Trouble Turning on System

[bookish]

Hi All,

Please help! This is a new system I just built, and I'm having trouble turning it on. Pictures attached.

Details:
48V batteries in parallel, BMS green. When I turn on the DC disconnect box the BMS flashes red -- not good.
At the battery terminals and at the bottom of the disconnect box I'm getting 49V. When the switch is turned on I'm getting 5.8V at the top of the disconnect box.
The DC fuse in there is rated at 50 amps, and I cannot see any indication it blew. Wouldn't know how to tell that, as a matter of fact.

The PV power coming in reads 101V at the leads on the Growatt unit, just what it should be. So batteries and PV array working. I blame my wiring. What have I done wrong? I kind of think if I bypassed the fuse it'd work, but I haven't dared that yet.

I'd really appreciate any advise on this.

 

[Primal1]

One thing is for certain, dont bypass the fuse, especially if you have an issue. That's all I can offer, Im sure someone else will be along just be patient.

 

[HRTKD]

I bet that fuse is too small. Batteries in most 48v systems spend most of their life above 50v.

Also, when you turn on the disconnect, is the inverter turned on? If so, turn it off and try again. Maybe the capacitors in your inverter are drawing a ton of amps.

 

[MisterSandals]

48V batteries in parallel, BMS green.

Do you have a BMS for each battery that you have in parallel?
Happen to have a pic of your battery setup and wiring?

 

[bookish]

The batteries are Renogy 48 V, 50 Ah LiFePo4. I tried leaving the BMSes unconnected, and then tried connecting the BMSes with an ethernet cable as shown in the manual. (The only thing the manual says about the ethernet cable connections is in the context of using their own monitoring screen or bluetooth module. I read somewhere that smart batteries don't need to have the BMSes plugged together to balance themselves in parallel, but now I have misplaced the source for that. ) At any rate, I tried both ways and get the same result, although when the BMSes are wired together the red LEDs go solid on instead of flashing. Thank goodness every time they recover back to green flashing within a minute.

The picture shows the battery connections.

 

[bookish]

I bet that fuse is too small. Batteries in most 48v systems spend most of their life above 50v.

Also, when you turn on the disconnect, is the inverter turned on? If so, turn it off and try again. Maybe the capacitors in your inverter are drawing a ton of amps.

I tried both ways, no dice.

 

[Sky-HHI]

Take your negative wires and run them thru the second fuse like you did with your positive wires. The negative bus bar may be connected to the metal case which also has your ground lug. This is common if this disconnect was designed for AC voltage. It is ok to use fuses or breakers on both the negative and positive wires.

 

[bookish]

YES! That worked. Thank you.

 

[Sky-HHI]

I am glad that worked for you, it is always better when people have a problem with their systems to include good pictures.