Q: I am considering a jHub power bank as an additional charging source for our two cameras when we travel. However, I do not know if it is safe to use it with our equipment.

I bought an extra battery kit for my new Sony RX100 Mark III. It came with a charger and a USB cord. I asked at the camera store if my husband's Casio (which charges similarly via a USB cable) could be plugged in to this charger. The clerk said absolutely not. He said each battery has a different voltage and warned that I could blow up the camera.

This leads to my question: If what the salesperson said is accurate, what keeps the same thing from happening with a power bank charger?

A: The salesman is wrong. USB is a universal charging standard, and with few exceptions, if you plug any USB device into any USB port it will charge. The speed might vary, but nothing is going to blow up.

With USB charging, the device you are charging determines how much current it draws, not the charger. For example, if you plug a device that charges at 1.5 amps into a 5-amp charger, the device will draw only 1.5 amps.

Where you run into problems is if you try to charge something with less current than it needs. For example, you have an iPhone 4 that included a 1-amp USB charger. You also have an iPad with the included 2.1-amp USB charger. You can use your iPad charger with the iPhone 4, but not the other way around. The iPad draws 2.1 amps, but the iPhone charger can supply only 1 amp. You probably will get a message that says, "Not Charging" or something similar. It actually might be charging, but it will be doing so very slowly.

As a rule of thumb, a more powerful charger won't charge a device any quicker than the charger that came with it. The exception is the latest iPhones. Users of the iPhone 6 and iPhone Plus can use the 2.1-amp iPad charger to charge their phones faster than the 1-amp charger included with the phone.

If you want to buy a jHub power bank, the model you want is the Elite. It offers 8,000 mAh capacity for under $25 and has two charging ports, including a 2.1-amp port that will work well with your Sony, which draws 1.5 amps. If you go in this direction, I'd get two, one for each camera.

I also recommend that you check out the Limefuel L150XR rugged power bank because it will fulfill your needs with just one device. I just finished testing the L150XR and was very impressed. It is dustproof, crush-proof, waterproof, vibration-proof and shockproof. It is heavy-duty, and you can feel the sturdiness in your hand. In fact, it's so sturdy that there are videos online of people driving their cars over it without causing damage.

The L150XR (tinyurl.com/ruggedlimefuel) has a capacity of 15,000 mAh and two 2.4-amp charging ports to charge both your cameras simultaneously at top speed. It also has auto on-off to help conserve battery power. It sells for $84.95 and includes an ingenious dual MicroUSB/Lighting cable that normally sells for $9.99 on its own.

I can attest to this power bank's performance and quality. It's an especially good choice if you do outdoor sports or anything involving dirt or water.

Send questions to Don Lindich at donlindich@gmail.com. Get recommendations and read past columns at www.soundadviceblog.com.