[transientbug]

It does have batteries on board however after its long life they appear to be dead.[1]

1 - http://www.thespacereview.com/article/1697/1

[makomk]

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.

[jeroen]

But that was near the beginning of its life, so the batteries would have worked.