Hi, Ioannis

just have a look to the NS Datasheet of the LM 350 page 10 ... there is a very simple Pb batt charger design ... easily usable with the 317 or 338 ( Paper datasheets included it in the 1982 Databook release ...).
fits the I - V charging method ... Roger looks for ...

But do not tell Roger ... he is a friend ...

Alain