Fewer components, less expensive, easier to install, better Tech Support, more mature product line.
Here is a typical StorEdge installation:
Features that make StorEdge better:
A) All of the StorEdge components (including the LG Chem battery) are exterior rated. The Sonnen is interior rated only. Most people do not have room in their garage for a Sonnen cabinet, let alone in their living room as shown in their brochures.
B) The StorEdge inverter is the solar inverter. Sonnen recharges from the grid, and requires the addition of solar equipment. The battery bank has the same high DC voltage and low amps as a solar array, so the inverter can easily invert the DC power to AC; whether it is coming from the solar array or battery.
C) StorEdge allows the homeowner to install solar now (to cut utility bills) and add the battery later. Sonnen is grid-tie battery backup only. Solar is NOT included.
D) StorEdge has the ability to perform Zero Export (do NOT backfeed the grid, self-consumption only) which is required for homeowners in Hawaii. Sonnen can NOT perform this function and requires the solar equipment, such as a SolarEdge install, to do it.
Many people wanting battery storage are familiar with the traditional 48v battery banks, but the StorEdge design is very different from the traditional 48V battery storage system.
Anybody with a SolarEdge 7600 that wants to add battery storage can get it with an Autoformer and a LG Chem battery.
The StorEdge marketing still makes a lot of noise about Powerwall 1 and 2 being compatible (which they are) but Powerwalls are NOT available to us through our distributors, so they are off the radar for DIY installs. The LG Chem is a very good battery made by a bankable company. They don’t have the media hype of Tesla, but it is every bit as good. I have seen the LG battery up-close and personal, and they did a nice job on the enclosure.
Here’s what makes the StorEdge design better:
1) The 350v of DC power coming from the Optimizers is fed DIRECTLY into the battery.
Note: In a traditional 48v battery system (such as the Sonnen), there is an Inverter/Charger that reduces the 350v to 48v. Eliminating this step simplifies the design, and is more efficient since there is no conversion loss as the Charge Controller circuits adjust the output power. It also eliminates an expensive piece of equipment, reducing the system price-point; as well as eliminating a point of failure. Moreover, an Inverter/Charger is generally expected to last 5+ years. Conversely, the StorEdge inverter life expectancy is 12 years minimum, with a 25 year warranty available. This significantly reduces the long-term cost.
Here is the wiring diagram from the StorEdge install manual that shows the straight-thru connection from the solar array to the battery:
2) What is the function of the Autoformer?
It only comes into play when the grid is down. Its job is to act like the grid so the inverter knows to create 60Hz and 240v split-phase power, for the loads. The innovative twist is it does it WITHOUT battery power . This also simplfies the install, since there is no need to have a battery connection.
Note: this is unusual because there are NO connections to the battery for it to draw DC power. Therefore it does NOT create a micro-grid, as is done in a traditional 48v system. The inverter’s job is to match the grid’s cycles (usually 60Hz) and voltage (usually 240v). However, when the grid goes offline, there is no grid to match anymore. The inverter needs a baseline to match, or it will shut down. The Autoformer provides the 60Hz and 240v grid baseline for the inverter to match, so the inverter comes back online, the Optimizers are asked to resume sending DC power, business as usual.
Here is the diagram showing only AC connections (and NO connections from the batteries) to the Autoformer:
3) What happens when the grid is down, and the batteries are charged?
Consider a scenario where it is the weekend, the homeowners are away (so loads are minimal), there is plenty of sun, the batteries are fully charged, and the grid goes offline. Normally the excess solar power is sent to the grid, but now the grid is down and will not accept power. Based on the wiring diagram, we see the solar power will be sent to the batteries. However, the lithium battery has an on-board Battery Management System (BMS) that is responsible for the care and feeding of the battery bank. When the BMS sees a bunch of DC power coming at the battery bank, knowing it is fully charged, it will disconnect from the in-coming power, to protect the lithium cells from being overcharged. (Overcharging a lithium battery cell will cause it to go into “thermal runaway”. the YouTube video of a laptop on fire is an example of thermal runaway.) Usually this “disconnect” is tripping a breaker, and a manual reset is required. However, StorEdge Tech Support says it goes into a Stand-By Mode, which implies an auto-reset is possible. This requires some communication between the inverter and the BMS. I believe this is implemented since there is a Battery Control shown in the wiring diagram.
A Stand-By function is much more elegant than a manual reset, but for it to work the BMS must be able to automatically re-establish the connection to the inverter when the loads require it; such as when the homeowner returns in the evening and turns on the air conditioner. What we do NOT want is a scenario where the BMS disconnects the battery, and the homeowner returns to find there is no power, yet the battery bank is fully charged.
What is coming in the future?
1) The current StorEdge configuration does NOT have the ability to incorporate an Auto-Start feature for a generator. It is “coming by the end of the year”, but I want to see it first. If they are smart it will be for a “2 wire start” generator, with the option to have an external device to support 3-wire start generators. Many people that are concerned about the grid will install a generator before battery storage, since a generator has lower up-front costs. Most will want to incorporate their generator as a stand-by power source in the event there is minimal solar power production due to poor weather conditions.
2) Only a single LG Chem RESU10H 10kWh battery can be used in a StorEdge system currently, but being able to hook-up two batteries is coming. When I talked with the LG Chem rep at the AEE Conference, he indicated they have configured two of the 10kWh batteries with StorEdge in the lab, and it worked fine. They are waiting for SolarEdge to certify the 2 battery design. Again, this certification will be “coming by the end of the year”, so stay tuned. This is important since lots of people are NOT off-gridders and want their creature comforts. That homeowner in Palms Springs wants their air conditioning to work, regardless of the cost. Having the solar array provide enough power to keep their air conditioner going in the day is fine, but having a battery reserve for the evening is the key. Otherwise, it can be a deal-breaker for many people.
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