Current sensing relay

fblevins1

Solar Enthusiast
Joined
Aug 14, 2021
Messages
103
Hi folks, one of the problems I am seeing with my system is even when the transfer switch switches over to grid power, the inverter remains powered up and continues to draw energy from the battery, over time that does cause the battery to drop below the 50 percent set point (12.3 volts in this case) So, what I would like to do is insert a device into the grid power so that when it transfers to grid, the current sensor reads that current and trips a relay connected to the inverter DC input, effectively turning off the inverter. I have seen some hall effect sensors with on board relays with Over current and over voltage protection but I don't know if those would do the trick. So I defer over to you guys on the chance that you might know what I am yammering on about and throw some advice my way. Or point me to a thread that discusses this. Thanks gals/guys.
 

DThames

Photon Sorcerer
Joined
Nov 22, 2019
Messages
1,773
If I understand correctly, you want to trigger off of current on the grid AC side. (is that correct?)

You mentioned a Hall meter with relay, the units like this are for DC, so not directly usable.

I have taken a ferrite toroid and with magnet wire, wound a current transformer that will light an LED. If you can light an LED you can use a relay similar to this, with a NC contact in series with your inverter switch....if it has a manual type switch. Note, on the current transformer, I wound a few dozen turns of something like #26 wire and then passed my AC leg wire one full turn (through the center twice) and have an LED that will light in my house when the remote well pump is running.
 

fblevins1

Solar Enthusiast
Joined
Aug 14, 2021
Messages
103
If I understand correctly, you want to trigger off of current on the grid AC side. (is that correct?)

You mentioned a Hall meter with relay, the units like this are for DC, so not directly usable.

I have taken a ferrite toroid and with magnet wire, wound a current transformer that will light an LED. If you can light an LED you can use a relay similar to this, with a NC contact in series with your inverter switch....if it has a manual type switch. Note, on the current transformer, I wound a few dozen turns of something like #26 wire and then passed my AC leg wire one full turn (through the center twice) and have an LED that will light in my house when the remote well pump is running.
I have the exact hall effect you mentioned above and you are correct. Even when I powered the unit with a DC power supply, the current sensor would only respond to dc current so yes, that idea is out the door. I gave it 25 amps at 60 Hz and it read nothing, switched to 25 amps DC and it read the value. So....I am going to take a peek at that second link and see what it can do for me. Thanks, let's see where this goes. It is possible that once I get the 4 panel and two 100 Amp Hour batteries all hooked up, the amount of draw my inverter pulls may not be enough to drag my system down. At the moment, I have to wheel my battery in and out of the house to charge it so once I move it inside the house, I am completely without a means to stop the battery from being milked of energy. My new set up will be semi-permanent with twice the charge and battery power so perhaps under those conditions, I won't care about minimal power drain from inserted devices, hell for all I know the transfer switch uses battery power to power up so add another drain. Thanks, I will keep punching away at this. If we do come up with a usable device, I would use that anyway to reduce the amount of parasitical drain.
 

fblevins1

Solar Enthusiast
Joined
Aug 14, 2021
Messages
103
Quick question.

How will you turn it back on when you need it?

Manually?
Whooops! OK, back to the drawing board. Granted, my purpose was to save the battery while we sleep as that was the cause of the over discharging, but yea...I did not think about that. It could be that when the other panels and battery arrive later this week, I won't need or care about a little parasitic drain and my system will be connected to the solar grid full time. For my small little one battery system it could drain from 12.3 down to 12.0 volts just from the inverter being on. I don't really know when the transfer switch kicked in so it cold have been hours or minutes, the battery was not completely full to start so....who knows. I can also check how much the inverter actually drains when not being loaded and see if that value is really relevant. I mean if the inverter uses 20 watts and that is causing me problems, then I definitely need to increase my battery power anyway. Thanks for pointing that out.
 

Short_Shot

Photon Sorcerer
Joined
Jul 13, 2021
Messages
1,816
Most inverters will idle and drop pretty low.

Unless you've got a really tight power budget it shouldn't be a major issue for daily use.

If it's only backup power, then you can just manually turn it on and off.
 

fblevins1

Solar Enthusiast
Joined
Aug 14, 2021
Messages
103
Most inverters will idle and drop pretty low.

Unless you've got a really tight power budget it shouldn't be a major issue for daily use.

If it's only backup power, then you can just manually turn it on and off.
The primary use for the system is to power a 100 watt electric heating pad for my wife at night. You are right, my power budget was just too tight and it is hard to react to the system while sleeping so that is where the problems were. I would wake up in the middle of the night to check on the system it would sitting at too low a battery voltage or the inverter would be crying for more power or it would drop so low that the inverter would just turn itself off. My battery was not going to last very long at the rate I was slamming the discharge depth. I think at this point I am going to just wait until my other panels and battery arrive later this week. Doubling the capacity should bring the system to a level where it can go the whole night without to much of a problem and off course once I installed the transfer switch it solved the problem with killing the battery, I was just not happy about it draining from 12.3 volts down to 12.0 volts simply because the inverter stayed on after the switch. I would still be open to a low cost solution as that can be applied to my set up even if I increase the total power available, or...maybe see if there are inverters that can shut themselves off when they see that demand drops below their own consumption. I have a super whammydyne blue tooth controlled inverter in storage but that thing is a beast and draws even more power when just sitting there. Thanks for chiming in.
 
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