question

kuri avatar image
kuri asked

Soft starter for larger systems

Looking for advice on soft starting larger systems

For exaple we have two 10k Quattros in parallel and 3 mppts, using Pylontech usually works no issues but we have switched to BSlBatt and they dont seem to have the same soft start, on a larger system they will go to alarm even with both inverters off the batteries still alarm and we have to start the system with AC to get the batteries online avoiding inrush spike.

Is there something we could add to the DC side to avoid this that an end customer could use and dosent need to be removed from the circuit? All I can think of is to have seperate DC breakers for each inverter and the MPPTs so we can start everything one by one.

Suprised more people dont have issues with the inrush current, I have seen Breakers fuse and even seen the battery cables move from this massive inrush!

Thanks

Pylontechquattro 10kvabslbatt
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4 Answers
mvas avatar image
mvas answered ·

Have you tried a pre-charge resistor circuit? A manual 1-Both-2 battery switch can be used. Battle Born and other vendors sell surge suppressors. This is a common problem with Li-Ion batteries (BMS). Many solutions are available

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kuri avatar image kuri commented ·
Hey thats great help thanks!
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Kevin Windrem avatar image
Kevin Windrem answered ·

REC also makes a soft start that is automatic. Victron also: the Lynx Smart BMS but it's very expensive.

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kuri avatar image kuri commented ·
Yeah the price of these parts is a shock, I found that even with the Quattros off they must still draw DC current on battery start up and tripped the batterys so im thinking to add a second 4 pole breaker on the Quattro DC side so I can switch on MPPTs first then the Quattros and lower the inrush turning everything on one by one. This would be the cheapest solution I can find so far.
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mvas avatar image mvas kuri commented ·
The cheapest solution is a pre-charge resistor and a toggle switch. Possibly less than $20
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Kevin Windrem avatar image
Kevin Windrem answered ·

An extra switch will not eliminate the inrush current. The inverter has large capacitors across its dc input and can cause a brief current of several hundred amps.

A manual precharge is simple. A switch in series with a resistor across an existing dc switch.


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joram avatar image
joram answered ·

Have you tried the 'soft start' procedure to start the batteries?

By connecting the batteries to the inverter, breaker in the ON position then switching the battery on via the reset button, this activates the pre-charge function of the inbuilt BMS.

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