Pylontech - The Right Buy for Me?

[BaronVerde]

I am planning a very similiar setup, but being at 29°N I get away with half of the material, that's ~10kW bifacial panels and 4-6 batteries of that or a similar type. I will also just use very little of the capacity at the beginning, but expect that to change when a small electric car replaces my aging litle diesel.

I understand the Pylontech batteries are simply but in parallel by connecting their plus poles in a row and the minus poles.

Aren't the cables that come with it too thin for that (25 or 35mm² I think) ?
What happens when let's say number 1 decides it is full, will there still be enough current for the later ones ?
Wouldn't it be better to connect each battery indiviually to a bus or will that irritate the BMS ?

 

[Mendoza]

we have 22KW of bifacial panels optimized perfectly for the 4 hours of sun on 21 December. No shade, no trees. We won't know until we try how much power we'll get but since it will be cold outside and snowy, it's possible they will produce more than 22KW of power each hour on that day. But we'll see.

That's a lot of panels? So presumably facing close to due south and angled to point more towards the horizon at a low angle.
And then for summer the logic I guess is you leave them in the same position which will be a terrible position for summer but doesn´t matter since you get enough solar anyway, and you wouldn´t use the extra you could get from a better summer position?
To point to the panels to the horizon, do you attach them on a side wall rather than a roof of a building? Or just have them away from buildings altogether?

 

[AlaskanNoob]

That's a lot of panels? So presumably facing close to due south and angled to point more towards the horizon at a low angle.
And then for summer the logic I guess is you leave them in the same position which will be a terrible position for summer but doesn´t matter since you get enough solar anyway, and you wouldn´t use the extra you could get from a better summer position?
To point to the panels to the horizon, do you attach them on a side wall rather than a roof of a building? Or just have them away from buildings altogether?

That's the plan. We'll see how it matches with reality. I have one spot on the property that gets sun on 21 December and it's on a south facing hill just to the north of a thousand foot bluff. On the other side of the bluff is ocean. So the slope keeps trees from shading the horizon and then it drops off to the water. There are about nine small trees I will cut (and use for lumber) and then it will see the sun directly for the full four hours if it's sunny. Directly south facing ground array, one axis angle so I can tilt panels up but will be straight up and down (6 degrees from optimum--although I will set them to 6 degrees and if snow isn't an issue just leave them there) during winter to keep snow off.

The batteries will be stored six feet underground in a culvert with an insulated roof/floor and shed over top (shed and floor not shown). Two rows of panels. South facing row is down slope to prevent it from shading the north row of panels.

Looking down into the culvert you can see where the Pylontech batteries will go through the wall and I'll have a door to access behind the wall. I will heavily insulate the batteries to ensure they stay at least 65F year round. Doing it this way allows for shorter cable runs from the front of the batteries to the other components. So hopefully the insulated batteries inside an insulated culvert underground will ensure 65F even when it's -4F outside. If that doesn't work, I'll look into heating pads.

And after going through all this effort and spending the money on the PV and the SCC to harness as much as I can during that four hours, I'm going to be very bummed if the Pylontech BMS throttles me. I guess we'll see.

This will be fun to see in the middle of a forest in Alaska in the middle of nowhere. A helicopter will deliver the panels up there once the snow melts.

Edit: Actually it looks like I'll only get 3 hours of sun on 21 December. So very important that these batteries take whatever charge they are given.

 

[AlaskanNoob]

I am planning a very similiar setup, but being at 29°N I get away with half of the material, that's ~10kW bifacial panels and 4-6 batteries of that or a similar type. I will also just use very little of the capacity at the beginning, but expect that to change when a small electric car replaces my aging litle diesel.

I understand the Pylontech batteries are simply but in parallel by connecting their plus poles in a row and the minus poles.

Aren't the cables that come with it too thin for that (25 or 35mm² I think) ?
What happens when let's say number 1 decides it is full, will there still be enough current for the later ones ?
Wouldn't it be better to connect each battery indiviually to a bus or will that irritate the BMS ?

Yes, the cables are another annoyance, but not really an issue. Or so it seems from my research. They use some kind of proprietary terminal connection that is limited to 130A or so. And the cables are limited to 100A continuous. So if you are going to put them in parallel you can only put two of them in parallel without using a bus bar. Otherwise you get more than 100A (assuming you're charging them at their max specified charging current and cutting their BMS out of the charging loop in order to get the advertised charging current despite losing your warranty for wanting to get what you paid for).

Or you can buy the extra 6 foot wires and wire each battery separately as you discuss and you won't have any issue (again, from my research as a complete neophyte who also lacks experience). They will still daisy chain with the communication cables, but the power is limited by their small 4AWG cables. But no issues if you want to get two 6 foot cables for each battery and wire that into your battery bus.

 

[Mendoza]

Alaska project seems pretty adventurous and exciting. I am not sure if I'll be hanging around the forum or not but if I did would be good to see an update.

 

[AlaskanNoob]

Alaska project seems pretty adventurous and exciting. I am not sure if I'll be hanging around the forum or not but if I did would be good to see an update.

How your Chile project install gone?

 

[Mendoza]

Batteries installed yesterday.

As soon as we went into discharging rather than charging mode (when the oven was switched on and we had 1800W load vs few hundred W solar) immediately the inverter starting beeping with a low battery warning and the inverter showing one bar out of four (indicating 0%-24% battery).

However the batteries were at that time showing 4 green lights, one flashing light, and one green light off. Which I assume indicates a high state of charge. Possibly four lights and a flashing fifth out of 6 might indicate more than 4/6 and less than 5/6 charge.

So the inverter and the batteries seemed to be in disagreement about the state of charge.

I'm slightly inclined to believe the battery more, because a) I guess (?) it would make sense that the batteries were delivered at a mid state of charge rather than kept at low and b) the batteries were charging for a while after installation and ought to have been charged up by about 0.5kWH-1KWH already (i.e. 0.25kWH-0.5kWH each).

I will try leaving it on SOL mode rather than SBU today, tonight, and tomorrow morning which should ensure battery charging and after that see if things settle down. Let me know if anyone has any thoughts on this, or maybe I need to start a new thread.

 

[Mendoza]

Also, the two batteries are touching each other, stacked one on top of the other, as there wasn't enough cable to install them side by side. At some point I'll get the proper bracket I think to stack them better with space between them. The installer thought this wasn't ideal due to heat build up but isn't a problem for some days (note batteries will be sat in a temperature of about 15C-28C mostly in this area for now).

Any comments on this. Is this OK for a) a short time like days or weeks b) indefinitely - leave them stacked for years c) not OK even for one day.

 

[Don B. Cilly]

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.



One thing though: those are in parallel, right? You should draw from the positive of one and the negative of the other.
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[Mendoza]

it is a parallel circuit, according to the installer, so the total current is the sum of the currents flowing through each component.

Thanks for the idea about the bits of wood.

Did you specifically choose that material for some reason, or would you equally as likely have used plastic or metal or whatever pieces of anything of the right size that were lying around?

I suppose wood is a poor electrical conductor, that might be a good reason for choice. I don't imagine there's any chance the wood could catch on fire due to heat or sparks - I guess not - I sometimes have a hard job setting wood on fire when I'm trying to do it deliberately.

 

[Don B. Cilly]

it is a parallel circuit, according to the installer,

So, according to the manual (and common sense ;·) you should draw from the positive of one and the negative of the other.

Did you specifically choose that material for some reason,

Well yes. It's teak. As good a wood as it gets. Some fifteen years ago, I was working on a house where they were building a swimming pool.
The sides of the pool they lined with teak flooring. Real teak. From Thailand. Millionaires... They threw the leftovers in a big pile in the dirt.
I said, can I take some? They said, sure, we'll burn it :·/. I still have some left.
If those batteries catch fire - very unlikely - the bits of wood would be the last of your worries :·)
Just connect one of the long cables to the other battery, though ;·)
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[wattmatters]

One thing though: those are in parallel, right? You should draw from the positive of one and the negative of the other.

This. Move one of the main supply cables to the lower battery. Doesn't matter which.

I note earlier you have this setting, and associated custom battery settings:

5. Battery Type: USE

Which means the inverter probably doesn't have a built in LiFePO4 set up.

And it also looks like the voltages for your battery are for a 15S battery (and not 16S).

I'd say the battery monitor on the inverter is reporting estimated battery level based on expected lead acid battery voltages and relative loads, which of course don't apply to your battery. I would go by the battery indicator, not the inverter's guesstimate.

Your batteries should be individually fully charged before connecting them in parallel.

The comms port on the inverter is more likely for connecting to other inverters for either parallel supply or for three phase set ups.

You might be interested in Solar Assistant, an inverter and battery monitoring system compatible with Voltronic inverters and Pylontech batteries:

Real-time solar monitoring from a Raspberry Pi | SolarAssistant Software

Real-time charts, analytics and power management from via a Raspberry pi - the most powerful, cost effective device on the planet.

solar-assistant.io

 

[Mendoza]

I'd say the battery monitor on the inverter is reporting estimated battery level based on expected lead acid battery voltages and relative loads, which of course don't apply to your battery. I would go by the battery indicator, not the inverter's guesstimate.

Makes sense, but that still leaves the problem that the inverter will beep continuously with low battery warning which will be audible in half the house. How can I make it shut up?

Will check the other points later.

 

[Mendoza]

Your batteries should be individually fully charged before connecting them in parallel.

thanks a lot for helping out. is it a bit late for that now, since they have already been connected?

 

[Mendoza]

So, according to the manual (and common sense ;·) you should draw from the positive of one and the negative of the other.

Just connect one of the long cables to the other battery, though ;·)
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Thanks for your help in explaining to this. I am afraid I am something of a beginner at this.

I don't find words explaining that in the manual, although the pictures seem to agree with you. Perhaps you are referring to the pictures.

Is this a good explanation of what you're both talking about: https://caravanchronicles.com/guides/how-to-connect-two-batteries-in-parallel/ in terms of reasons for doing this. Or should I ignore this?

This connection was done by friend who has a local business installing solar, he is a professional installer. I do not do any part of these connections myself, or tell him how to connect them. Is there any good explanation for this, anything I could have confused or overlooked, before I make a fool of myself by telling him he has done it wrong.

 

[AlaskanNoob]

Thanks for your help in explaining to this. I am afraid I am something of a beginner at this.

I don't find words explaining that in the manual, although the pictures seem to agree with you. Perhaps you are referring to the pictures.

Is this a good explanation of what you're both talking about: https://caravanchronicles.com/guides/how-to-connect-two-batteries-in-parallel/ in terms of reasons for doing this. Or should I ignore this?

This connection was done by friend who has a local business installing solar, he is a professional installer. I do not do any part of these connections myself, or tell him how to connect them. Is there any good explanation for this, anything I could have confused or overlooked, before I make a fool of myself by telling him he has done it wrong.

I think the issue is that when you parallel as you have done, and both positive and negative are coming from one battery to your charge controller or charger, you end up with one battery getting overcharged and one being undercharged.

So if you diagonal (with one positive going out from one battery and the negative going out from the other battery) you'll get more even charge/discharge to the bank. Although you can also do it in other ways too.

 

[AlaskanNoob]

I am also interested in a charger for the Pylontech batteries to allow using a generator to charge each battery up individually fully before wiring them in parallel. I haven't found anything to do this yet though.

Perhaps one single battery could be hooked up to your solar charger and charged until it is full (no discharge) and then swap them out until they are all full, then wire back in parallel and hook up to the inverter?

 

[Don B. Cilly]

Perhaps you are referring to the pictures.

I am. Chinese manuals text isn't usually very helpful.
In this case, the picture is a bit confusing too, but (page 16 of the PDF manual)

You can vaguely guess that the black cable on the left is connected to the bottom socket.
Anyway, that's the way to connect parallel batteries, the why has been amply explained.
Your installer friend must have been thinking about something else. It happens :·)

Note that on the next page there is a similar picture, with double cables. That is if you plan to exceed 120A draw (for any significant amount of time, like more than a second or two).
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[Mendoza]

OK, I will get the cable positions changed. I guess need to decide on the individual charging of each battery, whether to do that first. The LED lights showing state of charge have always been exactly the same on each battery every time I've looked - given this, are they probably close enough? Or is it worth doing what was suggested anyway (individual charging of each battery) to get it very precise. The only reason I am hesitant is I've either

a) got to get the installer back here I suppose 3 times to charge battery one, then battery two, then final connection
OR
b) do it all myself, which I suppose for some of you is such as easy job that mistake would be impossible, but believe me, I can struggle to hang a picture on a wall and have no basic knowledge of electronics - I could mess up something so obvious none of you would even think to tell me not to do it.....but I'll give it a go if it's really necessary

 

[Don B. Cilly]

got to get the installer back here I suppose 3 times to charge battery one, then battery two, then final connection

Well, if you "balance" them (charge them separately) when they're pretty much fully charged - like early afternoon on a sunny day, it shouldn't take long at all.
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