Starting Battery Partially Charged
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Senior Member
Joined: May 2021
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From: Shaker Heights, Ohio
2021 E450 All Terrain Wagon
Starting Battery Partially Charged
Regarding the MercedesMe app, i've always assumed that "Starter Battery Charged" meant that it was charged to full capacity. However, recently I've noticed that the app has gone from "Starter Battery Charged" to "Starter Battery Partially Charged" within as little as 20 minutes after I complete a drive; whereas, on other past occasions, it has remaiined at "Starter Battery Charged" for at least a day or two even if the car was sitting idle. Is it possible that there are levels of the battery being deemed "Charged" (e.g., minimally "Charged" after a 30 minute drive vs. maximally "Charged" after a 2 hour drive) and that these levels just aren't reflected on the MercedesMe app? Or could it just be that the weather has gotten colder and there is a greater drain on the battery? Thoughts on this would be appreciated. Thanks in advance.
Out Of Control!!
Joined: Nov 2018
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From: San Francisco Bay Area
2019 C63CS
Most batteries are technically partially charged most of the time. A battery is only fully charged at 100%, but at 99% it's technically partially charged. I don't know exactly what percentage MB considers fully charged. AGM batteries are used these days in most cars, because they can handle the power demands of all the electronics. But AGM batteries charge at a slower rate, so it takes longer drives for the battery to fully charge. On top of that, these cars don't completely shut off when parked, as they always maintain an Internet connection so the app can communicate with it. There's a standby mode you can activate which shuts everything off for extended idle time. Some cars also use lithium batteries, which are most happy when partially charged between 20-80%, so a lithium battery is rarely fully charged. Even the AGM batteries are often not actually fully charged to leave room for recuperation. Even non electrified models use the alternator to recoup some energy while you are coasting, so the battery management needs to leave room for that. Basically don't worry about it. If the SoC goes critical it will tell you. You'll get an alert on the phone and an email if the battery reaches critical charge. I've gotten some of those in the past while my car was in service and worked on, draining the battery.
Last edited by superswiss; Oct 7, 2022 at 01:51 PM.
Thread Starter
Senior Member
Joined: May 2021
Posts: 338
Likes: 101
From: Shaker Heights, Ohio
2021 E450 All Terrain Wagon
Most batteries are technically partially charged most of the time. A battery is only fully charged at 100%, but at 99% it's technically partially charged. I don't know exactly what percentage MB considers fully charged. AGM batteries are used these days in most cars, because they can handle the power demands of all the electronics. But AGM batteries charge at a slower rate, so it takes longer drives for the battery to fully charge. On top of that, these cars don't completely shut off when parked, as they always maintain an Internet connection so the app can communicate with it. There's a standby mode you can activate which shuts everything off for extended idle time. Some cars also use lithium batteries, which are most happy when partially charged between 20-80%, so a lithium battery is rarely fully charged. Even the AGM batteries are often not actually fully charged to leave room for recuperation. Even non electrified models use the alternator to recoup some energy while you are coasting, so the battery management needs to leave room for that. Basically don't worry about it. If the SoC goes critical it will tell you. You'll get an alert on the phone and an email if the battery reaches critical charge. I've gotten some of those in the past while my car was in service and worked on, draining the battery.
Out Of Control!!
Joined: Nov 2018
Posts: 11,432
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From: San Francisco Bay Area
2019 C63CS
Even in the MHEV vehicles as far as I know the battery shown in the app is the 12V battery, because the 48V battery can't be directly charged. I think even with the 48V ISG, there's a backup belt starter powered by the 12V battery. Once the engine is running, then the ISG is used to restart it.
Thread Starter
Senior Member
Joined: May 2021
Posts: 338
Likes: 101
From: Shaker Heights, Ohio
2021 E450 All Terrain Wagon
Even in the MHEV vehicles as far as I know the battery shown in the app is the 12V battery, because the 48V battery can't be directly charged. I think even with the 48V ISG, there's a backup belt starter powered by the 12V battery. Once the engine is running, then the ISG is used to restart it.
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TOYOTA
That’s a really interesting observation, and I’ve noticed similar behavior with the MercedesMe app. From what I understand, the “charged” status isn’t always a reflection of full battery health but rather the surface charge after driving. Factors like short trips, colder weather, and parasitic drain can cause fluctuations. In the middle of researching battery tech, I came across Stanford Advanced Materials, which highlights how different compositions and conditions affect charging efficiency. It makes sense that the app might simplify these levels instead of showing granular details.
Last edited by KorbinSipes; Sep 15, 2025 at 03:32 AM.
