Remotely turn on/off solar

nrm21

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Jan 4, 2018
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Hi,

I'd like to be able to remotely turn on/off my solar array as if I were standing in the room and flipped the circuit breaker manually. I've already got the ability to flip back and forth from my grid and (off grid) inverter power using these

https://www.amazon.com/Contactor-LC1D12-LC1D12G7-LC1-D12G7-120V/dp/B076Y1TW2C/

And a contactor tutorial I saw on Daniel Romers YT channel a while back.

But i need something that does, DC (90ish) Volts AND around 25 Amps max

What is the best way to do this? Can I use this AC contactor and just split the current 3 ways (I only need a single pole anyway of this 3-pole contactor), so each channel handles 1/3 of the current? I assume the max current in the specs is for each individual channel. Or do I need something special that might cost more?
 
You shouldn't use an AC rated switch of any kind for DC loads, unless it specifically states it can handle DC loads. The reason is because the disconnect arc from DC is sustained for a much longer period of time, and will wear out the contact pads of the switch. Even low voltage DC will damage AC switches given time.
Get a DC rated contactor, as Sean mentions.
The reason he also says to remove the load (turn off the loads) is because the more loads there are, the higher the current draw, the larger the arc can travel and the duration. Arcs can lead to failure, or fire
 
Yeah I found this page helpful a few mins ago at explaining it.

https://temcoindustrial.com/product-guides/contactors-and-overloads/ac-vs-dc-contactor

But I still think I'm failing to understand something here. How exactly do I remove the load if it's connected to the PIP inverter? That's the load right? Isn't the point of the contactor ITSELF to remove the load (by disconnection)? This would need to be done remotely so I might not be physically present to do such a thing.

What then would be the best way to handle that?
 
The load is the inverter, plus whateveris connected to its output- you can reduce the load by turning off everything on the AC output of the inverter, or just turn off the AC isolator.

Most breakers have a load carrying, and a load switching rating - the more expensive breakers will have a load switching rating at, or very close to, its load carrying rating.
 
Are you really only using 12A from the grid and inverter? That is hard to believe...
 
If you are talking to me... I'm using slightly more than 12A, I max at around 30A. It's because I'm not putting my whole house on solar. Just a small part of it (1 wall AC, 1 fridge, and some computers). I can probably add a bunch more resistive loads but I don't wanna add anymore inductive loads as I would need to upgrade my inverter.
 
nrm21 said:
If you are talking to me... I'm using slightly more than 12A, I max at around 30A.

Just for clarity, is that 30A AC or DC ?
 
If you are switching the DC from the solar before the charge controller / inverter then you can just use some FET's or a pre-built SSR.

SSR (Solid State Relay) that is DC rated for 150V like this one at 40 A only containt one or more MOSFET's in an array
https://uk.rs-online.com/web/p/solid-state-relays/9045778/
There are variations on Aliexpress (60V) that are 10% of the price... I seem to remember some 150V versions and trying to find some links.

With DC at 100V if there is no inductive load the issue on disconnecting under load will just be handling the terminal voltage without any issues of back EMF from coil discharge. The charge controllers / inverters all tend to have input capacitors to smooth out the FET switching current so these would counter any small inductive element of the inverter.

Some use 3 phase rated AC rated contactors/equipment and put the contacts in series to create a large enough air gap to cope with breaking the DC arc.

Use FET / solid state approach as you will then not have any issue with contact wear, coil drain power user while energised and noise if it is located somewhere it could be annoying :)


Use one of these :
https://www.aliexpress.com/item/SSR-40a-solid-state-switching-relays-3-32V-DC-to-5-220V-DC-relay-module-KS1/32659755841.html
 
Aliexpress SSR 40A is inside max rated for 6A so no wonder they are 10% the price!! Youtube it and you find many videos of it :p

The 3phase AC rated contactors we use are also DC rated. Never use AC rated that arent DC rated.
 
150V 100A power board 25 - just a few more FET's in parallel, it's only the same principal that inverters use to pulse switch on/off the DC inside.
https://www.aliexpress.com/item/147...0A-150A-100A-50A-BMS-Balance/32861352304.html

The china SSR's are heavily impacted by inadequate cooling as it is depends on the actual FET inside and the degredation at higher temperature operation. The SSR's have to be mounted on a heatsink, otherwise 6A may well heat them up to the point of failure just like any ordinary cheap FET with a high gate resistance.
 
I have blown up MANY and picked many appart and none of them work as a proper SSR do. Everyone have had crap components.
Note that they dont even get warm before they are blown... They just let the magic smoke up loooong before that. The last 25A i picked apart blew at a load of massive 1000W resistive load and you couldnt feel any heat :p

That powerboard have 10x the capability than the cheap SSR do have :D

The funny part is that I have picked apart China ssr with same mosfet in the 25A version such as the 40A version.

You might find SSRs that do work but yet I have not found that. I generally buy 40A version and then at most drive a couple of Ampere through it and it seem to hold ok.
 
The SSR he tore appart was 25A rated and the FET inside (BTA166600B) is only rated 16A RMS continuous.

As to the build quality at 09:32 into the video the two comments of :
"nothing that jumps out screaming one of these is a counterfit"
"and theres nothing that screams out that this one is a piece of grabage" - basically just usual name plate over rating

As to failure mode, the current spikes in DC can be very severe with large battery packs and blow SSR's quite easily, especially when switching anything connected to a battery pack that contains a capacitor as the surge can easily be well over the maximum FET short term current rating.

1000W at 48V = approx 20A and could have just been over the FET "china special over rated" rating for a 25A SSR...

As per all nearly chinese equipment, never buy and us it at it's rated current as they seem to always over rate almost "everything".

As to using FET's for any form of isolation, NEVER as they usually fail short unless you have a high enough fault current then they blow open, litterally in most cases.

Using FET's for battery charge protection on solar is bad if it is the only mans of over voltage protection because the solar will usually result in a short failure mode (due to the lack of a high enough current to blow an open circuit failure) and your battey could then easily over charge is this switching was the only means of over charge protection.
 
One of the SSR 40A from china i ripped apart had a mosfet rated 6A RMS on typical useage. Unfortunately I dont know the part number of it more ethan the 6A continues rating. Secondly it did not have proper contact with the case of the SSR either.

So its a gamble choosing china things we know that.

1000W load is 4A and it was AC.. 4A load on a 25A SSR....

Yeap the worst part is that they short when they fail. Thats why its generally better with a proper contactor where you need to be able to disconnect.
 
Just wondering what's the actual need behind "switching off the solar remotely"?
It is to stop charge, for safety isolation, ???
Might be other solutions?
 
30A DC, I believe... it's whatever these Voltronic type inverters are reporting. It's under 1600W power anyway so there's no way it could put out 30A continuous at our American 120v standard right? That would overload the inverter... so it's gotta be DC (I use a 48v battery but my grid is doing about 121v).


It's to stop charging if I'm at work and I need to for emergency. As things should work, the inverter will stop pulling so many watts once the battery approaches top SoC. If I get it balancing correctly then I won't need to turn off panels at all. BUT... I was having issues with my batrium system (and still am). And that's really what I need to fix. It doesn't seem to be balancing correctly at times, some cells get stuck in burn state and don't stop burning down when they should, causing other good cells to slowly go up and up way past correct top voltage.

I've been meaning to schedule some time with batrium to fix but life has gotten in the way and haven't had time.
 
Surely inverter output isn't really relevant here?
You're talking about the input to the batteries from the solar panels right (not the output from batteries > inverter > loads)?
You'd mentioned 90VDC from the solar and 25A.

Switching this can be done with a few paralleled mosfets (or probably a single expensive high rated one).
I searched some of the vendors & there's 100's of Nch devices rated for Vds 150V to 200V.
Some looked like they could do it with just one device.
You would just control the gate with 12VDC (+ a 15V zener & a 10ohm drive resistor).
A heatsink, suitable weather proof enclosure, cable seals, termination blocks, etc, etc would be wise...

Other methods might be better/safer depending on the need/purpose.
If (when) it goes wrong, it has to be "safe".

Real question is still "what is the underlying reason for doing this"?
 
Underlying reason is:

Because Batrium is sometimes not protecting each cell (since something is wrong with it right now and I need to Tshoot) so this would be emergency plan B (or maybe C). Truth be told I still haven't done it and have mostly talked myself out of it at this point... what I really need to do is figure out why Batruim isn't working correctly (maybe wiring?) than worry about shitting of solar remotely.
 
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