I used my Travelpower to power the battery charger for 6 years. I only had one set of batteries and alternator...and nothing 'cooked' ?
I would start the engine..then Travelpower..then battery charger.
We used it for the washing machine and also an electric kettle while travelling . I also had solar , so several forms of charging at the same time.
Only thing that was a serious problem...not just for myself but also a neighbour ...was the way the Beta engine was set up to power it.
My engine had a double pulley on the front...one before the other. My alternator and Travelpower alternator were on the same side and the subsequent force began to destroy the pulley and end of the crankshaft. At first it begins to work slightly loose on the taper, but once it gets underway it accelerates.
My neighbour had a 200 hour Beta engine and this happened. Once the pulley starts to wear a shoulder into the crankshaft you're doomed.
Beta eventually gave my neighbour a new engine and paid for fitting.
Its worth occasionally getting hold of the front end of the double pulley and waggling it. If you feel a slight movement, tighten the centre bolt.
An engineer told me that its fairly common and one of the root causes is that the crankshaft taper and pulley taper are slightly different. Whether that is true..I don't know ?
Unfortunately my engine wasn't under guarantee. I did come up with a 'fix' but it involved new style of pulley and much machining.
When this happened, I was in constant communication with Adrian at Beta. He told me that this was a recurring problem, and that they had tried several fixes, even welding the pulley and nut to the crankshaft, but the forces always won. I 'think' that if you have this type of setup , with double pulley, It would be OK if you checked it for sideways movement. Get hold of it good and tight and wobble it. You can then catch it before it becomes serious.
By the way...you need to remove the pullies to tighten the centre bolt....