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markus-power asked

Victron MultiPlus C12/2000/80-30 stops loading

Hello Victron Community

I'm operating a Victron MultiPlus C12/2000/80-30 in my campervan.

It's a new device which was installed 6 weeks ago.

My use case is, that I usually park the van in a garage on Sunday evenings, plug the van into the normal grid, the charger starts working in bulk mode and charges the battery. All as it should be.


Now comes Saturday morning, I return to the van after a working week has passed, and the battery capacity (240Ah Li) is on 75% and the charger does not charge the battery any more.

Only when I swich the charger off and on again on the remote control panel, the MultiPlus will start charging again.

I repeated this several weeks now and the pattern is stable. It's always the same percentage battery load left an the charger does not charge any longer.

I suspect that the charger loads the battery just fine up to 100% (which I have seen at an intermediate control visit) and then switches itself off after some time but always at the same time after the battery was fully charged - hence the stable 75% value of battery load when I come back to the van.

Also, I think that it must be the MultiPlus itself that consumes the 25% battery load in the meantime as there are no other devices running except from the display of the Battery monitor and the display of the heating system.

Why does the MultiPlus stop charging the battery after some time and why does it consume energy?

I'd be extremely grateful for any hints!

Many thanks, Markus

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1 Answer
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Paul B answered ·

The multi will charge in bulk to its set point of say 14.2v this is the 100% full value and then usually the BMS rebalances the cells, then it goes to absorption and holds 14.2 for the set time period. then it changes to float where the voltage drops to float at say 13.4volts

Most people dont like holding the lithiums at a 100% full value all the time so they drop them back to a reduced level

So now its 100% full at 14.2 and then as the unit switches to float the charger is basically turned off until the voltage reaches the float set point of say 13.4 so then this causes the batteries to discharge until float voltage is reached. you could raise the float voltage up somewhat if you wanted.

this is very noticeable in lithium batteries from time to time as there internal loss's are so LOW

so to solve this set your battery monitors charged voltage to the float voltage setting and the 100% should stay then until that voltage reduces below the float value.


hope the above is of some help and that it makes sense to you

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markus-power avatar image markus-power commented ·

Dear Paul, thanks a million for your help! Yes, this all makes great sense to me. If you allow, I will ask you follow up questions hoping it will not bother you and if it does, please ignore them :-)

My first question would be where / how I can see these preset thresholds of voltages and the time span the Multi stays in absorption.

Secondly, is there a threshold that will start the charging process again when in float and the voltage continues to drop? Or will the battery eventually discharge entirely?

Thirdly, I didn‘t understand this one part of your answer: this is very noticeable in lithium batteries from time to time as there internal loss's are so LOW

My battery appears to loose 25% (of 240Ah) within a week of hardly any power consumption. This seems not quite right. Would you think that‘s within the range of expectable?


Many thanks @Paul B and best wishes from Hamburg, Germany.

Markus


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Paul B avatar image Paul B markus-power commented ·


My first question would be where / how I can see these preset thresholds of voltages and the time span the Multi stays in absorption.

You need a MK3 which is a VE bus to USB converter then connect via VE configure program, or if you have a VRM connection through a Venus GX device then you can download the configuration and check and change it

Secondly, is there a threshold that will start the charging process again when in float and the voltage continues to drop? Or will the battery eventually discharge entirely?

it will supply any loads once the voltage is below the float voltage or it will auto restart when needed to bulk.

Thirdly, I didn‘t understand this one part of your answer: this is very noticeable in lithium batteries from time to time as there internal loss's are so LOW

Lead Acid batteries loose energy when charging by about 20% Lithium only loose around 5% plus the auto discharge of lithium is much lower as well, ie with LA you use 100amps you have to put back 125 amps. Lithium phosphate you use 100 amps you put back 105amps . plus the other loss's just readup on the difference of the two types of battery.

one other thing that uses power in a lithium battery is the BMS as it balances the cells at around 3.5v or above for each cell, but this is inside the battery and before the shunt so you dont really see that

My battery appears to loose 25% (of 240Ah) within a week of hardly any power consumption. This seems not quite right. Would you think that‘s within the range of expectable?
I has not lost it you have used it just by the consumption of what the inverter uses of about 2 to 4 amps that the inverter uses just by being ON it uses around 2 amps so for 24hrs is 48amp hours as a example, the standby usage is about 60 watts
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