Adding more batteries and panels

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simonjon
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Posts: 2
Joined: Sat Mar 05, 2016 2:52 pm
My RE system: Outback power single phase inverter/charger
IMARK MPPT Solar regulator
3kw solar array
6kwh Aquion saltwater batteries

Adding more batteries and panels

Post by simonjon » Sat May 16, 2020 2:02 am

Hi,

I've a couple of questions regarding the best way to add more batteries and solar panels to my off grid system.

Currently we have a 3.5kw solar array connected to an IMARK SRX-60 MPPT Solar regulator, an Outback Power VFXR3048E inverter charger and 4 x Aquion Energy 48v 2.3Kwh 47.3Ah batteries (48 volts 189.2Ah 9,2Kwh output) with a shunt and Outback Power Flexnet HUb conected to a Mate3.

I am looking to add another 3kw to 4kw solar array and 16 155Ah Sealed lead acid batteries in 4x banks in series connected in parallel (48volts 620Ah 29.76Kwh output)

The questions I have... so far...

1. What would be the best solution to adding the above new batteries and solar panels to the existing system?
2. Would I connect the new solar array to a new MPPT solar controler(ie an Outback FLEXmax 80 or 60) and connect that in parallel to the existing?
3. Would the existing inverter/charger need to be upgraded or can I stack another one on to handle the extra load (solar input and battery charging)?
4. Will there be problems with having 2 different types of batteries if both battery banks are connected in parallel?
5. The settings for the original Aquion batteries in the Mate 3 are set to sealed lead acid (the closest setting available), will this affect the readings in the FLEXnet Hub if they are connected all together in parallel?

The IMARK MPPT controller doesn't communicate with the Mate 3 (not a problem I just thought I should mention it??..)
I think that is all, I am still in the process of learning how this all works but I think i am getting there.

Thanks in advance for your help and advice!

Cheers Simon

pss
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My RE system: 8330 watts in three strings, Flexmax 60 x 3, Radian 8048A, GSLC load center, Mate 3S, Hub 10.3, FN-DC and 900 Amp, 48V Trojan T105-RE battery bank.

Re: Adding more batteries and panels

Post by pss » Sat May 16, 2020 7:05 am

Simon,
Lots to chew here.
First off the inverter could care less how big a battery bank you have. It consumes DC power from a source and inverts to AC. When it runs out of DC, it shuts off.
You only need a larger capacity inverter if you increase your loads to where the current inverter cannot handle it.
As for adding an array, about 1000 amps of batteries will require about 10,000 watts of panels in a good sunny geographic location. Compare your solar hours at your location to say San Diego county and adjust from there.
You can add batteries by connecting new and existing batteries to a buss bar that feeds into the inverter. The new batteries would be connected to a new charge controller which is connected to a new array properly sized for the charge controller's capacity.
You need to start by figuring out what space you have for the array and what size panels you get the best deal on, then post it and you will get help on sizing things up.
The battery strings need to be as close to equivalent as possible otherwise current will flow from one string into the other. The Flexnet hub doesn't make readings, it is not intelligent in this way. Using lithium batteries also is not something that the Outback system reports on because they are chemically very different than lead acid. You need to properly program the charge controller to charge them based on battery manufacturer information.

raysun
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Posts: 2234
Joined: Tue Jul 26, 2016 5:57 am
My RE system: Flexpower One: FX3048T, (2) FM80, MATE3s, FlexNetDC
Outback 200NC batteries (8 @ 48v)
Outback IBR3 battery enclosure
Suniva 330 watt panels (12 - 6 strings of 2 in series)
Hyundai 355 watt panels (6 - 3 strings of 2 in series)
Honda EU7000is gas fuel generator

Re: Adding more batteries and panels

Post by raysun » Sat May 16, 2020 9:13 am

Hey Simon,

See inline for comments on your questions.

1. What would be the best solution to adding the above new batteries and solar panels to the existing system?

The best solution will be to keep the two battery banks and charging sources completely isolated from each other. The different charging requirements and discharge characteristics will not allow them to be combined into a single battery.

2. Would I connect the new solar array to a new MPPT solar controler(ie an Outback FLEXmax 80 or 60) and connect that in parallel to the existing?

The current 3.5kW array charging a 48V battery bank would, at theoretical maximum provide 3500/48 = 72A of charging current. This is already over-rated for the 60A charge controller. That the controller hasn't failed is likely because the array doesn't reach full output for any appreciable period of time.

Prudent design would suggest adding a separate charge controller for the 2nd array. The FM80 would be the best choice.

In general, if adding a 2nd array and charge controller to a battery, it is connected in parallel with the 1st. In this case, the two battery types cannot be combined, so the charging systems would need to be separate in order to individually charge the two batteries.

3. Would the existing inverter/charger need to be upgraded or can I stack another one on to handle the extra load (solar input and battery charging)?

It's not mentioned which Inverter model is being used. Several are capable of being "stacked" in various configurations to provide higher output.

The Inverter actually has no bearing on the charging system and battery capacity insofar as charging is concerned. The Inverter draws charge from the battery, but doesn't "see" the process of charge being put into the battery.

With addition of the 2nd battery and charging source, it would actually be best to stand up an entire separate inverter system.

Most system architectures, Outback included, are predicated on a single, monolithic battery bank. The proposed addition of a 2nd battery bank of different characteristics precludes a single battery.

4. Will there be problems with having 2 different types of batteries if both battery banks are connected in parallel?

Yes.

5. The settings for the original Aquion batteries in the Mate 3 are set to sealed lead acid (the closest setting available), will this affect the readings in the FLEXnet Hub if they are connected all together in parallel?

Yes, in practice, the two disparate batteries cannot be combined in parallel, and the FNDC will not work well with them switched into the system in sequence. The logged results will be very confused.

raysun
Forum Emperor
Posts: 2234
Joined: Tue Jul 26, 2016 5:57 am
My RE system: Flexpower One: FX3048T, (2) FM80, MATE3s, FlexNetDC
Outback 200NC batteries (8 @ 48v)
Outback IBR3 battery enclosure
Suniva 330 watt panels (12 - 6 strings of 2 in series)
Hyundai 355 watt panels (6 - 3 strings of 2 in series)
Honda EU7000is gas fuel generator

Re: Adding more batteries and panels

Post by raysun » Sat May 16, 2020 11:04 am

"I am looking to add another 3kw to 4kw solar array and 16 155Ah Sealed lead acid batteries in 4x banks in series connected in parallel (48volts 620Ah 29.76Kwh output)"

It wasn't asked, so forgive (or simply dismiss) unbidden advice here.

The generally accepted best practice is to limit battery parallel branches to no more than three. The reasoning behind it is with increasing parallel branches it becomes more difficult to keep the individual branches in balance.

Lead-acid batteries are electro-chemical devices that rely of consistent 'physics' in each cell to remain in balance. It takes only very minor variations between cell characteristics to knock battery health into a cocked hat.

Sealed batteries are especially problematic because there is no practical way to monitor individual cells so it's more difficult to take corrective action. Avoiding the need to correct cell imbalance is preferable by far.

To avoid undue imbalance, the ideal configuration is a single string of battery cells of the target battery capacity. This is often not practical, so the parallel string configuration is used. If looking to build out a 600AH+ battery, it will pay to look for 200AH+ monoblocks and configure for 3 strings max.

Just my $0.02

simonjon
Forum Junior Member
Posts: 2
Joined: Sat Mar 05, 2016 2:52 pm
My RE system: Outback power single phase inverter/charger
IMARK MPPT Solar regulator
3kw solar array
6kwh Aquion saltwater batteries

Re: Adding more batteries and panels

Post by simonjon » Sun May 17, 2020 6:57 pm

Thanks pss and raysun,

Your information is truly helpful.

"As for adding an array, about 1000 amps of batteries will require about 10,000 watts of panels in a good sunny geographic location. Compare your solar hours at your location to say San Diego county and adjust from there."

I am based in Queensland Australia, the amount of sun receive is plenty. At our winter solstice we have 10 .5 hours o sunlight and are at a latitude of 26 deg.


"The current 3.5kW array charging a 48V battery bank would, at theoretical maximum provide 3500/48 = 72A of charging current. This is already over-rated for the 60A charge controller. That the controller hasn't failed is likely because the array doesn't reach full output for any appreciable period of time."

Our solar array is in two strings of 6 x 260 watt panels split into 4 lots 3 panels connected in series connected in parallel. I think this is how the original installer got around using the 60A Charge Controller.


"It's not mentioned which Inverter model is being used. Several are capable of being "stacked" in various configurations to provide higher output."

The Inverter we currently have is an Outback Power VFXR3048E inverter charger which is capable of stacking. Although now after reading and understanding the information so far I shouldn't need to stack as we aren't increasing the load, only the input and storage (mainly storage) that we currently have isn't sufficient.


"With addition of the 2nd battery and charging source, it would actually be best to stand up an entire separate inverter system."

I like the idea with adding the new array, the new string of batteries and the FM80 solar charge controller to connect in parallel with the existing.
I have been toying with the idea also though of keeping it its own separate system with another inverter.

My questions here about this would be
1. How to connect the two inverters power feeds to the main circuit board with out causing a problem with the sine waves clashing from the alternating current?
2. Would stacking work as I mentioned above using one as a master?
2a.Does this mean that only one battery bank is feeding the system at one time and the other lies dormant until it runs low and the second bank kicks in, or is there another way to set up the two inverters to draw from both battery banks?


Thanks again for your help it is starting to all come into place for me!

Simon

raysun
Forum Emperor
Posts: 2234
Joined: Tue Jul 26, 2016 5:57 am
My RE system: Flexpower One: FX3048T, (2) FM80, MATE3s, FlexNetDC
Outback 200NC batteries (8 @ 48v)
Outback IBR3 battery enclosure
Suniva 330 watt panels (12 - 6 strings of 2 in series)
Hyundai 355 watt panels (6 - 3 strings of 2 in series)
Honda EU7000is gas fuel generator

Re: Adding more batteries and panels

Post by raysun » Sun May 17, 2020 7:33 pm

simonjon wrote:
Sun May 17, 2020 6:57 pm
Thanks pss and raysun,

Your information is truly helpful.

"As for adding an array, about 1000 amps of batteries will require about 10,000 watts of panels in a good sunny geographic location. Compare your solar hours at your location to say San Diego county and adjust from there."

I am based in Queensland Australia, the amount of sun receive is plenty. At our winter solstice we have 10 .5 hours o sunlight and are at a latitude of 26 deg.


"The current 3.5kW array charging a 48V battery bank would, at theoretical maximum provide 3500/48 = 72A of charging current. This is already over-rated for the 60A charge controller. That the controller hasn't failed is likely because the array doesn't reach full output for any appreciable period of time."

Our solar array is in two strings of 6 x 260 watt panels split into 4 lots 3 panels connected in series connected in parallel. I think this is how the original installer got around using the 60A Charge Controller.


"It's not mentioned which Inverter model is being used. Several are capable of being "stacked" in various configurations to provide higher output."

The Inverter we currently have is an Outback Power VFXR3048E inverter charger which is capable of stacking. Although now after reading and understanding the information so far I shouldn't need to stack as we aren't increasing the load, only the input and storage (mainly storage) that we currently have isn't sufficient.


"With addition of the 2nd battery and charging source, it would actually be best to stand up an entire separate inverter system."

I like the idea with adding the new array, the new string of batteries and the FM80 solar charge controller to connect in parallel with the existing.
I have been toying with the idea also though of keeping it its own separate system with another inverter.

My questions here about this would be
1. How to connect the two inverters power feeds to the main circuit board with out causing a problem with the sine waves clashing from the alternating current?
2. Would stacking work as I mentioned above using one as a master?
2a.Does this mean that only one battery bank is feeding the system at one time and the other lies dormant until it runs low and the second bank kicks in, or is there another way to set up the two inverters to draw from both battery banks?


Thanks again for your help it is starting to all come into place for me!

Simon

"I am based in Queensland Australia, the amount of sun receive is plenty. At our winter solstice we have 10 .5 hours o sunlight and are at a latitude of 26 deg"

It's good to live in a location with lots of sunshine throughout the year. For PV solar panel production, the important metric is how many hours per day the panels are driven to the equivalent of full production. (To keep the math simple) for instance, if a 100W panel is driven to 50% output for 10 hours, it would be 5 solar hours per day. There are lots of online survey data in Oz that will determine that figure for your area.

"Our solar array is in two strings of 6 x 260 watt panels split into 4 lots 3 panels connected in series connected in parallel. I think this is how the original installer got around using the 60A Charge Controller."
12 - 260W panels into a 48V battery is roughly 60A+ max charging current which will probably be derated 20 -:30% due to heat in your locale.

My questions here about this would be
1. How to connect the two inverters power feeds to the main circuit board with out causing a problem with the sine waves clashing from the alternating current?

Actually, the two systems couldn't be combined into the same load panel safely. It would require splitting the loads into sub panels, each powered by an inverter. Sort of a clumsy arrangement but the two battery installation argues for it.

2. Would stacking work as I mentioned above using one as a master?

Somebody from Outback would need to weigh in on this. Their documents all specify a single battery source for stacking. My semi-informed opinion is this would not be supported with separate battery feeds.

2a.Does this mean that only one battery bank is feeding the system at one time and the other lies dormant until it runs low and the second bank kicks in, or is there another way to set up the two inverters to draw from both battery banks?
If wanting to used stacked inverters, the batteries would need to be switched in sequentially.

This will confuse the battery monitor and logging however. It will also make charging the batteries from the Inverter chargers a real fiddly hassle.

In the long run, it's a bit redundant needing another entire setup: inverter/mate/fndc/load panel, but the one battery - one inverter configuration is going to work most consistently and reliably.

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