I had the combiner on my motorhome conversion and bought it over 10 years ago.
Its solenoid failed after 1 season, when electronic board was still good.
Having bunch of automotive relays, I was planning to parallel 5 of them to do the job, but then in motorhome all batteries were in 1 compartment, so simple disconnect switch was doing the job just fine.
In motorhome I was using alternator to power AC, so you could see continuous 50 amp +