C4GP battery drain after battery change

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dudi0108
Posts: 3
Joined: 24 Apr 2024, 18:48

C4GP battery drain after battery change

Post by dudi0108 »

Hi everybody!

I haven't found anything similar to my problem, that's why i started this topic.
So, the car is a 2012 c4 grand picasso 1.6 e-hdi, which has a start stop system.
The old battery is a Varta AGM 70Ah 760CCA battery, which is like the original one accorsing to my findings.
The new battery what I installed aprox. 2 weeks ago is an Exide EK720 72Ah 760CCA, basically the same as the old one.
I think i did the BSI reset without any issues.
The old battery couls hold 12,1-12,3V thats why I changed it.
Today we finished a 2300+km long trip and the new battery measures 12,4-12,5V...
On idle the battery voltage is 14,6-14,8V which semms a bit high for me, but maybe its OK for the AGM battery. If we measure the voltage at around 2-3k rpm the voltage remains the same.
The intresting part:
I have a launch diagnostic tablet, and 1 week ago i was monitoring the DPF temps. Then the voltage during our trip dropped to 12,6-12,8V.
When the engine was idling its the normal 14,6, when we are traveling at 2k rpm the voltage drops.
Is it normal behavoir, or there might be some problem with the voltage regulator system, or should I try another BSI reset?
dudi0108
Posts: 3
Joined: 24 Apr 2024, 18:48

Re: C4GP battery drain after battery change

Post by dudi0108 »

Today I had some time, and I was playing with the car.
I was reading the battery status during engine idle speed, and while driving.
At the beginning the charge status was ~78% and after 5-10km's it went up to 83%. The charging current gradually decreased.(40A->20A->10A->4A)
I haven't really found proper informations, but for me it seems the system will shut down at around 85-90%.
It's a brand new battery, so it's confusing why it's not able to reach the 100%. We dont' use it daily, but we just arrived from 2000+km trip on wednesday.
Does anyone have similar experience?
I will monitor the battery charge on our longer trips, because I'm curious if it's able to reach 100% or not.
PaulC5
Donor 2024
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Joined: 06 Jun 2023, 15:26
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Re: C4GP battery drain after battery change

Post by PaulC5 »

If your car has a smart alternator it will vary its voltage depending on how much is needed. As an example with little need it might idle at 12.7 volts but if the headlights or other high amps users such as the window heater are on its voltage will increase. Rather than looking at charge status the voltage will be better to monitor.

You could check the alternator belt is in good condition and not slipping.
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xantia_v6
Forum Admin Team
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Joined: 09 Nov 2005, 23:03
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Re: C4GP battery drain after battery change

Post by xantia_v6 »

Your car has a "Lin Bus" alternator which has a variable output voltage controlled by the engine ECU.

The amount of charge going into the battery is reduced to save fuel and under normal conditions, the battery is not charged to 100%. Perhaps this is to allow some extra efficiency by putting more charge into the battery while coasting downhill?
dudi0108
Posts: 3
Joined: 24 Apr 2024, 18:48

Re: C4GP battery drain after battery change

Post by dudi0108 »

Thank you all your answers.
I did some more research and I found the same as you mentioned.
In the meantime I checked the battery state of charge with my launch diag. The maximum state of charge is 85%. When the battery reaches this state, the system will reduce the charging current, or shuts off completely.
It seems it's usual for the modern cars today, I doubt it's good for the battery, but probably car manufacturers knows better.