18650 DIY powerwall 48v

[OffGridInTheCity]

Slight clarification. The OP asked about a panel config rated for 21.7a - e.g. 2p. But the charge controller unit has a 18a max input. I'm not saying the panels would produce more than 21.7a but that they could produce up to 21.7a if requested by the MPPT algorithm. Even 19a is 87% of 21.7a and is higher than the18a max the unit gives.

I'm guessing that the built-in MPPT algorithm will try to maximize power but is not so smart as to be 'aware' of the unit's physical limits. Thus, I'm speculating that I personally wouldn't parallel my strings knowing the amps could exceed the max input amps explicitly given for a unit.

 

[Wolf]

The way I look at this is, you can buy a car that has an engine that redlines at 7000 RPM and if you constantly run this engine at 7500 RPM with some spurts to 8000 RPM you are asking for trouble. That engine will probably not run very long and you will have to replace it.
That engine, however, will run for a long time at 3500 RPM with an occasional spurt to 7000 RPM.
The manufacturer, of whatever equipment they make, have set limits to what it is capable of for a reason. They don't want their equipment to be destroyed potentially causing you harm or bodily injury.

As far as Solar Charge controllers if they say max input is 18A then that's it. They may handle 21.5A but for how long?
and at 450V those mosfets can turn into fuses real quick.
I still suggest 3s or maybe 6s and however many controllers you need. The other issue is if you have such a long series string you are left with the christmas tree light dilemma if one panel fails you loose the whole string.
Additionally there is the shading. Half a panel in a long string being shaded can really screw with your output. I know there are bypass diodes and all that to help eliminate some of that but it still has an affect.

I personally would not be fond of such high DC voltages, I'd rather have a lower DC voltage with more Amps. It is essentially the same as Watts are Watts no matter how you slice it.
I just know that the higher the voltage the easier it is to jump a gap, and once DC jumps its hard to stop it. Also the breakers that are required for safety shutoffs are certainly more expensive.
I use ABB S202 breakers which are some of the best in the world. The ABB Max rating for that MCB are 125V DC and 440V AC.
So you see this breaker can safely cut the AC voltage up to 440V with its internal arc chamber however only 125V for DC.
I would leave high voltage to the Solar farm professionals and keep this a DIY project where no one could get hurt.
Just my opinion.


Wolf

 

[cak]

I'm guessing that the built-in MPPT algorithm will try to maximize power but is not so smart as to be 'aware' of the unit's physical limits

In my experience the opposite of this is true. Any decent quality MPPT should know it's max current and adjust the MPPT curve to try and not exceed it's max. In my case with Victron it knows it's max and I can manually adjust it(I haven't tested if I can override it's design limits) which is helpful because I might have other parts of the system like the solar input breaker that have a limit lower than the MPPT. I don't hear people doing this in systems with batteries but in grid coupled systems it is actually very common to "overprovision" the solar capacity so that you get to max out your inverter(which uses an MPPT internally before doing the DC-AC conversion) more of the time in less than ideal solar conditions. For example since Net Metering rules in the USA limit such systems to 40kw AC if folks really want to maximize production they might put in 50kw DC of panel capacity but for legal and technical reasons the inverter/MPPT must still not exceed the 40kw AC limit so in full sun not all of the 50kw DC is used.

 

[kje]

With proper vetting of the cells you will eliminate wasted time testing cells that are no good and the additional bonus is you will eliminate virtually all heaters.

Does it mean if I measure IR and discard all cells over 70mOhm I will get rid of any heaters?

I finally got my RC3563 with holder.

I'm thinking a lot on what inverter I should go for. I strongly consider MPP MAX 11kw because of price. Only concern is idle draw.

I want to place my 18650 powerwall outside and not inside my house for safety, so I'm planning to build a little battery house. It's gonna take some time but hey...

It will be some distance between the battery house and the house fusebox for some reason. It's best to have the long cable on the AC side, right? So I assume it's best to have the inverter in the battery house and the long cable from inverter to the house fusebox?

 

[OffGridInTheCity]

Does it mean if I measure IR and discard all cells over 70mOhm I will get rid of any heaters?

Higher IR doesn't mean they are heaters. I would check for heaters independently of IR. I check by touching them as they near full charge during the test process. If they are too hot to hold a finger tip on them - then I'd discard. If they're only warm, then I keep them heater wise.

I finally got my RC3563 with holder.

I'm thinking a lot on what inverter I should go for. I strongly consider MPP MAX 11kw because of price. Only concern is idle draw.

I've had a 12,000w AIMS die and AIMS support has been stringing me along for replacement parts even though this is a purchase situation (not a warranty). So I'm thinking of what to do next myself as I need at least 8000w 240v/120v split-phase.

Hovering over SUNGOLDPOWER - https://www.amazon.com/UL1741-Inver...GOLDPOWER/dp/B0B21C2F9L/ref=asc_df_B0B21C2F9L and DOAMXAOMI - https://www.amazon.com/dp/B0B56L6QL1/ref=sspa_dk_detail_5 links thinking why pay a premium when support leaves you hanging anyway. I'll be interested to see what you choose.

I like MPP and have a 3048LV in my trailer. Unfortunately (for me) the MPP Max 11K is 240v single or 3-phase only. I'm US so I need 240v/120v split-phase.

Will single phase 240v or 3-phase 240v work for you're situation?

It will be some distance between the battery house and the house fusebox for some reason. It's best to have the long cable on the AC side, right? So I assume it's best to have the inverter in the battery house and the long cable from inverter to the house fusebox?

This is my situation and that's what I do. My battery/inverter area is 150ft from my main panel - so I connect the inverter output to a distribution panel right near it, then run 240v/120v to the main panel ATS/MTS. This let's me use regular US 6awg wiring and I don't need conduit etc. DC wiring needs conduit in my jurisdiction.

 

[Wolf]

Does it mean if I measure IR and discard all cells over 70mOhm I will get rid of any heaters?

Virtually all. I have to leave a little doubt. However by sticking to strict IR measurements on the cells I have processed I have not experienced any heaters.
Nevertheless if you have an INR chemistry battery with a normal IR of 15mΩ then 70mΩ would be to high.
So IR will fluctuate from chemistry to manufacturers to part number.
Many good ICR cells are generally in the 45mΩ to 55mΩ range and you will not get a heater.
However there are some LG S3 series cells (2200mAh) that are perfectly good with an IR of 70+mΩ although at 80mΩ their capacity falls of rapidly.
That being said the IR and capacity between cells should be kept at a minimum. the closer the IR and the capacity of the cells in the "whole" battery
the better it will perform.
Wolf

 

[kje]

Higher IR doesn't mean they are heaters. I would check for heaters independently of IR. I check by touching them as they near full charge during the test process. If they are too hot to hold a finger tip on them - then I'd discard. If they're only warm, then I keep them heater wise.

Sounds like a practical and "hands on" way to decide.

I've had a 12,000w AIMS die and AIMS support has been stringing me along for replacement parts even though this is a purchase situation (not a warranty). So I'm thinking of what to do next myself as I need at least 8000w 240v/120v split-phase.

Hovering over SUNGOLDPOWER - https://www.amazon.com/UL1741-Inver...GOLDPOWER/dp/B0B21C2F9L/ref=asc_df_B0B21C2F9L and DOAMXAOMI - https://www.amazon.com/dp/B0B56L6QL1/ref=sspa_dk_detail_5 links thinking why pay a premium when support leaves you hanging anyway. I'll be interested to see what you choose.

I like MPP and have a 3048LV in my trailer. Unfortunately (for me) the MPP Max 11K is 240v single or 3-phase only. I'm US so I need 240v/120v split-phase.

So MPP doesn't have that?

Will single phase 240v or 3-phase 240v work for you're situation?

I'm not sure of 3-phase or single phase, but single phase sounds the simplest for me at least. Any suggestions or way to determine are welcome.

 

[kje]

Virtually all. I have to leave a little doubt. However by sticking to strict IR measurements on the cells I have processed I have not experienced any heaters.

That's great! Did you use RC3563 with holder as well?

Nevertheless if you have an INR chemistry battery with a normal IR of 15mΩ then 70mΩ would be to high.
So IR will fluctuate from chemistry to manufacturers to part number.

How to distinguish between INR and ICR cells?

Many good ICR cells are generally in the 45mΩ to 55mΩ range and you will not get a heater.
However there are some LG S3 series cells (2200mAh) that are perfectly good with an IR of 70+mΩ although at 80mΩ their capacity falls of rapidly.
That being said the IR and capacity between cells should be kept at a minimum. the closer the IR and the capacity of the cells in the "whole" battery
the better it will perform.
Wolf

Nice, I'll try to remember that when I build the packs.

 

[OffGridInTheCity]

So MPP doesn't have that?
I'm not sure of 3-phase or single phase, but single phase sounds the simplest for me at least. Any suggestions or way to determine are welcome.

MPP has all types. There is 120v only. There is 240v only (The MAX 11K above). There is 240v/120v in split-phase (US) or 3-phase (Europe)

Here's a good pictorial the 3 base options - https://www.mppsolar.com/v3/splitphase-lv6548/

Some do 120v only (lights, refrigerator, microwave, TV, computers). Some do 240v only (mostly non US) - e.g. MPP Max 11K above looks like that.

In my case, I'm US and power both120v circuits and 240v circuits such as the Dryer, Cooktop, Whole House Heat-Pump. So I need the US 240v/120v split-phase option.

Typically, different models of inverters specialize in one of the 3 options so you have to decide what you need and then get a model that does what you need. Some can start with 120v and then you can expand to get 240v. MPP has models like this and EG4 does as well.

 

[kje]

MPP has all types. There is 120v only. There is 240v only (The MAX 11K above). There is 240v/120v in split-phase (US) or 3-phase (Europe)

Here's a good pictorial the 3 options - https://www.mppsolar.com/v3/splitphase-lv6548/

Could you use SPLIT PHASE LV6548 and make 2 in parallel for your usage?

We have 3-phase 230v in our house. Do I have to choose 3-phase inverter? If not, what determines what to choose?

 

[OffGridInTheCity]

Could you use SPLIT PHASE LV6548 and make 2 in parallel for your usage?

I could but MPP and EG4 (and others) are supposed to be mounted vertically. This isn't my 1st choice as I don't have a lot of vertical wall space. and these units are heavy.

I need to replace AIMS #1 below - it's mounted horizontally because it weighs 175lbs! - and would like to just slip in a replacement.

We have 3-phase 230v in our house. Do I have to choose 3-phase inverter? If not, what determines what to choose?

What's you're country? I'm pretty up on US stuff but not 3-phase households. It's possible you could do OK with single phase 240v such as MPP MAX 11K - similar to 120v situation in US. But I'll defer to others here for non-US advice!.

 

[kje]

I could but MPP and EG4 (and others) are supposed to be mounted vertically. This isn't my 1st choice as I don't have a lot of vertical wall space. and these units are heavy.

Maybe if you ensure good air flow you can mount the MPP horizontally?

I need to replace AIMS #1 below - it's mounted horizontally because it weighs 175lbs! - and would like to just slip in a replacement.

Yes you probably have to rebuild the mounting if it's possible to have the MPP horizontally.

View attachment 29016

What's you're country? I'm pretty up on US stuff but not 3-phase households. It's possible you could do OK with single phase 240v such as MPP MAX 11K - similar to 120v situation in US. But I'll defer to others here for non-US advice!.

I live in Norway, the voltage here is 230v and 50hz. I don't think everyone have 3-phase but we have.

Is it possible for me to connect the MPP MAX 11KW between the mains grid in and the house fusebox? So when there isn’t enough DC power available, from either the PV or Battery, the grid will go to the loads? Will there be some current limit?

 

[OffGridInTheCity]

Is it possible for me to connect the MPP MAX 11KW between the mains grid in and the house fusebox? So when there isn’t enough DC power available, from either the PV or Battery, the grid will go to the loads? Will there be some current limit?

For 3 phase using the 11K you'll need at least 3 x units - https://www.mppsolar.com/v3/pip-max/ Notice the 3-phase has 3 separate 240v lines p1, p2, and p3 and that's why you need 3 units to supply each 240v phase. The Single Phase only needs 1 unit.

In general, for many off-grid inverters, you can feed in grid power (grid assist) and route the power coming out to your home circuits. However, the inverter AC must be separated from the grid AC as you feed you're home circuits. Since you don't want to hard-wire you're home circuits to an inverter in case the inverter fails, you need a way to switch back/forth between Inverter AC power and Grid AC power. This can be done with an MTS or ATS or mechanical interlocks of sub-panels.

Grid-Tie and Hybrid inverters specialize in allowing you to mix inverter AC and the Grid AC in various ways.

If you look closely at MPP Solar's web site - https://www.mppsolar.com/v3/hv6048wp/ You'll see they break out "Off Grid Solar Inverters" from "Hybrid Solar Inverters". This is because off-grid is very different than Hybrid.

You need someone experienced with 3-phase home wiring to give you better guidance than I can - so I'll stop here. Sorry I can't take it further.

 

[kje]

For 3 phase using the 11K you'll need at least 3 x units - https://www.mppsolar.com/v3/pip-max/ Notice the 3-phase has 3 separate 240v lines p1, p2, and p3 and that's why you need 3 units to supply each 240v phase. The Single Phase only needs 1 unit.

Yes, I think the simplest for me is going 1-phase if it's possible.

In general, you can feed in grid power to the MPP and consume the power coming out. However, the power coming out must be connected to you're home wiring separate from the main panel via an MTS or ATS or sub-panel with interlock or xxx. You can't mix MPP output AC with grid AC on the circuit side. This would require an Hybrid or Grid-Tie system - which they make, but it's different than off-grid with grid-assist.

I trust you on that but I'm just curious. Why doesn't it work to cut the grid cable before the main panel so it's no power in the main panel. Then connect the grid cable to the inverter and from the inverter to the main panel?

We need someone experienced with 3-phase home wiring to give you the proper guidance - so I'll stop here. Sorry I can't take it further.

I don't think I'm going 3-phase unless I should or have to.

 

[grundholm]

Do you have appliances that depend on 3-phase? Washer/dryer - any motors etc.?

 

[OffGridInTheCity]

I trust you on that but I'm just curious. Why doesn't it work to cut the grid cable before the main panel so it's no power in the main panel. Then connect the grid cable to the inverter and from the inverter to the main panel?

Yes, one can do this. However, you'd need enough inverter power for the entire house which can be expensive.
You could do 2 sets of circuits - some grid only and some inverter only.

However, in either case, if the inverter(s) fail or you need to work on them you're house (or part of it) will go dark with grid right there available. So typically, one leaves a way to switch back to grid - even if it's temporary - since it's there / available. In my jurisdiction there might be some occupancy permit issues and/or fire insurance issues - don't know you're situation. Maybe others have reasons to avoid inverter only when it's not necessary.

Do inverter's fail? Sure - I just had one of my AIMS 12,000w inverters fail for no reason other than being 4yrs old. Would I depend on inverters only if grid was available - not unless I had too, but that's just me.

I would not be critical if you decided to go inverter only. That's the beauty of DIY - it's about sharing info and learning about different paths that people take in their journey.

 

[Wolf]

That's great! Did you use RC3563 with holder as well?

Yes I use the RC3563 with cell holder and have a python script and an VB macro to push the measurements into Excel.

How to distinguish between INR and ICR cells?

Research the cells part number. Some of them are obvious such as Samsung ICR18650-28A or INR18650-25R.
others are not so easy. But generally all low IR cells with a max of 40mΩ are going to be INR. You will also have some hybrids Panasonic CGR and NCR.
The LG brands such as the LGDC118650 which is a C1 series has a secondary number sometimes written below the part number ICR18650C1
and the LGEBM261865 M26 series INR18650M26.
So yes I have done the research and have a post on some valuable info.

The Passion of the Li-Ion 18650

As we all are aware there are hundreds of millions if not billions of 18650 cells in all kinds of devices and there will continue to be a demand and supply of this form factor. Too many designs for this form factor would have to be changed, molds redesigned, BMS redeveloped, loads recalculated...

secondlifestorage.com

Wolf

 

[kje]

Yes, one can do this. However, you'd need enough inverter power for the entire house which can be expensive.
You could do 2 sets of circuits - some grid only and some inverter only.

Yes that would be too expensive.

However, in either case, if the inverter(s) fail or you need to work on them you're house (or part of it) will go dark with grid right there available. So typically, one leaves a way to switch back to grid - even if it's temporary - since it's there / available.

This can be done with an MTS or ATS or mechanical interlocks? I have to read about this since I don't know much about it. Exciting to learn.

Do inverter's fail? Sure - I just had one of my AIMS 12,000w inverters fail for no reason other than being 4yrs old. Would I depend on inverters only if grid was available - not unless I had too, but that's just me.

Are you gonna replace it with a new identical AIMS inverter?

I would not be critical if you decided to go inverter only. That's the beauty of DIY - it's about sharing info and learning about different paths that people take in their journey.

Yes, sharing and learning. I have to say you and the others at this forum are really good at that!

I could off course go for hybrid inverter like the new MPP MPI 15kw but the price is about 5000 usd inkl shipping and vat. The MPP MAX 11KW I can get at about 1800 usd inkl shipping and vat.

 

[kje]

Do you have appliances that depend on 3-phase? Washer/dryer - any motors etc.?

We have washer and dryer and heat pump, but I don't know if they depend on 3-phase?

 

[100kwh-hunter]

We have washer and dryer and heat pump, but I don't know if they depend on 3-phase?

Check the wires. more than 3 is usual 3 phase.
Zero phase and ground (3)
or
3 phases ground and zero.

Those 3 phase systems looks nice, but do you need them?
I have some machinery in the shed that uses 3 phase.
In the near future there will be 2 ev's, for good charging i would like also 3 phase.
But one phase at 10kw can handle the job also.

I am working towards 3 inverters each 10kw
One for the house
One for the cars
ANd one for the shed, but that one will receiver a phase sifter/splitter
Or this one will be just a 3 phase inverter.

You can also check your fuse box coming from the grid.
Usual you will have 3 fuses bound together.
Or in case of a prelex (2 phases mostly for cooking) you will see 2 fuses together.

Can you post pictures of your fuse/breaker box and or plugs comming from your dryer washer and heatpump?