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jjackstone

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Posts: 57
Reply with quote  #21 
So, we have lots of information here but not enough input data to make an actual solution. Let's see if I have current known facts right.

1. You absolutely want to be able to either charge or use the laptop directly from solar panels during daylight hours.

2. Your current battery is around 55 or 60 watt hours capacity.

3. You would prefer not to carry a spare battery.

Question:

How long will your laptop normally run from fully charged without being plugged in?

If you know that answer you can determine how many watt hours are being consumed per hour.
From that info you can size your panel(s).

Example:
If your battery lasts 5 hours, then you are using 10 to 12 watt hours per hour.

So you would need a panel capable of producing probably 20% more energy to charge and run the laptop at the same time.
That would suggest a panel capable of a usable voltage of 12v with a 1 to 2 amp output. 
You should be able to determine what you need from this information.
As other have suggested you would likely need a dc-dc step up converter.



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lash

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Reply with quote  #22 
Quote:
How long will your laptop normally run from fully charged without being plugged in?


@jjackstone I can't remember how it was when it was new (it's pretty screwed now), but it was definitely over 2 hours in normal operation.

Quote:
That would suggest a panel capable of a usable voltage of 12v with a 1 to 2 amp output. 


The internal battery itself says 11V 5.3 Ah (I'm not so electrically savvy that I fully understand what Ah means, I thought A was the "bandwidth" of the current?) when you're writing 1-2 amps, is that in conflict with this number?

Quote:
you would likely need a dc-dc step up converter.


What does that do?
lash

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Posts: 11
Reply with quote  #23 
Quote:
Would an automobile (or decent boat) be available? 


@stmptwle no, just a bicycle would be available. Without dynamo, even %)
stmbtwle

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Reply with quote  #24 
Think of amp hours as capacity, like liters. Voltage is pressure. Your battery had 11 volts and 5.5 liters when new. If it lasted 2 hour, that means you were using 5.5/2 or 2.75 liters per hour (amps), @ 11 volts. When you use up the liters, the pressure (volts) drops to 0 and the computer won't run. So we need about 3 amps and 11 volts to run the computer.
Your charger puts out 20v, so obviously there is some kind of regulator in there, and the "excess" pressure is used to charge the 11v battery.

A "12v" solar panel puts out about 17v, with a maximum of 22v. The regulator should handle that with no problem, but MISTAKES CAN BE EXPENSIVE, which is why you should contact the tech help department. I have a 60w solar panel which puts out 3.3 amps @ 18v. It SHOULD run the computer just fine on a good day. On a cloudy day, it won't.
https://www.solarblvd.com/products/solar-cynergy-60-watt-12-volt-solar-panel/

A "buck boost" converter such as this can be adjusted to a constant 20v output (sorry I couldn't find a waterproof one) https://www.amazon.com/Ebotun-Converter-10-32V-Voltage-Charger/dp/B07DMGDKTC/ref=sr_1_11?s=electronics&ie=UTF8&qid=1529149477&sr=1-11&keywords=dc+boost+converter+150w

You can use the same converter with a 12v AGM battery. It'll be more reliable, more compact and less expensive than the solar panel but it'll be heavier, and you'll lose the "cool factor" (important).

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Solar is like the wind. It may be free, but putting it to work isn't!
Willie, Tampa Bay
jjackstone

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Posts: 57
Reply with quote  #25 
Quote:
Think of amp hours as capacity, like liters. Voltage is pressure. Your battery had 11 volts and 5.5 liters when new. If it lasted 2 hour, that means you were using 5.5/2 or 2.75 liters per hour (amps), @ 11 volts. When you use up the liters, the pressure (volts) drops to 0 and the computer won't run. So we need about 3 amps and 11 volts to run the computer.
Your charger puts out 20v, so obviously there is some kind of regulator in there, and the "excess" pressure is used to charge the 11v battery.


Great analogy.

A dc converter is essentially the same thing as a buck boost.It changes dc voltage from one level to another. In your case you would want to go from 12 volts to 20 volts for the "proper" charging level for your laptop.

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stmbtwle

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Reply with quote  #26 
Yep. When doing a search on ebay or amazon, if one term doesn't work, try the other.

Some convert up, some down. Be careful when ordering.

I found converters with a 19v output, but they didn't look suitable for solar.

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Solar is like the wind. It may be free, but putting it to work isn't!
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lash

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Reply with quote  #27 
Quote:
Think of amp hours as capacity, like liters....


Nice explanation, thanks!

Quote:
It changes dc voltage from one level to another


That comes at the cost of something, I presume? Like time periods or something?

Quote:
A "12v" solar panel puts out about 17v


Why 17v when 12v ?

Quote:
The regulator should handle that with no problem, but MISTAKES CAN BE EXPENSIVE


However, if I have some battery unit in between, this is not a problem right? Something like mentioned before:

https://www.amazon.com/MAXOAK-50000mAh-Portable-External-Notebook-Most/dp/B00YP823NA

stmbtwle

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Reply with quote  #28 
1) The way it's been explained to me, the dc-dc converter trades voltage for amperage. If you convert the voltage down, the amps go up. If voltage goes up, amps go down.  V1 x A1 = V2 x A2 with a small loss due to heat.

2) Solar panels are affected adversely by heat, so they're designed to put out a higher voltage so that when they get hot they'll still charge your battery (they're black, and they DO get hot).  But it also means you need some kind of "charge controller" or regulator to keep from OVER charging your battery.  The dc-dc converter mentioned above will work, IF properly adjusted. 

3) The battery acts as a "reservoir" and also stabilizes the voltage for the computer.  However you might actually need TWO voltage converters, a charge controller to drop the solar panel voltage down for the external battery, and a dc-dc converter to step it back it up again for the computer.   17v >> 12v >> 20v.  That's why I'm tempted to try the 17v directly to the computer, or with the boost converter (17v >> 20v). The internal regulator and battery should do the rest.

Rick may know a better way.

"No job is as easy as it looks"   Murphy's Law.


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Solar is like the wind. It may be free, but putting it to work isn't!
Willie, Tampa Bay
stmbtwle

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Reply with quote  #29 
This might work: https://www.ebay.com/itm/12V-Step-Up-To-19V-Power-Converter-152W-8A-Non-isolation-Voltage-Converter-8A/142441911008?rt=nc&_trkparms=aid%3D555018%26algo%3DPL.SIM%26ao%3D2%26asc%3D44039%26meid%3Dd072a48ac3554187a283e602f2aaa549%26pid%3D100005%26rk%3D1%26rkt%3D12%26sd%3D302390419235%26itm%3D142441911008&_trksid=p2047675.c100005.m1851

I
t looks like it was designed to convert power from a 12v battery to a computer, but the input range (8-22v) would accept power from a 12v solar panel.  You'd have the option of using a solar panel OR a battery (but not both at the same time).

A nice thing about that case is it's waterproof, and with some double sided tape you can stick it directly to the back of your solar panel.

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Solar is like the wind. It may be free, but putting it to work isn't!
Willie, Tampa Bay
stmbtwle

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Reply with quote  #30 
Just for grins, I've ordered one of these and will connect it to a spare 60w solar panel I have laying around, and we'll see if it can charge /operate a laptop.  https://www.ebay.com/itm/382370260699

It doesn't say what the input voltage tolerance is but we are going to find out.  I'll post the results here.  Wish me luck!

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Solar is like the wind. It may be free, but putting it to work isn't!
Willie, Tampa Bay
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