question

jeanmc avatar image
jeanmc asked

Pylontech battery cable spec

Hello,


Can someone please clarify the following:


The Pylontech 2m external power cables (both + and -) is labelled 4AWG. The Pylontech US3000 manual (page 12) rates this as a 120A cable. AWG 4 translates to a 21.2mm2 cable with a current carrying capability of 70A at 60 deg C. (https://en.wikipedia.org/wiki/American_wire_gauge)


A Pylontech US3000 battery (page 4 of manual) has recommended charge/discharge capacity of 37 A. This cable should work fine with a single module. However 2 modules in parallel will double the current capacity while voltage remain at 48V. Are we really using a 70A cable on a 74 A supply source? Obviously the max current per single US3000 is much higher.

The Pylontech cables does not appear to be a copper cable. The wire strands are silver.



Thank you

Jean

Pylontechwiring
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fideri avatar image fideri commented ·

Did you resolve the cable size issue @JeanMc?

I intend to buy 8 modules of US3000. According to Pylontech, you can use up to 8 battery modules without the need for a hub. Each module has 2 interconnection power cables. And each package has 2 power cables for connection to the inverter. These are however limited to 120 amps. Two questions:

1) Aren’t the cable connections severely limited for 3 modules or more? PolyTech recommends 37 amps charge capacity per module. That is potentially 37 x 8 = 296 amps in my case Yet Pylontech say their cable is rated at 120 amps. As Jean says, it doesn’t appear to be fit for the purpose.
2) For the same reasons above, aren’t the interconnection cables under speced by Pylontech?
I have read both Victron’s “wiring unlimited” and Guy’s comments but no answers.

Fideri

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dayandnight avatar image dayandnight commented ·

Hello @Fideri,

it is not just simple as it seems to be. I run a batteries block with 8 pieces USB2000B.

I connected to my bus bar one 2m cable from the very top unit and additionally one second 2m cable (each one for plus an minus) from the very bottom unit. But still all eight units are in daisy chain wiring. I am planning to change wiring and to work in two blocks whit 4 units in daisy chain and to have per block down and bottom one 2m cable to my busbar. So in total four cable sets per eight Pylontech units.

But there is another effect you have to think about. I recognized that depending on charging and on the temperature of the batteries, the Pylontech BMS limit in my system in the afternoon for hours the charging limit to 80 A for all 8 units. It make sense to think about wiring and cabling to use maximum current for charging - but keep in mind that the internal BMS has it's own demands and might regulates down the current. According to my monitoring the Pylontech BMS has always the final say and is the boss for the charge current. ;-)

Nevertheless I think it makes really sense to use as less as possible units in daisy chain. So the best would be, I think, to connect each Pylontech unit with it's own 2m cable directly to a bus bar or to use as best compromise as less as possible daisy chained units.

DayAndNight

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fideri avatar image fideri dayandnight commented ·

That is one neat installation. Thanks for the pic.

I hear you when you say it’s more complicated. Certainly it is pointless to adhere to wiring standards if the input/output is going to be throttled by BMS.
I have ordered 8 of US3000. I will order 8 more when I get the cash. I will try to keep them in banks of 4. So 4 x 4 parallel.
There is one thing I don’t get in pic. As I understand it, your top “master” power cable (2 metres) is going to your positive busbar, unfused, then your busbar connects to the charger/inverter with your own cable which can be fused. The bottom “slave” power cable (2 metres) goes to your negative busbar, then the busbar connects to the charger/inverter with your own unfused cable. What about the extra orange power cable at the “slave” and the extra black cable at the “master”? Are those going to your loads?

Fideri

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dayandnight avatar image dayandnight fideri commented ·

Hello @Fideri,

I think a picture say more than 1000 words! ;-) I did a drawing for you.

Of course I use fuses at the positive wiring. The three Multiplus-II (3-phase) are connected with 120 cm 35 mm² cables, for connecting the busbar to the victrons I used the Pylontech 200 cm 25 mm² cables. In the drawing I didn't show the net wiring, but this was done normally, with the serial cables delivered with the pylons and from the master to the Multiplus-II GX I used the special Victron/Pylontech CAN-Bus cable.

Here some photos of my busbar work:



Some more information about my first steps to realize my bus bar housing you can find here.

When I started, I didn't know the Victron Lynx system, which can be used for such an installation, too.

But I am satisfied with mine and I think I can upgrade each box for two additional Pylontech cables. I will guide one cable from the top and one from the botton into the housing and I will double connect the pyloncables to the busbar on the first and on the last terminal of the busbar.

DayAndNight

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fideri avatar image fideri dayandnight commented ·

Hello DayAndNight,

As clear as night and day :)

Thank you.
Fideri

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8 Answers
Guy Stewart (Victron Community Manager) avatar image
Guy Stewart (Victron Community Manager) answered ·

Hi @JeanMc,

The 4AWG cables supplied as part of the Pylontech cable kit have an insulation temperature rating of 105 degrees.

This allows for the much higher than normal current carrying capacity than you might be used to, or able to find in other cables.

7873-91c9dec5-c4c4-4002-b069-5cf7a70cd475.jpeg

7881-d230b1b6-2fdd-470a-b822-a176e59a49e7.png


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jeanmc avatar image jeanmc commented ·

Thank you for your reply Guy.


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Warwick Bruce Chapman avatar image Warwick Bruce Chapman commented ·
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Guy Stewart (Victron Community Manager) avatar image Guy Stewart (Victron Community Manager) ♦♦ Warwick Bruce Chapman commented ·

Unfortunately it is no longer available as a free standing (offline) app.

But you can still access it via this website:

http://wirewizard.bambachcables.com.au

Most phones allow you to add a website as a web app to the home screen of your phone.

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Warwick Bruce Chapman avatar image Warwick Bruce Chapman Guy Stewart (Victron Community Manager) ♦♦ commented ·

Thank you! Added.

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JohnC avatar image
JohnC answered ·

Hi @JeanMc

Great you're concerned.

A quick answer might be just to suggest you use both cables. And that the silver cable is actually high-end tinned copper, usually specced for marine use.

But I won't. There's more to it than that of course, and I encourage you to take a look through this: https://www.victronenergy.com/upload/documents/Wiring-Unlimited-EN.pdf

Come back if you have particular questions..

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jeanmc avatar image jeanmc commented ·

Hi John,

I've read Wiring Unlimited.

Pylontech is approved for use with Victron products. This specific installation will use a Multiplus ii 5000 and MPPT 250/100 charge controller with these batteries.

Pylontech provides the shorter inter link power cables with each module and you have to buy the longer 2m set separately. The reason we purchase these cables is because of the connectors. You stay with the "theme" and the installation looks neat. Obviously you can buy a set of these cables for each module and that would solve the problem but that is not how these cables are advertised and sold. You require one of these cable sets with 3 x US3000 modules or 4 x US2000 modules. If you have 4 x US3000 modules you have to buy an extra 2m cable set. In a 4 x US3000 scenario, I would definitely use one 2m set on 2 modules and the other 2m set on the other two modules. I am however still concerned about the cable rating vs the module rating.

My specific question is: Am I missing something here? Or are these cables not suitable?

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Michael Timler avatar image Michael Timler jeanmc commented ·

You can make your own cables:

https://www.mouser.de/ProductDetail/Amphenol-Industrial/SLPPA25BSB?qs=G2fvz%2F8gJKLF7L0%2F81ZKWQ%3D%3D&vip=1&gclid=EAIaIQobChMI-5vBk4uB6QIVGOd3Ch3uWAPaEAYYASABEgLbO_D_BwE

Unfortunately, the Radsock-Standard 5.7 plug is limited to 120A. Therefore, not only the 25mm²-Cables seem to be a bit unerrated. The Battery DC plugs are too.

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raymiller avatar image raymiller Michael Timler commented ·

I share your view, especially when the recommendations for battery cable mm2 to inverters are higher, to have the battery cable at 25mm2 * 2 for 4 batteries. The solution would be to reduce the number to less than 4 parallel batteries while using dual equal length cables. My system is 24V which makes the issue even worst than the 48V or higher voltage systems.

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kai avatar image
kai answered ·

A related comment on current carrying capacities - the figures are based on stated conditions (free air vs in conduct, air flow, any adjacent cables (that may also contribute to ambient temp), etc) in the steady state - it takes a while to get up to the "rated" temp. Cable selection should consider those factors, including and up to what the cable enclosure can take. PVC has a max op temp of around 60C for instance, and would not be suitable as conduit material if the cable is expected to heat up to >60C.

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cristimv avatar image
cristimv answered ·

Hi.

Sharing my own experience: using a Quattro 48/10000 and 8 US3000 Pylontech, split in 2 groups of 4, each group connected with 1 set of cables. From the busbar to Quattro, there are 2 sets of cables. On top, I've set the charging limit to 100A, which is enough to get batteries back to 100% until noon next day.

img-1508.jpg


img-1508.jpg (786.8 KiB)
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seb71 avatar image seb71 commented ·

I would put fuses on each positive wire from those two battery banks.

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netzerodude avatar image netzerodude commented ·
Hi @cristimv I am building something similar but starting with Quattro 48/10000 and 4 US5000C's split into two pairs, before I later add another 4 units. Just querying your comm cable setup. Looking at your picture it looks like the top right unit links to the bottom left, but does the top left then link to the Victron?
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Alexandra avatar image Alexandra ♦ netzerodude commented ·

@NetZeroDude

The manual describes how to link up the comms.

The one with empty Link Port 0 is the Master Battery Module, others are slaves.

The can port is then used to connect to the GX

screenshot-20220805-203850.jpg


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cristimv avatar image cristimv netzerodude commented ·

If you reffer to the communication cable, yes. At that moment the 8 batteries were all set as one string. in the meantime I added another 4, and I had to split in 2 strings of 6, and connect them via a lv-hub

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yoki avatar image
yoki answered ·

Hallo,

As I had to do an electrical diagram for one of my customers, attached are 2 solutions.

As Guy Stewart says and it's possible depending on the temperature, if the Pylontech 4AWG / 2m power cable can lead support up to 178A (not 120A as specified by Pylontech) => I would have put less 4AWG / cable 2m on my drawing.

Empillage batteries & Câblage_page 1-2.pdf

Empillage batteries & Câblage_page 2-2.pdf

Regards,

Yonas K.


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alaskannoob avatar image alaskannoob commented ·

Has it been confirmed that the cables can 178 amp? If so, why isn't Pylontech using that number?


I'm still trying to figure out how to wire my 8 x US5000 pylontech batteries to my two Lynx Distributors such that my two MultiPlus II 8000W inverters can pull 16KW from the battery.


Two stacks of 4 batteries, with each stack splitting the potential 333 amp draw from the bank. So the cables, I would think, would need to handle 167 amp. But Pylontech says their cables only handle 100 amp. So I'm not sure how to do this.


In my setup, assuming a 16KW draw, if it has been confirmed that the 4 AWG Pylontech cables can handle 178 amp (despite Pylontech only rating them at 100 amp) then I would wire A & B to 4, and G & H to 5 to connect my bank to the Lynx Distributors.

But if we assume Pylontech cables can only support 100 amp as they say, could I double up the 4 AWG wires and add E & F to 3, and C & D to 6 to be able to safely pull 16KW with individual cables only rated to 100 amp?

Many thanks for any help figuring this out.pylontech-wiring.jpg


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wkirby avatar image wkirby ♦♦ alaskannoob commented ·

Pylontech is not using the 178A number because the actual copper cable is only a part of the cable assembly. On one end is an Amphenol SurLok automotive connector which is rated at 120A.

https://www.amphenol-industrial.de/en/SLPPA25BSB/5-7MM-Surlok-Plus-Cable-Plug-Right-angled-25mm-black/p10192

So, 120A is the rating to be used.

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fideri avatar image
fideri answered ·

Hi @yoki

My design is very similar to your first drawing; the one of single phase. The only difference is that I have two mppts (250/100) connected to the busbar to charge my batteries and to power my loads directly. I suppose in your design, you charge the batteries from the inverter? My question concerns the second set of four battery modules: why are they split into two clusters of two battery modules each when one cluster of four modules can do? My understanding is that the lower set of batteries is just an option to connect them. Am I correct?

For your information, I have two clusters of four US3000s each, that is eight battery modules, both clusters connected like in the first set of batteries in your drawing.

Fideri

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yoki avatar image yoki commented ·

Hi Fideri,

Your understanding is correct. However, it depends on the inverter / inverter-charger you are using. In my case, I've a Quattro 15kVA and will draw a current of 312.5A but limited by the BMS to max. 296A (4 x 74A / US3000 module). This current is very high for the Pylontech 4AWG / 2m cable because it is specified for 120A. In the case of the first set of 4 batteries, the current will be 148A/cable (a little too much according to Pylotech's specification but Ok according to Guy Stewart's explanations). In the 2nd case, the second set of four battery splited into two cluster, it will be 74A/cable. In my case with Quattro 15kVA, my choice is to split into two cluster in order to comply with Pylontech specification.

Hope I have answered your questions.

Sincerely,

Yonas K.

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fideri avatar image
fideri answered ·

Thanks @yoki . It is very clear.

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away avatar image
away answered ·

@alakannoob, this is an interesting thread and I've been pondering this very issue for a while. In Australia the cable kit for the Pylontech seems to retail in the range of AUD$72 to AUD$90 which, to my mind is a bit over the top for a cable that clearly isn't going to work well if more than 3 x US3000C units are installed in parallel. Additionally, the cables are way longer than I really need as I'm running busbars close to my batteries and can get away with just 500mm cable length. Finally, I don't need the RJ45 cable that comes in the kit either. I'll be using the Victron (recommended) cable for that. So, I'm biting the bullet and making my own cables.

For the princely sum of AUD$25 per cable I will connect each of my 8 x Pylontech US3000C batteries individually to my busbar (still using 25mm cable as specified by Amphenol.) Cheaper and more efficient than having 2 banks of 4 batteries and not much more expensive, but definitely more efficient, than having 4 banks of 2 batteries.

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wkirby avatar image wkirby ♦♦ commented ·

It's easy to run more than three US3000C modules. I have four. It's the system current that you need to account for, not the maximum current rating of the units.
Even though I have four units in parallel, my battery bank doesn't see more than 100A. I plan to put another US3000C unit in and the system current would still have a maximum of only 100A. If I increased my load or charging capacity, then I would have to change something.

That sounds like it will be a neat setup that you have in mind. Making you own custom cables is much cheaper indeed.

Pay particular attention to current sharing between the batteries when paralleling them up to a busbar that way and especially with short cable connections between the battery unit and the busbar, the resistance matching becomes more difficult to achieve.

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