harald_richter5
Viano auxiliary battery woes
Summary of the thread
A Mercedes Viano owner experienced an auxiliary battery error, leading to weak cranking and general electronics issues, suspecting a charging problem. A suggestion was made to check the power management system and the Intelligent Battery Sensor (IBS) for potential voltage drop issues. It was advised to measure the battery voltage while the engine is running, aiming for at least 13.5V. Ultimately, the problem was diagnosed as a faulty auxiliary battery and charging circuit issue, which was resolved by replacing the battery and fixing the charging system.
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4 comment(s)
harald_richter5 (community.author)
IBS, huh? Where exactly is that located, and what voltage readings should I be seeing across the auxiliary battery with the engine running? I just want to rule out a simple bad connection before digging deeper.
gabrielhahn45
On the BMW, the IBS was connected to the negative terminal of the main battery. On your Viano, it will likely be similar. As for voltage, you should see at least 13.5V, ideally closer to 14.4V, when the engine is running. If it's significantly lower, or fluctuating wildly, it points to a charging issue. If it is not the IBS I would advise taking it to a shop.
harald_richter5 (community.author)
I appreciate the input. You were spot on. It ended up being a faulty auxiliary battery and associated charging circuit issue. The shop diagnosed it, replaced the battery, and sorted the charging issue. Total cost: 290€. The car electronics are behaving again.
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MERCEDES
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VIANOVITO
gabrielhahn45
Sounds familiar. I had similar grief with my old BMW, a different car I know. Voltage drop was the culprit. Check your power management system isn't throttling the charge to the auxiliary battery. The IBS, Intelligent Battery Sensor, might be playing up. Have you measured the battery voltage when the engine is running?