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marekp avatar image
marekp asked

How "2 signal BMS" can control MPPT 150/35 when MP-II fails to "externaly control" it?

My system has LFP battery with "2 signal BMS".

Signals are connected to MP-II but there is smartsolar MPPT 150/35 also charging the same battery.

When all is working properly MPPT is externally controlled, but what will happen when "external control" fails (MP-II stops controlling) and MPPT still charges my battery when BMS sends the signal to stop charging to MP-II but not to MPPT?

MPPT SmartSolarBMS
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1 Answer
nebulight avatar image
nebulight answered ·

I assume if you have a GX device (cerbo, venusgx, color control)? If not, you can use a ve.direct non-inverting cable to turn off the MPPT: VE.Direct non inverting remote on/off cable - Victron Energy

However if you have a GX device, the ve.direct cable is in use so you can't use this. This may not be the preferred method, but I use a smart battery protect between the battery and the OUTPUT of the MPPT. I wire the allow to charge BMS signal the remote port of the battery protect. So when the BMS doesn't want charge, it will open the battery protect and disconnect the mppt output from battery. This function would be the same as a drop in battery should the BMS disconnect and got confirmation that this won't damage the victron MPPTs.

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marekp avatar image marekp commented ·
@nebulight

Thank you for this info.

I have GX device in the system, so this cable cannot be used.

Do you know which model of battery protect should I use for this MPPT 150/35?

As a additional question.

In my system I have EasySolar-II GX. It has MPPT250/70 inside.

Do you know if this problem exists also with this internal MPPT?

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