After more than 30 years I'd have to consider any batteries suspect... Much less ones that spent their time in space.
Considering it was meant to spend its life at L1 it may not have any batteries. Then again it also doesn't have a computer so it should be fairly robust.
Damning praise on site populated by technorati.
It does have batteries on board however after its long life they appear to be dead.[1]
According to that article, it also lost power briefly for the same reason during a set of maneuvers that were used to repurpose it decades ago, so it's not the first time this problem has come up either.
But that was near the beginning of its life, so the batteries would have worked.