question

Spyros Tziakouris avatar image
Spyros Tziakouris asked

2 Smart Battery Protect 48V - 100A low voltage output

Hi,

A 48v system, has 4 victron lifepo4 12,8V 300Ah, 2 Battery Protect 48/100A. BP1 has the 48V loads connected. BP2 has one non-victron Inverter connected, 2.3kVA. BP48-100.jpg

Issue: While Battery Protect 1 is working fine, MCB of the second load is switched on. On that moment, BP2 is activated. BP1 seems to work fine, but voltage output is only around 5-10V. to fix this, MCB for BP 1 is switched off and on again.

Both BP get signal from VE.bus BMS. is this due to the surge current from inverter? Can we use BP with inverters rated below 2.5 kVA?


Regards,

Spyros


BMSBattery Protect
bp48-100.jpg (512.8 KiB)
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2 Answers
Matthias Lange - DE avatar image
Matthias Lange - DE answered ·

To cut off the inverter you should use a cyrix-li-load instead of the BP.

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Justin Cook avatar image
Justin Cook answered ·

@spyrostz, using the BP to directly disconnect the main DC line of an inverter (any inverter) is expressly forbidden. The only approved method of using a BP to trigger an inverter on/off is by using it as a trigger for the remote on/off of an inverter (if so equipped - Victrons have a remote on/off but you mention it's a non-Victron, so I don't know if you have one or not).

Please see the recently updated BatteryProtect user manual, which has several sample diagrams showing approved connections.

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Spyros Tziakouris avatar image Spyros Tziakouris commented ·

we will use external 48v relays to make use of the inverter's 'on/off'. but can the issue with the loads & the Battery Protect 1 be a hardware or software fault?

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Justin Cook avatar image Justin Cook ♦♦ Spyros Tziakouris commented ·

This is a symptom of the short-circuit current protection being activated; thus also why it resets when turned off and back on again. Voltage should theoretically drop to ~0 when the short circuit current protection has been activated, however, which indicates that through connection in non-supported configurations, damage has likely been caused to the BP.

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Spyros Tziakouris avatar image Spyros Tziakouris Justin Cook ♦♦ commented ·

BP1, the one for the 48v dc loads (around 500W IT-telecom loads) has the issue, not the one of the inverter.

BP2 is removed and inverter is wired directly and is controlled with remote on/off. now when the MCCB of the inverter is switched on for the 1st time and capacitors are charged, BP1 switches off and on instantly. probably due to a voltage surge. victron can add a delay of some ms to this and avoid the issue.

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