For many years I have run about 10W of solar panels into a pair of 7.2AH gel cells to power my radio shed in case of emergency. This system served me well throughout that time except that the power wasn't available anywhere but the shed. If we had an extended outage, I couldn't power lights or a television in the house. Thus, I decided to make the batteries removable.
The first order of business was finding an appropriate case for the batteries. Since it was going to be away from the main charger unit, I needed metering built-in. This necessitated a case slightly larger than the size of the batteries. I searched for a case for weeks without finding anything appropriate; I even tried to build my own of wood...not quite what I had in mind. Finally, in a "Back-to-school" advertisement, I found what I'd been seeking, a 3L clear plastic case with a locking lid for less than $5. Into that I placed the two batteries, reverse polarity diodes, and an LED Voltage Meter, self-powered, so the batteries can power the meter directly. That comprised the block called "Battery Pack" shown in the wiring diagram below.
Originally,the overall charging unit not only contained the charge controller for the batteries, but allowed either the batteries or the AC power supply to run my station. I decided to remove the charge controller and batteries from the rig power wiring and connect them manually if needed.
Following a relatively recent Amateur Radio convention, I used Anderson Power Poles configured to the RACES standard for my battery connections. I used speaker terminals and spade lugs for the solar panel connection.