Pylontech Cabling Master Class

Pylontech's 48 Volt batteries have unique cabling features. This video provides a thoroughly considered approach to sizing and wiring your battery bank.
📍Related Reading | Adding Capacity to a Pylontech Lithium Battery Bank: icmontana.com/blogs/technical...
Video chapters:
00:00 Introduction
00:12 What's included with each battery
01:11 What's purchased separately
2:44 Two batteries and one cable kit
3:44 Three batteries and two cable kits
4:03 Plylontech's power managing BMS in the real world
7:14 DVCC teaser
8:42 Five batteries and three cable kits
9:54 Avoiding bad math and sizing for success
11:50 Have questions? We've got answers.
#pylontech#lifepo4battery #cabling #energystorage #offgrid #offgridsolar #victronenergy

[@philiprothwell291]

This video covers a valid point. It's all about redundancy, especially in harsher climates. I can understand in extreme cold climates it's not always possible to climate control the battery room leading to reduced capacity and even a battery shutting down due too cold to charge a possibility Here in most of Australia due the hot summer weather 3 months of the year we always DERATE everything to 70% MAXIMUM CONTINUOUS current. That is BOTH with the batteries and inverter being usually in an air conditioned room set to a max of 27 degrees C when it can be 45 outside for the hottest hours of the day. When it's hot we have so much sun and long days so climate control of the battery room is so easy to do as we have surplus solar power. We always look at the best outcome for longevity of life for the hardware and reliability of day to day use as a worst case weather situation. Interestingly my Pylontech US5000-B battery label states 50 amps is the preferred CONTINUOUS CURRENT per battery and 100 amps Max , so my spec across 3 batteries is 150 amps x 48volts = 7.2Kw @ 240 volts is it's comfort zone. There is also up to 200 amps PEAK rating per battery for "seconds" on top of that and the inverter can do 22Kw peak to cope with induction motor starts such as air compressors, water pumps or large power tools and even welders My 3 x US5000-B batteries run 2 sets of end run cables giving 240 amps (cable amps continuous) that feed an 11kw inverter that is feeding a home demand load max CONTINUOUS LOAD of 7.2Kw (approx 70% max load) or what we call a (very common) 240 volts 32 amp circuit. This is fine for a small 120 sqm home. You will need double that for a large 240sqm plus family home with air conditioning by far the biggest current draw with cooking after that. Heat pumps are used for hot water and excel in hot climates using only 1-3 kwh per day so are not big power users. So even if 1 battery were to drop out of the 3 it would not be noticed in the home as 2 batteries can easily supply 75 amps each. Not ideal for longevity but any battery issue would likely be fixed in days or weeks and not months or years

[@nicklegrand5017]

@intelligent Controls very interesting video.. thx! one question though.. I have 6 batteries (US5000) and 4 sets of end runs in a 3 phase system with 3 Multiplus II 5000. do I need extra sets of end runs to connect 6 more batteries? I don't want extra power, just more storage. The power is limited by the Multiplus imho. I will not be using more amps with 12 instead of 6 batteries, right?

[@MikeKing-IC]

Something I forgot to mention near the end. Standard procedure is to fuse every set of end runs with a ~120A fuse. If you get your math wrong like I illustrated around 9:54 but took the time to fuse everything, all that will happen is a blown fuse rather than melting insulators. Stay safe out there!

[@ronaldod7116]

I can only find megafuses available of 100A or 125A. What should i choose?

[@MikeKing-IC]

@@ronaldod7116 125A megafuses are the way to go.

[@philiprothwell291]

We are lucky in that the Pylontech US5000-B model (specced and supplied just for the Australia standard) has the addition of a factory installed 125A circuit breaker on the front panel. Just wire straight to the inverter.

[@aFlynn1000]

Great video! I just have a question regarding connecting the end runs to the inverter through a Victron Lynx Distributor. Would I put both end runs on the end of the distributor at the same point(where the red and black covers are) or would I run them separately with fuses for each? I'm using Pylontech US5000B that have breakers.

[@nickwalton9330]

Great videos about PylontTech. Just one consideration for the feature of the BMS managing power distribution across different cable lengths - if the discipline of cabling is maintained where the installer does keep lengths the same, any BMS failure could be mitigated by the fallback physical implementation. Does this sound reasonable or does the BMS not really fail in this way (or are there safeguards in place)?

[@intelligentcontrols]

Hi Nick. The TLDR is that the BMS does the majority of balancing by just getting out of the way of physics so there is no wear and tear occurring. If the BMS board fails, you can't charge/discharge the battery anyway due to the now-deactivated MOSFETs, so there's no real advantage in planning a system to be redundant in that way. In a low-voltage parallel system, the natural balancing flow of current between batteries with a voltage (state of charge) imbalance will be more than enough to make up for any reasonable imbalance that comes from wire resistance IF the BMS allows it to happen. Most BMS boards are mated to cells that they are not truly calibrated for and make up for this with stricter safety protocols. This is why most batteries will throw an error code and isolate when this type of balancing is detected, hence the necessity to ensure that such imbalances never happen in the first place by being super consistent with wiring, aka that physical implementation you identified. The genius of the Pylontech BMS is that it is mated to and calibrated for their own in-house, self-manufactured cells, which allows them more room for these natural balancing flows to occur without creating a safety issue. If something were to go wrong, or for more aggressive active balancing, they also have the ability to close off the MOSFETs and isolate a single unit from the charge or discharge state of the battery bank until the other units come into enough parity for passive balancing to commence. By combining the ability to allow passive balancing to naturally occur, supplemented by active isolation-based balancing, we get some freedom from the normal constraints associated with most LFP batteries such as needing to match wire lengths or cycle counts/ages for the batteries in a bank.

[@jamesphillips2285]

Do the "shorty" connectors have some kind of communication you did not mention? How do the batteries know how the 120A cables are connected?

[@intelligentcontrols]

Hey James, sorry I wasn't super clear on that point. The battery cables do not have any communication protocol in them. In a closed-loop system with Victron equipment, the batteries communicate, via CAN-bus, how many of them are connected and how much current they can handle. If one goes offline, the overall charge/discharge current is decreased to compensate for the reduced capacity. In a system where you have limited capacity for current due to your wiring, such as 2 batteries with 1 end run, the upper limit imposed by the cabling should be hard-coded into the Victron system. This way, the inverter will always default to the lower of the two values given by the batteries via DVCC and the hard-coded limit set by the installer. In our next video, we'll go over those settings.

[@_Miner]

What would the pros/cons be of connecting all the batteries as 1 single stack and then either having a single end run for the stack or 2 end runs for the stack?

[@intelligentcontrols]

Hey Miner, it all depends on what your max loads are. If your inverter is incapable of pulling more than say 80A and your charger caps out at 50A, then there would be no pros to introducing a second end run and just the cons of added cost. If your loads are enough to pull or push more than 120A that's when you start adding additional end runs. The BMS actively manages the loads on the individual batteries so there is minimal/irrelevant gain in power distribution by introducing more end runs.

[@bryangarcia4455]

Sorry, I don't understand why if I have 5 batteries I only have 3X120A, and if I have two batteries I have 240A. Why I can't divide 5X120A by five in this array of five batteries? Can you explain that again? Thanks.

[@intelligentcontrols]

Hey Bryan, Sorry for the confusion, all of this is dependent on how many end runs you are using. Each one of those sets of wire is rated to handle 120A, even if the batteries can provide more than that, you still can't pull more current from a battery bank than the end runs can handle. So, if you have 5 Pylontech batteries and 3 sets of end runs, you are limited by the 3x120A capabilities of the end runs. If, for some reason, you expected to pull more current, which is highly unlikely in the real world, you could add 2 more end runs and access the full 5x120A current capabilities of the batteries.

[@jillyanddavedave280]

I personally don't think the cables are heavy enough,if you have three 5 kw inverters you could make those cables act as heating elements, do they not make heavy cables??

[@intelligentcontrols]

@@jillyanddavedave280 If you have 5x 5kva inverters in a 3-phase setup, that's 15kva or less of continuous output power. The batteries are ~52v which is only ~290A. In this case, the proper battery size would be at least 3 to 4 US5000s. Each end run would be capable of 100A, but I would recommend that every 2 batteries get an end run to the distributor. For 12 batteries with a cable set for every 2 battery combination, that would result in a current capability of 600A continuous. They are small wires, but their current capability adds up. The other option that you and most are familiar with is to just have a larger interconnect, say a couple of 4/0, but then it's very oversized for smaller systems and still undersized for large systems. Remember that 12 batteries in Pylontech's world is still a small system when the LV combiner hub allows us to go up to 96. Small systems with a couple of US5000s with a 3k inverter will make most small cabins work wonderfully.

[@PavolFilek]

Problem with this BMS is, that is not capable to handle 30 - 50 AMPS balance current, if I have MPPT / chrager, that is not able to communicate. Also there is problem, if I connect 20 % and 85 % SOC batteries in parall. With 50 A balance current, you have job done after few hours, with small balance current you have to wait till summer.,

[@intelligentcontrols]

Hi @PavolFilek The nice thing about the Pylontechs is that the BMS will allow the natural physics of the parallel connection to not only siphon a small balancing current but also actively balance in a far more proactive manner using charge and discharge loads. I have spreadsheets of data showing your exact scenario with 20% and 85% SOC batteries coming back into balance within

[@extremehosting5525]

Wait hold on, are you selling ethernet cables as communication cables 😂

[@intelligentcontrols]

Depends on what you mean by selling. Most batteries use CAN bus, which is a pretty standard protocol. The extra comms cables in Pylontech’s cable kit are just tossed in for free as a useful addition to the end runs. The Victron BMS cable is something you could do the research on and then pin out and solder yourself from an appropriate network cable if you wanted. Most people would rather just spend $14 for the convenience. Your mileage may vary.

[@christsitouridis2213]

So you're saying that it is better to pay 2000 euros instead of 50 euros on cables? The way I see it is if you run every battery to a lynx distributor you can achieve with just 3 batteries what you claim you can with 5. Each cable can handle 120amps and each battery can deliver it just as long as they are not connected to each other. In your example the batteries can deliver up to 600amps if each connected to a lynx distributor or a power in with a fruction of the cost of adding a sixth battery. Why don't you propose that?

[@intelligentcontrols]

Hello Chris. This is a question of system sizing. There are 2 factors to be considered when sizing a battery bank. The first is the total power reserve or energy storage, and the second is the ability to deliver that power in the form of current. The number of batteries is the limiting factor for both energy storage and current delivery, and the cabling is the other limiting factor for current delivery. There are very few practical situations where current delivery needs to be equivalent at a 1C rate to energy storage. The current capabilities of the wire runs do not need to match the current capabilities of the batteries, if the energy storage capacity of the batteries is greater than what the system is designed to draw in 1 hour of continuous use. This is where you can experience savings with Pylontech’s cabling system. So yes, if you want 3 batteries with 14.4KW of power reserve hooked up to a system that will draw that down in 1 hour by pulling 300A or 14,400W/Hr of continuous current, then you buy 3 batteries and 3 end runs and go to town. In the more likely scenario where we have 3 batteries and the system is designed to pull a max current of 50A giving you 6 hours of power reserve, you just saved $100 because you only need to purchase 1 end run. So the rule of thumb is to size your batteries to your energy storage needs, and size your cables to your power delivery needs. If that is a 1 to 1 ratio, so be it. If not, that's a win for Pylontech’s cabling system.

[@christsitouridis2213]

Thank you for the reply. Indeed you size the batteries based on the energy reserve and delivery you want. But in your example having e.g. 5 batteries I think is not optimum to connect them the way you display since by connecting them to a bus bar, you maintain energy capacity but you increase greatly energy the delivery potential from 360 to 600 while still evenly distributing the power demand. Anyway that's my 2pennys worth

[@intelligentcontrols]

@@christsitouridis2213 Not a problem, thanks for the question. By the standards of most batteries, you would be absolutely correct. The cool thing about the Pylontech BMS is that it can use the MOSFETs to regulate power distribution so we don't have to worry about getting our wiring perfectly symmetrical for the sake of even draws. You certainly could wire it differently though, if your system was designed to pull 24kw of power in 50 minutes.