Solar Power Netbook

[cmabc123]

Hi,

I had a question about a solar set up. I'm going to be doing some boondocking in the future and wanted to set up a solar/wind system that would indefinitely power a netbook. This is the only draw from the system, but the netbook runs about 17 hours a day. No internet, but I would be using it for general wordprocessing, watching video, and listening to audio files. The netbook is an Acer One Aspire. 

I'm new to alternative energy so I'm having a difficult time figuring out what exactly would work. I have purchased an adapter for the netbook that plugs into a cigarette lighter and then got a DC extender that the cigarette lighter plugs into and it has alligator clamps on the other end to connect to a deep cycle battery. I did this to remove the need for an inverter and it works great. Right now I'm using the netbook to write this and it's been running off the deep cycle battery for two days and 3 hours (37 hours). I don't know how long it will last before the battery runs out of power. 

Now I'm looking for a way to keep the battery charged indefinitely while running the netbook for 17 hours each day, every day. I thought a solar/wind combo would be perfect, but I thought I would take it step by step and ease into is slowly. What size of solar panel would keep a deep cycle battery charged while also running the netbook? The battery is a 115 ah marine battery but I could be using a smaller ah in the future. 

I'm going to be in a pickup cabover camper so space is limited. I would really like something that was somewhat portable (i.e. not mounted on the rv roof) - something I could lay out on the ground or lean against the truck once parked. 

Cost is somewhat of an entry barrier also, so the cheaper the better.

Thanks for any help.

cm

[DamonHD]

1) Do NOT run the battery right down: you'll ruin it.

2) Have you actually *measured* the power draw of your netbook doing various things such as work processing (ie mainly idle), watching videos, with the screen blanked and so on?

3) Have you set the netbook up to dim the screen and so on within a minute or two of you stopping using it as that will save a lot of energy?

Once you've done (2) and (3) then you can start doing the sums for the rest.

Note in particular that conservation, and avoiding the most power-hungry activities, is the very cheapest addition to your renewable energy system by a very long way.

Rgds

Damon

[cmabc123]

I appears as if an Acer Aspire One Netbook has an approx 15watt draw when under "normal" use and around 4.5 watts when idle; almost nothing when asleep (much more when actually running and charging its internal battery).

The test deep cycle battery I'm using is 115 ah. 

What I would like to do is keep the deep cycle battery topped off and have the solar panel "run" the netbook most of the time (during the day) and only draw down the deep cycle battery when it's dark (early morning, late evening). 

I figured:

Netbook  (15 watts / 19volts = .79 amps) [am I doing this right?] or is it 19volts / 15 watts = 1.27 amps?

Does this mean I need to match the amps consumption from the netbook with a solar panel that is producing at least this or more? So, either way above: if my solar panel is producing 1.5 - 2 amps on a regular basis then it will power the netbook most of the time and keep the deep cycle battery topped off?  Am I missing something here? Sure seems like it.

Thanks for any help.

cm

[mab]

I assume the 15watts is a manufacturer's estimate? Actual power consumption may be different.

I=P/V so your .79amps at 19v is correct,but you're more interested in the draw from the battery (i.e. at 12v:-

Acer draws 15w. So the 12v to 19v adaptor (assuming 80% efficiency) draws ~19w; so amps from battery =
19/12= ~1.6Amps.

1.6amps for 17 hrs/day = 27Ah/day

sizing the panel is a bit more complicated - depends on how reliable your sunlight is where you are; if you're prepared to re-position the panel every few hrs to make the most of it.

If we assume (arbitrarily) 6hrs of full sun a day then your panel would need an Imp rating of at least 27/6 =4.5Amps. Note that the battery isn't 100% efficient (i.e. you'll need to put more into it that you get out) so 5Amps would be better.

mab

[cmabc123]

Hey thanks for the reply.

So it looks to me that it would be cheaper overall to keep the battery topped off with a small generator and use the generator to power a cooker/hot plate when it's running to cook with, running a little bit each day. 

Last time I did this I used a deep cycle battery to power a tv, satellite system, and full size laptop. It would not last one day and the battery was flat. With a netbook I have my tv/movie videos + full functional laptop in a pint size package for a fraction of the power draw (lasting several days so far on one charge running the netbook 17+ hours a day).

I think for the all-in costs a small generator might be better, especially since I won't be getting peak performance out of the solar panel anyway, since I'll be boondocking in coastal areas where it's cloudy much of the time. 

Thanks very much for the info.

cm

[XeonPony]

A sunsaver 15 Mppt and 1 200w pannel and you'll have power to spare! Or to save money a 135w pannel.

I all ways use a 2 times the load + night draw formula and been running 3 years off solar with out a hitch! (Mind you I draw 80AH a night!)

Using the numbers pressent 27AH per day Times 2 = 54Ah / say worst case cenario 3.4h = 190w pannel Now becuase I am being insanely over estimating you could easily go at 120w pannel but with them being so cheap now days might as well go with the larger one!

And the MorningStar Sunsaver 15MppT is a great little controler with load function built in it will give you the best performance with "Just leaning it against the truck" and prevent over discharg!

Here in Canada that total rig up is 351 for the controler to the door (I made a temp sensor for it with a 10K ntc thermister)
and I had 270w of pannel so you just need one so 500 for the pannel, less for you most certainly!

[ghurd]

So it looks to me that it would be cheaper overall to keep the battery topped off with a small generator and use the generator to power a cooker/hot plate when it's running to cook with, running a little bit each day. 

I think for the all-in costs a small generator might be better, especially since I won't be getting peak performance out of the solar panel anyway, since I'll be boondocking in coastal areas where it's cloudy much of the time. 

Cheaper?  I am not so sure about that... unless this is a one-time deal and the stuff will never be used again.
Gas, decent battery charger, cheap disposable china genny, more gas?
Or gas, decent battery charger, good genny, more gas?

Better?  I say no.
The genny will be running full blast, and the battery charger will get the battery up to regulation voltage in a short time...
BUT
The battery will not be truely 'full charged' until its been at regulation voltage for a Long time (hours?), and most of that time the charge current would be very low (less than 3A).  The noise from the genny would drive me bonkers.

If I understand what you plan to do, I would do it different:
-  I would use the truck as the initial charger in the morning.  Long cheap (#10?) jumper cables to the deep cycle first, then start the truck and let it idle for 10~15~20 minutes.  Naturally, remove the jumper cables when finished.
-  Then I'd let the solar take over.
-  Repeat the truck procedure in a few hours if the solar is not keeping up.

I bet you could do it with an 80W panel on good days.
120 ~135W would obviously be better.
I would do it with TWO 60~80W-class panels instead of a giant single panel, because moving a 135W panel around is going to be a pain in the butt.

Not sure it would be worth the cost for MPPT in a situation like this.  Almost a $200 (actual retail) difference between SS-10 and SS-MPPT?
(MSRP $59 and $295)
That can buy a bigger panel, or another panel.

Like Damon said, Do NOT run the battery down.
I think keeping it above 12.2V is very important.
G-

[thirteen]

To me the biggest thing will be the cost of gasoline and alot of wear on the truck engine. You could always but a generator on a bike and peddle for power. I agree a 200 w solar panel would really help save on gas.

[ghurd]

I suppose it depends on where you are.
Around here, rust (body, frame, gas tank, etc) kills trucks.  Suspension and steering, etc, go before the motors.
The scrap yard shredder up the road eats a steady flow of vehicles (with good motors).

My line of thought was $100 ~ $150 ~ $250 genny and $75 battery charger not required, which would buy a lot of gas to idle a truck motor for a long time.  Not an ideal solution, but functional for a short boondocking vacation.

If I was doing it more often, or for long stays, maybe I'd build a gas powered DC charger (3.5HP B&S lawn mower engine and treadmill or ECM?), but I wouldn't use an 110VAC genny to a DC battery charger.
G-

[thirteen]

gas here is 3.89 today

[Bruce S]

If the ACER is the one that came with windows 7 basic, then I can say it's a real nice unit as that's one of the ones I'm testing out for our traveling people  . Difference is we get them with SIM cards that are 4G LTE ready.
Another thing you can do is go into the battery monitor section of the laptop and adjusting it's settings.
Tell it to turn off HD when idle more than 10Mins (or adjust it to your needs) dim the display, turn off a bunch of not needed "stuff".
The 15/19=.79A is correct. I'm curious about the cig-lighter adapter you have, send me a link even via PM if you don't mind, I'd like to look at these as well.
Once I have at least one, I'll pull it apart and measure current draw directly.
IF you're gonna be "camping" then like GHURD said a couple smaller panels will be easier the pack away and to lay around even on-top pf camper when parked. You could also top off the trucks battery with them if you chose to go with a smaller battery. 115Ahr seems pretty big if you're just using it to power the laptop.
Remember to have fun with it:-)
Bruce S

[XeonPony]

A 135w kyroshera is easy to hump around! I move my 4 around with me all the time, pain in the %$#%@ rear to bolt/unbolt them all the time but easy to move. espesialy just 1!

[birdhouse]

like said, a 135w panel is pretty easy to move.  i can carry a 245w panel up a ladder and onto a roof, and i'm a skinny 170lb guy. 

another option yet would be to yank the truck battery, and replace it with two trojan t-105s.  most trucks have enough room to fit them.  then you just start the truck from time to time to get your juice for the computer.  most truck alternators are in the 100-170 Amp range, that would charge up the trojans very well!

adam

[OperaHouse]

I started buying 45W panels because they were in a location that would have to be moved.  It was only a $13 premium for two over a 80W panel.  12V frankly is a looser.  Regulators for me in the future will 24V or a lot higher down to 12V.  You just can't operate a 12V array at power point and get any increased power.

[Bruce S]

I started buying 45W panels because they were in a location that would have to be moved.  It was only a $13 premium for two over a 80W panel.  12V frankly is a looser.  Regulators for me in the future will 24V or a lot higher down to 12V.  You just can't operate a 12V array at power point and get any increased power.

Operahouse;
For those off-grid you might be correct.
For us using PVs for house backup from storms, just like the one that rolled through Missouri last Saturday, I personally don't believe your statement about 12V being a looser to be true.
I can attest to the very fact my system worked flawlessly, even while cars and skylights were being demolished by baseball sized hail my poor little system was fairing quite well.
FOR the little system he's looking to hump around, a little 12V system is perfect.
Just my point of view 
Bruce S

 

[richhagen]

Well since he already has the 12V adapter for the net book, and is intent on using it in a pickup which likely already has a 12V electrical system with an alternator and a 12V starting battery, 12V makes a lot of sense for this project. 

You could probably come pretty close to powering that computer most of the time with a 100W or so of solar.  Since you have a handy 12V alternator in your vehicle already, I would probably scrap the generator in favor of rigging a system to charge the battery from the pickups electrical system for those times when you just can not get enough sun. 

I have charged 12V batteries from a vehicles system in a pinch by paralleling them with the starting battery while the engine is running using lengths of wire.  As long as the wire is selected to keep the charging rate within the amperage limits of the deep cycle battery, and under the output amperage of the vehicles alternator, and under the current limit of the cables wire gauge, it should be fine as long as you monitor the receiving batteries voltage and disconnect it before it were to overcharge. 

For example, a 100 feet of 10 gauge cut in half and used as a 50 ft cable could be used to connect the batteries.  It would have .1 Ohm of resistance in the line and with a difference of 4 volts between the systems would limit the current to 40 amps, which should work out ok for non enclosed occasional use provided your deep cycle could handle at least that much charging current.  If the difference between your depleted battery and your vehicles battery while charging was a greater voltage, you could use a bit longer cable.  Just throw 50 Amp clips on both ends, mark each end of one cable for positive and one for negative.  I would also put a break on one of the lines in between with clips or so to connect it so that I did not make or break the connection at the batteries themselves too.  I don't think it would give you much issue for occasional use when the solar panel(s) could not keep up with the charging, and it would beat carrying a generator around in my opinion.

[OperaHouse]

You totally missed my point.  Ther is no power point gain in going from a 12V panel to a 12V battery.  Buying a 90W panel gets you maybe 50W at best into a battery.  Two 45W panels in series with power point regulator will net you about 70W into a 12V battery.

[DamonHD]

OH: I'm not understanding you either.

A 12V 'nominal' panel is well above 12V Voc and Vmppt, and via an MPPT regulator/controller into 12V battery can be pretty much as efficient as at any other nominal system voltage.

Can you explain again what you mean?

Rgds

Damon

[OperaHouse]

Power point of panel is about 17.5V  and battery is 14.5V.  Blocking diode loss is another half volt.  Then there are lead losses.  Internal losses in a power point regulator are another volt.  Switching regulator efficiency is around 85%.  So there is no way to gain any power.  These voltage losses are fixed.  Adding a second panel in series is the only way to gain anything.

[DamonHD]

Hi,

Sorry, still not understanding you fully.

For example, a decent MPPT regulator may have a 'perfect diode' or the equivalent at its input, so no significant voltage drop.

Also, the time when you care most about getting Watt (hours) into your battery is when its voltage is low (say) around 12V, and your panel Vmpp may be higher because it's cold out there (ie winter).  Neither Vmpp nor Vbatt are fixed quantities.

For me MPPT seems to be very good news and I see a significant voltage differential between Vsolar and Vbattery which is largely being converted into extra amps AFAIK.

But I'm probably being slow, sorry, it's been a long day (well including a long and pleasant lunch chatting with SparWeb and sampling traditional London cuisine!)...

Rgds

Damon

PS. I note that the Morningstar SS-MPPT-15L that I have claims an efficiency of ~92% to 97% over most of its power range at 17Vmpp, in fact never below 90% and more typically above 95%.

[OperaHouse]

Well there you go.

I have an idea how they got those numbers and my opinion hasn't changed.   

[Bruce S]

Having found the cigarette lighter adapter and will probably order one .
The adapters he wrote about is a boost type. Takes in 12-13.5Vdc and boosts up to 15 -17Vdc or 18 - 20Vdc depending on which one you buy.

I still don't see the issue with having the 12Vdc setup for his unit. while out traveling up in the Banaue region of the Philippines with Rich Hagen, we used the little 10 watt panels and my little 5 watt fold-n-go unit and had no problem charging both the 12V NiCd packs and our cell and camera batteries.
Possibly Rich will pop back in here with the model of the controller, is a nice unit!! we strung a bunch of different stuff up to charge.

Cheers;
Bruce S

[richhagen]

The controllers were just basic units like these:
http://www.amazon.com/Solar-Panel-Charge-Controller-Volt/dp/B001THT0PY
They really don't seem to be much more than voltage switches. 

My take with regard to the system voltage would be that he already has a 12V battery, a 12V adapter for his laptop, and a vehicle with a 12V electrical system he can adapt as a backup charging mechanism.  I would see little advantage to spending what would be required to switch everything around to a different voltage, even if the efficiency was a reasonable percentage better.  If one doubles the voltage, the current gets cut in half to move the same power around and the line resistance losses, everything else being equal would be quartered, however, I don't think that those benefits justify all that he would have to purchase to accomplish his modest goals.  It seems far easier to just make it work with what he has and a small solar panel and an inexpensive controller such as Ghurd Heavy Industries model, or one similar to the little one we used out there.

[theshadownose]

Clarifying what I think Operahouse's point-    having 2 - 12 volt panels in parallel, or 1  24 volt  135 watt panel, run into an MPPT controller, set to output 12 volts to the 12 volt battery. 

benefit
"possibly" higher efficiency/ more power into battery.
less loss in wires from panel to MPPT

cost
requires more expensive controller? 

everything downstream remains the same-  still uses 12 volt battery, 12 volt adapter.

I have no opinion,  just trying to avoid the back and forth

[cmabc123]

Well since he already has the 12V adapter for the net book, and is intent on using it in a pickup which likely already has a 12V electrical system with an alternator and a 12V starting battery, 12V makes a lot of sense for this project. 

Hi rich. Thanks for the info here. In my previous attempt I had a truck/camper and a deep cycle marine battery. I had a wire run from the alternator to the deep cycle battery with a block in the middle to keep it from going the other direction (keep in mind, someone else set this up for me). The truck alternator charged up the battery while driving. I knew NOTHING about electrical and this was almost 20 years ago, so I was very power hungry (I needed a television, full sized laptop, satellite system, etc). It would draw down the deep cycle in less than 12 hours.  Plus, I was driving daily at least 20 minutes back and forth to work, so it had several chances to charge the battery.

My concern is how long it would take to top off a battery each day? Also, does the alternator charge the battery even if the truck is not moving (i.e. just idling in place)? Doesn't it have to reach a certain RPM? I will only be driving to town once a week, maybe only twice per month. The rest of the time I will be parked in one spot. But I will need to start the truck every day or so just to keep it running so this might work well.

Would it really be cheaper overall to charge it with the truck alternator than a small generator? Or is it the combination between the 100watt solar panel and the truck alternator? Would the truck alternator be enough, if I ran it 15 minutes a day to top off what I used the day before?

My concern about solar is my location will most likely be pretty cloudy/cool most of the time. It will be in the pacific northwest, in the coastal areas. Likewise, where I park will probably be under trees, by creeks, since I will have no air conditioning and will want to keep the camper cooler. But I will always be near a road/on a road so I will have access to open areas, and landings with wide open areas, so a solar might work well depending. 

I don't think it would give you much issue for occasional use when the solar panel(s) could not keep up with the charging, and it would beat carrying a generator around in my opinion.

This would not be an occasional situation. It would be full time boondocking with literally no shore power accessibility. So whatever system I had would need to be a close looped perpetual system, producing equal to or preferably more power than my netbook needed to run 17 hours each day, every day, 365/year. 

Thanks again to everyone for the info.

cm

[XeonPony]

In other word exactly what I'm doing!  I used to use 2 * 135w pannels and a  Morning star sunaver 15 mppt it ran me just fine even during cloudy days I'd pull in 260 to 300 wh a day and I run allot! So youd be vbest off spending the extra for a good quility mppt and 2 135w pannels or one 230w pannel.

[ghurd]

"vbest off spending the extra" $.
I disagree.
It's only a 115AH battery.
200W, PWM or MPPT, is going to get it up to regulation voltage quick enough either way.  After that, the MPPT is not helping, and the large panels are basically doing 'not much'.

Even a 60W panel in cood conditions will get an unloaded 115AH up to regulation voltage in a short time.

Instead of throwing more money at the charging system, I would put a bit toward a pair of 220AH 6V golf cart batteries ($160?).  That would store more power (2X) more efficiently, which would arguably allow for a bit smaller charging system.
G-

[birdhouse]

now learning that this is a "permanent" situation, not just a vacation fix, i'm with ghurd on this. 

i'd invest in a pair of 6v golf cart batteries.  sams club one are ~90 a piece now???  wire them series for 12v, and charge them from the "cheapest largest watt" (like that exists... ) panels you can find. 

to deal with the shady camp spots, you could even make a 75' extension cord with a few #10's pulled through an old garden hose to set the panels where the sun is??  this would surely beat lugging the panels AND the batteries out to the sunny spot!

most anything beats a generator, IMHO purely because of the noise factor.  even those super quiet honda EU 1000's get on my nerves after an hour or so. 

adam

[XeonPony]

You need the power to charge  the battery with out the power your just condeming the batery to early death!

I all ways base my systems off 2 times night time load @ Worst case, so no matter what the batteries all ways get to full float.

So I agree he will win with geting larger batteries but to go with the larger batteries he will need the solar to do it, So what first? The chicken or the egg?  In my books, with out the chicken there is nothing to roost the egg to hatching

So I'd go with maxing out the solar side of things, better to have more then enough solar then not enough! Then if he finds his batteries wanting, with all the money he'll save on gas can be used to upgrade the batteries.