I'll share my experience, I have a custom 400AH lifepo4 system in my van. We provide medical services in outback communities and remote areas and need reliable 12v power. the 200AH AGM (100AH useable, even then high loads at 100% SOC caused dreadful voltage drop) we had was only useful (mainly to get the tare weight) in full sun for a few hours. for the same weight and size we now have 400AH usable than can take large power draw. I had a a custom BMS unit made which utilises my 25AMP CETEK 240V charger, the 2 x CTEK 250S Dual chargers matched to a CETEK smartpass (stock SETEK unit charger) has an inbuilt cooling fan that activates at 50c all modified to be able to take 240v, alternator & solar concurrently up to 80amps (max rating of the smartpass) all contained in a custom box with custom electronics. The Lithium setup is much more efficient when charging, in similar circumstances we can get to 100% (4 x the AGM amount) in less than a third of the time it took with the AGM when on Solar - 495w roof, 120w portable. With lithium the voltage never drops below 12v, even at 5% SOC it is at 12.2v, the custom BMS box monitors each cell bank, will disconnect charging automatically when 99% SOC (this is a safety setting as you really don't need 100% SOC when you have 400AH) and disconnect all non critical 12v load at 20% and all load at 5% (all programmable) it can't over or undercharge, however we have not been able to use more that 53% currently, this is utilising inverters, satellite video comms & internet services, slide out external compressor fridge, foxtel, vast tv, coffee machine, thermomix, microwave and our air conditioner for a few hours if its too hot. we use a Victron 700 to monitor the bank and 2 x cell monitors, one close to the banks under the bed, one easily viewable in the van, this shows each individual cell voltage and will sound an alarm for over or under charge or if they drift out of balance. We have never had to balance the cells, they are constantly within 7mv of each other, this is testament to a well designed system.
The difference is like analogue to digital. I highly recommend but consider it as a system not a battery as it is much more sophisticated than lead acid. they are much more robust, you don't need a maintenance charge while stored or any other special treatment between uses, just use them and let the BMS charge when it thinks it needs it. Most of the packaged, sealed lithium units I found when I was researching last year were expensive per AH and didn't have cell balancing or very sophisticated BMS which means if 1 cell fails you have to throw the whole unit away, if you build up a cell based system with BMS, monitoring and cell balancing, should a cell fail you can inexpensively replace just that cell.
I couldn't be happier. Happy to recommend the guy that did my work, pm me for details.
Cheers
Rob
