Powering a Laptop With Solar Power

[aaron_c]

Hi Yall

I plan to be doing some off-the-grid camping and RV boondocking in the coming year and I'm trying to figure out how to power my consumer electronics with a 12V solar system. For smaller things like phones or even tablets it's not that complicated; there are cigarette lighter-style 12V USB outlets that supply enough power to keep those devices charged pretty easily. However for a laptop using as much as 90 watts one of those 12V cigarette lighter-style USB outlets won't cut it--they don't supply enough power. But people living off-grid must have a way to charge their laptops. How do yall do it?

Here's my thinking so far. If I've missed a simple solution then I'd love to hear about it, but otherwise here's my thought process and what I've come up with. In particular I'd appreciate feedback on whether option 3 is even possible. Anyhow, the options for charging a laptop with a 12 V solar system:

1. I just put up with sub-optimal charging. Actually, I'm not even sure that this would work at all. If a laptop expects to be charged via a USB cord at 20V 5A but it only has 5V 3A available, will it be able to take the lesser amount? In any case I'm not excited about this as it would mean that I wouldn't be able to work on my laptop for 8 hours a day, which I'd like to be able to do.

2. I use an inverter to power the 110V regulator that came with the laptop. However I don't want to do this for a few reasons: A) It'll waste power to convert DC current to AC current then convert back to DC current. B) I was hoping to limit my inverter use to appliances that didn't require a clean sine wave because "true" sine wave inverters are more expensive. C) I have health concerns regarding the dirty electricity coming from even most "true" sine wave inverters, so I don't want to keep the inverter on for hours at a time. I know not everyone thinks these are legit reasons but please, just humor me.

3. Find a way to combine the power from multiple 12V cigarette lighter-style USB outlets. I've read that this is what USB-Y cords are for, so in theory I should at least be able to combine the power from two plugs into one. At the very least this should let me combine two 5V 3A plugs to get 30 watts in total. Of course that's not enough so I'd need to combine two of THOSE together to get 60 watts, and then I might need to combine that with another 30 watts worth of power to get my 90 watts (which I've read is what a lot of laptops require). I'll try to make a diagram:

90 Watts of Power from USB
/ \
60 Watts 30 Watts
/ \ \
30 Watts 30 Watts 2X [5V 3A Plug]
/ \
2X [5V 3A Plug] 2X [5V 3A Plug]
​

So as you can (hopefully) see, in this scenario I'm trying to combine a total of six 5V 3A plugs into a single 90 watt power source for my laptop using USB Y-cords. Is it possible to use multiple layers of Y-cords like this? Is there some other, simpler solution that everyone uses? Thanks everyone!

 

[Optimist]

If you're after 18 volts DC, you could run 3 6-volt fork lift batteries to give you that, and most of the solar panels I've seen can be set to give that voltage. Charge at 6, pull 18 for use. I've done this 12/48 for some equipment in times past with lead acid batteries.

 

[HandLoad]

Howdy! Welcome!

Hey Aaron - after You get settled in, maybe go to New Member intros, and give a thumbnail of "You", if Ya wanna!

Here is what I know from waay over here, may not apply to You and Your equipment, so if You agree to double check everything and Hold Harmless Me, The Site, and Every Sentient Being that ever lived on this Ball o Dirt, here goes:

Most Laptop Power converters these days say something like : 86 - 265 VAC, 46 - 65 Hz. That tells you that they are what is called a "Switching Power Supply" - means that piece of gear is pretty INsensitive to Power input (within those very generous limits). So, You can use a Cheep Harbor Freight or Ling Wha inverter to put power in the AC Plug of the Power Converter/Charger. Really crappy inverters provide a really sorry Square Wave Approximation of a Sine Wave, but since you have a Switching Power Supply, it will be fine with that.

Yeah, you are losing maybe 50% of the Power from the Solar Panels going into the charger.

About the only effects you might notice are a humming/buzzing just a bit louder than when Laptop Power Converter is plugged into the Mains, and, a bit more heat at the Converter. If You are careful to not bury the converter in blankets, and maybe hang it up in free space, it will do OK. If it really gets hot, maybe smelly on a hot day, wait till ambient is a bit cooler, then run/charge.

Regards,

Big Ugly Guy

 

[HandLoad]

Oh Yeah: don't use Method 3. You might release the Magic Smoke!

And Method 1 won't work.

 

[The Branch Manager]

What is this magic smoke you speak of?

I'm probably interested right now.

 

[HandLoad]

If You climb to a Mountain Peak, Face the Rising Sun, and Say the Right Words, release of the "Magic Smoke" sometimes tastes funny, if You stand Downwind....

 

[aaron_c]

Handload, can you...I'm laughing, but can you be a bit more...explicit? Are you saying that the third method would fry my electronics?

It's good to hear that most rectifiers for electronics do fine with square wave power supplies, that's helpful. I still have health concerns though, and I really don't want to get into a discussion on that. So although I'm getting that most people seem to use an inverter to power their laptops I'm still curious to see if I can find a way around that.

Can you also clarify what you meant about the first method not working? Because I know that when I've used the wrong cord to charge my kindle it's taken a lot longer. It still charged though. So are you saying that for a laptop in a similar situation where the potential power demand for quick battery charging outstrips what the cord or outlet can supply, the laptop won't receive any power?

 

[HandLoad]

Every battery type, And even subtypes due to configuration, have different charging profiles. Think of batteries as buckets. Taller the bucket, the higher the final voltage must be to fill the bucket to the top (fully charged). You can push some charge into a 18- volt battery at one volt, but current will stop when the battery has same voltage as that supplied.

Using this analogy, you need a higher vessel to pour charge into Your "bucket". You will never fill your bucket by using a lower surface (voltage) of charge connected by pipe at bottom.

There are devices that can take charge of 5 Volts, and fill a 20-volt battery, but that requires the magic of a DC to DC converter, basically a solid-state Switching power supply in its own right, on one chip.

Not included or contemplated in Your original question, so I did not include in my answer.😁

 

[WhiteWolf]

After my last power outage and attempting to charge the ipad in the car... I bought a small inverter battery. I can charge it on it's adapter... or break down and buy the portable solar panels that are supposed to be able to charge it. Advantage of this thing, is it only weighs about 10 lbs and puts out a lot of power to different kinds of plugs.

https://www.amazon.com/gp/product/B07FFNTGZ6/ref=ppx_yo_dt_b_asin_title_o05_s05?ie=UTF8&psc=1

 

[aaron_c]

Every battery type, And even subtypes due to configuration, have different charging profiles. Think of batteries as buckets. Taller the bucket, the higher the final voltage must be to fill the bucket to the top (fully charged). You can push some charge into a 18- volt battery at one volt, but current will stop when the battery has same voltage as that supplied.

Using this analogy, you need a higher vessel to pour charge into Your "bucket". You will never fill your bucket by using a lower surface (voltage) of charge connected by pipe at bottom.

There are devices that can take charge of 5 Volts, and fill a 20-volt battery, but that requires the magic of a DC to DC converter, basically a solid-state Switching power supply in its own right, on one chip.

I get this, but where I get confused is how and whether this applies with USB and USB Y-connectors in particular.

So my understanding (and correct me if I'm wrong) is that when a device uses a USB connection to ask for power, there are ways for that device to ask for specific amounts of power and in specific formats. Sometimes, like with "Quick Charge" ports, both voltage and current can vary depending on a variety of circumstances including the battery's state of charge. So in that way USB ports are a bit different than, say, wiring a nominal 12V DC refrigerator to your battery bank; with a USB port the same port might put out 5V for one device and 15 V for another one.

So where I get particularly confused is when I think about what happens when I use a USB Y-connector. At least when used all by itself (that is, not stacked with other USB Y-connectors to make a sort of christmas tree like I described at the top of the page) a USB Y-connector is effective at combining the power from two different USB ports. But I can't quite tell if it does this by combining the voltage, combining the current, and/or giving the device more options in terms of charging (like giving it two "valves" to control instead of one in the electricity-as-water analogy).

 

[aaron_c]

After my last power outage and attempting to charge the ipad in the car... I bought a small inverter battery. I can charge it on it's adapter... or break down and buy the portable solar panels that are supposed to be able to charge it. Advantage of this thing, is it only weighs about 10 lbs and puts out a lot of power to different kinds of plugs.

https://www.amazon.com/gp/product/B07FFNTGZ6/ref=ppx_yo_dt_b_asin_title_o05_s05?ie=UTF8&psc=1

Thanks Sacajawea

Hmm...well, it's true that my health concerns are only in relation to the fluctuating magnetic field coming from the inverter and any AC wires used to power AC loads. So if I hooked up the regulator to the inverter and then ran a longish USB cord from the regulator to my laptop, that might be good enough from the health standpoint.

Still, I'm holding out hope that there's a way not to waste, as Handload said, about half of the power that would go into my laptop.

I don't know, it may be that the best I'll be able to do is to use a single USB Y-connector to combine the power from two high-power USB ports. Or failing that I'll just have to use a single powerful connector like this USB-C car charger which delivers a decent amount of power (45W). On second thought that's probably a better way to do it than the Y-connector.

Hmm. I suppose I could use the 45 W charger most of the time and then buy a small alternator to power the rectifier if I find I need it...thanks, this has been helpful!

 

[HandLoad]

It is generally considered bad practice to connect two solid state power supplies together in parallel, as what happens is that one does most or nearly all the work. And the other is just an inefficient heater.

 

[aaron_c]

It is generally considered bad practice to connect two solid state power supplies together in parallel, as what happens is that one does most or nearly all the work. And the other is just an inefficient heater.

Only if the two solid state power supplies don't have the same SOC, age, wear, capacity, brand, et though, right? But I would have thought that that wouldn't matter in my now-probably-defunct idea for using USB Y-connectors since they would both (or "all," if I'm using more than one Y-connector) have been pulling from the same battery bank. I would just have been using the Y-connector to make it possible to get more power in a single port than the car USB ports are generally rated for.

Anyhow, I appreciate all the time you and everyone here has taken to help me out. Thanks!

 

[john 1775]

After my last power outage and attempting to charge the ipad in the car... I bought a small inverter battery. I can charge it on it's adapter... or break down and buy the portable solar panels that are supposed to be able to charge it. Advantage of this thing, is it only weighs about 10 lbs and puts out a lot of power to different kinds of plugs.

https://www.amazon.com/gp/product/B07FFNTGZ6/ref=ppx_yo_dt_b_asin_title_o05_s05?ie=UTF8&psc=1

Curious to know how this is working out?

 

[240Geezer]

Welcome aaron c !!!
You’ve jumped right in it appears.
Could you give more info on your setup?
Are you off grid? Minimalist? Mobile?
I hear mention of inverter power which says to me something of the above.
Tap your DC side before inverter for charging laptop maybe?
Trouble with e/m fields?
Shielding is your friend.