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GMC Sierra, Bolt, Sky, Mach E
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Maybe a deep cycle or lithium could solve it?
These are most likely AGM, which are supposed to have very little vampire drain, unlike lead acid. My Bolt and Mach E both have AGM batteries, and I put a deep cycle AGM on my boat.

If you go to other EV forums, like Mach E or Rivian, the same battery issue seems to occur often on those as well. Not only that, but then because of the PAAK (phone as a key) feature, people also complain that the car apps cause the phone batteries to drain too fast. The phone and the vehicle are always trying to pick up a Bluetooth connection.
 

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GMC Sierra, Bolt, Sky, Mach E
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EVs have much more monitoring systems and the Hummer also has walk up and away light animation. Constantly looking for the fob.
Also, these vehicles are "connected" (4G/LTE or Wifi) and looking for OTA updates as well. The 12V should be charged when the vehicle is plugged in to an L2 charger and while driving. But when they sit at dealers for a while, they are likely not always plugged in. Also the 12V batteries in EVs are not used to crank the engine, so they are lower power batteries to begin with.
 

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GMC Sierra, Bolt, Sky, Mach E
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Don’t most trickle chargers have to be plugged in to a wall outlet? I used to have one when I stored my C7 in the winter. Do they make portable ones? Just curious so if I go park at an airport for 5 days I could hook up a trickle charger so it isn’t dead when I get back from traveling
I have parked my Bolt at the airport for up to 7 days, without any issue.
 

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GMC Sierra, Bolt, Sky, Mach E
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Why isn't there a "jumper" backup system built in? i.e. instead of having to lug around a sub-1kWh jump starter battery from Amazon why can't the 212kWh battery in the car "jump" itself? I'm assuming it already has to step down a charge without an alternator to keep the 12v up anyway.
The main high voltage battery is switched off when the truck is off. The 12V and a computer control the battery contactors to turn it back on. So when the 12V is dead, the other battery is not usable.
 

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GMC Sierra, Bolt, Sky, Mach E
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The EVSE is the unit most people call the charger you install in your garage. It is not actually a charger, the charger is in the truck. The EVSE is simply a switch that turns on 240V to the truck. There is a communications link in the J1772 plug that allows the truck to read the supply voltage and maximum current capability, and the truck can tell the EVSE when to turn on. The 240V to the truck can be turned on without the truck actually charging the high voltage battery. That 240V is converted to DC to run the HVAC system and to also charge and maintain the 12V battery, that is in addition to the ability to charge the main battery.
 
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