The Battery U link has a charge time graph (scroll down) that has what I need to make a time comparison to do a "0-90". Obviously the "90-100" times are of great interest, but I don't have that for FLA. Their graph does go to 100 on the capacity curve.
I will use my ugly graph figures without inflicting the graph on folks again, unless you all insist. I have it for a 55 amper on 220AH doing a 50-90 which is a 25% charging rate, so that makes it convenient. I just need to do it in proportion for a 100AH batt, easy! Same times at the 25% rate doing 25 amps on 100AH as 55 amps on 220AH.
The FLA Bulk ends at 72% SOC and tapers to 90%. the Batt U graph shows the time for when the capacity reaches 90% on their 100AH batt. It shows Bulk ending at 60% SOC then amps taper.
(Howls of outrage from the usual suspects!--so take that up with Batt U , not me)
So FLA first:
0-72AH at 25 amps = 2.88 hr = 173 min
72-90AH tapering = 86 min
Total time 0-90 = 259 min = 4.32 hr
Now the LFP:
0-60 at 100 amps = .6 hr = 36 min
60-90 tapering amps = 39 min
Total time 0-90 = 75 min = 1.25 hr and 4.32/1.25 = 3.46 times faster
It would look worse for the FLA if we added the 90-100 part.
What about a 40-90 though, perhaps more typical of camping?
FLA : 40-72 at 25 amps = 1.28 hr = 77 min
72-90 still 86 min
Total = 163 min = 2.72 hr
LFP: 40-60 at 100 amps = 12 min
60-90 still 39 min
Total = 51 min = .85 hr and 2.72/.85 = 3.2 times faster
So if you added the 90-100 times it would be more like the 4 times faster claim for a 0-100 looks like. (if anybody would ever do that with an FLA!)
EDIT--in real life an RVer might have a 100a charger and be used to doing 50-90s with his 460AH bank of FLAs. He might wonder how much gen time he could save getting the same AH restored (that matched his AH usage) if he switched to LFP.
Now he can't use the 4 times faster as with 1C vs .25C. He has to do a whole set of calculating to see how much gen time he would save with how many AH of LFP instead of his 460AH of LFP, assuming he will still use his 100a charger.
