-C20 current rating, which would be 1.2A down to 0.6A.

    Since you would be drawing such a high current, it isn't as easy as dividing AH by amp draw to get runtime, as the AH rating is based on a 20 hour (or 0.6A) draw. The higher the current draw, the shorter your runtime will be. So 6AH / 3.3A = 1.8 hours, but you probably won't get 1.5, maybe even down to just 1 hour. And as was already mentioned, taking a battery down to 50% DOD every day is going to be a quick way to kill it. Try to stay above 25% DOD.
  • Sammaron
    Sammaron Registered Users Posts: 15
    Re: Solar Laptop (not portable)

    Sorry for not being clear, I am using a provided solar charger, meant for this panel. If you need the stats, that's no problem (if you don't wanna wait, it's in the old thread.).

    My lack of knowledge shines again. It was my belief that battery's necessary voltage for a good charge was only linked to their voltage. Apparently, it is also linked to the manufacture of the battery as well. I'm afraid, unless their is a method to increase my solar panels output voltage, i'm stuck between a rock and a hard place. I do not have enough money to purchase another panel. I've read AGM should be charged at about 13.8v, which is still pretty high for a 15VPMax. If there is no feasible option, would it be possible to charge a 6 volt battery, even though the solar panel is meant for 12 volts? If I purchased a different charge controller?

    Oops:blush: I spent 15 minutes trying to decide how voltage could increase and current could stay the same. I guess it can't :) That factor of 10 killed that plan.

    And again, that problem would not be avoided by making the laptop drop to a 12 volt draw with a DC plug. Seems i'll be needing a larger battery, at least a 33AH. I'll look into it.

    Clearly, this is more trouble than I had originally planned for. I may drop this to charging small portable devices (PSP, cell phones, DS, ipods...). That may be a much better option.

    Thanks for all the help :) What do you fellas (fella-etes too, of course) think?
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Solar Laptop (not portable)

    Let's see if I've got the wiring concept straight:

    Solar Panel -> Charge Controller-> Battery-> 12V Adapter-> Laptop

    The battery here serves two functions; moderating current draw and holding reserve capacity.

    The basic problem is that the panel cannot supply enough power to run the laptop, much less run it and recharge the battery. Under optimum conditions that panel is only capable of recharging maybe 30 Amp/hrs - without running anything else - so putting in a bigger battery isn't going to help; eventually it will go dead.

    I think this needs a rethink, especially if you can't get a bigger panel.
  • Sammaron
    Sammaron Registered Users Posts: 15
    Re: Solar Laptop (not portable)

    That was the basic idea, but I wasn't intending to charge the battery via solar while charging the laptop. In either case, my laptop has quit working anyway, so the idea has been scrapped. Now I simply want to get a 15ah 12 volt battery for charging small portable devices. However, with a 15 VP max on my panel, the worry is it cannot provide enough power (~13.8v) to charge the typical 12v battery.

    This is what I am trying to do:

    Charge a ~15AH 12v battery, and use that to charge cellphones and portable gaming devices. It needs to be cheap, and not be harmful to my appliances.

    This is why I can't.
    The battery companies that are generally trusted (Deka, Crown, Trojan...) don't seem to be sold at that low capacity, and i have become hesitant to buy a generic store brand. Also, I have gotten the impression 15VPMax cannot safely charge any kind of 12volt battery.

    What I plan to do
    I see no alternative to buying a store brand battery, and hoping it works well. I will buy this battery, unless this will absolutely will not work. I do not need this to be perfect, just safe. If the 15VPmax is simply not sufficient, is there a way to bump this up without another solar panel? If not, am I screwed?

    :D This is tough stuff. Sorry if I come off rude or stupid. I'm simply worried I won't get this problem solved during this summer, and miss all the good sun. Thanks for all your alls help :D
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Solar Laptop (not portable)

    Go ahead and try your plans... The solar panel is not optimum for your needs--but will probably work just fine. May not equalize the battery very efficiently (voltage may be a bit low)--but with a sealed battery, you don't want to equalize at too high a voltage anyway (and cause the vents to blow).

    A simple PWM solar charge controller, with a voltage set point that matches the requirements of your battery, should work fine with your system.

    If you get several years of good service out of your system--you should be happy.

    You can always use a separate charger (like a 1 amp wall wart) for when you need a faster charge and/or bad weather. Don't leave the AC charger connected to the battery--I find that even the small charger will overcharge/kill the batteries if left on for days/weeks at a time.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    Re: Solar Laptop (not portable)
    Sammaron wrote: »
    Also, I have gotten the impression 15VPMax cannot safely charge any kind of 12volt battery.

    Well, that's the voltage for max power. if you draw less than that, you WILL get a bit higher voltage, maybe 17V.

    But the problem is, your charge controller. The series diode and FETS in it, may drop 2 volts. Maybe your best bet, is a well calibrated volt meter, and continually monitor the battery charge voltage, and when it gets too high, stop charging. That's really the same thing the PWM chargers work, only they are automatic, and need 2 volts of overhead.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,