Cobalt 2 battery issue

[maddog2]

My Cobalt 2 dive computer showed 0% battery charge at the end of my 1st dive on Sat. Oct 5th, even though it showed 93% the evening before. I had to abort my 2nd dive. When I got home and plugged the Cobalt in to charge it up, it went from 0% charge to 100% charge in about one hour (?). From last night (11:00 PM) to this Afternoon (12:30 PM) the battery has discharge from 100% to 91%. And I always put the Cobalt 2 into SLEEP mode after checking the battery charge and after my pre-dive check. The Dive log shows two dives instead of one for Oct. 5th. But the Dive Time and Max Depth fields are blank. I cannot view the dive profile and I cannot download the dives to my PC.

I opened the battery compartment (it was dry) and relubed the o-ring and put it back together. Everything seems to be normal now, but I have the feeling that the battery is getting to end-of-life as it doesn't hold a charge very long. It discharges anywhere from 5-10% in 24 hours. What can I do to determine what may have been the issue, or should I just order a new battery?

 

[RonR]

The battery is the most likely issue if the Cobalt is very old- how old is it, and what is the serial #? What you describe is much too rapid of a discharge rate, both in sleep and in use. In sleep mode you should see no more than 1-2% per day. When batteries start to fail, they will discharge more rapidly.

If you have the most recent posted firmware (2.49) installed, there are some diagnostics that might help determine if the battery is the issue or if there is something else drawing too much power.

To access the Cobalt's diagnostic and calibration mode, the user name needs to be changed to ATOMIC <space> <space><apace> A. That is, ATOMIC, followed by spaces, with an "A" in the last possible slot. When you have done this, if you navigate to the System Info screen, there will be a button at the bottom labeled Diagnostic. Select this, then select battery from the sub-menu that pops up. If you can take snapshots of the screen, that will let us know more about battery status and current draw. Once you are in that mode you can also go to the screen for brightness setting and see the current draw displayed as you scroll up and down brightness levels. At the middle level (5 bars) the draw should be about -59 mA. If it is significantly more than this let me know, the problem may not be with the battery. Keep me posted with what you find.

Ron

 

[maddog2]

Hi Ron. Thanks for the prompt reply. Serial # 3315-0760, Version 2.490/4. I suspect it's the battery because it draws more than 2-3% daily. I've had the Cobalt 2 for 4 or 5 years now. 1bar 34mA, 2 bar 39mA, 3 bar 44mA, 4 bar 51 mA, 5 bar 61 mA, 6 bar 72 mA, 7 bar 78 mA, 8 bar 85 mA, 9 bar 92 mA, 10 bar 96 mA.

 

[RonR]

You current usage is within normal ranges, which is good. This leaves two possibilities. One is the battery is failing and just not holding a charge. Depending on the number of cycles and the way the battery was stored, at 4-5 years you could be getting near the end. Getting a new battery in place would confirm if this is the correct solution. I'd check with Atomic about getting a new battery sent to you.
The other possibility is an issue with the current in sleep mode. We have seen a few instances where something- possibly ESD- has damaged some protection chips on the USB end and is preventing true sleep. If you are able to still connect to USB to download dives, update firmware, etc. this is less likely, but it is still a possibility. One question would be if this change in power use appeared suddenly- batteries usually fail very gradually. Checking sleep mode current (which should be 400-700 µA) requires a sensitive meter, it's something we can do if a new battery is not the solution.

-Ron

 

[grfrim]

Ron,

I know this is an old thread but on my Cobalt 2 there is an OPTION button on the System Info screen that seems to serve as the Diagnostic button. For Battery and Compass Diagnostics they seem to be available all the time. Other diagnostics are activated by the change in user name. Firmware is 2.5.

 

[RonR]

Ron,

I know this is an old thread but on my Cobalt 2 there is an OPTION button on the System Info screen that seems to serve as the Diagnostic button. For Battery and Compass Diagnostics they seem to be available all the time. Other diagnostics are activated by the change in user name. Firmware is 2.5.

Yes, you are correct. We modified the firmware so that users could access those two diagnostic screens directly without having to change the user name. These screens are informational, and particularly helpful if it is suspected a battery might be in need of replacement.

To access functions where settings could be changed, such as calibrating the high pressure sensor, it's still necessary to change the user name.

There will be a new firmware version I will post here soon, this new version adds a warning when the dive log is full (some of you use your Cobalts a LOT- the dive log stores about 1200 hours of diving at a 30 second sample storage rate). It prompts the diver to download dives if they have not done so, and tells them which of the oldest dives are about to be erased.

-Ron