Re: Solar generator
You might consider lead acid instead of AGM. Since it might not always be in the van, maintenance might not be an issue, and they're cheaper and come in about every size and shape. But 20 AH AGMs are also available in motorcycle sizes, just more expensive.
I managed to get a relatively cheap battery (8AH) by buying one of those emergency car jumper thingees; it wasn't too hard to take apart and as a bonus I got some heavy gauge copper wire, clamps, and cig lighter sockets. Sometimes they're cheaper than the battery inside would be sold separately.
What I should've done is installed a pigtail off my solar controller so I could switch it from the house batteries to the portable power pack (or some other destination). My house ones are often full, and attaching the power pack into the house DC circuit will charge, but not very well.
2001 Ford E250 Sportsmobile with Salem-Kroger 4x4 conversion