The picture showing EPE FPS-1000 and the key pad is an Uninteruptible Power Supply. We have just de-commisionned one at work. The back up side of ours consisted of 4 x 12VDC batteries in series for 48VDC. If it still works it would be a very good start to a RE system. i.e. it can be used as an inverter when powered by your 48VDC battery bank. The added bonus is you could top up your batteries with the built in charger if you had too assuming your are not running a huge battery bank. If I remember correctly the AC wave out of it was decent and the unit was rated at 4KVA. The display is also nice showing volts/amps/freq etc... in and out and it could be mounted remotely. (Check if yours can be removed, ours was just plugged in)

I will check tomorrow to see if there might still be a manual floating around if you need it.