Solid state relay for PV disconnect

Bobert

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I have a mttp charge controller that tends to get stuck at 62 volts if it is on when the sun start to come up. I was contemplating using a combination of something like this
And this https://www.amazon.com/gp/aw/d/B09HRX922Z

Does anyone have experience with solid state relays on a PV application? What is the expected longevity of this type of relay? I have 9 240 watt panels 3s3p unloaded in the sun they max out close to 120 volts. The typical scenario that I would be switching would be between 3 and 8 amps at 62 volts. The max amperage I could see at the relay is 24 amps but since my array is mounted more or less flat on my rv roof I doubt I will ever see that number. So far this year the best I have seen in full sun is just over 1800 watts. The typical full load voltage is around 90 volts. I don’t intend to use this as a disconnect just a method of releasing and reconnecting the solar in the morning without used a great deal of space near my charge controller. If I need to service it I will physically disconnect the mc4 connectors at the controller rather than trust a relay. My main limitation is space. A solid state relay uses almost no power and very little space the timer can be mounted a distance away from the relay and is much less of a concern. I’m willing to be the Guinea pig on this experiment but would like to learn from other’s mistakes and successes and not reinvent the wheel if someone else already has experience or knowledge.
 

DThames

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I think it should work. So your MPPT doesn't search for the proper power point if the input volts ramp up from a normal sunrise situation? What type of controller is that?
 

MisterSandals

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If I need to service it I will physically disconnect the mc4 connectors at the controller
This is dangerous if the array is energized.
So far this year the best I have seen in full sun is just over 1800 watts.
>Control Capacity: 0-250V AC, 1000W

My thought would be to figure out what is up with your SCC. Electronics "getting stuck at 62 volts" seems mighty odd.
 

Bobert

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This is dangerous if the array is energized.

>Control Capacity: 0-250V AC, 1000W

My thought would be to figure out what is up with your SCC. Electronics "getting stuck at 62 volts" seems mighty odd.
Yes I am using a Powmr 3500 watt hybrid inverter (AIO). I can actually watch it get stuck in the morning. At that time my panels produce almost no wattage but enough to initiate the charge controller if I disconnect the solar and reconnect it in the first half hour of light (sunrise) the controller gradually reduces voltage until it reaches max wattage at 62 ish volts. It still ranges between 60 and 64 volts but at that voltage range maximum wattage is reached at around 62 volts. I low light conditions the wattage is lower at 74v than it is at 62 volts but the max wattage is actually at somewhere around 86v. When the scc is at 64v the wattage drops when it raises or drops the voltage. If I disconnect and reconnect once I am over 2 amps output the max power point is discovered and my wattage usually at least doubles. I have been told this is not particularly unusual scenario on solar arrays that have heavy shade in the morning. If the batteries reach full charge any the solar quits charging when it restarts the charge controller starts at 60v and works it’s way up landing at 62 ish volts the highest wattage it will see in that direction since it will only hunt for a few volts either side of max. if the solar is unplugged the controller starts at the top of the voltage and works it’s way down and in that direction the max power point will be discovered. If I had a device that would prevent the PV from running until the panels reach 100v output voltage that would also work but it would have to be configurable not to disconnect if the voltage drops.
 

MisterSandals

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I have been told this is not particularly unusual scenario on solar arrays that have heavy shade in the morning.
Okay, this is new info. So your array is hampered.

Yah, i dunno. Maybe this is one of the downsides of saving money on an inexpensive AIO?

Wish i had something to offer for help, sorry.
Maybe start a thread with "Powmr 3500 AIO" in the title to attract the attention other owners/users?
 

DThames

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I have a mttp charge controller that tends to get stuck at 62 volts if it is on when the sun start to come up. I was contemplating using a combination of something like this
And this https://www.amazon.com/gp/aw/d/B09HRX922Z

Does anyone have experience with solid state relays on a PV application? What is the expected longevity of this type of relay? I have 9 240 watt panels 3s3p unloaded in the sun they max out close to 120 volts. The typical scenario that I would be switching would be between 3 and 8 amps at 62 volts. The max amperage I could see at the relay is 24 amps but since my array is mounted more or less flat on my rv roof I doubt I will ever see that number. So far this year the best I have seen in full sun is just over 1800 watts. The typical full load voltage is around 90 volts. I don’t intend to use this as a disconnect just a method of releasing and reconnecting the solar in the morning without used a great deal of space near my charge controller. If I need to service it I will physically disconnect the mc4 connectors at the controller rather than trust a relay. My main limitation is space. A solid state relay uses almost no power and very little space the timer can be mounted a distance away from the relay and is much less of a concern. I’m willing to be the Guinea pig on this experiment but would like to learn from other’s mistakes and successes and not reinvent the wheel if someone else already has experience or knowledge.
Did you notice that the timer output is rated for AC only?
 

Bobert

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This is dangerous if the array is energized.

>Control Capacity: 0-250V AC, 1000W

My thought would be to figure out what is up with your SCC. Electronics "getting stuck at 62 volts" seems mighty odd.
Did you notice that the timer output is rated for AC only?
I didn’t notice but I’m not sure it will matter as I will be dealing in miliamps for a trigger.
 

DerpsyDoodler

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I have been told this is not particularly unusual scenario on solar arrays that have heavy shade in the morning.

Who told you this? What data do they have to support that assertion? Was it the Powmr support folks? My BS meter is pegging.
 

DThames

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I didn’t notice that but I’m not sure it matters as the trigger amperage is in milliamps
Only would matter if it had a triac instead of a relay. I wouldn't expect it to but I would test it switching on that power relay, first thing.
 

Bobert

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This is dangerous if the array is energized.
I’m not asking this to be “smart” but how is this dangerous? I have a maximum possible output of 24 amps at about 90 volts true enough and I might get some arcing at that level but if I need to disconnect to reset the most I have ever had is 8 amps at 62 volts. My connectors are in a dry location and there is no voltage potential between the solar wires and anything else in that location. To get shocked I would need to disconnect the mc4 connectors from both sides of the array and stick a conductor in each of them and grab on to it. So far I have never even had an audible arc when disconnecting and no visual damage to the pins. Maybe I can get an arc large enough to get burned at 90v 24amps? I’ve never tried that not sure I want to. Am I missing something?
 

DerpsyDoodler

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That was back in January apparently I’m not the only one with this problem. https://diysolarforum.com/threads/mppt-sticks-at-60-volts.34084/
I see. I think I've read some other threads with similar problems. Their solution was a specific setting in their MPPT controller that adjusted how and when the unit rescanned. I think that was a Midnight brand controller. Have you looked for any possible settings like that in your AiO's config?
 

Bobert

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I see. I think I've read some other threads with similar problems. Their solution was a specific setting in their MPPT controller that adjusted and when the unit rescanned. I think that was a Midnight brand controller. Have you looked for any possible settings like that in your AiO's config?
I have not found any MPPT settings that can be configured from the inverter itself. It is ironic that you mentioned midnight solar the powmr unit I have is identical to in appearance to the 3500 watt diy series midnight solar AIO as a matter of fact the manual is identical except for the logo
 

DerpsyDoodler

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I have not found any MPPT settings that can be configured from the inverter itself. It is ironic that you mentioned midnight solar the powmr unit I have is identical to in appearance to the 3500 watt diy series midnight solar AIO as a matter of fact the manual is identical except for the logo
I wish i could remember the name of the setting. It would make it easy to search the forum for. Maybe someone will pop in and shed some light.
 

Bobert

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I have a mttp charge controller that tends to get stuck at 62 volts if it is on when the sun start to come up. I was contemplating using a combination of something like this
And this https://www.amazon.com/gp/aw/d/B09HRX922Z

Does anyone have experience with solid state relays on a PV application? What is the expected longevity of this type of relay? I have 9 240 watt panels 3s3p unloaded in the sun they max out close to 120 volts. The typical scenario that I would be switching would be between 3 and 8 amps at 62 volts. The max amperage I could see at the relay is 24 amps but since my array is mounted more or less flat on my rv roof I doubt I will ever see that number. So far this year the best I have seen in full sun is just over 1800 watts. The typical full load voltage is around 90 volts. I don’t intend to use this as a disconnect just a method of releasing and reconnecting the solar in the morning without used a great deal of space near my charge controller. If I need to service it I will physically disconnect the mc4 connectors at the controller rather than trust a relay. My main limitation is space. A solid state relay uses almost no power and very little space the timer can be mounted a distance away from the relay and is much less of a concern. I’m willing to be the Guinea pig on this experiment but would like to learn from other’s mistakes and successes and not reinvent the wheel if someone else already has experience or knowledge.
It looks like I’m back to the drawing board on this one the solid state relay has .25 ohms of internal resistance that means at full I will loose about 133 watts of power as heat. Not acceptable for my situation.
 

efficientPV

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I do this with my make sky blue controller and I have heard it happening with others. I have shade conditions where the 60V array will get stuck as low as 17V. I detect anytime the voltage drops below 42 for more than 30 seconds. That condition opens the array minus lead for 5 seconds and the controller resets to the 50's. Most controllers don't do full scans and can get stuck at several peaks in the curve. I just use multiple FET in parallel to get the resistance down. It is a matter of math. two FET in parallel produce 1/4 the heat of just one. Add another two and it is 1/16.
 

Bobert

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I do this with my make sky blue controller and I have heard it happening with others. I have shade conditions where the 60V array will get stuck as low as 17V. I detect anytime the voltage drops below 42 for more than 30 seconds. That condition opens the array minus lead for 5 seconds and the controller resets to the 50's. Most controllers don't do full scans and can get stuck at several peaks in the curve. I just use multiple FET in parallel to get the resistance down. It is a matter of math. two FET in parallel produce 1/4 the heat of just one. Add another two and it is 1/16.
Could you enlighten me on this a little more I have never used fets before. How do they work and what do they accomplish for me?
 
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