Pylontech batteries expansion

[DannyK]

Hello all,

I am a novice when it comes to Solar but I need some advice on expanding battery storage capability. Installed a 5000W PV array less than a year ago over a 8KW Victron inverter and 7Kwh pylontech batteries (2 x 3.5kwh). Now ready to increase battery storage to 21Kwh from 7 Kwh and also add additional PV arrays to take advantage of the 8KW viltron inverter. Meaning I will be adding an additional 4 x 3.5kwh to the battery bank.

My questions are:

1). How many  3.5KWh pylontech batteries can I connect together in parallel without making the interconnecting cables too hot and starting a fire? I have heard of cases where people connected 6 ZTE batteries (3.5KwH) together and cables were getting hot and melting. I don't know if this will be the case with the pylontech brand. I will definitely employ the services of a professional to do the job but just like to have an idea of what is to be done before embarking on the project. 

2). Can I go above 8KW on my PV Array since my inverter is 8KW without having any issue? Plan is to add additional 3600W or 5600W depending on available space.   

3). What other advices or tips can you give me based on my system configuration above.

Thank you all in advance. 

Much Appreciated. 

Danny

[___]

17 hours ago, DannyK said:

1). How many  3.5KWh pylontech batteries can I connect together in parallel without making the interconnecting cables too hot and starting a fire? I have heard of cases where people connected 6 ZTE batteries (3.5KwH) together and cables were getting hot and melting. I don't know if this will be the case with the pylontech brand. I will definitely employ the services of a professional to do the job but just like to have an idea of what is to be done before embarking on the project. 

Working at 1C discharge, it is 70A per module, and as I recall they ship with 25mm^2 cabling? Or is that that the US2500? In any case, two modules would be the max for 25mm^2 cabling, so 6 is definitely too much.

If you work with C/2 currents (the recommended maximum discharge), then it's 4 modules max.

Best would be to do some research on what Pylontech themselves recommends.

17 hours ago, DannyK said:

2). Can I go above 8KW on my PV Array since my inverter is 8KW without having any issue? Plan is to add additional 3600W or 5600W depending on available space.   

Yup, no problem. Just make sure the maximum charge current is somewhere between C/2 and 1C of the batteries, ie somewhere between 200A and 400A, and make sure your cabling is sized for that.

 

[DannyK]

2 hours ago, plonkster said:

Working at 1C discharge, it is 70A per module, and as I recall they ship with 25mm^2 cabling? Or is that that the US2500? In any case, two modules would be the max for 25mm^2 cabling, so 6 is definitely too much.

If you work with C/2 currents (the recommended maximum discharge), then it's 4 modules max.

Best would be to do some research on what Pylontech themselves recommends.

Yup, no problem. Just make sure the maximum charge current is somewhere between C/2 and 1C of the batteries, ie somewhere between 200A and 400A, and make sure your cabling is sized for that.

 

Thanks a lot Plonkster. The experience and knowledge you share as well as others like you on this forum makes it the best in the world. Appreciate you.

5.Pylon Battery Extention and Replace SOP.pdf

Now am sorry because am about to ask more questions.

... So if I connect 2 batteries max it means I have to use a bus bar to connect the other 4, right? I read through the pylontech manual (attached) and I notice they said 8 batteries maxcan be connected per battery group (what does this mean?)

lastly, When do I use the ADD dip switches? 

 

Many thanks.

US3000 Product manual 19BQSV0102.pdf

[___]

47 minutes ago, DannyK said:

So if I connect 2 batteries max it means I have to use a bus bar to connect the other 4, right?

Yes. You'd have to set up bus bars and split your batteries into groups, and tie each group separately to the bus bars. And then you'd have other cables from the bus bars to the inverter and the MPPTs.

Since the inverter is only 8kW, the max draw from the batteries would be around 160A. If you split them into two groups of three each, each side has to do about 80A, and the standard cabling will be sufficient for that.

Then you'd also fuse the battery connection to the rest of the system at 300A or so.

47 minutes ago, DannyK said:

they said 8 batteries maxcan be connected per battery group (what does this mean?)

On the batteries there is a link port, a communication bus. You link all the batteries together, and one of them becomes the master and the rest are slaves. The master makes decisions about shutting down and so forth for the entire stack. This stack can be max 8 batteries (it has to do with addressing between the master and slaves, not with the cable sizes). If you have more than 8 batteries, you divide them into groups and you combine the groups into a larger whole using a "LV hub".

47 minutes ago, DannyK said:

lastly, When do I use the ADD dip switches? 

The DIP switches come in when you have multiple groups tied together with an LV-hub. Then each group gets their own ADDress. For 8 batteries or less (with no LV-hub) you just leave the dip switches alone.

Edit: So to be clear, you'll electrically split the batteries into two groups of 3 each (because of cabling limitations), but from a data communications viewpoint it will be one group (ie all 6 will be daisy-chained using their link ports).

Edited July 1, 2020 by plonkster

[DannyK]

30 minutes ago, plonkster said:

Yes. You'd have to set up bus bars and split your batteries into groups, and tie each group separately to the bus bars. And then you'd have other cables from the bus bars to the inverter and the MPPTs.

Since the inverter is only 8kW, the max draw from the batteries would be around 160A. If you split them into two groups of three each, each side has to do about 80A, and the standard cabling will be sufficient for that.

Then you'd also fuse the battery connection to the rest of the system at 300A or so.

On the batteries there is a link port, a communication bus. You link all the batteries together, and one of them becomes the master and the rest are slaves. The master makes decisions about shutting down and so forth for the entire stack. This stack can be max 8 batteries (it has to do with addressing between the master and slaves, not with the cable sizes). If you have more than 8 batteries, you divide them into groups and you combine the groups into a larger whole using a "LV hub".

The DIP switches come in when you have multiple groups tied together with an LV-hub. Then each group gets their own ADDress. For 8 batteries or less (with no LV-hub) you just leave the dip switches alone.

Edit: So to be clear, you'll electrically split the batteries into two groups of 3 each (because of cabling limitations), but from a data communications viewpoint it will be one group (ie all 6 will be daisy-chained using their link ports).

Thanks again Plonkster, you are a superstar.

 

Any other tip to note as I embark on this expansion project? 

[jcdup]

On 2020/07/01 at 1:20 PM, DannyK said:

<snip>

5.Pylon Battery Extention and Replace SOP.pdf 460.96 kB · 2 downloads

Now am sorry because am about to ask more questions.

<snip>

Hi DannyK

Where did you get this document?

Thanks

Johann

[DannyK]

2 hours ago, [email protected] said:

Hi DannyK

Where did you get this document?

Thanks

Johann

Hello Johan,

It was sent to me during my research on the subject matter. Are there any concerns with the document?

Regards,

DannyK

[jcdup]

2 hours ago, DannyK said:

Hello Johan,

It was sent to me during my research on the subject matter. Are there any concerns with the document?

Regards,

DannyK

Not at all.  It is very useful and I wondered whether there is  perhaps more where that came from

It looks like chapter 5 of some bigger document

Thanks

[DannyK]

1 hour ago, [email protected] said:

Not at all.  It is very useful and I wondered whether there is  perhaps more where that came from

It looks like chapter 5 of some bigger document

Thanks

The document was actually sent to me by someone at Pylontech earlier this year when I contacted them on how to connect multiple batteries and they reply with the document and some useful tips (which I have now attached) but I felt my question to them was not fully answered, hence my post in this forum.

Maybe it was extracted from their full training manual.

[jcdup]

Thanks DannyK

 

[VisN]

I was intrigued by the question of the current carrying ability of the standard cables so I dug around a bit and found this https://community.victronenergy.com/answers/41649/view.html

 

Using the linked online calculator, it does give the same result.

Edited July 17, 2020 by VisN

[DannyK]

On 2020/07/17 at 2:19 AM, VisN said:

I was intrigued by the question of the current carrying ability of the standard cables so I dug around a bit and found this https://community.victronenergy.com/answers/41649/view.html

 

Using the linked online calculator, it does give the same result.

Hello VisN,

Thanks for sharing this very useful information. Also found it very interesting. With this new knowledge, I had to procure the 2m cable packs manufactured by Pylontech to use in my project. I will install them in a couple of days.  

cheers and keep well.

DannyK

 

[VisN]

17 hours ago, DannyK said:

Hello VisN,

Thanks for sharing this very useful information. Also found it very interesting. With this new knowledge, I had to procure the 2m cable packs manufactured by Pylontech to use in my project. I will install them in a couple of days.  

cheers and keep well.

DannyK

 

@DannyK, I was hoping to hear from people with real world experience. Maybe someone will chime in soon.

[FixAMess]

When I added an new  pylontec  battery, I discharged the old batteries down to 65% SoC. (New batteries come charged at about 60-70, as per forum experience)

I disconnected the old batteries from the inverter and then connected the new battery in parallel with the old batteries and then left them like that overnight, still disconnected.

When I connected them for the first day the pack would not get to 100% SoC.

I then discharged the pack down to 40% SoC and then recharged them. They all settled at 100% after that.

There was a discussion on the forum about how to add additional batteries to alleviate differences in SoC across the batteries.

[DannyK]

Hello all,

Project upgrade completed successfully. Added 4 extra batteries to make a total of 6 x 3.5KWh batteries. Added extra 420 x 12 solar panels to make a total of 10065W of PV array and also an extra MPPT for the new set of PV array. Everything is working perfectly fine as expected. Below are some pictures from the upgrade.

Also want to say a big thanks to @plonkster and others for the advices, tips and insights.

 

Much appreciated.

 

[DannyK]

3 hours ago, FixAMess said:

When I added an new  pylontec  battery, I discharged the old batteries down to 65% SoC. (New batteries come charged at about 60-70, as per forum experience)

I disconnected the old batteries from the inverter and then connected the new battery in parallel with the old batteries and then left them like that overnight, still disconnected.

When I connected them for the first day the pack would not get to 100% SoC.

I then discharged the pack down to 40% SoC and then recharged them. They all settled at 100% after that.

There was a discussion on the forum about how to add additional batteries to alleviate differences in SoC across the batteries.

The supplier for my new batteries told me that the new batteries were fully charged. So I charged the old batteries to 100% before disconnecting them to ensure there is very little voltage differences between the old and the new batteries when adding them. 

When I connected the whole 6 banks together with one of the newest ones as the master, I realised that the older 2 batteries were out of sync with the newer ones. It was like the older 2 were not added to the total capacity. I decided I leave them all connected together overnight to see if they will synchronise and balance out. I noticed some improvement the next morning and at the end of the second day all the 6 batteries were all in syn and balanced (All the SOC lights for all 6 batteries blinking together). 

I believe the batteries' BMS's just need time to balance the internal cells and ensure the same voltage across all the batteries or maybe I was just lucky .

 

Cheers!

DannyK.

 

[VisN]

Looks superb. Congratulations. Did you connect the batteries to a bus bar as described here? 

 

[DannyK]

1 hour ago, VisN said:

Looks superb. Congratulations. Did you connect the batteries to a bus bar as described here? 

 

Thanks VisN,

I must confess that I did not do the upgrade myself as a DIY. I employed the services of an installer but I insisted on what I wanted.

Yes bus bars were used. 2 batteries were connected together to make 3 groups of batteries. So I have 3 sets of cables running to the bus bars.

Attached is the graphical representation of my design.

451 Solar Installation Expansion.pdf

[faheem]

is a busbar necessary ?

i had a victron authorised installer come to add additional batteries in my setup and he said nothing about adding a busbar. i had initially 3 x 2.4kw pylontech batteries and have now added 2 x 3.5kw us3000 batteries to the setup. would not having the busbar be a problem ?

also how can i know if all my batteries are utilised in the system, it all looks the same to me if i look at the remote console.

Edited July 27, 2020 by faheem

[VisN]

22 hours ago, faheem said:

also how can i know if all my batteries are utilised in the system, it all looks the same to me if i look at the remote console.

Look in 'Pylontech battery' > 'Parameters' > 'Charge / Discharge'  . I have 2 x US3000 batteries i.e. 2 x 37A = 74A