Agm batteries if allowed to go weak will accept a surface charge but the damage is already done and it's life expectancy and ability to maintain a deep charge is gone. Read up on them.
Check the pickup and suv forums; the AGM batteries in the redesigns are AGM and are dying. After 7 days 1/2 of them won't start on dealer lots if not left in transport mode. This is with less than 1 month old vehicles that were charged for the 20 minute pdi mode charge.
AGM batteries require an AGM compatible charger set to AGM battery type. Charge it like a flooded battery and it's toast. Let it run down too low; just like the Fisker's Li-on and they basically brick.
The parasitic drain while sitting is very high due to all the electronics; especially the keyless entry and the anti theft so...
1- Keep it charged the right way with the correct charger set to agm if you use it for short trips. This includes trickle/maintainers ... check that it is compatible with or has a setting for AGM batteries!
2- use it for more than short trips frequently meaning >30 minutes ... Remember if you're the one with the radio volume at 40, blower on max and headlights on you are really discharging the battery ... they suck a lot of juice! Remember alternators are designed to maintain a full charge in a good fully charged battery ... NOT TO RECHARGE A WEAK OR DEAD BATTERY!
3- if not using it for >5 days turn her off in "transport mode".
Some customers may comment that there is a "Transport Mode On" message displayed in the DIC and/or the red battery light is flashing. The transport mode is intended for use on vehicles being shipped outside of the United States and Canada.
For the 2014 model year, some products will be shipped from the assembly plant with the Transportation Mode On. The feature reduces the electrical load on the battery when the vehicle is parked, which extends the battery stand time.
To alert the operator that the mode is on, the red battery telltale will be flashing and if equipped with a DIC, it will display a Transport Mode On message. When the Transport mode is on, the Remote Keyless Entry (key fobs) is disabled, as well content theft deterrent and exit lighting timers are reduced.
When the vehicle is running, the only difference in operation will be the DIC Message and Battery Telltale on. The Remote Keyless Entry function is restored with the ignition in run.
The intent of the feature is to prolong battery stand time. The mode may be left on while the vehicle is in dealer inventory. Also a customer may want to use the mode if the vehicle is going to be stored. The method to turn the mode off is the same to turn the mode on. Refer to the section below for the method to turn the mode off and on.
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2011-2014 Vehicle Procedure
To turn the Transport Mode On/Off, it will be necessary to start the engine, activate the hazard flashers, press the brake pedal (automatic transmission) or clutch pedal (manual transmission) then press and hold the Start/Stop button or turn the ignition key to the crank position for 15 seconds. The same steps are used to turn on the feature.
2010 Chevrolet Camaro Procedure
To turn the Transport Mode On/Off, it will be necessary to activate the hazard flashers, turn the ignition key to the crank position, and then hold it in the crank position for 15 seconds. The Transport Mode Off message will be displayed and the Battery light will turn off.
2010 Cadillac SRX Procedure
To turn the Transport Mode On/Off, it will be necessary to push and hold the Start/Stop button while the brake is applied for 15 seconds or until the Transport Mode Off message is displayed. For SRX, if Transport Mode is active, this causes the RKE system to only work when the ignition is On or the BCM is awake (approximately 20 minutes after ignition off).