Changing McMurdo SART RT9 Battery

SART battery beed to be replaced after its expiry date, usually around 4-5 years (the lifespan of the battery pack).

The replacement kit comes with the battery pack, expiry label sticker and 58 x 2mm O-ring seal. For older RT9 model, the kit will comes with lower plastic moulding and 6 screws (Allen key screws)

There is only 2 tools needed. A screwdriver (Philips head) and a small Allen key for the screws. For older RT9 model, flat face screwdriver is needed.

First dissassemble the lower part of the SART unit. There should be 3 screws there. Used the Philips screwdriver to do the job.

After removing the screws, separate the base which is also connected with the mast.

At the middle part of the unit, locate the Allen Key screws (in older model, it will be a normal screw)

Use the Allen Key to remove all the screws.

After all the screws are out, pull it to separate the battery housing from the circuit housing. Do this gently as there is still connection between the battery pack and the circuit unit.

One should able to spot the orange lower plastic moulding and the battery pack underneath.



The black sponge should be separated and returned to the base of the battery housing

Now disengage the connection from the old battery pack and the circuit board. Do this carefully. There is a retainer that keep the connection firm. Raise the retainer with a finger and pull the polarizing plug gently.

Now the old battery pack is removed. Remove the orange plastic moulding and keep it.

Remove the old O-ring and replaced it with a new O-ring at the neck area.


Now insert the battery pack inside the battery housing first. Then followed by the orange plastic moulding. Make sure the polrarizing plug and wire pass through the plastic moulding
Now align the battery housing and the circuit housing. Connect the polarizing plug to the circuit. Make sure it is secured properly with the retainer.


After that it is pretty easy, just align the 2 parts and fit the screw and tighten it with Allen key.

Then screw back the base to the SART unit.

Lastly, don't forget to stick the expiry label sticker on to indicate the new expiry date. The labels should overlap the previous expiry date. After finished installing, the SART unit need to be tested to ensure it is operational. If it doesn't activate, check the battery connection again and ensure it is not loose

That is the procedure. It's not that hard.