'not the weight or space restrictions'Spot on Trayon, no other...

'not the weight or space restrictions'
Spot on Trayon, no other technologies compare in those two at the moment. LiPo4 is the safest combination found so far, requiring 2/3rds the weight of current AGM & Lead Acid Batteries and a bit over half the size. You can use 'em upside-down, burn 'em or cut 'em up with an axe - no problem. Other Li chemistry combinations are where problems have occurred. Had LiPo4 running my Motorhome since they hit the scene and never regretted it. The pricing frightens many away but as usual, it's best to reflect on the economics which show they're actually cheaper than the other older forms due to their ability to be able to be run down lower without shortening their lifespan, last many more times doing this and charge up more
quickly (cycles, because Batteries can only be discharged and charged a certain number of times which is dependent on how far they're discharged to) and they accept a full charge straight off as opposed to AGM, Lead Acid & Gel (possibly a few of the alternates being looked at as well) that require an 'absorption' stage before becoming fully charged.
Anyways, the bottom line is there is just no alternative to Lithium for mobile applications at the moment and if one popped up from the Lab tomorrow it would take a minimum 10 years to prove it up.

Michael.