Hello.
100w panel will produce about 5amps in the best conditions, during 1 hour, you get 5Ah.
During 1 summer day, maybe you had 5h sun, 5days x 5hours x 5 ampères = 125Ah
Now, with shadow/bad weather, maybe it produces less than 1amp, you should measure it with the ammeter.
With 20A mppt...