Pylontech - The Right Buy for Me?

[Mendoza]

So the manual says recommended current of 25A and max current of 50-89A@60 sec.
However since I have two batteries I think that should be 50A and 100-178A.
Multiplying that by 50V should give recommended 2,500W and max 5000W-8900W.

Should I read that as "don't go above 2500W load on the battery for more than 60 seconds, ever" or perhaps more as "try not to do it excessively"? Am I Ok to run 4000W load at night? - this would mostly be for 2 to 6 minutes at a time for an average of less than once a day. Will going too high cause any damage to the battery, or will it just cut over to grid electricity or withhold power when it is under strain? I'll probably run an experiment and plug in two kettles after dark to see if the battery can handle 4000W. Let me know if this is a bad idea.

If the battery is overloaded, the battery management system (BMS) should cut power supply to the inverter. If I'm not mistaken this means your inverter will also shut down as it requires battery power operate.

Your batteries are not designed to supply high power so I suspect you will be confined to operate within your 2.5kW limit.

I decided, after dark, to fill and turn on two kettles. This brought the total house load to just over 4200W. I figured 4000W+ load at night is going to happen sooner or later so I may as well just do it at a convenient time and watch what happens.

The battery provided all the energy successfully without grid use or a power cut for about 4 minutes until the first of the kettles came to the boil and turned off. However a red light came on the master battery at some point. I ignored this and it still worked.

If the total load was 4200W that may indicate about 84-88A for 4 minutes, well above the recommended discharge of 50A total for the two batteries.

The manual states "if current exceeds 90A, battery protection will turn on". I assume I would have to draw about 180A across the two batteries to get to 90A on one, which would never happen since that is above the inverter´s power rating. Since the 50A discharge is just a reccomendation, I´d guess exceeding it occasionally just for a few minutes won´t be damaging to the battery.

 

[Mendoza]

Mine never get hot, so I don't think it's a problem. Still, I put five (four in the corners, one in the centre) bits of wood between them to separate them a bit. They're actually teak :·), I had them lying around.

View attachment 84918


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Found today some bits of wood lying around from a job last week and they were the precise length of the battery by good luck and even the height was pretty good. So I am copying your idea. See photos.

PS The batteries are NOT tilted at an angle. They are perfectly level. I must have had the phone a bit tilted when I took the photo.

 

[Don B. Cilly]

Well, I guess it's good to have a little air between them. And spending a lot of money on a cabinet... for just two batteries... :·/

Those bits of wood though. They don't exactly look like teak ;·)
I would at least put some linseed oil (or better) on them before the bugs eat them :·)
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[Mendoza]

I wouldn't worry about the insects. We don't usually have those sorts of problems here, maybe it's the dry climate. In previous years I've bought giant stacks of firewood at the end of summer and left them outside (under an overhanging roof). We do have ants, but they don't really go for wood.

However I'll keep an eye on it.

 

[Mendoza]

The system is still working well.

I've noticed that early morning kettle/microwave/toaster is, given the low state of charge in the battery at that time of day. enough to push the voltage to under 47V and trigger grid usage (47V is current setting 12).

Grid usage then continues for some time after because even when the load returns low the voltage only go back up to perhaps 48.3V or 48.5V. It looks like I would have to wait hours for the battery to charge enough for the voltage to come back to 49V (the current setting 13) and go back to solar. (I manually changed option 13 to 48V for a few seconds to fix problem each time.)

I think I am going to change setting 13 to 48V indefinitely from now on, if no-one here can come up with a good reason why not.

I appreciate that this could cause flicking back and forth between grid and solar, but thinking it through for my use case, I don't think it will much.

Is there any other reason to avoid having setting 13 as low as 48V - only 1V above setting 12?

 

[Don B. Cilly]

48V is pushing it a bit, 47 is definitely pushing it.
I would add more panels, if that doesn't work, more batteries.
Or change that early morning kettle/microwave/toaster to a more sensible gas cooker :·)


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[Mendoza]

My wife did buy a gas kettle as well to give us more flexibility. But it is a fossil fuel so I rarely use it.

The above chart you've posted shows that 51V-55V covers most of the battery capacity range. However mine tends to show around 48V-51V for much of its range, assuming discharging at low load.

I asked on another forum about this and I was told "The reason why you get a range of values provided for 48V lithium is Pylontech use 15 cells while most others use 16 cells. This then give you about 3V lower on the discharged side."

So letting it go down to 47V for Pylontech would be like letting it go down to 50V for other 16 cell batteries...I think? I could be wrong. All your figures on the graph are for 16 cell battery...need to be reduced by 3V for my case?

Actually quite happy with the amount of batteries and panels for now. The goal is to have solar energy all night for 3 seasons of the year and until 10pm on winter days. So far, looks like I've judged it correctly. It looks like increasing the system size would only add value in winter, so hard to justify at this point, especially since I can't sell to grid.

 

[Don B. Cilly]

Oh. I had no idea they had 15 cells.
Obviously the voltages have to be revised then.

About gas being a non-renewable fuel, it's not necessarily true.
You can buy bio-propane (maybe not in Chile) or simply make your own natural gas from dead grass and such.
And anyway, a gas cooker uses so little of it... and is so much better than electricity for cooking... :·)
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[wattmatters]

And anyway, a gas cooker uses so little of it... and is so much better than electricity for cooking... :·)

Induction for the win. I have a portable gas unit as an emergency though.

So letting it go down to 47V for Pylontech would be like letting it go down to 50V for other 16 cell batteries...I think?

Correct. 47/15 = 3.13V/cell. That's in the 10-20% SOC area so definitely cut off by that stage. Also individual cell differences mean one cell will be lower than the others.

 

[Don B. Cilly]

Induction for the win.

Did you mean "for the Epic Fail"? (in a Google sort of voice ;·)
Induction is simply no good for cooking... anything :·) Energy consumption aside, it's just plain useless. Gas is best.
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[wattmatters]

Induction is simply no good for cooking... anything

Use it all he time. It's fantastic. I've had gas cooktops, meh. Induction cooktops are highly heat controllable, have instant response and are by far the easiest cooktops to keep clean, and they look great. Plus they are electric, more efficient, with no noxious gases and can be powered 100% by (your own) renewable energy.

 

[Don B. Cilly]

 

[Mendoza]

I have heard numerous people making the argument that induction heaters are miles better than gas for many, many reasons on podcasts and articles. I won´t repeat the arguments as googling it would lead to better results that what I could remember. But it seems that pro-gas arguments are either a) due to the influence of the pro-gas lobby b) based on people´s understanding of outdated electric tech, not modern induction c) just due to resistance to change and people liking what they know.

It seems that induction heaters are better in every way, just superior.

However we have gas because everything electric in the house has to go through the 5kW inverter, and the installation of an electric cooker would be a hassle as we would have to look at the electrical supply and installations, which I don´t really want to do as we are renting the house.

I did actually search for bio gas a couple of years ago online, but I gave up without success.

You can get it in UK, but often it will be 10% mixed into the total. There just isn´t enough supply and it doesn´t look like there ever will be.

 

[Don B. Cilly]

I wonder what you cook. But real food (I'm Italian :·) needs gas. Gas is instant.
Gas will let you set the right temperature in milliseconds.
I have tried modern induction plates. My daughter rented a house a while ago that had them. She hated them. She likes cooking too.
In Italy, and Spain, the only reason people use induction is they don't like gas bottles inside the house, and it's complicated in some cases to have them outside. Most people don't care, they have them inside if they have to.

We don't even have pro-gas lobbies :·)
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[Mendoza]

The pro gas lobby is pretty strong in the US apparently, but glad there isn't any in Spain/Italy.

I will give you the advantage of gas being instant. That is certainly true.

For boiling water in pans, I try to reduce the climate change by boiling water in a kettle first and then pouring it into the pans.

 

[Don B. Cilly]

Apparently, propane does not create much CO2 at all, actually.
My wood stove certainly does, but I'm fine with that, for two reasons:
1) I'm a climate change denier. Actually, I would say sceptic, but dogmas and Inquisitions don't allow that ;·)
2) I don't like being cold :·)

Now, I'm a denier, not because I like fossil fuel lobbies, bur because I've extensively studied the stuff for many years, there are a lot of scientists in my family, I understand and appreciate the Scientific Method, and so-called climate science totally negates it - so I simply don't consider it science.
Just personal opinions, please let's not start (another) fruitless religious debate :·)
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[Mendoza]

It's telling that in order to defend the statement "propane does not create much CO2" you link only to the website of a vendor of propane, and the only (unsourced) evidence is that's it's not as bad as charcoal - which of course is rarely used. No attempt to say it's better than electric for CO2 which of course it isn't.

When you burn propane this is what happens: C3H8 + O2 = CO2 + H20

I am hoping to fit an electric heat pump in the house we let in the UK. I think what I will do is add a timer, a thermostat, insulation, and the ability to turn it on and off with a smart phone, even when not at home. With all of that it should always be warm all of the time someone is in the property. Hoping to get a quiet one so the heating can be programmed to come on for a few hours in the middle of the night when electricity is cheap. You only need the power of gas if you wake up to a clod, poorly insulated house or come home to a cold house. With programmable and remote and thermostatic heating control, the power of gas is neutralized and becomes irrelevant.

 

[Don B. Cilly]

Oh well, I said "apparently". Lots of sources seemed to confirm it, I just linked one. I haven't investigated. I don't really care. The fact that it's better than charcoal seems pretty obvious. Just as obvious is the fact that (in the emissions sense) it's not better than electric - unless you consider that oil might have been used to generate the electricity... but it seems to me a bit hair-splitting, considering the minute quantities used.

What I know for sure is that it's better for cooking.
Not for heating, no. For cooking. Proper cooking :·)
For heating, I agree, if you need to heat up a small space quickly, a gas stove can do, but not for long.
For heating, see my signature ;·)
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[wattmatters]

Apparently, propane does not create much CO2 at all, actually.

The fundamental chemical equation for the combustion of propane means it generates pretty much nothing else but CO2 and water. Statements such as the above are, frankly, absurd.

induction heaters

I'm talking about induction cooktops. Never heard of induction heaters but I guess they might be a thing somewhere.

Just as obvious is the fact that (in the emissions sense) it's not better than electric

This is a DIY solar forum. What do you think the source of the electrical energy for people here might be most interested in?

However we have gas because everything electric in the house has to go through the 5kW inverter, and the installation of an electric cooker would be a hassle as we would have to look at the electrical supply and installations, which I don´t really want to do as we are renting the house.

When the electrical supply has capacity limits, that's a reasonable factor when choosing the energy source for various basic services (e.g. cooking, space heating, water heating).

 

[wattmatters]

I haven't investigated. I don't really care.

Says a lot really.

To be so certain, so confident to proclaim something as true without even a basic check on the validity of the statement, like say checking something as basic as the chemical equation for the combustion of a fossil fuel.