I have a 12 year old DataMax II (it is a bottom timer, not a full on computer) with dead batteries that I contacted Oceanic about. They do not service this model anymore, but will give you a credit towards a new, current computer. Not a bad deal for something that is essentially useless otherwise.
Good to see there might be a DIY solution as well. I looked all over the web previously and found no information at all.
Info from Oceanic Customer Service
Unfortunately service on the DataMax and DataMax II is no longer
available. Due to the unavailability of some the critical components that
are required replacement during each service, we no longer offer a Full
Service and Calibration on this unit. When service was available the cost
was roughly $100.00. However, since this option is no longer available we
offer an upgrade to any of our current computers at roughly 40% off MSRP,
Computers such as to the Veo 100 for $175.00, or Veo 200 for $250.00.
ead Please be aware that the analog depth gauge does operate independently
of the digital timer, so as long as the depth is accurate the unit will
still function perfectly as a Depth Gage.
The Oceanic DataMax or DataMax II analog maximum depth gauge with built in
bottom timer, surface timer and dive counter. The Datamax was our very
first digital instrument, introduced in the early-eighties. Datamax II was
released a short while later with an increased battery life. Although
Datamax was extremely popular the Datamax series was discontinued many
years ago because advances in technology and declining demand for the
Datamax dramatically narrowed the price gap between Datamax and full
computers that have many more features.
As with virtually all digital dive instruments from that period of time,
the available technology did not allow any service in the field. Any needed
repairs, including battery change, required Factory Service and
Calibration. However, effective September 15, 2000, Oceanic is only able
offer an upgrade to a new computer (at a reduced price) if service is
requested for a Datamax or Datamax II. This is necessary because some of
the required replacement service parts can no longer be obtained.
Theoretically, we could have these parts custom-made, but the total cost
would force the charge to the owner to exceed the cost of a new instrument.
Please feel free to contact me personally if you would like to obtain an
Return Authorization Number to return your computer for an upgrade.