My two Iceco GO20's live in both my sailboat and campervan (one per). I have solar charging on both, with "house" storage batteries.
There are times, days, when solar just isn't as effective, and my house battery resting voltage is decreased to something below a nominal 12.5 VDC.
The GO20 app has the option to program the safe low voltage level, but this optional "step-up" transformer let's me add a layer of voltage "help" if my VDC falls too low.
Under load, the GO20 can reduce the VDC line to a level lower than it wants at the "safe" minimal level, it would then shut down.
I can control this with the step-up transformer.
I've gone 2 - 3 days of minimal solar charging before my battery levels become concerning, this transformer, for me, is a back-up piece of equipment that makes sense to have onboard.
I might not need it, but I'd rather have it in case.