I recently purchased a CTEK MXS 5.0 to charge my 2025 ES300h for the four months of the summer that it will be sitting idle. I have hooked it up red clip to the positive terminal in the fuse box with a ground to the engine. When I turn it on I get a solid green light. I have it set to Normal Battery Program with the AGM option. The green light stays solid for about two minutes and then starts blinking. It that indicating that the battery is fully charged or possibly something else? Your help would be appreciated.

 

With chargers I have used (not yours) with correct hook up if the battery is needing charge the green light comes on and cycles on and off during charging, when fully charged it is full green. Your cycling green light indicates to me that the battery needs charging.
I see that CTEK charger is very hi tech and has a battery maintenance feature for long periods of car not being used.
Have you taken a voltage reading across the + and - of the battery to determine the state of voltage?
A fully charged battery should be 12.6v or somewhat higher. Some chargers will even want to charge if the battery reads 12.8v.

Here is a brief video

https://www.bing.com/videos/rivervie...=0&FORM=VMSOVR

 

Here is your manual. On page 13 it seems to indicate that if a light is blinking it’s not charging because it’s not hooked up to the battery correctly.

https://www.ctek.com/storage/AEB64A2...-low-US-EN.pdf

I use a battery Maintainer on my Corvette and I’ve never seen a flashing light come on while using it. By the way, your charger is a really nice one.

 

For the 4 months idle I would be worried about the hybrid battery. I think in my manual for storage the hybrid should be charged within 3 months.

 

If you truly have a 12 Volt AGM battery in your vehicle then you need to put you CTEK into "Snowflake" mode and not use "Normal" mode. This is in the manual. An AGM battery needs to charge with a 14.7 volt potential. Normal mode only provides 14.3 volts. Only by using the Snowflake mode to charge will you fully charge your AGM battery. CTEK calls it Snowflake mode as this mode would also be recommended for a typical 12 Volt flooded lead battery when the environmental temperature hovers at or below freezing temperatures while charging. This is all documented in their fine manual nobody reads.

 

For those of you searching for the 'Snowflake' mode on your CTEK battery tenders and not finding it don't fret. The only CTEK chargers with the 'Snowflake' mode are the POLAR models. All the other CTEK chargers have an AGM mode for charging AGM batteries.