Hi Danny,
So say you have an input x of size (120, 1, 20) - (sequence, batch, input). Now you break it up into x1 with shape (60,1,20) and x2 with shape (60,1,20). Then to retain the hidden state from the end of x1 to the beginning of x2, you would do something like this-
model = nn.LSTM(input_size = 20, hidden_size = h_size)
out1, (h1,c1) = model(x1)
out2, (h2,c2) = model(x2, (h1,c1))

Does this answer your question?