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thorben avatar image
thorben asked

Multiplus 12/500/20: problems with Charging lifepo4 battery in camper van

Hi,

I have some issues with my multiplus 12/500/20 in battery charging mode. While charging a lifepo4 battery the multiplus shuts down the charging current when increasing battery voltage of 13.8V.

Since battery voltage drops with absence of charging current, the cycle starts again and again and again. Therefore battery can’t be fully charged

Any ideas what could potentially trigger the current shut down event when increasing 13.8V? (Multiplus is set to correct lifepo4 mode with the dip switches).

Further info: In the system there are also some loads, which lead to the negative currents. The system is also connected to a Victron solar charger which fully charges the battery without any issues.

Thanks for any ideas.

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33f9eb98-96d6-47c2-842e-ac8edd4779a6.jpeg (239.6 KiB)
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Alexandra avatar image Alexandra ♦ commented ·

@Thorben

Just a question, how do you know -for sure- that the Multiplus is set correctly with the dip switches?

It is possible it is overwhelming the battery with too much charge current and the BMS is tripping.

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5 Answers
mvas avatar image
mvas answered ·

Try setting the Absorb Voltage in the Multiplus to a value +0.1 v higher than your MPPT. See if that will temporarily solve the problem. Are you sharing the charging information between the Multiplus and MPPT?

Post an image of your battery and charging parameters.

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kevgermany avatar image
kevgermany answered ·

Looks as if the BMS is shutting down the charge, not the multiplus, as there's a big voltage spike immediately after the shut down point.

Is the solar charger running at the same time as these graphs above? Would help to see the graph from the solar charger at the same time.

What happens when it's just the multiplus charging?

How big is the battery? Max charge current? Solar charger model/output?


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thorben avatar image
thorben answered ·

hi all,

thanks for your quick replies. Here are the missing information:

  • General info: the camper van setup is the following: the lifepo4 battery can be charged either via solar (2*200W) MPPT 100/30, via AC (Multiplus 12/500/20) or via starter battery/alternator +DCDC converter (max. 25A) with LiFePO4 charging characteristics on the road. However only one (or none) of the options is used at the same time.
  • Therefore no charging information are shared among the devices.
  • The lifepo4 being used has an internal BMS which is accepting charging currents up to 100A (BullTron 12V 150Ah Basic). While charging on the road from DCDC converter the battery is accepting up to 25Amps without any issues.
  • The MPPT charger is used with two foldable 200W solar panels which however weren't plugged in when I noticed the suspicious behavior of the Multiplus.
  • I am not able to change any parameters of the multiplus (beside these which can be modified via dip switches) because I cannot access it via Bluetooth and I don’t have the VE smart dongle.

I hope these information will help to understand the issue and can lead to any kind of solution.

Thanks a lot

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kevgermany avatar image
kevgermany answered ·

Just a guess. Check the cabling from multiplus to batteries. Switches, fuses, connection tightness. I'm surprised by the low charge rate and cut outs.

Also check multiplus temperature. Is it getting hot/fan coming on?

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thorben avatar image thorben commented ·
Hi Kev,

I have already checked all these. Seems to be fine without any issues.

Check my latest additional information. There you can see, that the charging procedure up to a certain voltage ~13.8-13.9V is working flawless at max. current.

In my opinion any bad cabling or high temperature would have an impact already below the above mentioned certain voltage.

Thanks

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thorben avatar image
thorben answered ·

I have some more information right now. I stopped the charging process yesterday evening since I was not able to exceed 94% SoC.

Over night the soc dropped to 85% due to the running refrigerator and so I turned on the Multi again this morning. Now I can observe the same behaviour as last night but the recorded data is much clearer. First the charging works fine with like max. current and then the system enters the incorrectly behaviour again. See attached screenshots (the last images shows the whole charging process from 85% to 94% SoC)


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ce1c2f4d-264e-4420-84e1-ef9347e3aa99.jpeg (213.6 KiB)
b38f4b63-38cd-4b98-b48e-d3ced33584fa.jpeg (249.2 KiB)
c3f0aa66-4430-4b87-b99c-03057a41fd34.jpeg (223.2 KiB)
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