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Preventing Deadlock on 3-phase Multiplus & Lithium with internal BMS

Hello,

I built a 3 phase configuration in my camper with 3 Multiplus 24/3000 and 6 Lithium Batteries with internal BMS.

I did a test and did not supply any external power to discharge the batteries to their own minimum (so the internal BMS would shut down due to undervoltage). After power shutdown, I connected shorepower to recharge via one Multiplus (3phase out, 1phase in). This did not work due to the fact that the Multiplus Master did not start up properly because it was missing his slave untits. The units were not provided with any power since batteries were shut down by their internal BMS. So it seems I managed to run into a deadlock.

I solved the issue by using an external 24V charger to bring the batteries back to life so they finally provides some voltage for the Multiplus Set to boot up.

Anything I missed out here? Is there any way to get this configuration back to work without external charger?

I am also now working on a system upgrade to prevent complete battery drain by switching off the 24V / 12V section by a SOC controlled shut down (this should be doable with the Cerbo).

Best Regads


Multiplus-IIcharger3 phase
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2 Answers
Matthias Lange - DE avatar image
Matthias Lange - DE answered ·

No solar power or a connection to the alternator to recharge the battery?

Fist thing I would do is to set the low voltage cut-off of the MultiPlus' a bit higher than the BMS cut-off.

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nomad avatar image
nomad answered ·

Thanks for the input!

I have 3kw Peak Solar Power about to be installed, but I want to be safe in a scenario without any solar power (i.e. at night, or if the caravan is parked in the workshop). Since it is a "Wohnwagen" I have no alternator to recharge the battery.

The Multiplus low voltage cut-off wouldn't help since the batteries will be discharged not only by the Multis but also by the DC section (which is 24V and 12V provided by DC/DC converter.

So my approach is to install a Cerbo-controlled cut-of for the DC section (and utilizing the Multiplus Cut off as well) that is above the internal BMS shut off, therefore still having a chance to boot the system up again.

But it would be a lot easier if one could get to work the Master Multiplus as a charger without looking for his buddies before going to work.


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