Portable panel for portable sound system

[brewbeer]

I have a Sony BTX500 Bluetooth portable speaker system that has a built in lithium battery that I would like to run using a small portable solar panel for trips to the beach, out on the boat, etc. The speaker has a 15 volt 3 amp charger that will power it at full volume while charging the battery at the same time. On its own, the battery will run the speaker for 4 to 6 hours depending on the volume. While this is charging, it will also charge a cell phone via an integral 5 volt usb connection.

Is it feasible to power this speaker with portable equipment, or are its power requirements high enough that the resulting panel system would be too large to fit into a back pack?

[inetdog]

Well, 15V times 3A is only 45W. If you just want to be able to extend the time range by the number of hours of full near noon sun that day a 50W panel would probably be worth the effort. But since you are not really connecting to the Li battery, I doubt that you could safely use a standard 12V charge controller. Nor would I recommend trying to run from the panel directly into the charging port since the voltage could go as high as 20V from a nominal 12V panel.
If you are not interested in the "coolness" factor, just carrying around a larger 12V external battery that you recharge at home could be more practical.

[brewbeer]

Thanks inetdog. While the coolness factor is a factor, if it makes sense to extend the play time of the speaker with a rechargeable battery, then that works too. Any thoughts on how I might go about figuring out how much battery I need? The speaker uses an AC/DC "wall-wart" that has an output rating of 15 volts 3 amps. The charger will play the speaker at full volume, recharge a cell phone, AND recharge the speaker's internal battery at the site time. The specifications that came with the speaker indicates the internal battery will power the unit for 6 hours, so I'm thinking that the internal battery has a rating of somewhere in the 5-10 amp hour range? Does that sound about right? Thoughts on something like this?: www.powerstream.com/PST-MP3500-I.htm

[inetdog]

The internal battery might be even smaller than that given that audio equipment needs to get a moderately high peak power but may have a much lower average.
Looking only at your estimate that the charger can power and charge at the same time, 1.5A times 6 hours would be consistent with a 10 AH 12V battery.