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svgemini avatar image
svgemini asked

Smart BMS 12/200 with Balmar MC-612 cutting alternator input

Hello, firstly the setup.

Smart BMS 12/200

X3 Smart 200ah lithium

X2 100/30 smart mppt

X2 410 watt panels

X1 smart battery protect 100a for mppt charge

X1 smart battery protect 220a for load

Super AGM 110ah start battery

105 amp alternator

Balmar MC-612 regulator

(Balmar settings)

Bulk voltage 14.4

Bulk time .3 (factory)

Absorption voltage 14.4

Absorption time 2hrs

Float voltage 13.5

Float time .3 (factory)

Alt temp 108c

Positive voltage sense connected to starter battery. (Not lithium side)


Engine is running at 1200 RPM at the dock. I started charging via alt at 82% as seen in video the BMS % drops down as starter batt voltage reaches 13.92v. Slowly starts applying amperage until nearly 55amps (100amp fuse on alternator side of BMS) this only lasts until starter voltage climbs back up and repeat. The BMS doesn’t have charge settings so how do I get this issue solved

How do I stop this cut off?
The link for the video is below because the file format is not acceptable on this site for some reason. https://m.youtube.com/watch?v=Mu0TSW1yR4U

I have attached a pic of my wiring diagram and video of the problem.

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2dfe638e-7e18-4bfd-a6e4-2375c0488c3f.jpeg

Lithium BatteryBMSalternator
2dfe638e-7e18-4bfd-a6e4-2375c0488c3f.jpeg (523.8 KiB)
fb5f9562-af0a-4c2e-a890-1432f1e3aa5c.png (2.1 MiB)
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3 Answers
svgemini avatar image
svgemini answered ·

Update for those who are following. I figured out the problem. The batteries were balanced so that wasn’t the issue. The Balmar positive voltage sense absolutely matters where it’s is hooked up. Additionally it needs to read both battery banks. Connecting positive from start and positive after the battery protect the to positive sense pin now let’s the Balmar see a combined voltage and prevents the start battery from being overloaded and full field dumped after BMS cuts off lithium charge.

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Paul B avatar image
Paul B answered ·

first of all you need to check your batteries and make sure that the cells are balanced, if you have unbalanced cells then the bms maybe turning off due to one cell being high. please check this and advise

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svgemini avatar image svgemini commented ·
All three batteries are balanced as stated on their respective Victron connect app.
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Paul B avatar image Paul B svgemini commented ·

please send a screen shot of the cell voltages for ALL the batteries when the BMS cuts off

Edited _ I am presuming that the batteries have been connected correctly to the BMS

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northcaptain answered ·

I have almost the same problem with my new installation of a Balmar 618 regulator with a 250 A alternator, connected to a Smart BMS 12 200.


Balmar says " The voltage sense wire MUST be installed on the alternator side of any disconnect device. If a disconnect on the positive output cable of the alternator occurs -- such as a fuse blowing or a disconnect switch -- the sense wire must read the alternator output voltage and not the battery voltage. If the alternator is disconnected from the battery and the regulator is sensing the battery voltage, it will continue to output power, likely causing alternator damage.

I understand that with a 12-200 BMS we should disobey Balmar and install the voltage sense on the Li-Ion Bat+ stud.


Would be curious to see comments.

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Related Resources

Victron VE.Bus BMS product page

Victron 3rd party BMS compatibility page

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