Does the Energybar 250 come with the solar panels or do they have to be purchased separately?
No, the EnergyBar 250 alone does not include solar panels. In order to add the solar panels, you need to purchase 11-12099 (SUNSOCKET SOLAR GENERATOR) separately and daisy chain it to the EnergyBar.
The specs tab says that this backup battery takes a 15v input 4 amps to daisy chain. Will it charge (perhaps a bit slower) off of the 12 volt accessory port in my airplane?
Per the supplier: The 12 volt charger should charge at the same rate as when connected via an AC wall outlet. That would be about 5 hours for a full charge, as long the output voltage is 12-14 volts. The EnergyBar can also be charged from the Solar Panel Kit in about 5.5-6 hours with good sun.