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hello........ and system and component vetting for solar/lithium/all-in-one backup

ZorbatheGeek

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Hi....I'm new to the forum, about to pull the trigger on an install for lithium/all-in-one/pv backup.

I'd really appreciate any feedback (warnings) for the system design and components:
The system is to provide residential backup for poor grid supply (frequent random outages and voltage drops) in Africa, near equator.
Daily load = 7.9kWhr (could be cut to 5.5kWhr essential)
Absolute peak load 5.3 kW (very unlikely)
Proposed system:
2 x WECO LiFeO 4.95kWhr
1x Growatt SPF 5000TL HVM-WPV
10 x Suntech STP-330

5kVa backup genset on changeover if required. 220V grid supply when operational - power outages are unpredictable, usually do not last more than 6 hrs, but occasionally [once p.m.] can be 24 hrs or more.

The installer/supplier is offering a 10 year warranty on the WECO batteries, but only 2 years on the Growatt all-in-one..............should I be suspicious? Is this unit prone to problems?
Any other quality/performance issues from members experience?
Is the system sizing in the ball park?

Thanks for this forum!! Awesome stuff

*forgot to mention although it is a grid-tie there is no feed-in to the grid
 
Last edited:
:whistle:?
Hi....I'm new to the forum, about to pull the trigger on an install for lithium/all-in-one/pv backup.

I'd really appreciate any feedback (warnings) for the system design and components:
The system is to provide residential backup for poor grid supply (frequent random outages and voltage drops) in Africa, near equator.
Daily load = 7.9kWhr (could be cut to 5.5kWhr essential)
Absolute peak load 5.3 kW (very unlikely)
Proposed system:
2 x WECO LiFeO 4.95kWhr
1x Growatt SPF 5000TL HVM-WPV
10 x Suntech STP-330

5kVa backup genset on changeover if required. 220V grid supply when operational - power outages are unpredictable, usually do not last more than 6 hrs, but occasionally [once p.m.] can be 24 hrs or more.

The installer/supplier is offering a 10 year warranty on the WECO batteries, but only 2 years on the Growatt all-in-one..............should I be suspicious? Is this unit prone to problems?
Any other quality/performance issues from members experience?
Is the system sizing in the ball park?

Thanks for this forum!! Awesome stuff

*forgot to mention although it is a grid-tie there is no feed-in to the grid
 
Hi smoothJoey .......... not sure? I have a load spreadsheet and spec sheet for the WECO batteries (attached)
https://wecobatteries.com/
The panels will be mounted flat (and will be shade free for at least 6 hrs 10:00-16:00)
The grid outages are unpredictable........
I had a look at the "Wattage Worksheet" from your link, and realised I have underestimated the Peak surge wattage - more likely to be about 8.8kW surge.
Is the Growatt solid?
What else do I need to look at?
 

Attachments

  • WECO-4k4-wall-2019.pdf
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  • ALL LOADS.pdf
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  • ESSENTIAL LOADS.pdf
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By system diagram I mean a picture that shows all the components and how they will be connected together.
You won't have any dc loads, confirm?
 
By system diagram I mean a picture that shows all the components and how they will be connected together.
You won't have any dc loads, confirm?
Confirm no DC loads -
I have no system diagram :rolleyes:............ ? See attached - (it's nasty)
 

Attachments

  • System diagram.pdf
    288.8 KB · Views: 31
I thought that a Midnite combiner was for the pv side.
I would expect to see see good solid busbars instead.
 
Thanks smoothJoey...........replies below:

Its not grid-tie.
Its just an all in one until with and inverter, charger and automatic transfer switch.
Ok noted - what does grid-tie entail ?

I thought that a Midnite combiner was for the pv side.
I would expect to see see good solid busbars instead.
You are most likely correct - it's actually just a Midnite enclosure with DC breaker. The Lorentz does the PV side afik.
Re. busbars: still necessary for high DC voltage? As I understand it, the PV voltage must be as high as possible as the Growatt inverts it directly?
If using busbars, where does the disconnect go?
 
Ok noted - what does grid-tie entail ?

Grid-tie means your system feeds power back to the grid.
Grid-tie systems usually don't have pv panels as they use the grid for storage.

Re. busbars: still necessary for high DC voltage?
Its about amperage.
Your inverter is rated for 5000 watts.
5000 ac watts * 1.15 inverter efficiency / 48 volts low cutoff = 119.791666667 dc amps
I would guess that each of those batteries has a breaker rated to ~150 amps, confirm?
That power is aggregated before it goes to the rest of the system.
I would expect to see busbars rated to ~60 volts and ~300 amps here.

As I understand it, the PV voltage must be as high as possible as the Growatt inverts it directly?
If using busbars, where does the disconnect go?

The disconnect should go after the aggregation point to isolate the batteries from the rest of the system.
As I mentioned above I would that that each battery has its own breaker as well.
That means you can take either one offline and still have your system operate at reduced capacity.
What is the guage and temperature rating for the wires that come directly off the batteries?
Also they should be pure stranded copper, confirm?
 
Grid-tie means your system feeds power back to the grid.
Grid-tie systems usually don't have pv panels as they use the grid for storage.
Thanks for that - I have never really understood it

Its about amperage.
Your inverter is rated for 5000 watts.
5000 ac watts * 1.15 inverter efficiency / 48 volts low cutoff = 119.791666667 dc amps

OK I am with you on this now - basically 120amps possible through the battery-inverter cable. I was thinking of PV side of things.?
I would guess that each of those batteries has a breaker rated to ~150 amps, confirm?
It seems not - hence I was quoted for (one) 175A DC breaker. So 2 of these needed?

That power is aggregated before it goes to the rest of the system.
I would expect to see busbars rated to ~60 volts and ~300 amps here.

Got it - these are where the batteries are paralleled?

The disconnect should go after the aggregation point to isolate the batteries from the rest of the system.
As I mentioned above I would that that each battery has its own breaker as well.
That means you can take either one offline and still have your system operate at reduced capacity.

Ok........... so do I need both (disconnects and breakers) or is it enough to have DC breakers on each battery prior to busbars?
What is the guage and temperature rating for the wires that come directly off the batteries?
Also they should be pure stranded copper, confirm?

25mm wire from batteries to inverter - I will confirm wire quality. This is Africa - if its pure copper welding cable will that suffice?
How does one select wire gauge?
 
It seems not - hence I was quoted for (one) 175A DC breaker. So 2 of these needed?

A quality 150 amp breaker directly off the positive terminal of each battery is required.

Got it - these are where the batteries are paralleled?

Yes,

Ok........... so do I need both (disconnects and breakers) or is it enough to have DC breakers on each battery prior to busbars?

The breaker is the disconnect.

25mm wire from batteries to inverter - I will confirm wire quality. This is Africa - if its pure copper welding cable will that suffice?
How does one select wire gauge?

25 mm wire with a 150 amp breaker is good for the battery wires.
25 mm wire with a 150 amp fuse is good for the main wire.
welding cable is fine as long as its rated for 105c, if its not I will have to do some more math.
This is a quality breaker https://www.bluesea.com/products/7148/187-Series_Circuit_Breaker_-_Surface_Mount_150A
This is a quality busba, one postition must be unfused and the other 3 can be used fused or unfused https://www.bluesea.com/products/5196/MRBF_Surface_Mount_Fuse_Block_-_Common_Source
 
Have I sized the system loads and PV/storage correctly?
I will leave the pv side to someone more pv savvy.
If you don't mind my asking which country are you in?
I ask so that we can understand which flavour of mains power that you need.
I wonder if @pierre can help here, at the very least to make sure I didn't screw up the metric conversions :)
 
Thanks for the responses
This is all cool ..........learning like a baby.
I live in SA but the system is in Kenya (for my parents).

220Va.c. comes in different flavours??????? This is gonna be a rabbit hole I never suspected :oops::LOL:
 
Thanks for the responses
This is all cool ..........learning like a baby.
I live in SA but the system is in Kenya (for my parents).

220Va.c. comes in different flavours??????? This is gonna be a rabbit hole I never suspected :oops::LOL:

There is 220VAC@50hz, 230VAC@50hz, 240VAC@50hz.
Most things just work with between 220-240VAC as long as its 50hz.
Things like neutral/ground bonding and the requirement for residual current detection may vary from country to country and/or region to region.
 
I will leave the pv side to someone more pv savvy.
If you don't mind my asking which country are you in?
I ask so that we can understand which flavour of mains power that you need.
I wonder if @pierre can help here, at the very least to make sure I didn't screw up the metric conversions :)
:);)
 
A quality 150 amp breaker directly off the positive terminal of each battery is required.



Yes,



The breaker is the disconnect.



25 mm wire with a 150 amp breaker is good for the battery wires.
25 mm wire with a 150 amp fuse is good for the main wire.
welding cable is fine as long as its rated for 105c, if its not I will have to do some more math.
This is a quality breaker https://www.bluesea.com/products/7148/187-Series_Circuit_Breaker_-_Surface_Mount_150A
This is a quality busba, one postition must be unfused and the other 3 can be used fused or unfused https://www.bluesea.com/products/5196/MRBF_Surface_Mount_Fuse_Block_-_Common_Source


Doesn't the BMS limit the DC ? (max for the WECO 110A, nominal is -70A/60A) ? What does this actually mean?

Are the DC breakers then a backup failsafe?
 
Doesn't the BMS limit the DC ? (max for the WECO 110A, nominal is -70A/60A) ? What does this actually mean?

Are the DC breakers then a backup failsafe?
Actually the bms is the backup for the breaker.
I don't trust fet based bmss as a sole overcurrent protection device.
 
@smoothJoey " rated for 105c" - is this temperature rating or current (C rating of battery)?

Also - can you explain the difference:
"25 mm wire with a 150 amp breaker is good for the battery wires.
25 mm wire with a 150 amp fuse is good for the main wire "
 
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