Cross-checking my ideas for my Battery v2 after Battery v1 Nighmare

[silverstone]

I can't guarantee that the tech building they're in stays above 5C, but I still want to charge as much as possible. The batteries themselves are heated.



Regular. I only use treated wood when I absolutely have to (like a terrace/deck or my ground mounts for my panels).

I'm scared of termites eating my box .

I'm just thinking of adding some fibergips on the inside to make it more fire resistant. But then there will be dust everywhere, I'll need to put a polycarbonate plate to make sure dust doesn't fly everywhere, etc.

Especially for the breaker box front compartment that would not be good (some dusts falling into the breaker power terminals when e.g. trying to connect the wire from the battery).

 

[upnorthandpersonal]

termites

No such thing in Denmark

 

[silverstone]

No such thing in Denmark

You seem to know Denmark better than me .

But the fibergips I'm hesitating ...

And tongue+groove you used for some reason or just because you had them around ? It's much more available "normal" wood around here.

 

[upnorthandpersonal]

just because you had them around ?

^ this

 

[Brucey]

Currently they're sitting on a shelf-like thing, but they still have the wooden fixture. I don't think that will change unless I'm going to be serious about building a 1MWh container.

No reason you can't start smaller but designed to scale out to 1MWh, start at one end and expand out as prices drop further?

 

[upnorthandpersonal]

Remember, the original goal was to build the entire system, including the batteries, panels, ground mount, inverter, charge controller, etc. for < 10k Euro. It started here:

This could be interesting

So, instead of just doing the usual and buying some Victron and Batrium equipment and calling it a day, I went shopping on Alibaba and Aliexpress to see if I could build my entire 32x280Ah and 10kW solar panels system for under 10K Euro, keeping in mind the power and charge requirements - so not...

diysolarforum.com

 

[silverstone]

Remember, the original goal was to build the entire system, including the batteries, panels, ground mount, inverter, charge controller, etc. for < 10k Euro. It started here:

This could be interesting

So, instead of just doing the usual and buying some Victron and Batrium equipment and calling it a day, I went shopping on Alibaba and Aliexpress to see if I could build my entire 32x280Ah and 10kW solar panels system for under 10K Euro, keeping in mind the power and charge requirements - so not...

diysolarforum.com

And the goal has changed with the new battery ?

 

[upnorthandpersonal]

No reason you can't start smaller but designed to scale out to 1MWh, start at one end and expand out as prices drop further?

Might be just easier to build one dedicated for that size. The space would have to be different anyway (think container) and I can just as well add the inverters and charge controllers there too.

 

[upnorthandpersonal]

And the goal has changed with the new battery ?

For this stage, no, I just want 100kWh (for various reasons, but I also like round numbers)

 

[silverstone]

Might be just easier to build one dedicated for that size. The space would have to be different anyway (think container) and I can just as well add the inverters and charge controllers there too.

Well if you go that route they for sure are easy to stack (the containers). Not sure about maintenance if you have to go up with a forklift or something though ...

 

[upnorthandpersonal]

Well if you go that route they for sure are easy to stack (the containers). Not sure about maintenance if you have to go up with a forklift or something though ...

Hmmm... 2MWh... yeah

 

[silverstone]

For this stage, no, I just want 100kWh (for various reasons, but I also like round numbers)

Well I have space for 8 batteries in my garage (8 x 15 kWh = 120 kWh), up to 10 batteries if I can squeeze the box a bit.

But since capacity drops quite a bit (~ 10%) in the first 500 cycles or so, it's good to have a bit more than needed.

Just saw this LF280k vs LF304

So actually LF304 is almost half the cycles ... That being said if one cycle is considered 0% to 100% and 2.5VDC to 3.65VDC then I don't think I do even 1-2 cycle per week right now ...

vs

 

[upnorthandpersonal]

But since capacity drops quite a bit (~ 10%) in the first 500 cycles or so, it's good to have a bit more than needed.

After 4 years, I don't think I even get close to 500 cycles. And that's with 4 packs. The more you add, the less cycles you tend to have.

Just saw this LF280k vs LF304

So actually LF304 is almost half the cycles ...

Different C rate. Also the graph you posted is from different temperatures: something much more important to manage to extend battery life.

 

[silverstone]

Different C rate. Also the graph you posted is from different temperatures: something much more important to manage to extend battery life.

They both have graphs for 25°C and 45°C (with crossed colors).



Agreed on the cycle numbers ... if you install ~ 100 kWh it basically means, neglecting losses and charging power etc, that you can use PERMANENTLY 4kW of Power all day long. Or you could survive 4 days at 1kW daily average after a sunny day in case there is rain/fog.

 

[upnorthandpersonal]

They both have graphs for 25°C and 45°C (with crossed colors).

Yes, but I meant that temperature is much more important. The reason for the cycle life difference between 280k and 304 is that they test them at different C rates: 0.5C vs 1C

 

[silverstone]

Yes, but I meant that temperature is much more important. The reason for the cycle life difference between 280k and 304 is that they test them at different C rates: 0.5C vs 1C

True, it's almost 1C according to the datasheet I found here on the forum (250A / 304Ah ~ 0.8 C).

Didn't see that above the chart like in LF280K but you are right, it's in the table.



And I'm going to run 100A at most through them .

If I can manage 6+ batteries I might be able to fully stress the 30kW peak of my solar system (52V / 100A / ~ 5kW / ~ 15kWh) .

 

[Brucey]

Might be just easier to build one dedicated for that size. The space would have to be different anyway (think container) and I can just as well add the inverters and charge controllers there too.

Most of the designs I've seen have most of the space dedicated to the racks on one end and then inverters etc on the other end:

 

[LydMekk]

Looks nice overall . Here in Denmark it's usually much cooler (not as cool as in Finland though ).

I'm a bit concerned for the BMS and Fuse Holder heating up directly on the plywood.

That's why I'm considering to put a layer of fibergips on the inside part of the wood, to make it more fire resistant / retardant (won't be fireproof anyway).

How big did your box turn out to be ? Are the 2x2 that you added on the inside for structural integrity (to make it more "stiff") ? Or for which purpose ?

I put 4 pcs. 1cm rubber feet under the BMS. When running it stays at around 25-28c degrees. Room at 20-21c.
No issues with overheating the plywood ^^.
Don't overthink it

 

[silverstone]

I put 4 pcs. 1cm rubber feet under the BMS. When running it stays at around 25-28c degrees. Room at 20-21c.
No issues with overheating the plywood ^^.
Don't overthink it

"Don't overthink it "... Have you seen the battery v1 in the 1st post ?????

 

[silverstone]

For protection im using fuse and breaker, with a shunt trip unit.

My plan was to use a temperature relay to trigger it (and smoke detector), but this relay is the only I could find on aliexpress and is only limited to 45°C. On TME.eu they cost at least 2-3x as much and they are the cheap option.

I saw another from India but couldn't figure out where to source if from. Rs online and farnell were super expensive.

The much cheaper option might be a few termoswitches wired in series around the perimeter of the battery (in the inside of course). Super cheap and wide variety of available temperatures. Not sure about reliability and if DC voltage could be an issue (DC 24V should in theory be okish for 250 vac but you never know on aliexpress...).

Any thoughts?