diy solar

diy solar

Inverter with a transfer switch but without charging from AC

tamron

tamron

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Aug 4, 2020
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I have a small solar system, 2 panels (~500W), a charge controller, and a battery. I'm doing it at my house. I'm powering small load like yard lights, computer/wifi, security cameras. I'd like to be able to power a small fridge, 1000W surge. I really need like 400W continuous only. I may add another two panels and build a DIY powerwall later out of Nissan Leaf power packs.
This is an off-grid system, not intending to feedback to the grid.

Is there a pure sine wave inverter with a transfer switch but without charging from AC?
My goal is to use solar when available, then use the battery, then fallback to the grid till the sunrise. Never charge from the grid.

Gridtie inverters with the limiter seemed like a good idea but scarce selection and bad reviews.
MPP all-in-one seems to fit the bill but too many bad experiences shared online, so I'm looking now into inverters with a transfer switch.

This one Aims 600 Watt PICOGLF6W12V120V https://invertersrus.com/product/aims-picoglf6w12v120v/ seems promising, but the manual says that it will always charge the battery if the grid is present and voltage is low. Is this the right understanding?

I also found Samlex EVO-1212F-HW it seems to operate the same.
Is there inverters with a transfer switch but without charger?

What are my options? What would you recommend?
 
What you want is atypical. These systems aren't designed for that. You're likely going to have to come up with your own solution if you insist on filling the exact parameters.

It's the "no solar" trigger that's unique. You need something that says, "if no solar, switch to grid power." I wouldn't concern yourself with the detail of having grid not charge the batteries. When solar cuts out, the battery charge will likely be very high, so the grid is mostly going to float them and just keep them healthy at little cost.

If you can adjust that or a similar unit's switch over voltage to something pretty high, like 12.5V (purely a guess, you'd have to experiment), you could have it switch over very near the time solar goes unavailable and battery is still at a high state of charge. This isn't exactly what you want, but it could likely simulate is pretty closely with a little tweaking.

Assuming lead-acid batteries, keeping them fully charged prolongs their life. It's probably worth giving up a little of what you save back to the grid to keep your batteries healthy.
 
Arguable I can have it with Moes Automatic Transfer switch $110
It would transfer to the grid when the battery is depleted, based on the voltage

Code: 
                          PV panel
                             |
                         solar charger
                             |
             Inverter <- battery
load <- ATS /
            \ Grid
But the transfer will not be fast enough as the inverter is not synched to the grid, so I was looking for the inverted with built-in ATS
 
tamron said:
Arguable I can have it with Moes Automatic Transfer switch $110
It would transfer to the grid when the battery is depleted, based on the voltage

Code: 
                          PV panel
                             |
                         solar charger
                             |
             Inverter <- battery
load <- ATS /
            \ Grid
But the transfer will not be fast enough as the inverter is not synched to the grid, so I was looking for the inverted with built-in ATS
Click to expand...


Look at Will’s review of that unit.

It was fast enough to not dump the computer.
 
That unit is only available for single phase 120 or 240V. It won't work split phase. It will accomplish essentially the same thing as raising the inverter undervolt protection. You'd need to experiment with what works.

Ad material says it happens without interruption.
 
From the manual of Samlex EVO-1212 it appears that I can set the "BULK CURRENT" to 0. I expect it to effectively turn off the grid charging.
I wonder if anyone has done it.
EVO-1212 and GO POWER 1500WATT are about the same price. $600 Is that my lowest price range?
 
Yes, my $3,500 Outback Skybox does that and more. I thought the OP was looking for something a lot less expensive and around 1000 Watts.
 
tamron said:
From the manual of Samlex EVO-1212 it appears that I can set the "BULK CURRENT" to 0. I expect it to effectively turn off the grid charging.
Click to expand...
I would verify that assumption. Bulk charging is the constant current stage of two stage charging. That setting may apply universally to charging from solar or charging from grid, unless it has separate settings for each.
 
Last edited:
If I understand you correctly you want exactly what I have used in the past. solar and battery first then fall back to grid when both solar and PV are exhausted. I used a standard Hybrid inverter non grid tie which had a selectable option to not charge from AC mains, it would charge from PV during the day, fall back to battery at sun down and switch back to mains when the battery was empty this is what I used https://www.photonicuniverse.com/en...T-solar-controller-and-20A-mains-charger.html im in the UK @220v but i'm sure there is an equivalent 110v option. they also sell them in 12,24 & 48v options.
 
tamron said:
Why did you stop?
The link that you gave appears to be a clone of mpp solar all-in-one controller. Did you have any problem with it?
Click to expand...

It worked so well to power my office, bar and garage that I decided to go full solar for the whole house, so I have 22kW of PV being installed on the main roof of my house. I never had any issues with it bar getting the correct charge settings setup which members on here helped me with, it was very reliable for a 24v system and my battery system powered my items through the night. As for a clone, the serial number checked out as a genuine third party re-badge and even took the official MPP firmware.
 
shavermcspud said:
It worked so well to power my office, bar and garage that I decided to go full solar for the whole house, so I have 22kW of PV being installed on the main roof of my house. ...
Click to expand...
Do you regret now that you spent time and money going with residential off-grid while you could have jumped into grid-tied 22kW from the start?
I doubt you could re-use many pieces of the previous set-up. Do you plan to run them alongside or do you plan to retire your Iconica solution?
 
tamron said:
Do you regret now that you spent time and money going with residential off-grid while you could have jumped into grid-tied 22kW from the start?
I doubt you could re-use many pieces of the previous set-up. Do you plan to run them alongside or do you plan to retire your Iconica solution?
Click to expand...

It started out as a small project just to see if i could DIY it as I have an interest in Electronics in general. Ive now sold all my original equipment at a loss of about $200 / £180
 
tamron said:
Arguable I can have it with Moes Automatic Transfer switch $110
It would transfer to the grid when the battery is depleted, based on the voltage . . .
But the transfer will not be fast enough as the inverter is not synched to the grid, so I was looking for the inverted with built-in ATS
Click to expand...
I have this ATS, it works fine and switches to grid quickly (10 ms if I remember the spec correctly). I have not tried it with a computer, but motors/compressors (2 fridges and a freezer) don't miss a beat (not too many cycles are missed during 10 ms). The only down side to this device is if your battery voltage is good but your inverter quits, it won't switch to grid because it doesn't know any better. (I added a supplemental relay to take care of that situation, but this is really not worth the trouble for most folks.)
 
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