I have a 12V 24 aH (13.8V 24,000 maH) LiFePo as the largest practical size pack. I have two sets of Anderson Power Poles for 12V gear and two 12V to USB-C plug 5V 3A step-down inverters (for raspberry Pi + QHD screen or whatever). I got it to power my FTdx10, but of course it's fine for my FT817ND (and optionally PAs). It's charged by 2 x "100 W" solar panels easy enough to put in a small car. I mean to get a car charger and mains charger. The MPPT controller is a Victron (cheap model with no BT, so I had to interface the TTL serial to change it from Lead Acid to LiFePO4.)
Lives in a carry-case with shoulder strap along with LED meters.
The LiFePO4 has 3000+ full cycles rating (down to 10%) and a 1/3rd of weight of Lead Acid. Safer than LiPoly/LiIon. The cheap Lead Acid Gel / SLA for emergency backup (UPS, lights, Alarms) don't even quote cycles. The more expensive ones (more expensive now than LiFePO4) are about 100 to 200 cycles, but only if not fully discharged. The 200 cycles is about 70% usage.
Mike EI9FEB