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alfa avatar image
alfa asked

2 Victron Quattro's in split phase not starting

Hi,

I have finished installing 2 Quattro's 48/3000/35-50/50 in split phase with 2 each 48V EG4-LL battery in parallel. As soon I'm switching on the batteries I'm getting error on the 2 batteries, "protected (DOC)" discharging over current protection and the Quattro's doesn't start, not even one at the time. I disconnected the DC (+) from one of them and it's working, I done the same with the 2nd one and it works as well. So the system works with only one but not with the 2 Quattro's connected at the same time to the DC Victron distributer. I Don't know if this have to do with my problem, the firmware are not the same on boot, they are the 27xxx one is the 430 and the 2nd is 481. Please help. Thanks Dan

split phase
2 |3000
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1 Answer
Kevin Windrem avatar image
Kevin Windrem answered ·

All inits in a multi-phase or parallel system should be on the same firmware. That could be your problem.

The batteries may not be able to handle the current surge when connecting the Quatros. You should consider adding a soft start circuit that allows the capacitor across the Quatro's DC inputs to charge slowly. The discharged capacitors act as a direct short for a split second. That may be more than the BMS for your batteries will tolerate. One Quatro by it self may be within the BMS surge rating.

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alfa avatar image alfa commented ·
Kevin, Thanks for the reply. Can you point me to a “soft start circuit that allows the capacitor across the Quatro's DC inputs to charge slowly”.
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Kevin Windrem avatar image Kevin Windrem alfa commented ·

You may find this under "Pre-Charge" as well.


Victron includes a soft start in their Lynx BMS but that's pretty expensive if that's all you need. (It also has a shunt and the BMS for Victron LFP batteries.)


REC-BMS also sells a pre-charge unit that will work with a contractor (relay) for the battery on/off function.

https://www.rec-bms.com/rec-accessories/

I built my own manual one: a switch in series with a resistor across the battery on/off switch.

You can also do this manually by placing a resistor across the open battery on/off switch until the inverter voltage gets close to the battery voltage.

The size of the resistor depends on the battery voltage. For 12 volts, I used a 5 ohm 30 watt resistor. That reduces the inrush current to 2.4 amps and charges the capacitors in my Multi Compact in just a few seconds. A larger inverter would have larger capacitors so would take longer to charge. Caps for a larger battery voltage will most likely be smaller.


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