If you bought an ACK E04 ELT when they were new back in 2011 then the time is coming to change the main battery in the ELT. Hopefully this will help you to change yours properly and save you some money as well. These batteries must be changed every 5 years. The battery expiration date is etched into the side of the battery pack.
I'm sure ACK would like you to buy their replacement battery pack but if you didn't disassemble this when you got it, you probably don't know that the cells are standard D Size 3 Volt Lithium Sulfur Dioxide (LiSO2) cells made by Saft, P/N LO26SX , and replacement requires simple disassembly and no soldering.
Aviation outlets charge $153 and up (some want to tack on HAZMAT shipping for another $35) for the replacement pack. You can buy the cells only for $71.80 and $9.95 shipping and in a few minutes be on your way. In fact I bought 3 sets with a couple of local RVators and we split the shipping cost 3 ways.
Step 1 - Order the correct battery cells (might be a good idea to verify your ELT has the same cells I did before ordering). The cheapest place I found was batteries2batteries.com: http://www.battery2batteries.com/saft-lo26sx-battery-3v-lithium-d-cell/
Step 2 - Remove the ELT from the aircraft. Before you do this it might be a good idea to perform a self test, to make sure it is working before doing anything to it. The current manual outlining the self test procedure can be found here: http://www.ackavionics.com/pdf/E-04_REV_1.7_SINGLE_PAGE_REDUCED.pdf
Once that is done, take note of how the unit is anchored and how the cables are secured and particularly how the GPS input connector is secured. You will need to remove the BNC antenna connector and the modular telephone style jack to the RCPI (Remote Control Panel Indicator).
Step 3 - Switch the ELT to "OFF"
Step 4 - Mark your ELT. ACK claims there are features to prevent improper clocking of the battery but I didn't see any on mine so I marked all 3 pieces to be sure. If you did clock things wrong you could install the battery backwards (and ruin your ELT) or clock it in such a way that there is no connection made to the battery - so it will not function. So I marked all 3 components prior to disassembly. I marked them with "TOP" so it would be sure to go back into the tray in the same orientation.
This shows the cells being removed. Note that there are no polarity signs!
Step 5 - Add polarity signs so you don't install the cells backwards! (note that it's best to do this before removing the cells)
Step 6 - Carefully inspect the base of the pack housing and the cap with the battery contacts protruding through to ensure there is no corrosion that would prevent electrical connections between cells or between the battery pack and the transmitter. Then install the new cells:
Step 7 - inspect the two O-rings and replace if they are cracked or overly stretched. Use some silicone O-ring grease on the O-rings and carefully install the cap on the battery pack. The springs pushing up on the cells will make this tricky as you have to push down on the cap to get the screws started. Use blue loctite and tighten the screws holding the cap of the battery pack to the base evenly, a couple of turns at a time on each screw. ACK's manual says 3.5-4.0 in-Lbs. Note the sticker for the SAR folks if you ever set one of these off inadvertently:
Step 8 - Verify polarity and voltage for the reassembled battery pack. I also checked the old batteries to compare voltage and they were within .01V of each other. ACK's manual has a more in-depth test procedure with a load test using an automotive light bulb which is a good idea as long as you don't run it for very long.
Step 9 - Inspect the transmitter PCB (Printed Circuit Board) for corrosion or damage, particularly where the battery electrodes interface with the transmitter PCB. Reinstall the transmitter onto the battery pack using the same screw torque and blue loctite on the screws - again tightening evenly.
Step 10 - Mark the new expiration date on the outside of the pack.
Step 11 - Now might be a good time to verify the GPS signal is reaching the ELT in accordance with the procedure in the installation manual, if your installation provides GPS to the ELT. Then put the switch in the "ARM" postion, install the red cap, and reinstall the ELT in the aircraft. Perform a self-test of the unit prior to making a log entry with the new ELT battery expiration date and placing the unit back in service.
ACK claims that cell replacement is forbidden by the battery TSO (TSO-C142a) and your ELT will not be airworthy if you do this. But feel free to but check the TSO yourself; I could find no such language: http://tinyurl.com/ze2vb7q
However, this is not to be taken lightly; this HAS to work when called upon, so if you are not 100% confident in your ability to do this job properly, then buy the replacement pack for the extra money and be done with it. I would recommend that at a minimum, this should be done under the supervision of an IA, A&P, or repairman authorized to work on your aircraft.
Note that there are 2 other batteries in the ELT subsystem; one in the RCPI (Remote Control Panel Indicator) and one in the audio alert indicator. The RCPI blinks and the audio alert beeps when performing an ELT self test. These batteries have a 10 year replacement (if lithium), or 5 years (if alkaline). My RCPI shipped from ACK with a lithium, and I installed a lithium in the audio alert indicator since that shipped with no battery from the factory. Thus in 5 more years everything will get replaced. It's a good idea to make a log entry indicating when those are due as well if you don't have it marked somewhere that you can't miss it.
