kieran-mcmonagle avatar image
kieran-mcmonagle asked

Alternator Charging - Orion vs BMS CL 12/100


I'm planning a set up for charging a Victron Smart Lithium 12v 200ah battery from the alternator of my van (a 2012 Mercedes Sprinter 313cdi).

I will have Dometic Freshwell 3000 air conditioning unit in the back of the van which I would like to be able to use while driving and on hookup. The plan is to run it through a Multiplus Compact 12 2000 as it requires 230v AC - 4.2amps to run.

4.2a @ 230v = ~1000W, the Multiplus will need maybe 1250W supply when considering losses?, more losses in getting the power to the multiplus, through the leisure battery, from the charger/alternator means maybe working on the basis that 1500W is required from the 12v alternator?

125amps required from the alternator - is that a fair estimate?

I need to check the alternator I have fitted but could look at upgrading if it is not 180a+

What is the best way to ensure that the supply of power from the alternator/starter battery to the leisure battery is enough to offset the demand of the multiplus/aircon and not result in flattening the battery(s) on long journeys?

Options that might work:

  • Multiple Orions in parallel - seems over the top to have 4+ orions in parallel just to achieve 120amps
  • 1x BMS CL 12/100 for 100amps, in parallel with 1x orion for 130amps total - benefit of BMS included and the voltage controlled charging from the orion to help top up the Lithium battery.

Any suggestions on how to make this work are much appreciated.



MultiPlus Quattro Inverter ChargerLithium BatteryBMSorion-tr smartalternator
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2 Answers
Matthias Lange - DE avatar image
Matthias Lange - DE answered ·

I think only the BMS 12/100 is enough.
The aircon won't need the full power all the time and it won't run non-stop for hours, after a while it will draw less power and will switch off if the set temperature is reached.

If possible you should always cool down the car with shore power so the aircon only have to hold the temperature during driving and not have to cool it down from 35°C.

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kieran-mcmonagle avatar image kieran-mcmonagle commented ·

will the BMS CL 12/100 work with a 'smart' alternator?

I guess not as it is similar to a split charge relay which I understand wont work for long periods of a journey.

My alternator has been confirmed yesterday as a 'smart' alternator, i.e. ECU controlled.

Is it possible to have both the B2B Orion for continuous 30amp charge, and the BMS CL 12/100 for the additional max of 100amps?

I think this would be similar to the CTEK D250SE + SMARTPASS arrangement?



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Matthias Lange - DE avatar image Matthias Lange - DE ♦ kieran-mcmonagle commented ·

A smart alternator can be a problem.
The voltage of the alternator have to be higher than the voltage of the lithium batteries to charge them via the BMS. If the alternator voltage will be reduced to much the charging through the BMS will stop.
The Orion can boost the alternator voltage to continue charging even with a lower alternator voltage.

So it is hard to say if it will work or not because it depends on how exactly the smart alternator will work.

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kieran-mcmonagle avatar image
kieran-mcmonagle answered ·

Ok thanks for the advice.

Is it possible to add the Orion in parallel as well?

I may have jumped the gun and purchased one a while back before I decided to add air con!

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