You can set initial charging priority e.g. 80% engine battery and 20% leisure battery. - Maximum solar input power: 160W (12V system) / 320W (24V system). Can the unit work with only one battery?. You can add a second battery later.
eBay
SmallRig V Mount Battery Plate V-Lock Mount Battery Plate with Dual 15mm Rod Clamp for Camera Power Supply Battery Plates -3016
Aliexpress UK
Suitable for solar panels upto a maximum of around 260w. 20 amp DUAL battery regulator with remote LCD display. Reverse polarity protection. Not suitable for house type panels which are generally for a 24v system (it will say Vmp 36v or thereabouts) unless you run a 24v battery.
eBay
BG-R10 Vertical Battery Grip Holder w/ Dual Battery Slots for Canon EOS R5/R6/R5C/R6 mark ii Battery Grip LP-E6NH/ LP-E6N/ LP-E6
Aliexpress UK
For solar panels up to 390W (12V system) / 780W (24V system) up to 100V. The most advanced MPPT technology to ensure high efficiency (>95%) of your solar system. Current limiting function (30A) allows the possibility of adding more solar panels to your solar system in the future.
eBay
300A Auto 12V 24V 48V Battery Disconnect SwitchMarine Car Dual Battery Switch 2 Position Battery Selector Switch for Car Boat
Aliexpress UK
Charging Current: 30A / 10A (selectable model). Built-in protection: short circuit, open circuit, reverse polarity, and overload protection. USB Output: 5V / 2.5A (dual USB ports). Dual USB outputs support charging for iPhones and other devices with a maximum current of 2.5A.
eBay
SOECOPO Portable 10000W Solar System:Store Solar Energy Home, Camping, Car 2×600W Panels,110V/220V Inverter, 100A Controller
Aliexpress UK
Dual USB 5V/3A output ports built-in. A: (1)Battery --->(2)Solar panels ---> (3)DC load. Disconnect order is (1)DC load --->(2)Solar panels ---> (3) Battery. Solar Panel Cables. Solar Connectors. Solar Tools.
eBay
Li-ion Battery Replacement Kit Charge Protection Circuit Board Repair Kit Parts for Makita 18V Battery BL1815 BL1860 LXT400
Aliexpress UK
eBay
Long-Lasting 9V Rechargeable Battery 6800mAh Type-C Fast Charge Battery for Multimeter, Guitar Pedal, Microphone, Smoke Detector
Aliexpress UK
【Battery Type】 Adaptable to User, Flooded, AGM, GEL, LifePO4, Lithium, and other customized battery types. USB Output:5V/2A×2. Battery Typel:User, Flooded, AGM, GEL, LifePO4, Lithium. Protection Category:IP44.
eBay
AIPEKE 3.2V 18650 LiFePo4 Rechargeable Battery with Welding Tabs 100% Original 18650 2000mAh Batteries for Charge 1800 Cycle
Aliexpress UK
Current: 30A. Solar panels. ●Outdoor solar panels can effectively convert sunlight into electricity. Colour: Black. Short circuit current: 2.6A. USB output: 2-way USB output 5V/2.5A (Max). Working current: 5.78A.
eBay
1-10pcs Original 3.7V Li polymer GSP 1029102A For JBL Charge 3 6000mAh Speaker Battery Rechargeable Li-polymer Battery
Aliexpress UK