Cobalt 1 help: What to do if your battery is dead

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It's not surprising for the Cobalts to require charging after a long time idle, but they should start up once charged. I'm guessing you have confirmed that the cables and adapter are all OK, also the charger if you are using also. I've seen some situations like this where the A/C charger turned out to be the issue.

One thing to try with the Cobalt 2's is to connect them to a PC/ Mac and go through the firmware updating process. See: Cobalt Firmware Downloads - Atomic Aquatics They should show up on the computer desktop as "BOOTLOADER", even if the battery is missing. If so, just drag the new firmware file onto this and wait a minute or so for it to copy, then eject BOOTLOADER and restart the Cobalt. Here is a link to the latest firmware version for the Cobalt 2.

I'd be happy to take a look at them to diagnose if that doesn't work. I will sen you a message with information.

You have been great support for us over the years. I have a Cobalt 1 that due to covid has been unused for some time. I tried to charge it, the computer comes up on the charger the battery showed to be charged but when charger was removed the computer died. Opened the battery compartment and battery has leaked. I have read about the replacement program, I would be interested in that. How will it be communicated to the public?

I went ahead and cleaned it up and new battery will not be an option. The first pin is almost gone, either melted or was eaten away from whatever came out of the battery.


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You have been great support for us over the years. I have a Cobalt 1 that due to covid has been unused for some time. I tried to charge it, the computer comes up on the charger the battery showed to be charged but when charger was removed the computer died. Opened the battery compartment and battery has leaked. I have read about the replacement program, that would work for me. Would there be a viable battery replacement, that could also work if compartment could be cleaned up. Any thoughts.
I think that battery is toast. However, the battery compartment is isolated from the rest of the electronics, so long as the three pins for the battery connection are intact all that should be needed is a little cleanup and a new battery.

I will send you a direct message re. getting a replacement battery.

The Cobalt 1 was produced between 2010 and 2014. If your Cobalt has a firmware version that starts with a “1”, then it is a Cobalt 1. Serial #’s would begin with xx10, xx11, xx12, or xx13, the last two digits representing the year of manufacture.

One potential issue with Cobalt 1’s is what to do if the battery has run down completely in storage. A fully charged battery should provide about 6 months of “sleep mode” power, but left longer, or not fully charged, you may discover the Cobalt won't wake. If the battery goes completely dead, ideally you need to charge it first with the A/C charger. Using the USB charger on a depleted battery will charge the battery, but the unit won't get the reset pulse it needs in order to restart the program. The Cobalt will appear to be dead, but it will actually be in “boot mode”, looking for a firmware update. The display will be off. Once the battery has any charge, connecting A/C won't generate a reset either- you need charge a dead battery by using the A/C charger first.

However, if you started charging with USB you have several options:
  1. One is to just wait until the battery runs down again and re-start the charging process using the A/C adapter. Since the Cobalt is in boot mode and not sleep, it is using considerable battery power and this may only take a couple of days.
  2. Another is to connect the Cobalt to the updater program on your Mac or PC and try updating the firmware. Essentially the computer is in the mode you put it into when pressing Select in the "Connect to PC" screen. The Mac program is a bit more forgiving in this respect when it comes to recognizing the Cobalt in Boot mode. But either is worth a try. A firmware update forces the Cobalt to reset.
  3. The third option is to open the battery compartment up, remove the battery, and reinstall it. That forces a hard restart. If neither of the other options work I would do this, if only to make sure there is nothing wrong with the battery itself. Computers this age are getting to the point that some of the batteries are needing to be replaced. Typically they don't fail completely, though, they just don't take as much charge or run down more rapidly than usual. Here is a link to an instruction sheet for doing this: Dropbox - BatteryReplace.pdf - Simplify your life
If your battery is no longer holding as much charge as it should, it may be reaching the end of its lifespan. Replacements can be obtained from Atomic.

To be clear for everyone else, this is only an issue with the Cobalt 1, pre 2014. Cobalt 2 computers have a built in reset function accessed by holding down the Back and Select buttons for at least 11 seconds. That enables a reset even if you charged a dead battery via USB.
Thanks. Reset cobalt 2 and used AC charger and my cobalt 2 came back to life.
My Cobalt 1 came back too, it's been an excellent dive computer, don't get the smacktalk about them.
Hi Ron,
last week, during my trip to Sardinia, my Cobalt 1 died during a dive. It has been a great and reliable computer for the last 10 years.
At home, I opened the back of the computer only to find the battery has leaked. I searched for a new battery online, but it seems this battery is not being sold anymore. Are there compatible replacement batteries or is my beloved Cobalt now dead?


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I don't know what Atomic's current support is in Europe, but I do know they still have batteries in the US and will replace them. Posts on this thread around #25-30 discuss finding the battery directly from China. Since we added a thermistor to the battery to detect any overheating or too low temperature, I don't expect that a replacement will be easy to find, the earlier poster here needed to solder the old battery's PCB onto the one he sourced.

Unfortunately sending Li-ion batteries internationally is difficult unless they are installed in devices. It may be that the easiest path is to send your Cobalt to the US to have a replacement battery installed. Replacing the battery door seal would be a good idea as well.

I will message you directly regarding some options.

@RonR I have both a cobalt 1 and 2. Both haven't been used in about 5 years. I charged both yesterday to 100% and the cobalt 2 is fine and only lost about 2% battery in 12 hours vs the cobalt 1 where I lost 24% in the same timeframe. I followed the instructions in the thread and attached is the battery output. I live in the US, but plan on diving in Cozumel the week of April 17th. I would love to replace the battery, but I don't think I have time to send it in. Can you send me some options on acquiring a battery myself or would you just deal with the battery not holding a charge like it should?


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Based on the photos you sent, I'd say that battery has leaked badly and is well past its lifespan.It's kind of amazing you are getting power at all.
Lithium batteries do best when a mid level charge, say 40% to 80%, is maintained.
I will send you a direct message/ conversation here to suggest a way to get a replacement battery in time.

Good to know. So I don't damage the cobalt 2, do you think a good rule of thumb is to charge them every couple months?

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