diy solar

diy solar

Please help me learn why this happened so I don’t do it again!!

To really check it, you need to remove the cables and remove those four screws to look at the contacts. But I suspect they are fine.
If you do that, the back plate is under a little spring pressure but nothing will go flying.
Ah ok will do that and report back.
 
Iv just thought, the battery was turned off via the bms when I turned the switch. Would that cause the problem?
 
12v or 80v is not going to make any significant difference. Especially not at the voltage and current levels of 2 panels.
Yes, if switch is fully open or fully close. But when you do switching - high voltage will cause an electric arch. Higher voltage - longer arc(in time and distance). An electric arch is generating high frequency RF emission and current pulsations. Inductors and capacitors inside of MPPT may generate a voltage spike due to this. MOSFETs, transistors, diodes and IC can be killed by high voltage very fast and you don't need many joules to do it. Always stop your charger and/or invertor first before battery or panel connection/disconnection.
 
I opened it up and all looks fine.
Why are there two wires going in and two wires going out of your switch? When you turn that switch on it connects the wires between the two lugs. You seem to be creating a short whenever you close the switch.

There should be one positive wire going from the PV to one lug of the switch. And then there should be positive wire from the other lug of the switch to the positive PV input of the SCC. There should be no negative wires connected to the switch at all.
 
Why are there two wires going in and two wires going out of your switch? When you turn that switch on it connects the wires between the two lugs. You seem to be creating a short whenever you close the switch.

Good catch. I only noticed that the switch was still assembled.
 
Why are there two wires going in and two wires going out of your switch? When you turn that switch on it connects the wires between the two lugs. You seem to be creating a short whenever you close the switch.

There should be one positive wire going from the PV to one lug of the switch. And then there should be positive wire from the other lug of the switch to the positive PV input of the SCC. There should be no negative wires connected to the switch at all.

I did that, as a kid in a class. Battery, light bulb, switch. When switch was closed, light went out.

When OP turned panels off he turned switch on (not off) he was shorting out the capacitors. Sometimes, that is destructive.
<corrected>

Iv just thought, the battery was turned off via the bms when I turned the switch. Would that cause the problem?

And that is possible. The higher the charge current, the more likely. An SCC has current running through an inductor, which would cause a voltage spike when BMS disconnects. I think some sort of transient voltage suppressor is needed in BMS and/or SCC for protection. Maybe they have one already?
 
Last edited:
When OP turned switch off (not on) he was shorting out the capacitors.
With the four wires connected to the two switch lugs as shown in the picture, with the switch in the off position everything should actually work just as if there was no switch at all. When the switch is in the on position then it is as if all four wires were connected together as one. And that's very bad.
 
Why are there two wires going in and two wires going out of your switch? When you turn that switch on it connects the wires between the two lugs. You seem to be creating a short whenever you close the switch.

There should be one positive wire going from the PV to one lug of the switch. And then there should be positive wire from the other lug of the switch to the positive PV input of the SCC. There should be no negative wires connected to the switch at all.
Ah yes that makes perfect sense, my mistake. I had it like that’s for months!!! Oops!! Il chance the switch to the correct way straight away. Thankyou for sporting that.

maybe creating a short like this was the cause.
 
I did that, as a kid in a class. Battery, light bulb, switch. When switch was closed, light went out.

When OP turned panels off he turned switch on (not off) he was shorting out the capacitors. Sometimes, that is destructive.
<corrected>



And that is possible. The higher the charge current, the more likely. An SCC has current running through an inductor, which would cause a voltage spike when BMS disconnects. I think some sort of transient voltage suppressor is needed in BMS and/or SCC for protection. Maybe they have one already?
I did wonder why when the switch was in the OFF position the panels turned on and when it was in the ON position the panels turned off!!! ?
 
The max amount of current the panels supply will always be the same. It's not like they somehow magically store up a few hundred amps. And with just two 160w panels, i just don't see it being an issue.
Well it seems that OP has found the reason for his failure.

SIDEBAR:
I’m not an EE nor can I recall the term, but there is a phenomenon where not-clean breaks in a circuit can create higher voltage surges from a battery in boats and vehicles. I’ve seen once personally and heard of a number of times where starting a boat motor that the moment the starter is realeased the sonar/gps and/or vhf burns out. From a surge that occurs at disconnect.

I don’t know: does that not apply to panels and batteries? Maybe not because there is no load, the battery is the ‘load’ under charging?

Back to OP problem:

Never disconnect batteries before disconnecting panels.
Shut of all loads possible. Remove the power (panels). THEN remove the batteries connection
 
I’m not an EE nor can I recall the term, but there is a phenomenon where not-clean breaks in a circuit can create higher voltage surges from a battery in boats and vehicles. I’ve seen once personally and heard of a number of times where starting a boat motor that the moment the starter is realeased the sonar/gps and/or vhf burns out. From a surge that occurs at disconnect.

Inductive kick.
If current is flowing through a coil of wire, energy is stored in magnetic field. It needs to be released as Amps x Volts x Seconds
If the circuit is opened so Amps goes to zero, Volts goes to infinity (or high enough that something breaks down.)

You can get a variety of transient suppressor devices for that. MOV, TVS, spark gap.
We normally use something like a diode (clips reverse polarity kick, doesn't conduct in normal polarity), or series RC circuit as a "snubber"

Good equipment is specified/designed/tested/certified to handle various transients and ESD. But combining SCC with BMS may be something those parts weren't planned for.

In OP's case, I don't think there was an inductive kick. But shorting out the capacitors on input of SCC discharged all their energy instantly. The high current could have burned out a trace, or could have caused capacitors to fail. Either way I'm guessing it wasn't semiconductors that were damaged, so could be easy to diagnose (look for burned/burst parts) and repair.
 
Back
Top