Recently installed hybrid system with LiFePO4 battery bank

[Rick Jones]

Greetings forum members,

I installed a new hybrid solar power system about four and a half months ago that I had been designing for some time. The system components consists of an Outback Radian GS4048A, a Midnite Classic 150 CC, a Midnite Epanel, 3600 watts of PV, and a 195 AH LiFePO4 HiPower battery bank. The panels are 72 cell 300 watts and are configured 6 strings of 2 in series. PV voltage in averages 64 volts, max is 75 and min 56. Max charging amperage I have seen is about 64 amps. I have morning and evening shading, which is why I over paneled a bit. In the design I was shooting for about 10 kWh per day average. So far over 136 days the average is 9.3 kWh.

This system is of course grid tied and mainly intended as a whole house backup system, however I do use it to offset grid power consumption. We have a 1000 sq ft home and our energy consumption is 20 to 24 kWh in the summer and 8 to 12 kWh in the winter. (You can probably guess that I live in North Florida.) The difference between winter and summer numbers is just air conditioning, so producing the average winter consumption will do if grid power is lost.

So, when I say whole house it doesn't mean everything. It doesn't include the range/stovetop/oven, or the electric clothes dryer. Everything else is included. The lights (LEDs), fans, entertainment system, microwave, refrigerator, freezer, heat pump water heater, and a 2 stage 24000 BTU heat pump for A/C and heating. I can already hear you saying, "a 24000 BTU heat pump on a 4000 watt inverter?" :eek: Well there is a reason for it.
*
Well, I've got to go for now, but I'll be back later to say more on the inverter and the battery bank.

Rick

[Rob Beckers]

Very nice Rick!
So the Outback is set up to sell-back to the grid when the batteries are full? I assume you have net-metering over there.

Please do tell more about in particular the battery bank. I've been eyeing Li-ion batteries for some time, of course cost is an issue...

One application that could be done quite nicely is load-shaving; we have time-of-use metering where it's more expensive certain hours of the day vs. others. By using the batteries during the expensive times and recharging during the low-cost hours it should be possible to lower our electricity bill quite a bit.

-RoB-

[Rick Jones]

Hi Rob, thanks for the comment.

Although the utility does net metering, I did not sign an agreement to sell to the grid. I use a function/mode in the OB Radian inverter called grid zero to offset grid consumption. It is quite an amazing feature and a lot of fun to use. It basically uses the grid to supply the loads however, it can be configured to use any where from 1 to 15 amps at 240V supplied by the inverter from the battery bank to bring grid use down to a minimum of 1 amp at 240V. It can be a set it and forget it system if the battery bank and array are big enough.

Mine is not. So I can get more production by monitoring and dynamically adjusting the system based on the loads and power production. Managing the dynamics and trying different strategies is really a lot of fun. Of course I could set it to manage itself, but at the loss of a kWh or two a day, but where's the fun in that.

It can of course be used as an off grid system, and I will be able to use that mode as winter approaches. I have tested the system in mini grid mode (off grid) and it carries the loads well, including the 2 ton heat pump. The reason for this is that it starts in the first stage which is really 16000 BTU. The start surge is about 35 amps for 1 or 2 seconds and the inverter does groan while picking up that load. The real test came when hurricane Hermine moved through Tallahassee Florida in early September and we lost power for 4 days. I did use the A/C, set to 80 degrees, several hours in the afternoon when the batteries were full for three of those days, but I would not use the A/C in that mode under normal circumstances. With grid zero available, it is just not necessary to put that kind of stress on the system. I did find an interesting thing with the heat pump water heater. It likes to test it's 4500 watt element occasionally for about a minute, and as you can guess, the inverter was looking at 5 kW and shutdown at about 30 seconds. I have subsequently changed that element to 1500 watts. Oh, I forgot to say, the water heater is a Geospring 50 gallon model.

I will continue with the battery bank tomorrow. Thanks for following and enduring this continuing post. Hopefully it will yield some useful information.

Rick

[Rick Jones]

Lithium iron phosphate batteries carry an undeserved trepidation about using them without a BMS, (battery management system). While a BMS is necessary in the application where you usually find large LFP prismatic batteries, i.e. in electric vehicles, I didn't and still don't agree that they are necessary in the solar power application.

Several forum members on various forums including myself all think that the reason the EV industry needs to use a BMS to keep the LFP cells balanced is because of the high current used in the acceleration of these vehicles. They easily draw hundreds of amps from these cells. The main reason for the imbalance is that, even though a given set of batteries have the same manufacturer and labeled amp hour rating, they will not have exactly the same capacity. The variance can be as much as 5%.

As an example, 16 200 AH cells can be anywhere between 190 and 210 amp hours. The amount of power in each cell is different, so each cell delivers it's amperage at a slightly different rate. High amperage demand magnifies this and as a result the voltage of the various cells will slowly diverge. So BMS needed.

In solar power applications, this is not the case. Instead of amperage draws of 2 to 5 times the capacity, as in the EV application, much lower amperage is demanded from the cells. For most of us, probably not more than C/4, thus the effect of varying capacity is of far less impact, especially when the cells are top balanced, and charged to 90% SOC and discharged to 20 to 40% SOC. Voltage divergence does still occur, however the rate is slow and easily managed without a BMS.

In the 138 days since my installation, the widest difference in cell voltage is .009 volts/ nine thousandths of a volt just this week. So how long till the difference requires a manual rebalancing of the battery bank? I don't know. It may be a year at this rate, maybe more. However if at some point one becomes uncomfortable with the difference, say 1/100, 2/100 or even 1/10 of a volt, then the battery bank can be easily rebalanced over night.

So what other maintenance do they require? None. What do you have to be concerned with? Besides balance, the battery can not be charged at or below 32F, over charge or over discharge 1 time and they will be history.

The costs? EXPENSIVE. A dollar per amp hour is a very good price. However 2000 to 3000 cycles does help make it more palatable.

Benefits? They do not have to be fully charged everyday. In fact they do not have to be charged at all, and can be left sitting for months at 30 to 70% SOC. They can be charged at anywhere from 1 amp to C/3 with no ill effect, and so, are very flexible in this application.

I think it was well worth the risk to be a pioneer in this area of battery tech and I will be updating this thread on the state of the battery bank in the months to come.

My settings: Absorb to 55V, EA 8 amps (2% of C per 100AH), Float at 54

I will try to upload some low res pics of the system.

Thanks,

Rick

[Ralph Day]

You make things sound pretty sweet Rick. What's the cost like (or am I just too lazy to re-read the whole thread)?

Ralph

[Ihab Seidy]

hi Rick
was really interesting to follow your design and other members comments

i have technical question for you , as u mentioned battery should not be charged most of the days , is that mean the power u capture from your solar panels thru the charge controller Midnight will inverted directy to your AC ( main panel ) to cover your loads ..
in that case , the radian take the DC from the panel to your grid directly without any waste or less efficiency thru the journey thru the batteries ,,do you understand my point ?

can u share with me the average voltage from all panels

thanx
ihab

[Rick Jones]

You make things sound pretty sweet Rick. What's the cost like (or am I just too lazy to re-read the whole thread)?

Ralph

Hi Ralph,

If you mean the entire system, that's about 15,000 dollars. If you're talking about the batteries alone. I bought 16 195 AH cells for 185 dollars each. They were discounted because they were about 9 months old and HiPower, the company that makes them had gone out of business, so no warranty. However, ElectricCarPartsCompany.com where I bought them, gave me a 1 month guarantee that were unused and in good working order.

New batteries under warranty are about $1.15 to $1.25 per amp hour.

This is the battery page on their website, http://www.electriccarpartscompany.com/Prismatic-Lithium-Batteries_c_1.html

LFP battery internal resistance can vary by brand and size from 2 milliohms down to .2 milliohms. Of course lower is better and it's something I would consider if I purchased again.

If I can be of further assistance just ask.

Rick

[Rick Jones]

hi Rick
was really interesting to follow your design and other members comments

i have technical question for you , as u mentioned battery should not be charged most of the days , is that mean the power u capture from your solar panels thru the charge controller Midnight will inverted directy to your AC ( main panel ) to cover your loads ..
in that case , the radian take the DC from the panel to your grid directly without any waste or less efficiency thru the journey thru the batteries ,,do you understand my point ?

can u share with me the average voltage from all panels

thanx
ihab

Hi ihab,

I did not intend to suggest that the batteries should not be charged most days. I meant that if a full or close to full charge cannot be achieved, it will do no harm to the battery as opposed to lead acid which needs to be 90% or better in order to keep from being damaged.
I would still rather get a full, (90%) charge so that power is available in the evening.
From what I can tell, these batteries are about 98% efficient. AC is produced by the inverter and then blended with or sold to the grid. So their are system losses. Including panel losses this system is 67.5% efficient.

Panel string voltage is 73volts, 2 times panel VMP

Hope this answers your question

Rick

[Rob Beckers]

Rick, what Voltage is each battery?
I'm trying to put the price and 195 Ah in perspective vs. lead-acid, but to do so it depends on the actual energy per battery, and for that Ah alone is not enough, I'd need to know Voltage as well (energy stored = Ah x Volt).

How are those batteries rated? For LiFe you can't discharge below 80% DOD without doing permanent damage. Is the 195Ah the available energy? Or is it 0.8 x 195 = 156 Ah that you have "to work with"?

Thanks!

-RoB-

[Rick Jones]

Rick, what Voltage is each battery?
I'm trying to put the price and 195 Ah in perspective vs. lead-acid, but to do so it depends on the actual energy per battery, and for that Ah alone is not enough, I'd need to know Voltage as well (energy stored = Ah x Volt).

How are those batteries rated? For LiFe you can't discharge below 80% DOD without doing permanent damage. Is the 195Ah the available energy? Or is it 0.8 x 195 = 156 Ah that you have "to work with"?

Thanks!

-RoB-

Hello again Rob,

The Primatic cells are 3.2 volts nominal and a typical "48 volt system" will take 16 of them for a total of 51.2 volts. So, 51.2 volts times 195 AH = 9.984 kWh
They are rated at the 20 hour rate. No one who cares about their wallet stuffing will take them below 80% DOD. I will not even go below 70%. I would say, a conservative estimate of usable battery space is about 60%. 70% is the more technical boundary. And that is if they are top balanced. Bottom at 80% DOD and top at 90% SOC. Also, 10% less DOD gives you a 1000 more cycles.

Oh, one other thing, The batteries can not be used in parallel strings. If you need 400 AH battery bank, then you have to buy 400 AH cells. etc.

Rick

[Ihab Seidy]

Rick
let me interact more here about specific point here
so according your system , most of the time during the bright sun u r getting almost daily 9.3 kw ,,direct inverting from your panels to the panel 48 vdc tol 230AC ,,i dont know your grid specs ,,,but wish to know how u managed to measure the efficiency in the panel ,,,this very hard to measure , where the power coming from your radian willl blended or mixed with main power coming from grid ..
i think if i am not wrong , may be it would more efficient and cheaper to use just grid tied inverter ,,as long the usage of batteries not heavy or significant ,,
correct me if i am wrong

[Rick Jones]

Rick
let me interact more here about specific point here
so according your system , most of the time during the bright sun u r getting almost daily 9.3 kw ,,direct inverting from your panels to the panel 48 vdc tol 230AC ,,i dont know your grid specs ,,,but wish to know how u managed to measure the efficiency in the panel ,,,this very hard to measure , where the power coming from your radian willl blended or mixed with main power coming from grid ..
i think if i am not wrong , may be it would more efficient and cheaper to use just grid tied inverter ,,as long the usage of batteries not heavy or significant ,,
correct me if i am wrong

Ihab,

You are quite correct, selling to the grid would be more efficient but my priority is not saving money. It's learning about the system with hands on experience. It's about recreation and pursuing an interest until I am satisfied that I understand it adequately.

I am interested in cycling the batteries daily to see how well they compare to other battery chemistries in solar power systems.

Thanks,

Rick

[Ihab Seidy]

I am really happy that you are sharing your experience with us
Actually I m willing to buy radian inverter like with 4 kwp..but I am willing to use very small batter bank
4 battery each 12v only 100 amo
P
I am willing to feed my battery thru wind alternator gives 100-120 vdc
But I am willing to use the radian as self consumption for my loads which is around 20kw..

Can u give me any advices from your experience Rick

Even if u can any expert or consultant help me design the system pls recommend me ..
I can send u my private email if u don't like do that openly .
Thanx

[Rick Jones]

I am really happy that you are sharing your experience with us
Actually I m willing to buy radian inverter like with 4 kwp..but I am willing to use very small batter bank
4 battery each 12v only 100 amo
P
I am willing to feed my battery thru wind alternator gives 100-120 vdc
But I am willing to use the radian as self consumption for my loads which is around 20kw..

Can u give me any advices from your experience Rick

Even if u can any expert or consultant help me design the system pls recommend me ..
I can send u my private email if u don't like do that openly .
Thanx

Ihab,

I appreciate the offer to help design a system with you, but I am really not qualified. It took me months of reading and searching for the right combination of components. Keep in mind, your about to spend thousands of dollars and if it's not a balanced system, you'll spend more to fix it. Do what I did, frequent the forums, read about the systems, the problems, and the solutions. Familiarize yourself with a wide range of components and what it takes to design a balanced system. Soon you'll have all you need to do it yourself. It's an adventure.

The Outback Radian GS4048A is a good inverter and I do recommend it. However please research it and it's features and find out if it fits your particular needs. As an example Outback Power recommends at least a 200 AH lead acid based battery bank for this inverter, 400 preferred.

I have no idea how you could integrate 120V DC from a wind alternator into a 240 volt Radian system.

Here are a couple of links to active solar forums that have some very knowledgeable members.

http://forum.solar-electric.com/categories
https://www.solarpaneltalk.com/

Best of luck,

Rick

[Ihab Seidy]

actually i do what u recommend me long time ago
i am intending to use similar midnight charge controller to limit my charging volatge within 48 for the battery
but the inverter will work normal to invert 48 vdc to 240 VAC ,,
my concern and philiosphy is based ,,i wish i could not allow the amps Not to pass thru the batteries to minimize the waste of amps as long my batteries is fully charged ..

this is the area i am trying to resolve ,,is radian offer this feature from your experience
i mean if the battery is fully charge and the volatge and amps is enough for my needs will it invert it directly to AC for my main panel usage ? or it must go thru batteries

i dont see any pooint to high amps battery , if we managed to get steady generation from our DC soruce either solar panel or wind turbine ,,and i heard good reveiws about radian really

i will continue asking and checking Rick ,,coz as u said it is some thing costy and any mistake will cost double to fix it ,,

[Rick Jones]

actually i do what u recommend me long time ago
i am intending to use similar midnight charge controller to limit my charging volatge within 48 for the battery
but the inverter will work normal to invert 48 vdc to 240 VAC ,,
my concern and philiosphy is based ,,i wish i could not allow the amps Not to pass thru the batteries to minimize the waste of amps as long my batteries is fully charged ..

this is the area i am trying to resolve ,,is radian offer this feature from your experience
i mean if the battery is fully charge and the volatge and amps is enough for my needs will it invert it directly to AC for my main panel usage ? or it must go thru batteries

i dont see any pooint to high amps battery , if we managed to get steady generation from our DC soruce either solar panel or wind turbine ,,and i heard good reveiws about radian really

i will continue asking and checking Rick ,,coz as u said it is some thing costy and any mistake will cost double to fix it ,,

Ihab,

I believe that I understand what your goal is. From what I understand if the battery is full, the power produced by the PV does directly supply the inverter. As I understand it there are two issues that a small battery bank can cause. If you sell to the grid the battery needs to be big enough to buffer the system against the grid and the other is insufficient capacity to carry the loads for any appreciable length of time after sundown. If you are going to self consume production while the sun shines then I don't see a problem with it as long as you can live with the limitations of such a specialized system. Also, keep in mind that the charging amperage must match the capacity of the battery bank. For a 100 amp hour bank with AGM batteries that would be 20 amps or more depending on the manufacturers recommendations. Try to consider every possible thing.

Rick

[Ihab Seidy]

so can i ask the crazy question ,,if in the case of full battery the power goes directly to the inverter ,,in this case if you can make a try , by disconnecting the battery bank totally from your Inverter and see how things going during the bright sun around 1-3 PM ...
i have asked this question to many and no one can give me direct answer ,,
can i use instead of the battery any thing work like bridge bewteen my DC source and the inverter ? ,,i know this is programming in the radian , it may allows you to that ?

if any one see me i am stupid or unexperienced ,,i am really sorry , all i do i am trying to understand , but i am raising question to learn from you guys ..

i was thinking to use ATS < automatic transfer system to disconnect the battery from the inverter and alllow the power goes directly to the inverter to get max efficiency ,,i am not talking about saving or being smart or whatever ,,i am just sharing ideas about of the box might be wrong or right ,,

[Ihab Seidy]

for the radian , i think they dont have 2 MPPT ?
i have also basic question if any one can help me by answering it would be very grateful , if we use some of the latest hybrid inverter with storage 2 MPPT , it that mean we should use 2 charge controller feed each MPPT comping from panel group ? for exampel , we have some panel towards north and other towards south

[Rick Jones]

so can i ask the crazy question ,,if in the case of full battery the power goes directly to the inverter ,,in this case if you can make a try , by disconnecting the battery bank totally from your Inverter and see how things going during the bright sun around 1-3 PM ...
i have asked this question to many and no one can give me direct answer ,,
can i use instead of the battery any thing work like bridge bewteen my DC source and the inverter ? ,,i know this is programming in the radian , it may allows you to that ?

if any one see me i am stupid or unexperienced ,,i am really sorry , all i do i am trying to understand , but i am raising question to learn from you guys ..

i was thinking to use ATS < automatic transfer system to disconnect the battery from the inverter and alllow the power goes directly to the inverter to get max efficiency ,,i am not talking about saving or being smart or whatever ,,i am just sharing ideas about of the box might be wrong or right ,,

You defiantly cannot disconnect the battery. The battery stabilizes the voltage and defines the amount of amperage available to the inverter. It also helps handle any surge demanded by the inverter. The battery requires a charger and the charger will not work without it's power source, the battery.

Rick

[Rick Jones]

for the radian , i think they dont have 2 MPPT ?
i have also basic question if any one can help me by answering it would be very grateful , if we use some of the latest hybrid inverter with storage 2 MPPT , it that mean we should use 2 charge controller feed each MPPT comping from panel group ? for exampel , we have some panel towards north and other towards south

Hybrid inverters in the US are not like the ones in Asia. It is only an inverter that has grid tie capability. There is no builtin charge controller.

With 2 controllers you can face the arrays in any direction you choose, but I would never face one north, unless south of the equator of course. Southeast and southwest might be best. It depends on how much amperage the arrays produce because it increases charging amps in the morning and afternoon and decreases it during midday.

Rick

[Rob Beckers]

Rick, just catching up on a flood of messages, and to get back to your usable capacity post: My back-of-the-envelope calculation puts your battery cost at just about 2x that of good quality deep-cycle lead-acid (for similar usable capacity). That is a VERY good price for LiFe, likely cheapest I've seen to date.

You made a good deal!

If only regular pricing for lithium-ion batteries would fall to those levels... They are better batteries than lead-acid, though I believe that a BMS is needed for the average Joe to safely use them (as in not killing them in short order by under- and over-charging, and possibly balancing though you make a good point showing it's not needed).

Very interesting info! Thank you!

-RoB-

[Rick Jones]

Rick, just catching up on a flood of messages, and to get back to your usable capacity post: My back-of-the-envelope calculation puts your battery cost at just about 2x that of good quality deep-cycle lead-acid (for similar usable capacity). That is a VERY good price for LiFe, likely cheapest I've seen to date.

You made a good deal!

If only regular pricing for lithium-ion batteries would fall to those levels... They are better batteries than lead-acid, though I believe that a BMS is needed for the average Joe to safely use them (as in not killing them in short order by under- and over-charging, and possibly balancing though you make a good point showing it's not needed).

Very interesting info! Thank you!

-RoB-

Thanks Rob,

I agree about charging and discharging too far. Although the charge controller can protect from over charging and LVD setting in the inverter can protect from over discharging, I still installed a couple of 400 amp 60 volt DC disconnect relays in my setup for redundancy.
The issue of needing a BMS, to me, is a non issue. I'm quite surprised at how well they stay in balance and even more surprised that more solar enthusiast are not using them. I guess there are not many who have been willing to risk a few thousand dollars to find out.

Have a good day and thank you for this great forum,

Rick

[Rob Beckers]

Well, one reason more don't try them is simply price: You lucked out, and were willing to take a risk with a (still) substantial amount of money.

Cheapest 'regular' Li-ion batteries I've heard about would be Tesla's Powerwall, and that rings in at about 4x the price of lead-acid (on a usable-per-kWh basis). From there on prices just keep going further north. Single cells from China are not too bad (for those willing to build their own bank, and deal with the BMS-or-no-BMS question themselves), though still above that 4x lead-acid price. A ready-made solution, with BMS, from other manufacturers is in the 7x - 25x price range vs. lead-acid.

IMO first Li-ion would first have to get to the bracket of what you paid, about 2x lead-acid, before more will adopt it. Given that it's been around quite a while now, and is widely manufactured in low-wage countries, I don't see that happening any time soon (if it could easily be made cheaper it would have happened by now).

-RoB-

[Rick Jones]

Well, one reason more don't try them is simply price: You lucked out, and were willing to take a risk with a (still) substantial amount of money.

Cheapest 'regular' Li-ion batteries I've heard about would be Tesla's Powerwall, and that rings in at about 4x the price of lead-acid (on a usable-per-kWh basis). From there on prices just keep going further north. Single cells from China are not too bad (for those willing to build their own bank, and deal with the BMS-or-no-BMS question themselves), though still above that 4x lead-acid price. A ready-made solution, with BMS, from other manufacturers is in the 7x - 25x price range vs. lead-acid.

IMO first Li-ion would first have to get to the bracket of what you paid, about 2x lead-acid, before more will adopt it. Given that it's been around quite a while now, and is widely manufactured in low-wage countries, I don't see that happening any time soon (if it could easily be made cheaper it would have happened by now).

-RoB-

Hi Rob,

I certainly agree, they are expensive. I mainly wanted to let everyone know that I have the batteries installed in a live production system, doing daily cycling with no BMS, and will be reporting on their performance from time to time.

Thanks again,

Rick

[Rick Jones]

6 month update: System doing well, maximum variation in the 16 cell LFP bank is 10 millivolt, which is fine. Still a long way to go before needing to rebalance.

[Ian Speer]

Hi Rick thanks for taking time to record all your observations here. I am looking at a Li battery system anam interested to know what your maximum charging voltage is set at?
Ian

[Rick Jones]

Hi Ian,
I'm going to give you a little more information than you asked for because there are several basic things you need to know if you are going to set up a LFP battery bank.

First thing is balancing the cells. I recommend charging each cell completely full with a 3.65 volt lithium battery charger. When the last cell has rested 2 hours, connect them all in parallel for 8 hours, then connect them all in series to configure you bank. This process can take some time, but it will pay off in the long run.

Absorb setting should be 3.425 to 3.450 volts per cell. What's the difference? Well, aside from the fact that the 3.450 setting will charge a little faster, the difference is headroom.
This voltage is where the cells will be when they are at the end of absorb. The cell max is 3.65 volts. The headroom is the range between cell voltage the end of absorb and 3.65 volts. It's the space or buffer you have against overcharging an individual cell. Over time the cell voltages will diverge, and the more room you have to accommodate that the better. The divergence is not a tremendous amount though. At the end of 16 months my cells had diverged only 25 millivolts. I charge at 3.425 per cell, so the measurement at the end of absorb showed the highest cell was 3.436 and lowest was 3.411. So you see that 200 to 225 millivolts of headroom is really sufficient to protect against overcharging due to the cell voltages drifting. Maybe you will want to rebalance when the divergence is 50 millivolts, maybe more, It's really what ever you are comfortable with.

I don't recommend floating the LFP bank above 90% SOC, which would be 3.331 volts per cell.

I recommend using end amps (EA) to end absorb. I'd set it a little higher than 1% of C per 100 amp hours. Actually the higher the better, within reason. For example, my 195AH bank EA setting is 16 amps.

Also recommend getting a larger battery than is needed if it can be afforded. It will allow the battery to discharge less deeply and not reach the end of absorb as often. With LFP, ending absorb is really only necessary to reset your battery monitor. If you don't need the amp hours above 90%, going there less often is better for the battery in the long run and contributes to a longer battery life.

I also recommend a redundant high and low voltage battery disconnect of some type.

Any questions, let me know.

Rick

[Ian Speer]

Rick thank you for the thoughtful and informative reply. I am keen to restrict the charging voltage to avoid shortening the battery life. I found a BMS system by a company called Orion and it seems to offer a highly configurable setup to manage a solar storage battery bank as well as taking care of potential in balance issues.

I installed a 5kW pv setup with Enphase micro inverters 2 years ago due to a complex roof layout and shading issues. It turns out that it is not straightforward to use this setup off grid however I am getting there.

I have had the full Enphase monitoring System in place for almost a year and will probably add another 1 to 2kW to enable self sufficiency for the whole year without needing to resort to a backup generator. I will still have one.

I am currently working on sourcing an inverter and a charger that will be able to communicate with the Orion unit as well as controlling the output from the Enphase micro inverters. I would prefer a pair of charger inverters which can operate in parallel for redundancy as well as handling the occasional demand peaks.

If you have any ideas or experience with suitable equipment I would be interested. This is part of a long project to achieve energy independence.

Ian

[Rick Jones]

Hi Ian,
I have heard good things about the Orion BMS. Balances cells internally with no balance boards. Also good redundant safety features. I would think the absorb and float settings I just posted will work with it if you will be using LiFePO4 chemistry.

I don't have any experience with standard grid tie systems, but I know that they are difficult to adapt for off grid power as they are configured. I do believe a hybrid inverter with a Lithium battery bank is a match made in heaven, because it can be set up to work for long periods of time unattended. Just my opinion based on my own experience.

I wish you success in your endeavor.

Rick

[Rick Jones]

Well, decided to add a 17th cell to the bank a few months ago which upped the capacity from 195AH at 51.2 volts to 207AH at 54.4 volts. Rebalanced the cells in this process, system installed 2 years on 18th of this month.

Rick