I believe jrnyman7 comments are fairly close to the mark. The consensus from the primary fora that discuss LFP (Cruise and Sailing with 4000 posts on one LFP thread, Northern Arizona, Solar Panel and varied Aussie RV For a) is that 80% DOD (there is a severe dropoff at 90% DOD) is good for several thousand cycles. Liberty Coaches claims over 2000 cycles to below 80% and a Liberty Coach owner ($1.8 M and up) wrote on another RV.net forum that they have now trialed to over 3000 cycles. Liberty Coach is handling their information fairly closely since they probably consider it proprietary.
The primary reason we went with LFP as opposed to previous glass mat is weight. Basically you have 25% of the weight with the same usable W-hrs. We have 9.6 kW-hrs in our LFP bank and it weighs 256# or so. We would have to go to 800# or more to get the same. This would put us over or near over pin weight/dualie rear axle loading. The battery bank of 4 x 12V nominal batteries fits nicely into the forward compartment of our 5th wheel. This compartment was designed for a propane Onan 5.6 kW generator and the manufacturer rep told me that it should support 400#. 800 # might have us with a lot of expensive trash on the road if we hit a few topes in Yucatan at high speed.
Cube is also important. Where do you put what would have to be about 14 kW-hrs of lead acid (to get the same usable kW-hrs) in most RVs. Large motor homes are designed to carry this weight and cube but most TTs and 5th wheels do not have the space.
NinerBikes - Peukert advantage (or rather the lack of Peukert disadvantage) is discussed in detail by folk who know the subject. LFP charges almost linearly up to float stage. This means that if you do have to use your generator to charge, it will be done in a few hours. We trialed this once when we were -3 kW-hrs with our 1 kW Honda. It took about two hours since we were also charging around 1 kW from solar. The EV folks charge at extremely high rates C5. A safe rate seems to be as below:
Charge: Up to C/1 rate up to 3.6 V, then constant voltage at 3.6 V until I < C/24. This is the advantage of a BMS. A lot of folks just set the system at 3.4 V per cell and do not use a BMS. With the initial cost as high as it is, our son (the designer and fabricator for our system) went with top of the line BMS and monitors.
Reed and Elaine
