How do I build a USB hook up to create power for my laptop / cell phone

[matencio]

I'm one of those guys that always runs out of power on my cell or laptop when I need it most. Can anyone tell me how to build a USB circuit so I can recharge my laptop or phone from a set of solar panels when I'm in the field? I live in a remote area and it's terrible to not have power when I need it. Laptop batteries are a small fortune and inconvenient to drag around with me.

How do I figure out how much / or many solar panels I need? I'm going to use those 2.3 v solar panels that are on the solar lights for my garden. How do I figure out how many do I need so I won't under or over charge my batteries?

Second question: Does anyone know about a "wireless" USB connector coming out soon? USB 3.0
Thanks

 

[MikeMl]

To run your laptop, you will need about 5000 of the solar panels from the yard lights.

A solar panel suitable for charging the batteries in a laptop would put out about 18V at ~2A; a 36W panel. Here is one **broken link removed**. Notice the cost.

btw:, you cannot charge the batteries inside a laptop by backfeeding the USB port.

 

[matencio]

Thanks for the reply about the charger.

Regarding Can I create a charger for the laptop battery itself? Or plug it into a solar power inverter?

If I was in the mountains with my laptop taking a reading. I wouldn't be able to plug into a vehicle, building, rock or tree. So how would I charge the battery itself or provide a system that I could create enough power to channel into an inverter for recharging the battery inside the computer?

I like to write a lot in addition to taking my kids on trips. First use is for movies for them but I also write articles about mountains, forestry etc. My degree is in geography and I take GPS readings sometimes and make a map later at home to go with the article. I'd sure like to be able to recharge at my camp or on site while looking at the terrain.

As for the panel, I was thinking about a flexible solar panel they make. It's not as efficient but the lack of rigidity is a plus factor for comfort and mounting while I hike.

So, how would I get enough power into the PC? Parallel or in-series circuits? I found a power pack but it's six hundred dollars! I know I can build it cheaper than that and have fun doing so.

BTW I knew I was going to need a bigger supply for the PC. I was thinking something with a reostat to adjust the power output for anything from a phone up to a pc.

 

[MikeMl]

The Laptop has an internal charging regulator; it just needs to be connected to an external voltage source which can supply sufficient current to both charge the internal batteries, and supply enough current to run the laptop. My laptop (Dell Latitude D505) requires 19.5V at 3.3A (64W) to run the laptop (if the internal battery is totally dead). 3.3A will run everything during peak loads (such as hard drive seeks, high intensity backlight on the LCD), and during times when all of the 3.3A is not needed, the excess goes into charging the battery.

If you don't boot up the laptop, you could connect it to a source that can deliver much less than 3.3A, and the battery would still charge, albeit much slower than with a 3.3A source. You would have to charge 3 to 5 hours for every hour the laptop is booted up.

 

[matencio]

I was thinking, the internal regulator would take a beating if it was being charged by solar power directly. It would wear it out. I think it would be better to charge a battery out of the laptop and then put the battery in. Probably would need two batteries, one to charge while the other is used. I'm not an expert but I have read a little and I now recall a comment about that regulator problem. That would have to be addressed first. The regulator would be cheap to replace but getting a tech to do it would cost a fortune. What's your take?

 

[MikeMl]

The battery pack in the laptop is not just a simple two-terminal battery; it has about 10 connections, with internal temperature sensors, and who knows what else. I've no idea how to charge it externally, or what all those contacts do. The only way I know how to charge it is via the two-terminal coaxial plug on the rear of the laptop.

The external power supply for my laptop is just a switching power supply which puts out 19.5V at 3.3A. Any DC power supply which puts out 19.5V could be substituted and the laptop would not know it...

In my case, my laptop's external power supply will operate from 12-15Vdc from a vehicle battery (it steps up the voltage to 19.5V), so if I wanted to solar power it, I could get a panel, a 12V solar charge controller, and a 5 to 10AH 12V SLA battery. Since the external power supply is about 80% efficient, I would loose about 20% of the power between the 12V battery and the laptop...

 

[matencio]

Okay, I think I should reexamine this. I know I'll put a second marine battery in my boat for radio and GPS etc. I can hook an inverter to that when I'm on the lake but camping wouldn't work that well. Can't hike with a 12 v marine battery on my back! Where am I going to carry my other equipment? I won't give up, just put this on the back burner for later. Thanks for the replies so quick. It is really appreciated.
:>)