Search 'Nigel Calder TPPL' - what he hasn't written you don't need to know. Consider TPPL's a halfway house between LA and LifePO4's. Discharge down to 50% max 40% and charge acceptance rate's higher than most charging
systems are capable of generating. Biggest challenge is adapting charging system to live with high charge acceptance rates i.e. over-heated alternators (if not derated), need for bigger cables
, Poly-v belts (if done properly) higher amp rated circuit breakers etc - all of which are good things as the recharge rates compared to LA are much shorter. You still have the limited 'bandwidth' of about 40% (50-90% SOC) of LA batteries (unlike the LifePO4's which can be routinely discharged down to 20% SOC). I completed a 3 year circumnavigation
using Odyssey 2150's (x2) in Sept 2013 - they are good, but wish I had LifePO4's. In some way's less complicated than LifePO4's, but if you optimize the charging regime and HW - the step to LifePO4's is less challenging.