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2017 C Coupe C200
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10 Posts
Discussion Starter · #1 ·
Hi guys,

I recently changed my battery and everything works fine.

When I went into the voltage check function on my dash.

The UB was 14.3 when engine is on and 12.6 when engine off

My question is I do understand IB is negative when the engine is off and as soon as you start the car it goes positive which mine does that. But at idle, the IB gradually drops and stays around 7.2~7.5 amps.

Is this normal?
 

W163 and General M Gremlin
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Welcome to the forum jjkh58,

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2020 Mercedes C300
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155 Posts
What do you mean by "UB" and "IB".

The voltage goes up when the car is running and the alternator is charging the battery. Different cars have different methods of regulating voltage when the car is running. It may come down again once the battery is sufficiently charged.
 

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2017 C Coupe C200
Joined
10 Posts
Discussion Starter · #5 ·
@calonzo UB: Battery voltage - Votage and IB: Battery current - Amp, you can find this in the hidden menu of the dash interface. IB should be positive when the engine is on, which is what its doing on my car but it drops to 5~7.5 when idling and when driving its higher than that. So I was wondering what is this IB/ amp measure should be for benz. I have seen a lot of article that talks about UB but not many on IB so.
 

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2017 C Coupe C200
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10 Posts
Discussion Starter · #7 ·
Yes I get that. But my question is, is it normal to drop regardless of whether you are idling or driving? The IB increase up 30~40 amp when the engine starts but then it slowly drops to 4~7 and I was wondering if this is normal. I guess it is as long as it stays in plus range but why the amp drops while the voltage is stable at about 14.3v
 
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