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796 Battery Invalid

gyoung

Well Known Member
I thought I would be proactive and replace my 796 battery since it didn't seem to keep a charge as long as I thought it should (not really a problem since it's panel mounted) and the plastic was starting to get gooey. Garmin labeled packs are ~$200 and the generic are half that. So I went cheap(er). Got it, it fit, unit powered on so all seemed good. I put it in the plane. When I went to fly the next day it powered up like normal but after a minute or two displayed an "Invalid battery detected" message. Hitting OK caused it to reboot. Endless cycle, always a reboot so the 796 is worthless with that battery

The battery obviously powered the unit. I got all the normal displays until it got deep enough into its routine to trigger the battery check. It wouldn't even let me run it off the hard wired power. Garmin does a lot of things right but then they do something chicken s@#t like this that wipes out all the good. Unless someone has a fix it looks like I blew $100. I doubt I'll be able to return it. Be forewarned.
 
Good to know.
Since those are typically just standard sized batteries soldered in and packaged with the proprietary circuitry, they can probably be refurbished by a place like Batteries Plus, Interstate Batteries, etc. That would only involve swapping out the batteries not the circuitry, so I imagine it would work better for this sort of thing. Just a thought.
 
Greg,

I'm not sure about these specifics so I'll ask a couple of questions and share a couple of thoughts.

Are there just 2 wires to the battery pack on the Garmin unit? If not there may be a temp sensor or such for the charging circuit on the Garmin unit. The charging circuit can be a critical part of battery powered units.

Does Garmin sell the replacement battery packs or are they a service item? If they are a service item then maybe there is a routine that is run after a battery replacement. I guess there could even be instructions included in the replacement battery pack for reinitialization on battery replacement.

If there are only 2 wires and Garmin does sell the replacement batteries then then to detect an incorrect battery either the voltage is different or the charging current has been detected as different.

In battery powered devices often the external power simply applies power to the battery charging circuit. This may explain why the unit won't work on external power after you have changed the battery.

Take a close look at the battery specs and do a comparison.
 
It's a molded plastic pack made to be replaced by the user. It has 8 contacts that connect to spring loaded tabs when installed. It could be made by the same Chinese factory that makes them for Garmin and just be a true failure. Batteries should just work. The 796 design shouldn't just shut down if it is still getting power. Nag me if you must but don't shut down. I've bragged about how rock solid my 796 was when my iPad shuts down in the Texas heat. Now I'm not so sure. I'll try to fight with the vendor, if I can find them, but really shouldn't have this kind of hassle with a battery.
 
Good news on the refund. The vendor was Batteryship.com. I sent an email and got a quick personal response. Turns out I got the first of 2 batteries just released by their factory. He suspected a battery programming issue and asked for a pic and video of the failure to send to their engineers. He sent a prepaid return shipping label for the refund. He did say it may be months before they update the programming so I'll probably pop for the more expensive Garmin battery. Lack of hassle on the refund was a pleasant surprise.
 
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