The 45 amper should take approx 5 hours to do a 50-90 on four batts, where two hours is at 45 ( a PD will taper in here, where it should stay constant at 45--can't be helped-- so add some time) and three hours of tapering to end up at 90% SOC. If you recharge beyond 90% you just add many more hours for that last little bit. If you don't do that with the boost voltage on using the CW, then add even more hours.
That is a long time for a generator recharge. I use a 100 amp smart charger (not a PD) on four 6s and it takes 2 hours (instead of 5 with 45a) to do that 50-90. But you need a bigger generator to run that 100 amper.
"Some solar" would help here for sure. If you had even 120w for under $200, you could get by with much less generator time and not need to get more of a charger or a bigger gen to have that reduced gen time.