Smart BMS 12/200 not getting full charge from Sprinter alternator

Hello, I have a Smart BMS 12/200 with 100A fuse connected to the starter battery of my 2017 Mercedes Sprinter.

In theory I should be getting 90A of charge based on the 100A fuse, but I am only getting max 25% of charge current (25A). Is this something to do with the Sprinter's alternator? It seems like I should be able to pull more than 25A with the stock Sprinter alternator. Is there something in the setup that needs to be changed?

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klim8skeptic ♦ commented · Jan 31, 2023 at 08:36 PM

Your alternator/starter voltage is very low.

To charge your battery up to 14.2v, you need the alternator/starter voltage to get to ~14.4v.

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pwfarnell commented · Jan 31, 2023 at 09:06 PM

Is this a smart alternator as in a Euro 6 engine, if so the engine ECU can lower the alternator voltage to reduce load on the engine when high power is not required by the vehicle systems. Search for Euro 6 on this forum or caravan forums to find about poor charging of domestic batteries from such alternators.

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