The portable battery box is in my toad, in case we are in the back country somewhere in it and come back to a dead battery or low tire (many if not most of such boxes include inflators). In fact, I was glad to have it in 2012 at a campsite when I stepped out of the coach to go into town and discovered a slightly unlatched door had caused the courtesy lights to stay on all night. The incident also presented another lesson: remember to plug in and fully charge the box every few months, or it may prove useless when you need it. Fortunately I could plug it in to park power in camp (or have used the genset in dry camp), and after a couple hours it was up to snuff and cranked the toad back to life.
Though I've not had to try it, I like to think the box could be used to start the coach's genset, and from that then the engine. Which elicits another point: the most common cause of bad alternators is damage from owners starting a coach following a day or more of dry camping. As pointed out in this Forum many times, the excess heat an alternator puts out trying to recover discharged batteries will destroy it, and is likely what happened to Roy's. Rule number one of dry camping is start the genset and use its charger to recover used juice well before trying to start the engine.
That's where, in theory at least, a portable box may come in handy for the coach some day - jump starting the generator when house bats are low also, and the Start Boost switch therefore won't work. You shouldn't try to jump a dead coach with your toad either; one 500 amp battery won't do the job of two putting out 2000, and the attempt may do in sensitive components in the toad.
Joel
