Using grid tie solar panels off grid

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Norman Elliott

Joined Jan 29, 2016
One other idea I had was to use a bunch of PC power supplies in series and thus be able to pick off suitable voltages to charge batteries.
For example I have a 150 watt inverter which is designed for use in a car so could provide lighting throughout my home if nothing else.


Joined Mar 3, 2014
I fitted solar in our motorhome (RV) 150w panel and 80ah gel leisure battery. I fitted a 2 pole changeover switch to select either grid hook up or PSW inverter. With a central 'off' position both can never be selected.


Joined Apr 3, 2014
Your string of solar panels is likely to be nominally around 300-350 volts. The problem with switching the high voltage DC out of your panels is in the switch. High voltage DC rated switches are not cheap. This is because high voltage DC likes to arc. The switch needs to be designed to quench an arc created during switching and to be tested against it as well.
OK. Solar has a BIG advantage to utilities. It shaves peak power, so it reduces the need for larger power plants. Air conditioning is working the hardest when the sun is shining.

Solar farms, inverter technology, have another useful purpose they can "locally" modify the power factor which is a good thing.

Based on a seminar I went to:
Nuclear and Hydro do the bulk of the power generation.
Wind, you have to take it when it's available.
Solar does peak shaving and can do power factor correction.
Coal, not sure where that fits in.
Diesel/natural gas is the regulator of the grid. You can instantaneously change the generation.

"gid-tie". You want to save on your electric bill and you don't want to the hassle of dealing with batteries, so it's the best option. Now, the utility can do "net metering" or the solar system would directly offset the power you use and the utility pays you the wholesale rate when your generating excess electricity. That option isn't too good, because your at work and the air conditioning in in your house might be be reduced because no one is home.

grid-tie has the biggest problem of if no power, you have no electricity.

If you happen to generate 240/120V electricity when the grid is down, the 9600 V to 240 V transformer is perfectly happy operating I reverse generating 9600 V on the main distribution system putting the people repairing the systemin extreme danger.

And yes, the grid tie system tries to inject current to raise the voltage of the grid slightly. I've never seen a schmatic of a grid-tie inverter. So, if the AC voltage isn't there, there should be no output and if it is, it would try to generate to the max allowed. If that voltage is met, it would have to shut down. It also syncs to the grid. So, it really has to be a currrent generator.

I think master/slave DC supplies act in the same way. They use identical power supplies, so they each supply about 1/2 the current. One operates as Voltage source slightly less than the desired voltage at half the desired current. The other acts as a current source with a voltage compliance at the desired voltage.

If you want back-up power, it's probably best to have a natural gas generator or fuel cell. e.g. Bloom energy. Bloom seems to be better suited for larger installations.

Battery technology is definitely getting better considering the electric car.

Another comment about solar is there is the issue of shading, so you definately need blocking diodes or you can use micro-inverters. These are inverters at each panel. There is also dust and snow to deal with.

I got involved in trouble-shooting a solar installation back in the 1990's. No one could figure it out. The inverter would start up and then usually shutdown. It turned out that the array specs didn't match the panels. e.g. Voc, Isc, Vmp, Imp were out of bounds. I just found the problem and the panel manufacturer reconfigured the arrays.

The task I was assigned (pre internet) was to instrument a system to allow data collection/activation for a Demand Side management study remotely. Someone was living in the house which was, at one time, a research facility for solar and even thermal storage.

I designed the system, purchased the parts, but I did not build it, nor design the experiments. Some variables were temperature/humidity inside and out, Power consumption of the AC system (that was not instrumented by me), Solar radiation, Solar power generated and the ability to simulate a shower, so I could dump a specific quantity of water from the water heater remotely. They also studied, what if, the array was used to pre-heat water in the water heater.
It ended up being a published paper. It was an intense project because of time constraints and definitely an interesting one.

Until my involvement, the grid-tie inverter was there for show. There wasn;t enough money to purchase another grid-tie inverter, but all I had to do is figure out why it didn't work.


Joined Apr 3, 2014
...thought I could use a high power high voltage mosfet...
Are you going to test it to see how it fares in use? There's a reason my moniker is "Lo_volt". High voltages tend to do things you don't expect.

Outages rarely last longer than 4 hours where I live. I do have what amounts to a UPS for my water pump. I have a well with my own pump, so if the power goes out, I don't normally have water. The UPS allows me a few hours of water usage. If the power is still out after a few hours, I use a gasoline generator for backup. Between buying the inverter, batteries and all of the wire and accessories, I spent over 2500 USD. That was more than I should have spent on it, but it's given me peace of mind a few times. I go to the Tesla website to drool over the Powerwall. As yet, though, I can't justify spending the money on a Powerwall when the backup generator was soooo cheap.


Joined Jan 23, 2018
There are designs for switcher supplies to go from almost any voltage to almost any other voltage, and also a lot of DC to DC devices for sale. But avoid youtoob and amazon and ebay as the technical knowledge is often less than what a mouse knows.
Unfortunately, I need to implement what I need.

The neighbor did drainage really well until another renter moved in. He put up a tent for his vehicle. So, a noce solid surface that can divert water into a window well or side of the house.

There was a water alarm there. It broke and it wasn't replaced. It was wireless to the bedroom. The ide would be if a breach occurred, I would grab a wet vac and empty the french drain.

There is also a water alarm sitting on a towel on a basement window sill. I can;t hear it if I'm upstairs.

Prevention is to make sure plastic edging along the neighbor's driveway is intact.

So. mom and I end up in the hospital and there was a breach. It took out the scanner of an all-in-one printer and made a water mess.

There is a window well that CAN fill up with water and that's what the alarm in the window is for. There is a bilge pump that usually isn't on that can deal with water from the well. This is usually a problem when there are hurricaines and large storms, this the power supply for the pump has to manually be turned on.

What had actually happened is in a middle of a hurricaine, there was no way to pump out water. All the sump pumps in the stores were sold out. I went to a boat store and grabbed a bilge pump and some garden hose fittings. It's been there ever since.

A never executed plan was to build a current meter box and use a wall wart instead of a lab supply for the pump.
That way I can tell if the pump is running from the porch. I haven't done that.

Thirdly, testing a sump pump requires that you make sure water gets pumped out, not just the motor runs. Guess what, I won;t do that again. The sump pump rarely runs, but it is important. Now that the neighbor has installed a pump, it's even more important.

So thoughts are:

1) A comprehensive monitoring system. it would include stuff besides water.
2) Inspect edging
3) Check sump pump (Install a sump alarm)
4) Make the window well pump run off a power brick.
5) Make up the necessary cables such that the car battery in the car can be used to:
a) Run the window well pump
b) Allow the window well pump to be moved to the sump pump area so that:
b1) water gets discharged in a laundry sink
b2) sump pump can be removed and wires routed outside through the discharge and connected to the car.

Just havn't got there yet.


Joined Jan 23, 2018
I offer an additional suggestion that if it can be used, will probably easy the flooding issue. That is to add to the upper edge of the window well, and then add enough additional fill earth around the outside to cause the ground to slope away from the window well. Another option is a clear plastic dome to prevent water entrance into the window well. Based on the amount of loss suffered so far, that may be a wise act no matter what you can do with the pumps.
Further, depending on local codes and ordinances, have both pumps discharge to a point outside the house and hopefully downhill from the window well. In the event that water entry is due to a drain backup, discharging into the drain line is a futile waste of pumping effort. The sump pump that I have installed for a client most recently keeps a large section of their lawn green all summer, while preventing basement floods as well.
The entire development is built on a hill and each usually has a hill, maybe 3' high on two sides, so the window well is a perfect target. My house is at the bottom of this very long hill (10 houses in length). Between each house there is about 10' of grass and a driveway.

The pic "back" and "side" are a continuation of each other.

P1010491 Side (640 x 480) annoated.jpg

Shown is part complete and part anticipated. The black erosion barrier is gone as well.

The neighbor HAD a raised flower bed that channeled water to the edge of his house (full left). When you added a tent (back of picture) and took away that raised bed, you added hard a surface that just dumped surface water in the direction of the well.

The tent's gone now, but the grey edging has to be intact. I think I calculated 40 gpm. The entire front gutter and 1/3 of 1/2 the roof (corrogated) discharges to a pop-up 14" from the curb. There is a gutter discharge for 1/2 the neighbor's roof about 10' to the left. It has moved. It could be 3 to 10' in front of the tent.

"The plan" was to make this a swale with ez-drain under it and pick up the back gutter. The soil is clay. Overload happens when the grey edging is breached and entry is through the french perimeter drain. There is no sump pump on this side of the house and it won't be handled by the window well pump./ So, it's tent run-off (which is gone) and 1/2 the neighbor's roof. That water discharge sometimes is diverted with corrogated by the neighbor.

I also want to add about 1' of drainage rock along the right of the edging with a mostly impervios bottom. e.g. paver underlayment with edging.

I've thought about making two water paths. One solid and one ez-drain. The tree is a large fig bush which has an extensive surface root system. I would like to change the soil type in this area too.

I do need some design ideas. This 1620310462890.png

is EZ-Drain. Corrogated slotted pipe wrapped in peanuts.

Unseen, the gutter goes into the side of a catch basin and to the storm grate. Unseen, and "in front of the picture", then the path is 2 lengths of SDR pipe and a length of ez-drain, a flex coupling and solid under a side walk, a flex coupling and about 24" of solid with holes drilled in it and lawn fabric on top of drainage rock. It crosses a water line there.

P1010489 Back (640 x 480) annotated.jpg

The window well with the bilge pump is behind the tree. The gutter discharge behind the tree for abut 2/3 of 1/2 the roof is still in place. Shown as the corrogated pipe in the "catching" pic.

Sloping away is not an option because it's at the bottom of a hill. Diverting, pumping or catching is.

The window grate is behind the tree and to the right of this picture is the tent behind the wooden fence. That pump discharges through a garden hose to the front of the house. Note the hill slope to the left.

The sump pump behind the tree in the window well is only needed in severe storms like nearby hurricanes, but it is needed. It's also the time power can go out.

Next to the french is a hedge. he plan was to put a swale there and a catch basin in the path of the swale. The gutter and sump pump would discharge into that.

03-P1010209 (catching).JPG

This was pre-construction, so you can see the neighbor's water (surface water) at the white discharge and 2/3 of 1/2 the roof in the corrugated. The soil type is clay.

P1010397(porch front).JPG
This is the opposite side of the house, about 30' to the left of the window well. That's a porch about 10-12' out. That's just water coming down the hill. At the corner right after the gutter is a driveway and the sump pump is about 25' to the right. That's the other 2/3 of the roof and the porch roof that discharges on top of the sidewalk.

Although the neighbor has burried gutter discharges for his back and front gutters, the discharge has no no where to go.
Instead of "fixing" the problem, he added a sump pump which is another source of water, but it has to go under the concrete slab. Along the driveway, there is a curb for the length of the porch.

So, recently the house picked up another water source. It has cracked the driveway in the center for about 40' which has been repaired and at the end the driveway at the street, there is a corner crack. There is about 3' of grass (an easment for utilities) of grass from the street and then a sidewalk. At the property line, along a sidewalk seam, you can see water running and you can put a 12" ruler in that crack before you hit a solid bottom.

I had the county come out and look and they said they can do nothing about it. Somewhere I have pics of that too.

I really don't want to be dependent on having power, but I am somewhat. I do want to know when stuff isn't working.
Unless the neighbor is aiming water at you, there is nothing you can do. I did get permission to have the discharge near the street, otherwise 1/2 the setback distance is the norm. I put one of those curb snow-markers out during the winter, so I know where to clear the snow.
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