My daughter is in Thailand and she has been using a solar device to charge her Samsung Galaxy3 tablet (7 in.) This method is no longer charging the tablet sufficiently for use. She has a universal travel charger with a 5v output and short cirucuit protection so I was wondering if she could use that to charge her tablet safely? Samsung advised purchasing a Samsung travel charger over there but there are none available where she is.
Yes. Any USB charger can be used for it. It's all standard 5V USB.
The only thing you need to pay attention to is the current rating of the charger, especially with a tablet. If the charger can't supply enough current, the device will charge slower than it should, if it will even be able to charge at all with the device on.
I'm not sure about the 7" tablets, but the 10" tablets will charge at up to 2.5 amps, whereas a typical smartphone charger will only put out 1 amp or so, meaning it will take at least 2.5x as long to charge on the latter.