Can I charge my van's car battery directly from its lithium ion "house battery"?
New question.
Maybe, the 10A 12V limit will be exceeded with a dead battery so a 10A 12V lamps in series might be possible to use as a current limiter to get 50% charge @ 12V.

“ The Goal Zero Yeti 1000 Lithium can be charged in 9 - 18 hours by plugging into your vehicle's 12V outlet using the Goal Zero Yeti Lithium 12V Car Charging Cable. NOTE: Do not attempt to charge your Yeti Lithium from a 12V source using any other cable. Doing so may cause damage to the unit”

it must be able to measure battery current independent of the load to limit the exposure time during CV soak overcharge.
keep a record of voltage in each cell monthly.  When one drops, it is a sign of end of life.  The battery is only as good as the weakest cell. Each cell must very well matched. If the entire string is ok but 1 cell is overcharged or under, this stage of aging will deteriorate rapidly under the balancer does its job.