About Sonnen operating modes with Grid charging
Users have several different modes to choose from depending on their goals and usage. The sonnen battery system can charge from three primary sources; solar, the grid, or a generator (only in Back-Up mode). Which mode the sonnen is set to establishes the source of the energy in the battery. This blog will focus on modes of operation when the grid is up.
For purposes of this blog, I will be referencing sonnen’s Eco 10 or larger systems, and examples will be from my sonnen, an Eco 17.5 with a 9 kW solar system. My sonnen system feeds a protected load panel (PLP) which has the circuits I want backed up when the power is out.
There are three modes on a sonnen battery; Time of Use, Back Up, and Self-Consumption. Most of our users prefer the Time of Use (TOU) mode as it saves money daily, allows a buffer of stored energy for back-up power, and is arguably the most environmentally efficient. Back-Up mode is our second most popular option which maximizes back-up power stored for an outage and can also be used as a temporary option when outages are forecasted. Finally, Self-Consumption mode provides maximum autonomy from the grid, usually retains a smaller back-up buffer for outages, is considered environmentally efficient, and allows the maximum amount of power to be use/stored locally, minimizing importing or exporting to the grid.
Time of Use mode (TOU):
Let’s first look how the system works using the Time of Use mode. Sonnen is an AC coupled system, which means the solar first covers a home’s electrical loads before charging the batteries or exporting power to the grid. The order of using solar power is:
- Cover the household loads
- Charge the battery system
- Export excess power to the grid
For example, it is currently August and my solar system usually turns on around 7am. On sunny days, by 8am my solar power is producing more then my home needs and so my battery begins charging. My sonnen system can charge at up to 7 KW (kilo watt), which means my 17.5 KWH sonnen can be fully charged from solar on a sunny day in just over two hours and my system is usually fully charged by about 10:30am. From 10:30am until about 6:30pm I export power to the grid, receiving credits based on my PG&E rate schedule (I am on EV2).
At 6:30pm, rather than buying expensive power from Sonoma Clean Power/PG&E, I “peak shave” and use my battery power charged by solar, instead of the utility. At midnight my sonnen system gets to rest, and power for the home is imported from the grid (while it is least expensive) until my solar wakes up and begins a new day. I can also set a back-up buffer. (On my system, due to the current fires in the area I have mine set to 75%.)
Back-up buffer sets a State of Charge (SOC) floor and it will not discharge past that floor allowing me a comfortable safety net in case the power goes out. Another option available is to enable grid charging, which will allow you to charge at 250 watts per hour from the grid, per battery module during low tariff /cost windows. In most of our systems, this feature is turned off, meaning we are charging the battery from solar only.
Self-Consumption mode:
Self-consumption mode operates almost exactly as Time of Use mode, except it is not based on time (Time of Use mode is often called partial self-consumption.) In Self-Consumption mode, as long as solar power exceeds usage, the system uses solar to power the home. When consumption exceeds solar production, it will first discharge from the battery system down to your reserve buffer setting, regardless of the time of day (and PG&E rates) before drawing from the grid. So using my house as an example, if I were in Self-consumption mode, at midnight rather than my battery turning off in the example above, it would continue to discharge the battery until the solar system produces more power than my house uses or until my SOC reaches my reserve buffer. Self-Consumption does allow maximum autonomy from the utility, however this mode is the least popular option of our users as it is not as efficient or financial advantageous as TOU and leaves a smaller buffer reserve then backup mode.
Back-Up mode:
The sonnen system can also be set into Back-Up mode, saving 100% of the battery for power outages. Some of our customers have their system always in this mode, while others put it into this mode when PG&E announces a Public Safety Power Shut-off (PSPS), when rolling black outs are announce, or when other disasters occur. In Back-Up mode, the system will charge the battery from the moment it is activated, regardless of time, and will use the grid and/or solar. The charge rate in Back-Up mode is 250 watts per battery module (an Eco 10, Generation 3.1 system has 4, 2.5 KWH battery modules) and can take between 8-10 hours to fully charge batteries without solar. In this mode it will keep the batteries charged at 100% until it senses the grid is down when it will power your PLP circuits and recharge from your solar.
Modified Time of Use mode:
Another option that is very similar and more cost effective, is to stay in TOU mode and move the reserve buffer to 100%. This still keeps your battery at a 100% charge, but will only charge from the grid during low cost tariffs. In TOU mode you can also either disable grid charging so it is only charges from solar or enable grid charging which will charge at 250 watts per module, with or without the solar.
One final tip I like to recommend is to remember the primary purpose for buying your storage system. If the primary purpose was to save money, you should be in a TOU mode with a low buffer. If your primary goal is to have power when the grid is down, you should be in TOU mode with a high buffer, or you should be in Back-Up mode. Personally, I prefer to run my system in TOU mode. My battery and solar usually cover all of my PLP usage during high tariff windows (3 pm to midnight). This not only saves money, but it also minimizes the need for natural gas driven peaker plants, reduces the demand on utility infrastructure and still provides me a good buffer for power outages.
So, How do I change the mode of operation???
This is exactly what I was going to ask! If I could change modes easily via an app or via an API I can automate charging of the battery for agile tariffs which can change every 30 minutes here in the UK.
You can find this information in the Sonnen user manual or follow this link.
https://www.synsolar.com/fall-2020-sonnen-system-updates/
Hi, I also am a PGE customer in rural northern california. Question … when using TOU, do I also have to set my PGE account to TOU. FYI … I have 4 new ECO 12.5 batteries (about two weeks since commissioning) and am undecided if TOU or Self Consumption modes are best.
Hello Tony,
So TOU setups on the Sonnen are used to minimize cost (Peak Shave) peak cost time frames from lower cost off peak times. Most PG&E rate schedules have a Peak of 4-9 pm, Some like EV2 (3-4PM and 9-12 PM) have a partial Peak. So if you have a TOU schedule you would set the Sonnen to charge off-peak and discharge during peak and in my case also partial peak. Self consumption just maximizes power used from the battery without relation to the schedule – IE starts when solar production falls below usage and continues till, Battery hits its buffer limits, runs out of juice or solar production again exceeds usage (usually the following day).
Another Question … I have a 8kv Generac generator. It’s integrated it into my system but I am unclear how to get the benefit using Sonnen’s “Generator” feature (the one in the settings tab on the Sonnen configuration portal).
Thanks!
Hello Tony,
The generator needs to be connected to the sonnen which has a Generator port. I will assume the Generac has a two wire start kit. The software setting in the sonnen can be set that when the battery reaches a certain percentage – say 10%, the generator will start and charge the battery up to 95% and then automatically shut off. If two wire connection is not available a manual generator can be use (make sure the solar is turned off) and manually started and turned of. Please discuss with sonnen or your installer.
I shave an Eco10 Sonnen with 5 units.
We just survived Hurricane Fiona in Puerto Rico. The grid is out. My batteries drained down past the 25% buffer and the system shut down. A technician visited yesterday and restarted the system. Today is the first day I have use of solar. The batteries charged to 93%. Strong sunshine. System is only producing 38 watts. Is this because the excess power can’t be fed to the grid?
Hello Enrique,
I have had similar experiences up here in Sonoma County, strong sunshine but limited charging. I assume your question is why isn’t the system charging to 100%. So the way I understand it from sonnen, when charging in off grid mode using solar, the system will charge to 95% (your 93% may also be a local setting) and will not charge again till the system reaches roughly 89% discharge at which time it will begin charging again. my guess if your system is like mine the 38 watts is a meter reading issue (sonnen is aware of this) and it is actually 0. During my first off-grid event my system was stopping charge at 91% and not changing again till around 86% Had sonnen adjust it to 95 and 89. Another reason they do this is as you may know, as the battery gets more full, the charging has to be significantly reduce, as more heat is generated so 93-95% seems like a normal number.
You can test this by turning the solar off, letting the battery discharge to 80% and then turning the solar back on.
Let me know if this turns out to also be tour experience.
Jeff
Got this connected last month. Thanks for the guidance. Can you explain Sonnen’s Reenabling feature and recommend some settings use cases? Thx.
Hello Tony,
So There are two things I would pay attention to here.
1) Ensure the Sonnen has enough juice to “start up” or wake up after a battery runs out in a grid down situation. This can be done by setting the reserve higher for when the sonnen turns off. This is not to be confused with the buffer which is used to stop consumption at a level that works for you when the grid is up so it can be used if the grid drops.
2) Depending on your location set the three wake-up times to coincide with when you system has extra power to charge. So if your home is using 3,000 watts at 9 am, and your solar is producing 2,700 watts – not a good wake up as all the solar is going to usage and we also want the battery to charge. So I have mine set 10 am, noon and 1:30 pm. So it has plenty of charge to cover usage and charging.
Hope this answers you questions.
Jeff
Hi
I’m with a wholesale electricity company that provides a battery management service to tracks the wholesale price of consumption and feed-in and varies the configuration of the battery to take advantage of the highs and lows. Average consumption is probably around the 10c/kWh but peaks in the evenings (and sometimes morning) at orders of magnitude higher.
Their system automatically discharges the battery onto the grid at these peak times and blocks feed-in when feed-in tariffs go negative, avoiding being charged for sending energy to the grid when they don’t want it and getting paid top dollar when they really do want it.
This usually results on profits every month depending on the size of solar system and battery etc.
However, they don’t yet support sonnen batteries, so I have to figure out how to manipulate the battery manual. I have a home automation system that can be integrated into the providers system so that I can get instant data of tariff changed but I need to figure out how to manipulate the battery via API to take advantage of the changes.
Is there any example of how people are doing this out there? I plan to use Node-Red to do this in my ‘Home Assistant’ system.
Hello Robert, The use case you are describing will be beneficial under the new net billing tariff (NEM 3) here in California. WE are not aware of anyone who is doing that currently with Sonnen systems.