The German Tribe
Coming out of North Hessen, the Batavians originally were a part of the tribe of the Chatti. In 50 BCE the Batavians came to what is now know as The Netherlands. In those days it was a part of Germania. The Batavians followede the Rhine and settled in the area now called 'Betuwe', they used to refer to it as "The Island", as it was the piece of land between the Rhine and the Waal.
The Batavians 'capital' was Noviomagus Batavodurum (present day Nijmegen).
According to the not so trustful, but ever amusing historian Tacitus the Batavians were the bravest and most feared tribe of alle the German tribes when he wrote: "They are like weapons and armour - only to be used in war'.

Their Gods
Donar was the chief of the Batavians Gods, his Scandinavic counterpart was Thor. The centre of the Batavian cultus was near present-day Nijmegen, where two temples dedicated to Donar were found. Another temple was found near Elst, in the center of the Betuwe. The Batavians used to sing their warsongs in his name, and he was worshipped open temples. These temples were more like open places with just a small fence; the Batavians did not believe it was appropriate to limit their gods by using walls and ceilings.
The Romans named the Batavian chief god Hercules Magusanus. He resembled their mythological hero Hercule, who was, just as Donar, a protector of the people. The name Magusanus means 'the wealthy' and some even think that the name Novio Magus was taken from this addjective. This, however, is not true.
The name Hercules Magusanus is found on braclets, coins and althars such as in Houten Tiellandt and Ubbergen have been found. Inscriptions with this name were found by Ruimel, where St. Willibrord destroyed a temple which was dedicated to Hercules Magusanus to put a church on the very same spot. They are also found in Westkappelle as well as in Rome, Vetera, Bonn and as far north as Hadrians Wall.
The reason why his name travelled this far is because a lot of Batavians had entered the Roman service and spread it allover the Empire. And because Donar was a god of battle, he was particularly populair with the Batavian warriors. In Empel an inscription was found of a former Batavian legionair, which says: "For Hercules Magusanus. By Julius Genialis, veteran of the Tenth Legion, also known as the Double, the Just and the Faithfull, has pleasantly and with reason payed a debt.
The Batavians also worshipped Wodan, his Latin name would be Mercurius Friausius (of Eriasus). Friausius can be explained as 'free, loveable' and seems more applicable to Wodan's wife Frigga. In Ubbergen an althar dedicated to Wodan was found. In Nijmegen the name Mercurius Rex (=king) has been found.

Triple Goddess
The Batavians had a lot of goddesses. In the Rhine area between Nijmegen and Cologne the so calles 'Matrones' were worshipped. This was a group of three goddesses, who function were variable such as healing, justice and war. They can be compared to the Nornen (Germanic fate goddesses) as well as The Morrigan (the Celtic triple goddess).
The cultus of the Matrones was extremely popular and were introduces into the Roman Empire by Germanic soldiers. The three goddesses were later replaced by three gods, among which Donar and Wodan. The third is not known for sure.
By the time the former German tribes had become christians, the believe in the triple gods/goddesses was so deep that they could not simply be discharged. That's why today we know several 'christian' believes such as 'the father, the son and the holy ghost' as well as 'Faith, Hope & Love'.
The most well-known Batavian goddess would have been Hel, the goddess of the Underworld. Her name even refers to the name of present Elst, where several temples were found, as we saw above.

Other parts of the cultus
Apart from the goddesses, female seers had high places. The one most known is Veleda, she had a great part in the revolt of Julius Civilis. The Batavians used to worship her as a goddess. In 77 CE she was taken prisoner by the Romans, taken to Rome and never heard from again.
The Batavians had great respect for nature, both flora and fauna. They had sacred groves, sacres stones, sacres hills and so fort, but also anmimals had their own spirituality.