My PLAN B for off the power grid camping is to have a 2KW Honda Generator and B&D VEC1093DBD 40AMP smart mode portable charger.
I can start up my generator and plug in my portable B&D 40AMP battery charger and usually can jump start any car battery in 5 min of normal charge. The VEC1093DBD also has a 100AMP jump start output but I have never had to use that. Usually when someone runs down their battery I can bring it back enough to get their truck started in around 5 minutes of normal charge mode.
The second reason I have the portable smart mode charger is I can recharge mt trailer battery bank back up to its 90% charge state in around three hours of running the generator with the 40AMp charger plugged in.
I can also plug the trailer shore power cable into the 2KW generator 120VAC receptacle using a RV30A-15A adapter ans use the on-board smart mode converter/charger and recharge the battery bank back up to the 90% charge in a three hour generator run...
Pretty good PLAN B for me...
Roy Ken