HC says battery on main board is low. Gemini web server says battery at 2.066 volts. Mount is operating normally. I checked the battery with volt meter and it reads 3.2volts. Been a while since I updated the HC and mainboard. Using GM8 with the tall mainboard. Pls advise.?

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Hmm,?

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Have you tried doing an HGM reset then pulling out the battery and letting it sit 10 minutes before powering it up and then installing the battery with the Gemini 2 still powered up???

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On Wed, Dec 11, 2024 at 08:01 PM, Kevin Hannon wrote:

HC says battery on main board is low. Gemini web server says battery at 2.066 volts. Mount is operating normally. I checked the battery with volt meter and it reads 3.2volts. Been a while since I updated the HC and mainboard. Using GM8 with the tall mainboard. Pls advise.?

On Wed, Dec 11, 2024 at 05:01 PM, Kevin Hannon wrote:

HC says battery on main board is low. Gemini web server says battery at 2.066 volts. Mount is operating normally. I checked the battery with volt meter and it reads 3.2volts. Been a while since I updated the HC and mainboard. Using GM8 with the tall mainboard. Pls advise.?

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Hi Kevin,

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How did you check the battery voltage?? The standard measurement method of a coin cell is out of circuit, in other words the battery should be removed from the battery holder to get an accurate measurement.? If you have a recently calibrated DMM and the battery is reading 3.2v this sounds like a nearly new battery and it seem like this is not the source of your voltage reading error.?

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You could try the HGM reset trick I posted and see if this fixes your incorrect battery voltage reading.? But if the low battery voltage display doesn't impact anything maybe don't mess with it until you see other strange behaviors.? ?

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I will clean the connections and try again.?

Unless your meter has a battery check setting the cell is under no load. I used to use the 9v battery check on my meter and toss a battery if under 2.9 volts under load.

Now use a Tenergy t-333 battery tester .

On Fri, Dec 13, 2024 at 09:44 AM, BrianH wrote:

Unless your meter has a battery check setting the cell is under no load. I used to use the 9v battery check on my meter and toss a battery if under 2.9 volts under load.

Now use a Tenergy t-333 battery tester .

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The usual way most folks test a coin cell is open circuit.? The reason this is suggested is few people will have a battery tester that can be set with the correct load for the particular cell type and chemistry of the battery under test.? Even fewer people will have an accurate recently calibrated DMM which can accurately measure and display voltage below 0.01 volts.?

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If you do have a better DMM basic accuracy of 0.5% + 3 lab most of which start at $150-$600 and up you know how easy it is easy to look up the specs for a particular type and chemistry of the cell and use an inexpensive resistor with the correct value in line to see the drop.?

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On Sat, Dec 14, 2024 at 09:47 AM, Michael A. Covington wrote:

I? have had a lot of experience testing coin cells, and I don't think
the open-circuit voltage is deceptive.? It is higher than the voltage
under load, of course, but if it's reading 3.2 V open circuit, the coin
cell is good and the problem lies elsewhere. You could substitute
another one just in case -- easier than getting a new tester.

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Agreed.? No load coin cell voltage is the standard used by the battery manufacturer associations.? A new manufacturer small lithium coin cell can read over 3.3v out of the package, typically 3.2v on the shelf and after 6 to 12 months in my Gemini 2 minis 3.0v in a warm room.

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Once the hit 2.9v in a warm room I toss them due to having and seeing too many experiences with bad behavior at this voltage level with Gemini 2 controllers. The industry standards say that once the unloaded voltage falls 10% of nominal new voltage it is worn out.?

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This is not to say they don't still mostly work just that this is considered an exhausted cell. But this checks out with my experiences in the field in the cold.? Some people report not having issues with voltage readings below 2.9v in a warm room but if there is anything that can ruin a night in the field it is strange Gemini 2 behavior.? If you have to do an HSM default? reset or replacing the battery solved the problem it can be traced back to a marginal battery and most folks don't recognize it.??

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Believe me, 2.9v unloaded on a warm room is a marginal battery in the field on a cold night. It may not happen that night but the low voltage battery caused data corruption will eventually disrupt your night.??

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The other major bummer is an old power pack battery.? This can also cause issues with Gemini 2 data corruption and can look like a bad internal battery. Most lead acid chemistry batteries unless very fresh and freshly charged are marginal in the cold.? Modern LiFePo4 chemistry batteries with onboard battery management and regulation do not display this problem.??

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On Thu, Dec 12, 2024 at 12:48 PM, Kevin Hannon wrote:

I will clean the connections and try again.?

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Hi Kevin,

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So did the contact cleaning make the Gemini reported voltage match the DMM readings?? The curious want to know.??

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Cleaning contacts did not solve the problem. Problem was that I was connecting Gemini usb 2.0 port to a Pegasus power box/usb hub 3.0 port. Once I connected to a USB 2.0 port on the Pegasus, the hand controller stopped reporting a low mainboard voltage and the Gemini web server showed the expected 3.2 volts.

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The mount had no operating issues when the web server showed the battery at near 2.0 volts.?

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On Sat, Dec 28, 2024 at 06:13 PM, Kevin Hannon wrote:

Cleaning contacts did not solve the problem. Problem was that I was connecting Gemini usb 2.0 port to a Pegasus power box/usb hub 3.0 port. Once I connected to a USB 2.0 port on the Pegasus, the hand controller stopped reporting a low mainboard voltage and the Gemini web server showed the expected 3.2 volts.

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The mount had no operating issues when the web server showed the battery at near 2.0 volts.?

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That's weird.? Which USB port were you connected to? The rectangular USB type A or the square? type B?? Were you controlling the Gemini 2 over the USB port?

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