Generic home battery wiring diagram? - Page 1
Forum section: electronics / general

author: Kirkhaan
author_rank: Frequent Contributor
timestamp: November 11, 2018, 09:23:05 pm
content: I'm looking for a generic home battery wiring diagram. Does anyone happen to have a good picture?I just want to better understand how such system typically looks like.I've already checked the documentation of Tesla Powerwall and some others, but they only show pretty high-level installation pictures.The most comprehensive diagram that I've found so far is fromFenecon(attached).Thanks in advance!

author: digsys
author_rank: Unknown
timestamp: November 11, 2018, 10:44:37 pm
content: Try these people ...https://secondlifestorage.com... you may get a lot of valuable information / ideas from them.

author: electrodacus
author_rank: Super Contributor
timestamp: November 12, 2018, 08:04:33 pm
content: Why will you want to add a battery to a grid connected house ?

author: NiHaoMike
author_rank: Super Contributor
timestamp: November 13, 2018, 03:47:31 am
content: Quote from: electrodacus on November 12, 2018, 08:04:33 pmTo not have to rely on the grid as much, either in case it goes down or as a step towards going off grid.

author: HackedFridgeMagnet
author_rank: Super Contributor
timestamp: November 13, 2018, 04:06:48 am
content: Quote from: electrodacus on November 12, 2018, 08:04:33 pmOften there are different tariffs at different times.Also sometimes if there is a high level of Solar Generation in an area the voltage goes over the allowable limit and the grid will not accept more. In this case you could store energy and then feed the grid later.BTW i am not saying these will be cost effective strategies.

author: mtdoc
author_rank: Super Contributor
timestamp: November 13, 2018, 04:51:58 am
content: Have a look at some of thedocuments on the Midnite Solar website. Lots of stuff there but in amongst the other stuff are some detailed wiring diagrams.BTW - lots of scenarios where grid tie with battery back up make sense - either due to being in an area where grid power is unreliable and/or because of financial incentives offered by utilities for home power production.

author: electrodacus
author_rank: Super Contributor
timestamp: November 14, 2018, 05:18:07 am
content: Quote from: NiHaoMike on November 13, 2018, 03:47:31 amQuote from: HackedFridgeMagnet on November 13, 2018, 04:06:48 amQuote from: NiHaoMike on November 13, 2018, 03:47:31 amAs long as there is already a grid connection it will not be cost effective to connect a grid battery.For example a Tesla PowerWall 2 including accessories and installation costs with have a typical cost amortization of at least 55cent/kWh (I can provide a detailed calculation if anyone is interested).That means that each kWh you get out of the battery will cost you 55 cent/kWh + the amount energy you put in cost's.Using the available solar PV as needed directly by the house and exporting the excess to grid is way more cost effective than involving a battery even if the grid pays nothing for excess and grid energy is very expensive.Having a DIY type battery is not acceptable for the grid but even then with best LiFePO4 you are still looking at around 20 cent/kWh just for the battery cost amortization and you need to add an inverter/charger also that has his own additional cost amortization.Going offgrid is a different story as there you will need a battery.I'm fully offgird with my own custom solution that includes PV heating not just electricity but in order for this to be cost effective (and it is actually the most cost effective energy solution) I used thermal storage for the heating part that only has a 1cent/kWh amortization cost.I have a small energy efficient house 65m^2 (~700sqft) close to passive house standard of insulation and my total bill (amortization cost for the life of the system that was paid in advanced) for heating + electricity comes to around $42 about half of that for heating and half for electricity.To be even more precise the cost for electricity is around 17.5cent/kWh and for heating around 4.2cent/kWh thus electricity similar to grid price while heating better than natural gas.And as a disclosure yes my open source project is available onKickstarterso you may think I'm biased but I can prove all the claims about my system. I also need to note that to get to this low costs only material costs where included no labor cost so is in case of DIY.Battery cost will need to drop dramatically in order to be cost effective in grid connected systems and still best type of battery LiFePO4 has the same cost it did about 7 years ago when I got my first test cells.Grid in most countries is extremely reliable and I never had more than a few hours not even once a year with grid down time while I was grid connected in the past.

author: kripton2035
author_rank: Super Contributor
timestamp: November 14, 2018, 07:18:39 am
content: I was looking for a system like a PV priority system over the grid.you buy solar PV when you can afford them.you have the grid, but each time there is enough PV energy, you use them in priority over the gridyou need some small battery to switch from PV to grid without power lossI did not find any schematic for some device like that, that could handle some 5-10kWh for small houses.anytime, you must sell your pv energy to the grid company, or you can use all of it.

author: electrodacus
author_rank: Super Contributor
timestamp: November 14, 2018, 07:35:28 am
content: Quote from: kripton2035 on November 14, 2018, 07:18:39 amAll PV power from a grid connected system will first provide the house and if there is any excess that will be exported to the grid.No battery is needed and any currently available battery added will make for a bad investment.

author: Kibi
author_rank: Unknown
timestamp: November 14, 2018, 04:07:22 pm
content: Quote from: kripton2035 on November 14, 2018, 07:18:39 amI think you are after an Energy Storage System or "ESS"I have a Victron based systems running. I have AC Coupled PV on the output of the inverter so that PV still powers loads and can charge battery by backfeeding through the output of the battery inverter even in a grid network failure. I also have more conventional DC coupled PV via MPPT charge controllers. I do not have PV on the grid side.Here is a good diagram:https://www.victronenergy.com/blog/2016/12/12/ccgx-v2-00-ess-and-many-more-improvements/

author: kripton2035
author_rank: Super Contributor
timestamp: November 14, 2018, 04:31:36 pm
content: and there are none simple DIY pv-grid switch ? only pro systems ?

author: NiHaoMike
author_rank: Super Contributor
timestamp: November 15, 2018, 03:35:26 am
content: Ohmconnect, where it's available, seems to be one of the few instances where a fairly small battery (on the order of a few kWh) can pay for itself in a reasonable time. It's a program that rewards users to conserve energy for up to an hour per week in order to reduce the peak load, and using a battery is one solution to dropping the load to zero in that time. (Presumably, it could be possible to export energy for even more points, but last I checked, that's not supported.)

author: electrodacus
author_rank: Super Contributor
timestamp: November 15, 2018, 04:19:07 am
content: Quote from: NiHaoMike on November 15, 2018, 03:35:26 amIf you are using a battery then you are not conserving energyStill based on a short search and reading about Ohmconnect it will not seem like there will be much if any gains to be had. They look at your past energy usage and estimate (forecast) what you will be using at a certain hour where they think in next 24h may be a peak and that is typically less than 1kWh for that hour from the example I seen and it makes sense so your savings assuming you switch off everything for that one hour is less than 1kWh and the reward is some number of points.Now that mean you can save best case around 300kWh and assuming that will be rewarded with say 50cent/kWh in average that will get you around $150/year (a fair bit of work to actually replay to those requests and deal with the savings).Now in about 10 years you may save $1500 (assuming Ohmconnect will still be around in 10 years) so not much of a battery can be had for that including inverters and other equipment so I doubt this will save anything most likely have quite a bit of loss.Also if they (grid company) can pay this amount or better (Ohmconnect gets his own cut) then they will be way better off with investing in their own battery that will be way more predictable and cheaper.

author: Kirkhaan
author_rank: Frequent Contributor
timestamp: November 15, 2018, 06:56:11 am
content: Thanks for all your replies and stories!Background of my question is an upcoming (DIY) renovation of my house.I want to make sure that I take future installation changes into consideration and e.g. have enough empty electricity pipes running through my home.At the moment I only have grid connected PV panels and I am exploring what my next step could be.For me the cost-effectiveness is not the most important. I worry about climate and want to contribute my bit, even if this is at an expense.

author: electrodacus
author_rank: Super Contributor
timestamp: November 15, 2018, 07:38:18 am
content: Quote from: Kirkhaan on November 15, 2018, 06:56:11 amUsing less (including energy) is the best way to do thing if you worry about climate.As an extreme example driving an old inefficient 8 cylinder vehicle just 3000km / year with be way better than driving 10x more 30000km / year in an EVAdding a battery is not only a bad investment but also not helpful for the environment. Grid can do a much better just for storage than you can do so if storage is needed they can add that much better.It may be the case that grid can no longer compete with individual off grid but for short therm that will only happen in the rural areas and cities will need to have at least micro grids because of the way cities where designed.My motivation was to reduce my costs as close as possible to zero and do that in a cost effective way and as a side effect my impact on climate is very low.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: November 19, 2018, 05:34:32 am
content: Math is a dangerous thing. Electrodacus, I have not checked your spreadsheet, but I do not dispute your calculations. However for your blanket statement that local storage never pays to be true you must have assumed one or more of several things. Including, but not limited to:1. Grid power is reliable2. There are no costs for loss of electric power3. Cost of energy are not wildly variable with time.There are places and people who find one or more of these assumptions incorrect. One of the most blatant examples is large businesses which pay a lot of money to have utility lines routed to their business from two or more different substations to reduce the likelihood of a substantial power outages. (Actually in my location they negotiate a contract with the utility which has large penalties for non-delivery of power and the utility then decides how much extra equipment to use to get best return on the contract, but that is just a detail of how the money flow is managed.)Each person or business making one of these economic decisions must understand how they allocate value to a wide range of things and how the costs of various solutions vary in their location. In some cases the answers will be wildly different for different entities.

author: electrodacus
author_rank: Super Contributor
timestamp: November 19, 2018, 06:27:22 am
content: Quote from: CatalinaWOW on November 19, 2018, 05:34:32 am1. Seems to me as a good assumption to make in a developed country. The only reason for an outage are extreme weather events and even with those grid is back in a few hours.2. Most people will not have a significant loss if power is lost for a few hours and even if that is occasionally the case a generator while expensive in $/kWh is way more cost effective as this only happens maybe once a year.3. Cost of energy is a bit variable but not to the level where $0.55/kWh best case for a TeslaPower wall amortization will make sense.Even if there are small exceptions for the large majority of the cases over 99% it will make no sense to consider grid connected energy storage.Problem is most people do not understand this and think that adding battery storage to a grid connected solar installation will have economic benefits when the opposite is true.Math is never dangerous

author: NiHaoMike
author_rank: Super Contributor
timestamp: November 19, 2018, 02:39:07 pm
content: Quote from: electrodacus on November 19, 2018, 06:27:22 amYou can easily buy a kWh or two of Nissan Leaf modules for the price of a cheap propane generator, let alone a good one.I'm surprised Tesla isn't targeting RV owners for their Powerwall solution. It's easiest to compete against the grid when the grid is often not an option.

author: electrodacus
author_rank: Super Contributor
timestamp: November 19, 2018, 06:53:52 pm
content: Quote from: NiHaoMike on November 19, 2018, 02:39:07 pmMy point was that typical one or two hours once a year will not require any backup if backup is needed for longer blackouts say a day or two once or twice a year then a cheap gasoline generator will be way more cost effective (never mentioned a propane generator but those are also inexpensive as they are basically the same thing).A small battery + inverter / charger (UPS basically) will not be able to deal with more than a few hours backup for a fridge or something like that.Powerwall was not designed for offgrid (they had a version for that but decided not to release that version). I do not think they can even deal with the demand for grid connected PowerWalls so why will they get complicated. Also they need an internet connection at all times so they can monitor and update the PowerWall not so easy to do for RV's

author: CatalinaWOW
author_rank: Super Contributor
timestamp: November 19, 2018, 07:34:14 pm
content: It is funny how things work sometimes. In my fairly remote location I was experiencing brief outages (from minutes to hours) several times a year, and not terribly distant neighbors experienced outages of up to a couple of days. I found a too good to pass up deal on a gasoline generator sufficient to run the refrigerator, freezer and water pump and in the subsequent three years power has been rock solid. Best preventative purchase I have ever made.

author: dekra54
author_rank: Unknown
timestamp: November 20, 2018, 04:21:42 am
content: Quote from: Kirkhaan on November 15, 2018, 06:56:11 amI think for future planning the high level diagrams provide enough information as the detailed installation diagrams are very different for each manufacturer.If you run a 5x6mm²,2 Ethernet and maybe a 2x2x0.75mm² Phone cable to the point where the Storage will maybe in the future you are "safe".Most of the systems require a Power connection (should be obvious), a Network connection to the Internet and 1 or 2 network or RS485 connections to the Main distribution Panel for Metering. Completely off grid will not be happening in the near future i think.

author: NiHaoMike
author_rank: Super Contributor
timestamp: November 20, 2018, 06:05:20 am
content: Quote from: electrodacus on November 19, 2018, 06:53:52 pmI mention propane since it stores for an indefinite period of time, unlike gasoline. Gasoline is actually a poor choice for something used infrequently since it never seems to work when you need it...I also don't see why an off grid Powerwall would need any IoT absurdity. Make it accessible on the LAN, sure, but I see no value add in connecting it to the cloud. Even the on grid version just needs a very limited bit of cloud connectivity to coordinate to grid conditions.

author: electrodacus
author_rank: Super Contributor
timestamp: November 20, 2018, 06:10:46 am
content: Quote from: NiHaoMike on November 20, 2018, 06:05:20 amIt is not needed but Tesla wants all the data generated so if you want the warranty they require you to be connected to them.

author: dekra54
author_rank: Unknown
timestamp: November 20, 2018, 06:19:11 am
content: Quote from: electrodacus on November 19, 2018, 06:53:52 pmTechnically there is absolutely no reason for that you're right. But the Powerwall system that our Company installs has some nice features where this is needed.You can "send" the power generated at your home to I think two other households but this has to be calculated on time (how much power is generated and consumed at the moment ). You can use "your" power at different EV charging stations to charge your EV. And you can use the "Storage Cloud" where you can store your PV generated power beyond your battery capacity and get it back later for no additional cost.And I know technically it isn't your Power that is beeing used to charge your EV or send to other households but it is billed as it would be.