EVE 280K battery and used 255W solar panels.

[Dacian Todea (electrodacus)]

I had the plan to install 36x 255W PV array to supply a 14kWh LiFePO4 made as 8s2p with EVE 280K cells and a 34kWh thermal storage mde out of a 450L stainless steel water barrel.

Unfortunately winter came a bit earlier and stronger than expected (there are -18C right now).

First the PV array installed at a back of the house is just 12x 255W panels (3x 255W and 9x 260W actually) the 255W and 260W look exactly the same but in total I have more of the 255W available.

Below a photo with the 12 panels we were able to install just before the snowstorm

 

Next day it looked like this

The new array in the background.

Now inside the house in a corner of the entry hole I build a "table" for the 450L barrel on top for thermal storage and the LiFePO4 battery under and place for inverter and connections.

Size of this is about 90 x 90 cm and 80cm high (about 3ftx3ft and a bit less than 3ft tall).

The battery construction

 

The inverter 3500W with 3000VA isolation transformer under and prototype DSSR50's for charging.

Closer look at the DSSR50

And just now I took two photos of the SBMS0.

It is a bit cloudy not quite clear and up to now today I saw just 105A max but I expect it will be more in a proper cold and sunny day.

It is a bit close to the limit of the 125A breaker but will need to test and see the DSSR50's are fine with 60A each peak's

When I get a few proper sunny days I may do a battery capacity as of now I did not even made a full charge.

It will have been much easier with all 36 panels in dual PV array setup.

[Dave Festing]

WOW, a serious setup!

I raised the roof panels and added another two panels (the highest ones), pointed North and at 70 degrees to increase PV power during June/July.

Only had to run the microhydro for about 20 hours this last winter to keep the 5KWH battery above 50%. 

 

The dual PV setup is a great feature.  I had to add my own hi-side PFET switches and another ESP32 to control the 2 new panels.

[Habana7]

That looks very good Dacian, Solid construction of your panels, also a nice construction with those pressure springs on your cels.

I've been using your SBMS0 for a year now and I'm very satisfied with it, only the WiFi was a bit weak due to the location, but I solved that with a TP-Link RE450 repeater that works great.

Winter doesn't look like that with us in the Netherlands..brrr 

Looking good Dave, nice place you have there..    

Op donderdag 10 november 2022 om 21:35:57 UTC+1 schreef Dave Festing:

[Dacian Todea (electrodacus)]

Dave,

Yes the dual PV setup was a good way to bring a future that existed on the DMPPT450 by just adding software to SBMS0.

PV panels are much cheaper than batteries so dual PV array makes economic sense if there is space for larger array.

It is even more useful when excess from the dual PV array can be used for heating.

Yesterday I was able to get the battery fully charged so I did a discharge test over night and will do another post later today or tomorrow posting the results of capacity test.

Jan,

Yes I used the same type of construction with the compression springs on the A123 Battery (main house battery) and it works great.

Those heatsinks where just better value than solid thick aluminium plates when I purchased them in summer.

It is below average at this time of year right now (morning is -24C) but there are huge variations in temperature and solar from year to year.

[Sergio Veltri]

Great work Dacian! I would love to see more details on the tank installation when you get a chance.

Thanks!

[Dacian Todea (electrodacus)]

Sergio,

Water tank is not installed at the moment and will likely be done only for next winter season as since I only installed 12 out of 36 panels it will not have any usefulness.

This new array is basically mostly for November and December when the main array is not enough after that the daylight time increases and while it is colder is also less cloudy so this secondary system is not required.

The plan is to drill holes in to the top cap to install heating elements and add a small servo motor connected to a small propeller to mix the water so that there is less temperature stratification (especially since I heat from the top)
There will need to also be an water level sensor so that if to much evaporates it will need to be added so heating elements are immersed.

[Sergio Veltri]

Sounds good. I am working on a similar setup but I also wanted to add an external heat exchanger so I can use the tank for two services (Domestic Hot Water and Floor Heating).

Initially I was thinking of inserting a corrugated stainless steel pipe inside the tank but I am concerned about maintenance if something breaks so thats why the external heat exchanger idea. Still in draft and calculation mode.

Take care

[Oberon Robinson]

Dacian,

I recommend a toilet tank filler valve, it's a cheap and proven technology to maintain water level in your tank.

You could also use an RC underwater thruster for water circulation, though I'm less sure about their long-term reliability.

Oberon

[Dacian Todea (electrodacus)]

Oberon,

The barrel is not connected to a water source.  The amount of evaporation will be small probably at most 1 liter of water every few months so it will be filed manually.

I will have an electric water level switch normal close that will open the remote to the heating element stopping the heating if water level is under the safe operation level.

The servo motor (very small 22W one) will drive a long axel propeller. So motor will be outside at room temperature and will connect to the long stainless steel propeller axle exiting through the top same place the heating elements are installed.

[Plamen]

   Hi Dacian, 

Is that a wood frame the PVs are mounted on?

It's been a while since i've build my pack, and think the different springs force was color marked. Also remember that for my Winston 400Ah cells was needed about 1000 kg compression.

 Now seeing the same spring as mine and only 4 of them per cell pack makes me wonder if i've miscalculated it. Probably the surface of yours is half mines but even so i have 16 springs. And not long ago i noticed that the 12 mm tick aluminium plate is slightly bended.

    Is it your  temporary spring load or i've messed up something?

[Dacian Todea (electrodacus)]

Your cells are clearly way larger surface as they are thinner higher capacity and lower energy density.

Quick search says you cells are 277mm * 461mm so 1277 cm^2

The EVE 280K that I have are just 174mm * 204mm so 355cm^2 that makes them 3.6x lower side surface.

16 springs divided by 3.6 is 4.4

The springs I have are brown so yes the strongest available.   

[Plamen]

Thanks, so the springs are fine, just the 12mm. plates are not enough for them.

[Dave Festing]

Plamen,

Where did you get a spec for the compression?  I asked Winston support and was told 30kG for the 220AH units.

Thanks,

Dave

[Dacian Todea (electrodacus)]

Are you sure the plate is bent and not just an optical illusion ?

I do not see any space between cells at the corners.

[Plamen]

Hi Dave, there was a chart of the cycle life vs. compression for Lifepo4 on the forum here, think Dacian posted it. The range was too large, basically better any compression than none. I'll try to find it.

[Plamen]

There is a gap of about 4mm. 

[Plamen]

On Sunday, November 20, 2022 at 11:57:27 PM UTC+1 Dave Festing wrote:

[Dave Festing]

So, about 5-10psi.  Thanks for that

[Plamen]

I took 12,5 psi which gives me 0,879 kg./cm^2. And for the 1277 cm^2 of my cell it's 1122 kg. The 30kg. you mention is nothing if for the whole battery and if per square cm. .......it will crash the cells.

[Dave Festing]

My understanding the 30kg was a "clamping force", ie over the whole face of the 200AH cells.  Looks like I have got "nothing".  I will try to get in contact with them again.

Thank you.  

[Charlie G]

Love your battery setup above. Couple questions. 

Can you tell me where you obtained the terminals and flexible metal cables from? 

Additionally, where did you acquire the aluminum end plates and compression springs?

I am currently using Eves 304Ah cells that require 300 KGF (Per Cell??) for compression when charging at a 1C rate. However, my application involves running 8S2P with a maximum charging current of around 150 amps, which equates to only 0.25C.

For the four cells depicted in the above pictures, what level of tension should be applied?

Best regards.

[Dacian Todea (electrodacus)]

Charlie,

The end plates are heatsinks I got on Amazon 200 x 220 x 18mm as they were about the same cost as thick enough aluminium plates 9mm

The flexible bus bars came with the cells but you can find them separately on Aliexpress here is an example https://www.aliexpress.us/item/1005004773890059.html

Yes 300kg is about right for these cells and that is what is applied by the 4 springs that I installed.

Here are the springs I used https://www.amazon.ca/gp/product/B07Z3D4J6L  and each spring can provide about 75kg of compression force, a total max 300kg for 4 of them.  You should aim for the same 300kg as that is needed no matter what charge rate you use.

Prices are also out of control with very significant increases for all components not just semiconductors even passives that should have nothing to do with the semiconductor shortages. 

[hk]

Hi Dacian,

what did you put between the cells and why? Just something to increase the friction, so everything keeps together nicely just by compression?

[Dacian Todea (electrodacus)]

I put some thin silicone thermal pads for electrical isolation as that is what I already had left over from an old project and you need something as electrical isolation between cells as you can not trust the thin blue insulation that comes on the cells.

[Habana7]

Hi Dacian, I received the three DSSR50  in good order , thanks for that, 

One question on photo of the DSSR50 you connected the fuse on the PV side, but the manual on the Batt side , is there a reason why you changed this

Op zondag 11 juni 2023 om 19:13:21 UTC+2 schreef electr...@gmail.com:

[Dacian Todea (electrodacus)]

The fuse or circuit breaker on battery side is mandatory as it is there to protect the wire between battery and DSSR50.  The circuit breaker on the PV side is there just as a switch as PV panels are constant current sources so they will never be able to trip that breaker and current from battery can not get on that side due to ideal diode inside the DSSR50.

In photo there is a large breaker just after the current shunts protecting the wires going to DSSR50's in case those wires are ever shorted to GND (battery negative).

I used thick 16mm^2 silicone wire to connect battery+ side of the DSSR50 those they can be protected by a single 125A breaker. In the manual I showed an individual 63A max breaker for each DSSR50.

[Habana7]

Yeah overlooked the big breaker in the other photo, so was little confused.

I am curious about the operation of the DSSR50 (x3), two off these replace a Victron 150/35 MPPT, six panels 1680Watt total, three West and three on East.

Op vrijdag 8 september 2023 om 17:01:01 UTC+2 schreef electr...@gmail.com:

[Dacian Todea (electrodacus)]

So you have 6x 280W panels.  Panels will need to be groups of two in parallel but it may also be a group of 3 panels in parallel if the panels max fuse rating is 20A instead of more typical 15A.

If panels have this 20A fuse limit then you could just use a single DSSR50 with the 3 panels on the west connected to PVA and the 3 panels on the east connected to PVB.

I'm guessing the panels where in series when connected to the Victron 150/35 MPPT.

You can still connect a group of 3 panels in parallel even if they are only 15A max fuse rating but then you will need to add a 15A fuse for each panel so much less convenient and more expensive than just using two DSSR50 assuming quality MC4 fuse holders are more than 15CAD each.

Looking at amazon I see MC4 15A fuses for around 18CAD but not sure about the quality 18x 6 = 108CAD so a bit more than an extra DSSR50 but you may have a single pair of 10AWG cables going to the 3 panels and then it may be more continent to use a single DSSR50 and some MC4 fuses.

I'm not a fan of MC4 fuses as I had some installed initially and half of them failed fairly fast due to low quality of those holders.

[Habana7]

I have all the tools and parts such as fuses,breakers,cables in all shapes and sizes, the system with the Victron/SBMS0 has been working perfectly for three years now and is satisfactory,

for me its more about the experience and is mainly a hobby for me, it must function well, it must be properly maintained. / neat appearance and safety above all.

The approach was 3 panels West (20deg) slope on one DSSR50 and one DSSR50 for the East side(20deg), and at a later stage maybe one panel on the greenhouse(60deg South) with the third DSSR50 as a dual PV, for little help in the wintertime. 

Op vrijdag 8 september 2023 om 20:31:10 UTC+2 schreef electr...@gmail.com: