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Paul Thornton avatar image
Paul Thornton asked

BMS 12/200 Reduced Alternator Input with Balmar MC618 Regulator

I am having a problem with the BMS 12/200 and a Balmar MC618 regulator controlling a 150A alternator. The 600 AH lithium battery bank is at 50% discharge. The alternator outputs high current for 15 minutes and then starts cutting back it's output, this is because after 15 minutes (the default setting) the Balmar regulator senses the voltage of the start battery and determines that it is fully charged. The sensing period of the regulator can be extended in increments up to 2 hours, meaning it would demand high output for that period, but I am concerned that the start battery may be damaged by seeing a high voltage for an extended period while it is fully charged. The start battery is a Victron AGM. Any suggestions regarding this problem would be appreciated.

battery chargingBMS
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2 Answers
pwfarnell avatar image
pwfarnell answered ·

The BMS 12/200 is designed for an unregulated alternator to make installation on basic engines easy where the engine start battery is always at circa 14.4V. Having the Balmar controller on the alternator is therefore not ideal with this BMS. You either need to set the float voltage higher or hold the absorption voltage for a longer fixed period if you keep the current BMS. Otherwise consider changing to the VE Bus BMS V2 with the alternator charging the house batteries and use an Orion DC to DC for the start battery. The Balmar regulator would then be set to a lithium profile with a derating factor if required charging . Wire the Balmar regulator ignition through the VE Bus BMS "allow to charge relay" to shut the alternator down if there is a battery problem.

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Paul B avatar image
Paul B answered ·

More info needed

ie

voltage at the lithium bank when the balmar is starting to cut back,

is this one bank or is there multi bms units connected.

really the engine battery should be charged with a dc to dc charger and then the alternator sense could be connected to the lithium batteries via a charge cutoff control. the bms 12/200 is not my favorite device. (note this is a personal comment)

anyway the 12/200 bms output is controlled by the fuse size, so make sure its allowing the full 150amps to pass and play with the fuse size to get whats needed.


or maybe a redesign of the bms battery cutoff if need be would be needed.


a lithium bank should take the full 150 amps all the way until its full. unless the batteries you have have internal bms inside them then the bms maybe turning individual batteries off,

so look at the batteries and monitor each batteries cell voltages.


before you start playing with the balmar

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