Fuse blows when Lynx Dist powered. Why?!

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duswami asked May 26, '22

Fuse blows when Lynx Dist powered. Why?!

When I turn on (close) the battery disconnect to power the lynx distributor the 125A 48V (Victron) fuse blows on the battery connection In the Lynx. The only thing connected to the bus bars on the lynx distributor distributor is the inverter and the batteries. I checked and rechecked polarity and everything is correct. The 48v batteries are reading 53V. The inverter is off. A smart shunt if correctly installed between the bat negative and the negative bus bar on the distributor. The shunt bat plus and aux cables are connected to the bat pos terminal and the mid point positive. As far as I can tell everything is connected properly and secure and there is no reverse polarity. What would cause the fuse to blow When the Disconnect is closed (on) and the distributor is powered?

Multiplus-II battery fuses lynx shunt busbar

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seb71 answered · May 26, 2022 at 09:29 AM

What happens if you disconnect the inverter wires from Lynx Distributor and only then you connect the battery to the Lynx Distributor (close the switch)? Also remove all the positive wires from the SmartShunt, just in case. And check for any short between the positive and negative busbars (like a piece of wire). The Lynx fuse still blows or not?

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Try to precharge the inverter capacitors, before connecting it to the battery (before turning on the disconnect switch). You can use an incandescent light bulb or a resistor for that.

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duswami commented · May 26, 2022 at 12:18 PM

Well I thought about trying that , that would entail blowing another $30 victron fuse :/ Before I try that. Any other thoughts? The battery is obviously 'capable' of more than 125a... being 200ah and a 48v system I calculated 107.60A as being the wire/fuse rating Making a 125a fuse even slightly over-sized, but using 1/0 wire..

Incidentally, the next fuse found the bus bar, inverter fuse, did not blow.

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duswami commented · May 26, 2022 at 04:04 PM

I found the short! It WAS at the inverter. There was an infinitesimal bit of solder between the battery terminals bridging the connection. Like a hair thick and maybe 2mm long. Wow... thanks for the help.

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himehran2000 commented · Jul 28 at 07:07 PM

How do you actually do precharge?

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pwfarnell himehran2000 commented · Jul 28 at 08:53 PM

You put a resistor across the open terminals of the inverter isolator to allow some current to flow from the battery to the inverter to precharge the capacitors. For a 12V model something like a 7 Ohm 50 Watt resistor. When the resistor has been connected for a few seconds, the isolator is then closed (turned on) and there is much less inrush current. Another way if you have solar is to start the solar to precharge the inverter capacitors. Apparently Victron have a precharge device in development.

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