Thanks for watching, if you want more content like this it would mean a lot to me if you would consider subscribing to my channel. For details of how I chose my battery system watch this: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-gnvTuAenYHI.html Watch this video for a break down of all the components that went into the system and the costs: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-2gSYZGaDVok.html&t
Good video. We started in 2018 and went for solar first looking to be able to generate as much as possible. We have 2x5kw inverters with 10.6kw of panels. For the battery sizing I used the average yield of the solar over the year to get the balance point for the size, this came out at around 25kwh. This means we have 6x2.4kwh pylontech and 3x3.5kwh and 5kwh pylontech which comes to just under 24kwh usable storage with 80% depth of discharge. For discharge rate the inverters can manage 7 to 7.2 kw, which is enough for most loads. We average 9.5MWh a year and our export started at 75% without batteries and is now around the 20% mark with the battery storage. Having the 24kwh means we manage winter days with charging on off peak and running the whole day on batteries most of the time. The odd snow day does not help, and if we wanted more storage we would need yet another inverter and battery pile to keep within the off peak window. I have wondered about using a bus bar for the batteries instead of linking them in parallel. The manual is not specific either way and in many respects putting them on a bus bar would reduce losses and likely protect the pile from generating hotspots. It is interesting that there is now a 12kw Lux inverter available in Europe and Austrailia which would happily to the same as my setup but with one unit. Car charging is an interesting one. The round trip efficiency of inverter and batteries is about 85%. It is still best to consume power as it is generated, there are less losses in general. For charging the car we normally either use cheap rate off peak on Octopus Go or set the car to charge using the Zappi during the day and know that the ebb and flow of the solar is soaked up by the battery storage. Between April and September we can average over 30kwh which is more than we need for the house, so charging the car from low to medium is easy enough. On a good summers day we can go from empty to full and still have power in the house batteries. pvoutout.org is a good research tool for sizing Solar and provides real world examples of generation and consumption. Finally there is heating. We have a mixergy tank, which I have to say is brilliant. We always have hot water and given we heat using electricity it is very cheap to run. We are looking at heat pumps at the moment but have yet to finalize on the unit. Cost wise, with load shifting and the solar, we save a lot on electricity bills. We reckon about 70% overall. Keep up the good work !
Sounds like a great system, I'm excited to get some solar added to my system. Thanks for the link to pvoutput.org/ I'd not come across that one before, looks like it could be very interesting. I've been using the output from re.jrc.ec.europa.eu/pvg_tools/en/tools.html to try and get an idea of how many kW of panels I might need.
Great to see the effort being made to show the different use cases… I particularly like the oversizing point… I wonder how many people’s setups rinse the batteries from zero to 100% each day potentially devastating the lifespan of their setups? I would like to see the battery capacity stay within 20-80% of that “actual” capacity… manufacturers usable capacity limits may obfuscate this calculation.
Thanks for watching and taking the time to comment. I think over winter I've been guilty of pushing my batteries too far, when it's cold and the heat pump is working hard they are easily going from 100% down to 10% in a day, It's why I want to add another 4 to provide that buffer and prolong their life.
My recommendation, is a battery with the capacity to meet your full electrical demand for 24 hours, without input from any power source. For most people, this battery will typically be discharged daily to 60% depth of discharge, with plenty of reserve. After reviewing cycle life graphs for Lead Acid batteries, that amount of capacity will yield the lowest possible cost per kWh of stored energy. Further calculations have shown, that this rule applies to Lithium Iron Phosphate batteries,(what yours are) or Lithium Nickel Cobalt Manganese, and I suspect, even Nickel Iron batteries. Once you've decided how much power your house can use in 24 hours, and have chosen a battery just big enough to supply that, it's time to size the photovoltaic array. (solar panels). I live in Northern Utah, in Western United States. For me, where I live, a solar panel will produce ~4 times its rated capacity in kWh in a day. More in the summer, less in the winter. If you have a 30 kWh battery system, it should be paired with at least 7.5 kW of installed solar capacity. If there's shadowing, or, you can't face the array South, (if you live North of the Equator) or North, (if you live South of the equator) then you will need to increase your installed solar capacity. Another huge factor, is your latitude. The farther from the equator, the more installed capacity needed, to meet daily demand. If you have an electric vehicle, consider adding your average daily power consumption from driving to the capacity of the (solar) battery.
Load shifting is a good idea whenever you have a cheaper off-peak tariff, but it has a lot or practical limits, for example we run our washing machine every night during off-peek, but often need a second load on during the day. For me our biggest load by far is the heat pump and you just can't shift that into the off-peek period.
I have 4x my daily consumption , and the ability to charge 50% of that in 5 Hrs, so being able to get 2 days of charge in that time for the cheapest price possible. saving money that way. so 100 KWh is what we have in the garage.
I recently wrote a simulator that pulls in historical solar, tariff and usage data then simulates generation and battery usage over a year at 30 minute intervals. I played with a lot of different scenarios. Currently the best payback seems to be Octopus Flux, filling the batteries on the cheap rate then running them empty in the evening rate with solar either topping off the batteries or going straight to grid when the batteries are full. The tricky bit is making sure the batteries hit minimum right at the end of the peak evening rate. In the winter you lose a lot if you just dump them at the start of the evening rate. The optimum battery capacity seems to 2-3x the inverter charge/discharge capacity. Increasing the battery to try to time shift any extra solar generation has poor payback. I experimented with octopus agile but the payback isn't anywhere close even if you spend a lot of time tweaking values depending on current pricing. My current planned system is 8kWp solar with a 6kW inverter (5kW battery charge/discharge rate) and around 10kWh usable from the battery. I'm still waiting on the G99 application. Here are the estimated battery payback figures for a few battery capacities with my setup on Octopus Flux at current rates: 5kWh: £330/year 10kWh: £590/year 15kWh: £800/year 20kWh: £863/year 25kWh: £872/year Interestingly solar generation has surprisingly little effect on battery payback. For instance with zero solar 10kWh pays back about £520. It all comes down to the difference between night rate and peak rate. If that tariff goes away, so do your profits. These numbers don't include the profit from solar generation. They are just the added payback you get from the system by adding battery storage. They also don't include depreciation or any allowance for the cost of the installation.
Hello Rod, Thanks for your very detailed and helpful explanation. Have you looked at / considered using busbars for your battery banks rather than daisy chaining them? There are a few videos that seem to show that you lose less energy from the cooler cable runs and more importantly the batteries charge and discharge more evenly, rather than from top down or top up. Happy to subscribe and follow your journey!
Hi, I didn't really considered it and I'm not sure the benefit is worth the added cost and complexity, I might look at changing my design to have 3 or possibly 2 batteries chained instead of 4, probably a reasonable compromise. But even that is an expensive upgrade for a small efficiency boost that might never pay for itself. I need to do more research before making a decision. Really appreciate the subscribe and thanks for watching.
Hi Rod, interesting video as always. Quick question - it looks like you have your US3000C's set up in two banks of four modules. And it also looks like you have the four modules in each bank daisy-chained with the Pylontech standard cables. Since these cables are only 21mm2 and rated at around 100-125A, what fuses do you have in the fuse carriers to protect them from overload? I ask because I have two US5000 modules and I ended up buying a Lynx Battery In which I converted to become a Lynx Distributor with 125A mega fuses protecting two sets of battery cables, one for each battery module. In other words, I decided not to daisy-chain my US5000 modules because I felt like that was at risk of overloading the cables. The US5000 can charge and discharge at 100A (80A recommended) so if I had daisy chained my two modules together, that's 160-200A on a set of battery cables rated for 100-125A. I realise I can control the charge and discharge rates in software but I still felt that from an efficiency point of view, I needed more than 21mm2 of copper between my batteries and my main bus bar. I only have a single Multiplus-II 5000VA inverter so my charge current will never be more than 70A from that, but I'm about to install a solar PV array with two MPPT 250/60 charge controllers so in theory could be pushing 120+70 = 190A although it's very unlikely I would be charging from the grid and from solar at the same time. The other factor is the maximum inverter DC draw which normally will be around 100A at full power, but in off-grid or islanding mode, it could go considerably higher as it can run at 9000w for a short period. That equates to around 180A of DC draw for a single inverter which is the main use-case my extra set of battery cables is designed to accommodate. Lastly, I don't know about you but I do worry a bit that companies like Octopus might not be able to sustain schemes such as Octopus Go and therefore there is a risk that designing a system around the existence of such a tariff could be unwise long term. That said, I've been on Octopus Go for several years and am currently on Octopus Go Faster 5h which gives me 5 hours of electricity at 8.25p/kWh between 21:30 and 02:30. That time slot allows us to also run washing machine, tumble drier and dishwasher without needing to have those appliances running while we are asleep which I was never comfortable with. But I see that Octopus have apparently stopped the Go Faster tariff so who knows what will be on offer in August when my current tariff expires. Hopefully by that time I'll have solar up and running which will help for sure. We also have an EV btw. Sorry, that "quick question" took longer than expected... 😂
Hi Craig, I think you should probably win a prize for the longest comment I've had yet 😂 I believe the cables are AWG4 25mm with a high spec insulation that allows them to run at high temperatures, the cables themselves can handle 178A but the connectors are only rated at 120A, so Pylonthech advertises these as 120A cables. You are correct, I currently have a single set of cables on each bank of 4 US300Cs. The fuse carriers have 125A fuses which should be more than adequate to protect the cables. If I was just looking at the ability of the batteries to deliver or absorb current, 3 US3000Cs would be 111A and the 4 I have in each bank can do 148A so a bit over the rating of the cables. With my current setup, with 2 MP2 5000s my max charge rate is 140A but split across the 2 banks so only 70A for each set of cables, I currently have my parallel MP2s configured with a max draw of 9000W and the max DC current I've ever seen is around the 200A I would expect, so again this is bellow the 120A rating of the cables. I've not decided yet what MPPTs I'll get but with your example of two MPPT 250/60, the max charge rate would be 120A, but realistically a fair bit lower as some of that 120A will be going to the inverters to run the house, so split across the 2 banks that again should't be a problem. I would not be planning on running the MP2 in an overloaded state for any length of time. The 9000w peek rating on the MP2 5000 is only going to work for a very short period of time (
@@RodMcBain haha, yeah it wouldn't be the first time for me that a "quick question" was anything but! 😂 Just some "quick" follow up below. Note this is not meant to be argumentative - I just want to improve my understanding and I can see that you know your stuff! The cables are indeed 4AWG but this equals 21.1506mm not 25mm. I know this because my first attempt at a DC distribution required me to cut the Pylontech cables and install my own lugs. These were 25mm attached with a proper hydraulic crimper but were loose and I had to go to the 16mm crimp die to squeeze them up a bit further. I guess I could have sourced AWG lugs and a crimp die but didn't seem worth it. So I expect that will reduce the current capacity a bit. I know they state 105C on the insulation but do we really want our battery cables running so hot? That heat will raise overall temps in my cupboard and represents power losses. I've certainly noticed quite a difference in the temperature of my battery cables since I switched to one pair of cables per battery module. There is also voltage drop and ripple to think about. Where did you get the 178A figure from? From the BS7671 OSG I see that even 25mm cable clipped direct only has 114A rating or 146A if on a ventilated cable tray spaced apart. Again, I acknowledge that the quality of the Pylontech cable is probably a bit higher than this but as mentioned above, the CSA is 21.1mm not 25mm. I thought I read somewhere that the Pylontech cable was rated at 120A but the Amphenol battery connector was only rated at 100A but I could be wrong. Your setup sounds fine honestly. Sizing DC distribution is a bit different to AC and with BMSs and other software involved, there are a lot of relevant factors and mitigations to consider. I'm just keen to reduce round trip losses and keep my cupboard and equipment cooler. Still learning though... My MPPT setup is really designed to avoid having more than 2 parallel strings which then requires diodes and/or string fuses which makes the solar distribution a dog's dinner IMO. It's different if using optimisers but we can't use those with Victron MPPTs as far as I am aware. I could have gone to a larger MPPT which would have been marginally cheaper than two 250/60 units but I like the idea of having a bit of redundancy in the system so I can run on one MPPT if the other failed for example. Two smaller MPPTs also fits my available space more easily than a larger unit. I will have 16 of 425w Trina Vertex S panels split into 4 strings of 4 panels with 2 such strings feeding each MPPT. So 4 series, 2 parallel per MPPT essentially. That gives me just over 200V open circuit at -10C which is well within the 250V max of the 250/60. And I don't need any diodes or string fuses or combiner boxes etc. Max current from PV to MPPT will be just over 21A per unit so within MC4 spec so I can just use a Y connector to combine the series strings. I'm using 6mm solar cable as my runs are quite long (~30m) and 10mm 4 core armoured cable to bring the strings under the ground from garage where the panels will be mounted, to the house. So there you go - my "quick" follow up! 😂
@@craigchamberlain I don't know what size the cable "really" is, I guess the only way to know for sure would be to measure the diameter of each strand, work out the area and then multiply by the number of strands to get the true cross sectional area of the cable, for obvious reasons I can't be bothered with that 😂 I'm just going by the advertised spec and writing on the side of the cable. I purchased my cables from Bimble solar, they advertise them as 25mm and sell them in bundles with 25mm lugs ( www.bimblesolar.com/pylon-cable-kit-2-modules-US2000-US3000 ). They also state the spec as 100A continuous and 125A peek, so I'm happy that still falls within the current my inverters will draw. The 178A figure came from an answer here ( community.victronenergy.com/questions/41642/pylontech-battery-cable-spec.html ) by Guy Stewart (Victron Community Manager), but either way it's just vaguely interesting, doesn't change usable rating of the cable. I'm certainly not arguing that more battery cables is wrong, It's never going to hurt and like you said running less current through each cable will reduce losses and the cables temp. So even if I'm safe to use 1 cable set per 4 batteries I would be better off with more, it just adds cost and complexity, but is something I might consider in the future. I have been swithering between a larger MPPT with multiple trackers or several smaller ones, I think like you I'm leaning towards multiple smaller for the same reason.
@@RodMcBain yeah I'm only going by a website which converts AWG to mm2 but as you say we'd really need to know the individual diameter of each strand and no of strands. Not keen on doing that either! 100A continuous and 125A peak seems fair to me - not sure I'd want to push 178A continuous regardless of what Guy says. I'm active on the Victron forum as user "craigc" by the way. I certainly don't think your setup is unsafe and you are more than savvy enough to recognise if temps or voltage drops or whatever was becoming a problem. If I had US3000C batteries I would probably have gone with a bank of 4 as you have, and I'd probably be fine with those all on one cable set. But I plan to add a third US5000 to my setup later in the year once I have solar PV installed, and I definitely shouldn't put three US5000's on a single cable set and didn't want to have a setup with two on one cable and one on a second cable for balance reasons. So that's why I have invested now in the pair of Lynx Power-In units and will have each battery on a separate connection via a 125A mega fuse and then the other four connections will be for the inverter and two MPPTs with a spare connection for a third MPPT (maybe wind turbine or a wall mounted "winter PV array"). Really looking forward to getting the solar PV installed although the weather recently in sunny North Ayrshire hasn't exactly been conducive to PV generation...
@@edc1569 Doesn't that leave you open to cable failure under continuous loads which are above the cable rating but below the fuse rating? Fuses are normally designed to accommodate overload of varying amounts for a certain period before blowing. For example, the Littelfuse 70V-SF51 which I use to protect my Pylontech battery cables is rated as follows: % of rating Breaking time min to max 75% Infinite 100% 4 hours to infinite 135% 2 mins to 30 mins 150% 20 sec to 450 sec 200% 1 sec to 15 sec 350% 0.3 sec to 5 sec 600% 0.1 sec to 1 sec So, in my opinion we should select fuses rated for the maximum expected continuous, non-fault current and let the design of the fuse handle fault conditions.
Not sure about your comments on supporting an EV. We’ve been off grid for a number of years now and I’m looking at getting an EV and what changes I’d need to make to the system to support an EV. I plan to add more panels to support charging but also I want to add around 20kWh of storage to capture the solar energy as most days the EV will not be at the property during the day. Without the battery storage, the EV will get very little solar energy.
I think the point I was trying to make was there are inefficiencies involved in charging and discharging a home battery. Charging a home battery and using that stored energy to charge your car battery is best avoided if possible, every time you do, you're slightly degrading both batteries and losing energy in process. But in cases like yours where there is little other choice it can be done.
Use case 2 is pointless in my opinion - whilst it feels nice to have a few days of stored energy in the case of crap weather, if you’re grid connected then having an oversized battery will never use the full capacity - the payback is far higher - I have 4kWp of PV which over 10 years has sufficed for daytime use and free hot water for 250 days of the year. In November last year I added a US5000 (4.8kWh) to cover the 2.5-3kWh of overnight use - winter was pretty grim but importantly it reduced import massively although the battery takes precedence over the HW diversion so more gas was used 😞 That said in April we imported just 0.1kWh of electricity and had to use gas for HW on just one day so I’d say the sizing is pretty spot on 👍 It would be nice to store extra once we start exporting on a bright day but still pointless unless we use the extra overnight - it may as well go to our neighbours - the DoD is set to 20% and only very occasionally did I let it drop to 10% knowing that the sun was coming up that day 😊
I get what your saying and I think I did describe it as an extension of use case 1 and also mentioned that in most cases it's probably not going to be cost effective by itself. It almost doesn't deserve to be a stand alone use case but is certainly a useful case to keep in mind when combining solar and time shifting in winter. With current prices time shifting your winter grid consumption alone justifies the cost of a larger battery so the fact that you can make extra use of that storage in summer for use on overcast days or as backup power is a big bonus worth keeping in mind.
@@RodMcBain I think it was more for the benefit of others - there does seem to be a mindset of bigger = better with batteries - it’s similar to the EV use case where everyone wants comparable range to ICE based vehicle but that range will rarely be used in one go and it just results in inefficiency with lugging the extra weight - for a static battery that’s not the case but extraneous capacity is still a wasted resource if it’s only rarely used. You touched upon V2x which I think will be the killer application since most EVs will have a battery far greater in capacity than a domestic property will ever need - with the EV and an adequately sized static pack this would solve the dilemma - for some people at least 🤔
With so many variables, this is going to be different for every house. It's also worth considering that it's not always about saving money, although admittedly that's usually going to be the main driver in someone getting batteries.
I have a strong opinion on this subject - we should only use the materials that we need to not just load up on batteries because we have an addiction to ticking scenario boxes of. The load shifting saving is impressive but those batteries are £1500 a piece! It will take years to break even and really most people only need 1 or 2 of those pylontecs. We have limited resources we shouldn’t be hoarding these to cover doomsday scenarios. The grid is extremely useful and good value. The costs of effectively deleting it at no loss of convenience is HUGE!
That's an interesting perceptive, not sure I agree.The grid is great but also massively inefficient, the generation and transmission losses in the network are huge. Some of the most wasteful and pouting grid level generation is needed to smooth out dips in renewable generation and peeks in demand. Having localised generation and storage would go a long way to mitigating a lot of this waste and pollution. Hopefully going forward the government will sort out the energy market to start insentivising feed-in from clean local storage instead of firing up coal fired power stations, tariffs like Octopus Flex are starting to head in the right direction, with higher feed in tariffs during peek demand. The solution to the climate crisis lies in technology, not in being frugal.
Possibly not, but who said this was only for people building their own battery systems, if you're going to get a third party to do the installation it's better to go into that having a good idea of what use cases you want to support and have some idea of how much storage you want installed.
Hi Rod, really enjoyed the video -watched it a few times. I am a total newbie to solar and battery charging etc and recently installed the following: 8 x 430w panels Jinko JKM435N-54HL-4R-B Tiger Neo 435Wp TOPCon N-Type 54cell all black Monocrystalline Inverter Solis 3kW SOL-3K-RHI-48ES-5G-DC EH1 Hybrid 5G inverter Battery Pylontech 4.8kWh Pylon US5000 4.8kWh Li-ion solar battery 48v I have a question regarding the current AMPS for charge and discharge as I have been advised that the battery max is 80Amps. But I should set it to 50Amps. To reduce battery wear and degradation. I'm working out how much energy I need at home to run from battery as I feel 1 battery may not be enough. I've only had the system for 2 months now and its winter time in UK -so won't get much insight into the amount of solar charging I get. Finally, am I right in thinking that a 3kW inverter will restrict the battery charging and therefore if I add another battery the same would apply? I'm a total novice and don't understand it all just now! Any guidance provided based on your experience will help. Thanks
Hi, The manual for the US5000 recommends a charge current of 50A with a max sustained charge current of 100A, it's probably a good idea to stick with the recommended 50A unless you need more. However your inverter has a max charge current of 62.5A, if it were my setup I would be comfortable leaving the charge current at 62.5A, it's not far off the 50A and way below the 100A max. Working out how many batteries you need is complex, with many variables to consider, that's one of the great things about the modularity of the pylontech batteries, you can start small and work your way up to what works for you. Just watch constraints on your inverter, it won't be long before its bottlenecking how much you can charge / consume from the batteries. If you added another US5000 you still only have 62.5A available from the inverter so each battery would charge at 31.25A.
Hi Rod, thanks for your response. I will read it a few times. I have also asked Solis support to change the Solis inverter AMPs to 50. Will come back to you in due course. Thanks again
