If memory serves me correctly Landyacht has an ideal setup for jump starting. A dial adjustment for voltage regulator setting. Connect the cables then tweak the voltage up to 14.8 and wait a few minutes. You would not believe the effect seven or eight-tenths volt has on amperage.
Can't use it on today's cars but my cold weather jump start system using a 6 and a 8 volt battery in series was almost magic. In the short battery series cable was a Delco relay wire and pushbutton.
Customer cranked engine, I pressed the button and suddenly his engine was fooling with 13 volts not 9 volts. Ignition engines had way more spark and my bread and butter, Mercedes diesels cranked twice as fast.
High altitude and cold temperatures brought forth diesel starting assist of the 14 volt battery plus a slug of pure 02 down the air filter inlet.
As far as the lithium battery boosters are concerned, a large majority of five star reviews is a good clue that the lithium model will work OK.
From what I've read an 85 amp hour lithium battery is quite a walletfull for use with a BiPAP.
