Battery Monitor on Cerbo GX not accurate when charging via alternator

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sagascoigne asked Aug 10, '21

Battery Monitor on Cerbo GX not accurate when charging via alternator

I have a new Widebeam canal boat which has a complete Victron system.

Cerbo GX with screen, 2 solar chargers, inverter, smartshunt, galvanic isolator and 3 200ah Lithium batteries.

My problem is when charging from the alternator on the engine the battery indicator on the Cerbo only goes up by say 10 to 20 % after 6 or 7 hours of cruising. The voltage get to 14.2 volts and the alternator stops charging but the meter on the screen only shows 30 to 40% charged. If however I charge from a portable generator the boat fully charges in about an hour and a half and the indictator shows 100% charge

Is there a setting that needs to be changed, I have contacted my supplier several times, but having no joy.

Thanks

cerbo gx battery charging alternator

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Answer 1 · 2021-08-10T12:28:02Z

Matthias Lange - DE answered · Aug 10, 2021 at 12:28 PM

I guess the alternator charging current bypasses the SmartShunt and can't be counted.

Do you see the charging current at the Cerbo or SmartShunt (using VictronConnect)?

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Answer 2 · 2021-08-10T17:01:42Z

pwfarnell answered · Aug 10, 2021 at 05:01 PM

Do you have "has DC system" enabled so you see a small box between the battery and the solar on the Cebo screen.

my new narrowboat has a similar system to your s but i have AGM batteries and it counts the alternator OK. Most UK canal boat engines return the negative from the alternator through the alternator case and the engine to the negative wire. My guess is that your negative wire has been returned to the battery rather than the load side of the shunt. Mine is on the load side.

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pwfarnell commented · Aug 10, 2021 at 06:06 PM

I should also add that the negative connection to the hull earth point should also be made to the load side of the shunt and the negative link between starter and domestic batteries should also be to the load side of the shunt. If either of those is connected to the battery side of the shunt you can get alternative routes for current bypassing the shunt.

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