At 40 pounds it used lead acid batteries, in the description it says it uses 2 batteries. It's just a bigger version of a small jump starter.
Yes you can charge it with your solar controller. As long as your controller doesnt exceed the 12 volt receptacle amp limit (most have a 15 amp fuse). If your controller puts out more amps, you can connect it to the jumper cables directly, then there is no limit to the amps you can charge it with. Connecting through the jumper cables you bypass all the electronics and go directly to the battery.
I use to connect my small jump pack (17 ah agm) directly to my ecoworthy 20 amp mppt controller and 240 watt solar panel. I used it as a house battery for many months until I got a bigger batttery. When battery is fully charged it floats at less than 1 amp. You can keep them connected to solar all the time, just reduce the float voltage to 13 volts if you have any concerns.
For a unit that large, a large solar panel will charge it quickly, theres no way a solar panel will ever overcharge/damage a lead acid battery. All my jumppacks I actually modified them (with xt60 connectors) so I can plug them directly to my mppt controller. Those batteries (agm) like being charged at high amps. I read some of the reviews that said it take 40 hours to fully charge, that kind of charging will kill the batteries in the long run. For longlife the battery needs to be charge at 14.4 volts at high amps for many hours at a time. The wall wart if it takes 40 hours, its only trickle charging the battery.
