Solar Panel for USB devices

Hi all,

It is a significant challenge on extended trips to keep devices such as my Samsung Galaxy S2 mobile phone charged. I carry spare batteries and have even begun using high capacity batteries that make the phone less slim-line. However, no matter how big the battery, it is going to run out sooner or later. Tricks like turning the device into flight mode, ensuring bluetooth is off and using apps like Juice Defender do lead to longer run times but all things come to an end.

The biggest demand when using the phone in the field is running GPS applications – especially if having track logging on. Trekbuddy is lighter on the juice than Androzic, but both certainly consume. Also, if I am in mobile range and on a Summits on the Air activation, I try to also use an APRS app on the phone so people can track my progress towards the summit so they then have some idea when I am likely to come on air. I need a solution if I go on a week long SOTA trip and I would still like the phone alive at the end.

Solar Charging Panel

On a trip last year with Glenn VK3YY, I saw him using a small solar panel on the top of his pack. I looked around on ebay, but most USB solar charging devices really are just a (not always so) big external battery with a small solar panel. I would think many of the panels would be around 1 watt or even less.

Glenn alerted me to a 2W 6V solar panel on ebay. The seller provided a Schottky diode and a female USB socket. Upon receiving it, I soldered the diode and the socket on, and found the voltage was 6V up to 6.5V in the sun. The phone refused to recognise it.

Regulation

Separate to this, I purchased a 12V to 5V regulator with a USB socket. This was so I could charge phones in the car, but also in the field off LiPO batteries. I put Anderson Powerpoles on the 12V side. Here’s a pic of the device:

12V to 5V (USB) regulator

12V to 5V (USB) regulator

This device works quite well with a 12V input. My experience with similar buck regulation devices is that they tend to hold the output voltage even when fed something only a small greater input voltage, meaning that I should be able to get 5V out with 6V in. I removed the USB socket from the solar panel and made up a about 5cm of conductors to put a set of Anderson Powerpoles on. I left the Schottky diode in place, so that the solar panel would not be exposed to any voltage coming up the other way.

I put a small amount of duck tape on the outside of the panel to protect the edges, and here is the finished product:

Completed Solar Panel with Anderson Powerpole connector

Completed Solar Panel with Anderson Powerpole connector

Testing even in fairly low sunlight showed that the phone accepts charging from this setup. I’ll have to see how it goes in the field on a trip, but it is looking good. I’ll be interested to see if I get something like the 2W out of this panel in good sunlight – however being near winter, we might only really know in 6 months.

73, Regards, Wayne VK3WAM

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Generation X Plus SP-1 signal booster

Hi all,

On one of my recent SOTA (Summits on the Air) trips a few weeks ago, I made up my mind to give one of these Generation X signal boosters a go. They are not expensive, but I could not really find much of value on the net about how good or bad they were.

(I should point out that I have no association with the sellers of these products – I just bought some).

Do they work? I think they do. Here is a pic with two installed in a Samsung Galaxy S2

Samsung Galaxy s2 with 2 Generation X Plus SP1 signal boosters installed

Samsung Galaxy s2 with 2 signal boosters installed

I tried installing them both horizontally and vertically. It appears a vertical installation (as pictured) has more effect. As can be seen, I installed 2 of them. Most of the improvement was with one installed, but the second still had a small noticeable improvement. I would guess 2dB. Better than nothing!

How much effect? I would say about 6dB to 8dB. In terms of bars, this is about 1 and half bars. It is not always easy to tell the difference because there are many factors with mobile networks. The effect is most obvious in areas where the signal is very marginal, say at the edge of a service area, or well within a building. It is here where the phone and the network may be limited in choices such as handover to a better tower. The tower may already have the phone on max power level.

There is one spot in the church I go to on Sundays where the signal is right on the edge. A Bible app I use has to pull data from a server over the mobile phone network. I am generally kicked to 2G, and struggle to pull any data. With these things installed, I was able to maintain a solid 3G signal. A friend installed it in a Samsung Galaxy S3 and was able to maintain a phone call for the first time ever in parts of his house where he typically can only get SMS service. He has had to go outside or even up the street to get reliable phone service in the past.

I also have noticed improvements in rural areas. The signal is basically stronger for longer. Of course, once right out of service area, you still won’t get anything. In urban areas, I notice that it is often changing between towers at much higher signal levels than before.

Overall, at least in terms of my Galaxy S2 and my friend’s Galaxy S3, it appears that this device was worth it. As for the non SP1 Generation X, I have not tried it and cannot comment on it.

Regards,
Wayne Merry