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Solar grid tie battery
3

Solar grid tie battery

Solar grid tie battery

(OP)
Trying to build a system that has a couple of solar panels to charge a bank of batteries.
Once the battery bank is fully charged (the normal state) the solar transitions to grid tie.
The bank is only for power failure backup.

Anyone doing this or have any experience with it? Suggested equipment?

A couple hundred watts. Output 120V.

I've combed ebay for a while but I'm not seeing it.
It's such a logical configuration it makes me think there's a different way everyone does this that I haven't recognized yet.

Keith Cress
kcress - http://www.flaminsystems.com

RE: Solar grid tie battery

Are you expecting a lot of power failures?
Normal grid supply is pretty dependable with a long time between outages, but I know that there are exceptions.
Have you considered charging the batteries slowly with something like a wall wart?
Your project has at least three design challenges;
1. Transitioning from a grid tie inverter to UPS mode on power failure.
2. Using the batteries only when in UPS mode.
3. Charging the batteries.
The design challenge of charging the batteries may possibly be solved by the use of a small independent charger and charging the batteries over a fairly long time period.
If you start with charged batteries, you don't need much current to maintain the batteries.

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: Solar grid tie battery

I think you're overparsing the problem. I think the typical grid tie prioritizes direct loads over the grid, i.e., if you have a demand prior to the grid, that gets satisfied before power goes to the grid, so the standard grid tie system will essentially do what you ask for without any additional design requirements.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
FAQ731-376: Eng-Tips.com Forum Policies forum1529: Translation Assistance for Engineers Entire Forum list http://www.eng-tips.com/forumlist.cfm

RE: Solar grid tie battery

A standard grid tie inverter knows nothing of loads, local or remote. All it does is pump Watts out the point of connection at a voltage that enables the flow. Watt, Ohm, and Kirchhoff see to it that "local" load is fed from the "local" source and that any left over capacity feeds "remote" load.

Probably change the focus from inverter plus batteries to batteries plus PV and see what the battery energy storage folks can do for you. I think you'll do better building it around the storage system than trying to build it around the PV.

RE: Solar grid tie battery

Yes there are solar inverter's that are designed for that called grid tie-battery backup. It also requires specialize switches. inverters are very specialized pieces of equipment. first they must be able to frequency syn to your inverter to the utility system. the inverter must convert dc to ac at the required voltages and cycles and on and on . All these problems have been solved by the mfg of the inverters but they are all very different. So you need to pick one that does what you need. Check with your solar store, vendor or on line mfg hot lines. Goggle YouTube too. Also the switching arrangement is complicated-it requires transfer switches. Putting the wrong inverter or switching incorrectly can cause the switches or inverter to explode. Remember utility voltages are very dangerous if you are not trained for handling electricity-you may need to get a solar electrician to help you out. Saving a few bucks to do it yourself is not worth injury or death. After saying the that the key to your problem is to select the correct inverter and switches and connecting them together properly. If you are qualified to handle electricity The gird tie- battery backup inverter have connection diagrams to configure the switches and wiring to do what you want.

RE: Solar grid tie battery

(OP)
Thanks everyone for your sage advice.

Bill, you make an excellent point about usage from the battery bank (probably) being very infrequent so charging it in any form is not particularly important.

A grid tie inverter, by definition, only feeds into a bigger active supply so they don't typically become standard inverters and if they did you'd have the dead grid connection problem anyway.

As advidana mentions a transfer switch is needed to safely switch from grid tie generation to inverter service.


advidana I'll look for a "grid tie battery backup" and see what I come up with. Thanks.

Keith Cress
kcress - http://www.flaminsystems.com

RE: Solar grid tie battery

An off the shelf solution may be two devices:
1. A grid tie inverter without batteries.
2. A ups with the battery charging dialed way down.
Now the problem becomes finding or designing a unit where a single inverter serves both functions.
You will need at least one contactor to provide galvanic isolation from the grid and a synchronizing circuit to reconnect "on the fly" to the grid when power is restored.
You have two problems:
1. A Grid Tie Inverter. By itself not a problem.
2. A UPS. Old mature technology and not a problem.
It is not always possible to solve two issues with one solution.
The challenge now is to find a solution such that neither the Grid Tie Inverter nor the UPS compromise the action of the other device.
Please share your findings with us. (Prices also if possible.)

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: Solar grid tie battery

You might want to find out whether your utility, presumably, PG&E, has installed, or can install, a net meter (https://www.sunrun.com/sites/default/files/Welcome... pg. 29). It's supposed to keep track of power flows, and that's where the adjudication of which way power is flowing is done on my installation.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
FAQ731-376: Eng-Tips.com Forum Policies forum1529: Translation Assistance for Engineers Entire Forum list http://www.eng-tips.com/forumlist.cfm

RE: Solar grid tie battery

Most of the electronic meters that are in common use now may be configured to record both positive and negative power flow.
This makes it easy to set and bill different tariffs for positive and negative power flow.
The old mechanical meters indicated net power. They ran backwards on reversed power flow.
Some utilities did not credit consumers for the VARHrs produced by a leading power factor during light loading. In these instances a ratchet could be installed to prevent the meter from running backwards.

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: Solar grid tie battery

There are definitely off the shelf solar / battery / grid-tie /islanded units that can do all of that on the market.

However, they're much larger than the size you're talking about. Some of the units end up being 3 or 4 different pieces of equipment, some are 'all in one' units. The Nedap PowerRouter is one device that can handle the entire lot (at 48V DC for the batteries, rather than 120V), I don't have a link unfortunately.

The Outback Power Radian Inverter is one that requires a separate interface for the solar to battery stage, but handles the connection to grid seamlessly (it has internal relays, and separate connections for the powered load and the grid connection).

All of them start at about 1.2kVA though, which is a bit bigger than what you're looking for.

EDMS Australia

RE: Solar grid tie battery

A couple of hundred Watts doesn't seem worth the time to even think about grid tie ins.
How about just a UPS?
Disable the battery charger and charge the batteries direct from the solar cells.
I suspect that there is a good reason why not. Can't wait to find out why. grin

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: Solar grid tie battery

(OP)
Freddy you're right, those Grid tie / battery / island units are crazy expensive. They seem to start about $2.7k.

Bill; The price of solar is so low now.. Way below $1/watt for panels that even 500W has short ROI. Then only $49 for a 300W micro-grid-tie inverter. Combined about $1/watt. This pays back quickly by its shaving the higher tier power off call it 30ยข/kWHr power. That's fast payback with the addition of some short term backup power.

Here's what I'm thinking of trying: Put a PWM charge controller for battery charging in parallel with the grid tie inverter across the panels. The MPPT function of the grid-tie will just throttle back thinking (maybe) "clouds" while the PWM charge controller is topping up the battery bank. As the bank goes to trickle the MPPT G.Tie will crank back up to maximum output.

Keith Cress
kcress - http://www.flaminsystems.com

RE: Solar grid tie battery

itsmoked: here's the route I went. I put two 250W panels on opposite sides of the N-S ridge on my garage, each with a grid-tied microinverter. With panels oriented E-W, I spread my generation out over the longest period of each day, and the microinverters make sure that part shade (one panel in shade, the other in sun) doesn't matter. That tiny system does behind the meter "peak shedding". I have a lot of mature trees, so not enough sun-exposed roof for a system large enough to pay back the permits and other fees associated with a full-on micro- FIT installation, so this is the most I can do.

I could fit and use a few more panels, but because I am not be allowed to back-feed any electricity into the grid, I would need a means to measure my demand and supply and shut off panels/inverters to get the two to match my demand but NEVER backfeed. I haven't found the clever and inexpensive way to do that- yet- but hope one day someone will figure that out for me!

The grid-tied inverters I have now are safe to linesmen working on the lines in a power failure because they must have grid power to sync to, and of course also useless to me during power outages.

My UPS needs are limited to my sump pump and, should a long power failure occur in winter, my boiler and its circulator. For those, I have a separate 150 W 12V panel with a cheap PWM charge controller and a couple deep cycle 12V floodies. The main AC sump pump is backed up by a 12V bilge pump connected to the floodies directly, so no inverter needed. If I need to back up the boiler/circulator, I have a standalone inverter capable of driving them, but I'd have to run an extension cord and I'd become the "transfer switch". In a long-term emergency, I have 18.5 kWh stored in my EV battery which I could use, if I really wanted it badly enough.

For fun, I also use the 12V system to operate a garden fountain pump, some garden LED lighting, and a little pump which uses water from the sump to automatically water my wife's hanging baskets- saves getting someone to come by to water them when we're on vacation.



RE: Solar grid tie battery

Quote (itsmoked)

Bill; The price of solar is so low now
Keith, can you post some links to your suppliers?
I have a customer who has been bugging me for 10 years or more about a solar installation.
My answer has been, unless you can get the government to pay, forget it.
It looks like that has changed and it's time to get to work on a system for him.

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: Solar grid tie battery

For areas where export to the grid is not feasible.
Search Ebay for
"grid tie inverter with limiter"
Link

Quote (Gaia Defender)

*** If the Solar Panel is producing less power and the GTI cannot deliver all the power needed by the load, then powe will be supplemented by the Grid.

*** Power Meters (Except smart meter) are not aware of the direction of Power flow. The user then pays for the power exported and delivered by the Grid.
Do Not Worry! No Problem .

* Now ,we have the limiter type inverter , if you do not want to sell electric power.
What is not mentioned is that these systems monitor only one line of the 120/240 Volt service.
For the proper functioning of the power limiter, the inverter must be used on 120 Volts, and must be connected to the side of the line that the monitor sensor is connected to.
The third generation may address this limitation, we hope.

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: Solar grid tie battery

(OP)
Cat: Thanks for the links though they're way expensive and generally too small.

Thanks Molt! Understood.
Here's the inverter Bill was alluding to. It uses a clamp-on sensor to prevent back-feeding.
No Net Backfeed Grid tie Inverter

Your case would sort of be like what I'm trying to do. You could warehouse your afternoon power in a DIY power wall and then feed it back during night hours staying net zero.

Speaking of which:
Get a load of this setup!
Youtube link to a LARGE DIY Solar/Power-Wall/Grid-Tie system

Bill;
Micro Inverter

Common Micro Inverter

Micro Inverter with lots of informational feedback

Typical sub dollar/watt panel offerings follow.
A typical solar install costs a fortune, like a new car $20K+ which really does demand a subsidy to make sense. And, virtually all subsidies demand installation by "a company" which in my opinion renders the subsidy a null-event. However, if you can do your own installs, these days, you can shop for and buy sub dollar/watt panels and come in well below the cost of null-subsidized installs for about half the time to full payback.

Typical Inexpensive Used Panel find - Pickup Yourself limitation

Free Shipping Panels #1

Free Shipping Panels #2

Free Shipping Panels #3

Free Shipping Panels #4 W/self mounting

A you must Pick-up panel, local to me, I'll likely get

I've seen flexible and adhesive backed panels for a little more than $1/watt.

Lets say I use two of the 260W panels. (total $300) And a 1kW MPPT grid-tie. ($120)

Total hardware cost = $300 + $120 = $420

Call it 5 hours a day solar.
260W x 2 x 5hr/day = 2.6kWHr/day
30day/month x 2.6kWHr/day = 78kWHr/month

I pay 0.29/kWhr in tier 2.
0.29/kWhr x 78kWHr/month = $22.62/month

$420/$22.62/month = 18.5 months... To me that's a no-brainer investment.
Isn't that something like a return of 64% on the money a year?

Keith Cress
kcress - http://www.flaminsystems.com

RE: Solar grid tie battery

I'm puzzled how you can use a simple AC current transformer on the power feed lines to the house to differentiate between 1A of forward current being fed to the house from the lines outside, and 1A of reverse current flowing from the inverter BACK into the grid- both would show up as 1A of AC current to that current transformer, wouldn't they? How is the direction of the AC current flow actually detected, and what scheme could I use to do so, given that I'm not going to throw out my microinverters so I'd have to do this detection myself if I wanted to add more panels? Is this done with some kind of phase shift measurement? That's the part I just don't get- maybe I'm being thick, but it's likely I just don't understand AC well enough. The fact that the inverter web page you linked to is full of spelling errors doesn't inspire confidence in their ability to explain how this thing actually works, either...I'd love it if one of ye who are so learned in all things electrical can explain this one to me in language a chemical engineer can understand!

As to the calcs, I know I can only make about 1000 kWh/yr per kW of installed panel capacity given my latitude and panel orientation, and even so my little system has a meaningful payback period because it is so simple and so low in capital- and because rates here are weighted heavily for time of use, with noon to 5pm being on-peak in summer.

If I had more roof area in sun I'd go off grid entirely during peak periods, drawing from the grid only to top up a battery off-peak and maybe to run the clothes dryer off peak too. I'd end up using a battery from a crashed Chevy Volt likely- at the very modest current demands of running a house, those batteries would likely last forever if you have a decent BMS on them to keep them within a safe range of SOC. But I'm not cutting down trees to feed sun to solar panels- the trees are worth more to me than the dollars I'm feeding the local utility, and the local grid here is already pretty green- the trees are doing more environmental good than I would be by dropping my power consumption really.



RE: Solar grid tie battery

Amps -90 to +90 degrees of the corresponding phase voltage are forward and amps 90 to 270 degrees of the corresponding phase voltage are reverse. How's the meter set up, forward might be into the service or it might be into the system.

RE: Solar grid tie battery

If the sensor shuts the inverter off at zero Volts, there will be no reverse power.
But for dependability the current is probably compared to the voltage.
The single sensor system is dependable only for 120 Volt inverters.
The two hot lines of a residential service are often unbalanced with regards to current.
Consider a few lights and a toaster are turned on. The toaster draws about 1200 Watts.
The lights happen to be on the other line.
So we have 200 Watts on one line and 1200 watts on the other line.
If the sensor is on the side with the toaster, it will allow a 240 Volt inverter to push out 2400 Watts before it starts to limit the power. That is 1200 Watts on each line.
So our total load is 1200 Watts plus 200 Watts or 1400 watts. The inverter is pushing out 2400 Watts. That is 1000 Watts going into the grid on the line without the sensor.
With the default setting on a modern meter, you will be charged for that 100 Watts as if you were consuming it.
Moral: If you are using current limit with a single sensor, stick with 120 Volts.

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: Solar grid tie battery

I was wondering if someone would mention that HBPowerwall install:

Quote (itsmoked)

Speaking of which:
Get a load of this setup!
Youtube link to a LARGE DIY Solar/Power-Wall/Grid-Tie system

That install is an excellent example of DIY and a number of the pitfalls involved in such an exercise, including exposed conductive surfaces, the likelihood that the circuit breakers aren't adequately rated to break the possible fault current and so on. As I understand it, that system is not a grid connect one, as its quite unlikely that it would be accepted by a utility for connection to their network.

In all seriousness though, if you forgo the need to 'use' the extra solar once the batteries are charged (or the ability to seamlessly transition to and from the grid), its quite possible (and a lot cheaper) to run a small solar install with an MPPT controller, batteries, and an inverter. Something like this is still likely too large for your overall needs, but I can't recall any of the smaller units off the top of my head.

Moltenmetal, the CT is only part of the picture, any grid connect inverter already monitors the voltage and can establish direction based on both of these aspects, effectively as what davidbeach said. Some units have that equipment internally, some do need a CT (often called a 'Power Measurement Unit') at the connection point to detect. Expect that most units on the market won't just accept a standard CT being connected, rather they'll all have their own specific unit to do a similar function.

EDMS Australia

RE: Solar grid tie battery

(OP)
Molt; PVWATTS is nice - thanks.

And, to agree with Freddy the current coil is connected to the inverter that knows the voltage waveform intimately since it has to correctly drive into the grid.

Bill; I'm pretty sure that inverter is 120V only 1 or 2kW so the coil only needs to see one phase.

Keith Cress
kcress - http://www.flaminsystems.com

RE: Solar grid tie battery

moltenmetal, this is probably the device you'd need in order to manage the export capability, although there's probably a different regional variant.

Attempting to DIY may be possible if you can work out how it communicates with the inverters (and your inverter units are compatible...) but generally isn't worth the effort compared to what it costs to buy one.

EDMS Australia

RE: Solar grid tie battery

Two issues Keith.
1. They are offering 240 Volt inverters with only one CT.
2. These inverters are plug connected. If the unit works properly plugged into the top connection of a split receptacle, it won't limit properly plugged into the bottom half.
Just something to be aware of.

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: Solar grid tie battery

Freddy- an excellent solution if I were to have about 10 panels over which to amortize its $480 USD cost. However, that represents more than I paid for the two Enphase microinverters I have, which themselves cost almost as much as each panel I bought...

Thanks for the explanation davidbeach: I guess I understood AC a little better than I thought. So people are assuming that the inverter is comparing the phase angle of the current waveform it is generating with that of the power entering/exiting the house to determine the direction of current flow. We agree that the device would be of no use on a 240 V split phase AC setup i.e. most North American homes, because the draw on each phase can be highly imbalanced. It would be best to use two separate 120V units if you were to go this route.

Obviously I won't be doing any of this due to cost and complexity. I'm still hoping someone has a nice simple analog circuit that would allow AC current direction detection by comparing the phase angle of the voltage and current waveforms on each phase. Regrettably, even that wouldn't be all that useful to me, as all I can do with my microinverters is connect or disconnect them to/from the grid, and they seem to take several minutes before they start generating power after they are reconnected to the grid- no doubt a safety measure. They claim per the datasheet to consume only 65 mW when dark, but last I checked, they were drawing a non-negligible amount of current when their panels were dark.


RE: Solar grid tie battery

I saw a clip yesterday by an MIT professor, and his team that made molten salt magnesium/antimony battery for a grid-scale energy storage, but this is way out of most individual's league at the moment. For short-term 200-800 W power, I would stick with not more than a few lead acid batteries, charge them using a charge controller powered by PV panel(s), and never attach the inverter until needed. Or use a UPS properly scaled for the specific application.

RE: Solar grid tie battery

I have been wondering about grid tie inverters for customers who have automatic backup generators.
I hope that the no-backfeed feature is switch selectable. That would be a solution for a grid tie inverter that DOES NOT back feed into a standby generator.

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: Solar grid tie battery

(OP)
Bill; This is part of the reason for this exploration, a learning opportunity. :)

Seems to me a grid tie inverter could always use an external input that stops the function. This would allow any kind of reverse power relay or generator ON relay to dump the output. But, maybe they look at the "grid" and decide the little generator doesn't look stable enough or is 59Hz or 60.4Hz and out of spec. None of the data sheets seems to go into any of this.

Keith Cress
kcress - http://www.flaminsystems.com

RE: Solar grid tie battery

A grid tie inverter must have some frequency agility. The grid is not 100% stable. At one time I had a background display that showed the actual grid frequency and recent history in real time in the Pacific North West. I don't remember the range of deviation, but a grid tie inverter would have to track frequency.
No problem with the inverter reducing the load on the generator. When the load on the generator is zero, and back feeding is a concern, the frequency with 3% droop will be 61.8 Hz on a good quality residential set.

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: Solar grid tie battery

(OP)
Point taken.

I've seen a lot of UPSs that considered any generator to be "bad power" and would run constantly until dead taking down the "protected" load.

Keith Cress
kcress - http://www.flaminsystems.com

RE: Solar grid tie battery

waross, itsmoked, you're right, they do track frequency, the key is being able to set the allowable frequency deviation. Some inverter units will allow for a 'generator' mode selection that has a much wider frequency range than what would be expected for grid, usually the ones with inbuilt relays. Those sorts of units generally allow for charging of the battery under low sun conditions, and often have capabilities (sometimes with additional accessories) that can start the generator, load the generator up by charging the batteries quickly, and then shutting off the set again.

As an aside, a lot of these systems are DC coupled, rather than AC coupled, thus the issue of reverse powering the generator is not the same as running it AC coupled against a standard grid connect inverter, those units will run flat out unless there's some means to tell them not to (like an export metering unit).

Most UPS units (at least within a certain size and cost range anyway) expect to only see grid level deviations, running a set in droop will often result in the UPS considering it outside acceptable frequency and not transition back to mains.

EDMS Australia

RE: Solar grid tie battery

Keith,
I take it you are not interested in selling the power, since the revenue from your pittance of kWhr would not likely make up for the fees you pay for the privilege.

If you had a device that would do the below, would you be satisfied?
It's not on the market any more, but they can still be bought used for ~300 USD (yeah e-bay)

This excerpt if from my Xantrex SW series machine. The Xantrex DR series is smaller, cheaper, does the same stuff.
These devices have 20 other modes of operation so if this isn't suitable, maybe another is.

Something I notice in your OP is the hint of an assumption that the inverter would be involved in charging the batteries in conjunction with the solar panels.
Normally it wouldn't be, since the solar panels can charge the batteries directly, or through a charge controller (which is better).
This device, being an inverter/charger, not just an inverter, would allow you to charge the batteries from the grid, if necessary after many cloudy days, for example.

STF

RE: Solar grid tie battery

(OP)
Thanks for the info Spar!

I was actually considering building something that does this. I hadn't seen anything that did it except the guy in here with the solar refrigerator controller thingy, but then his has never actually made it to the market.

The DR series is nice.

Amazing how fast Xantrex dumps it's products. It's almost as bad as APC with their absurd number of UPSs.

Keith Cress
kcress - http://www.flaminsystems.com

RE: Solar grid tie battery

Quote (itsmoked)

Amazing how fast Xantrex dumps it's products. It's almost as bad as APC with their absurd number of UPSs.

That's because they're both owned by the same parent company...

EDMS Australia

RE: Solar grid tie battery

Glad I could help.
The DR and SW inverter/chargers are not on the market any more, true, but 20 years ain't bad in the electronics world, IMHO, which is why they still aren't hard to find on e-bay. (They were introduced in the late 80's).
Devices with similar capabilities are on the market, but the "super-size me" culture has driven them well above the operating range you're looking for.

I'm a bit of a shill for their equipment because I still run a bunch of that stuff here. Just tweaked the charge controller this morning, in fact.

Like Freddy, I'm having trouble keeping up with the Schneider changes, too.

STF

RE: Solar grid tie battery

Any of you ever fear getting in trouble with your utility when using a peak shaving type system?

The service agreement with my utility requires that I apply for and use their generation rate plan if "any portion of the load is not served by the utility". So, just ensuring that I do not back feed the utility is irrelevant. I've been collecting dust on a panel I got for free a while back out of fear that the utility would (1) somehow notice the change in my use behavior (to become aware that I've done something, despite not back feeding through the smart meter), and then (2) bill/sue me for lost revenue. The generation rate plan is structured such that you will need a rather massive PV system to overcome the steep increase in energy charges compared to a standard rate plan. This utility also decided to no longer allow net metering back in 2015. thumbsdown

RE: Solar grid tie battery

I've seen the post of ITSMOKED to set a PWM-charger in parallel of a grid tie inverter.
The question is whether the solar charger will start charging, since they both use the voltage across the solar panels to determine wheter they should work. Possibly the voltage will drop across the solar panels because the inverter will start working. The solar charger will be thinking the voltage is to low and wont work.

There is possibly another solution: put a SPDT relay between the solar panels and the inverters.
The relay should be connected with the NC to the solar charger, the NO to the inverter, common to the solar panels.
When the sun comes up you wait till the battery is fully charged. This is the case when the solar panels voltage is 1 V higher then the battery voltage. Then you switch to the inverter. Then you wait till the voltage drops below 5 or 6 V, and you switch back to the solar charger. It can be done with an analog opamp system. (Schmidt trigger) If you're using the backup system, and you want to return to solar instead of the invertor, you can detect the net voltage (relay, opto-coupler) or measure the discharge current of the battery. The voltage measurement may be a little tricky, cause some solar chargers are connected to the + of the battery, and switch the - side.
https://res.cloudinary.com/engineering-com/image/upload/v1510248138/tips/Solar_pzpdak.bmp

RE: Solar grid tie battery

(OP)
wroggent; I'm not worrying about it for 500 measly watts. The inverter just plugs into an outlet. I also have a 'dumb' meter that turns backwards with reverse power. it's also single phase 120V. My house probably uses about 350W during the afternoon.

I picked up the panels today! So shortly I should be experimenting.


EddyVl; Thanks for the suggestion.

Part of this project is for learning. I'll try the paralleled charger and inverter and see what happens. They may play together or not.. we'll see! :) I'll feedback here so we all learn something.

Keith Cress
kcress - http://www.flaminsystems.com

RE: Solar grid tie battery

Personally, I would connect the solar panel to the electrical network and, through an independent battery charger, connected to the electric network, I would charge the batteries. Otherwise you need a grid connection inverter to UPS mode in case of power failure.

I believe, as Waross said, that the issue of charging the batteries can possibly be solved by using a small independent charger and charging the batteries for a fairly long period of time. You can use a digital battery charger that monitors the voltage values of the battery, or an automatic battery charger, which will load automatically. There are some compact battery monitoring systems that can solve the problem. are you ask us for a suggested equipment ?, it would be very difficult to select a battery charger in particular, I could suggest the Amperis brand, but it all depends on your budget.

Greetings and luck

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