LG Chem RESU Batteries
If you are in the market for a home battery and are tempted to buy a Powerwall, then I urge you to also consider the new range of LG Chem batteries announced last week.
Whilst LG have been unable to compete with Elon Musk for mainstream media coverage, the LG Chem RESU, or Residential Energy Storage Unit for the long winded, has been one of the biggest successes in on-grid home energy storage in Australia. While solid figures are hard to come by, it may have been used in almost half of all on-grid home battery installations.
While it was popular, ye olde RESU6.4 is no more. LG Chem has replaced it with something better. And not just with an updated version of itself, but with a whole slew of new RESU.
There are now 5 RESU systems to choose from with nominal capacities ranging from 3.3 to 9.8 kWh. Three of the new RESU use 48 volt DC power:
The usable capacity of the lower voltage systems is around 90% of their nominal capacity. As they are lithium-ion battery systems, their capacity will gradually decline with use and over time.
The two different voltages allows for a wide range of installation options including DC coupling and AC coupling. No matter what type of coupling you prefer, you can do it with an LG Chem RESU. And they are suitable for on-grid or off-grid use.
The 48 volt RESUs have higher power than most comparable battery systems and are lighter and much more compact than the competition. They are warrantied to retain at least 60% of their nominal capacity for 10 years or until they have stored slightly under 2,500 kilowatt-hours for each kilowatt-hour of nominal capacity. Taking an estimate of battery degradation into account this is approximately 3,200 cycles. When cycled once per day it will take around 8 years and 9 months to reach that point.
RESUs’ Vital Statistics
In order to save me having to make a table, I have grabbed a screen shots off the new RESUs datasheets. Here are the vital statistics for the 48 Volt systems:
Indoors Or Outdoors Installation Is Okay
The Enclosure Protection Rating of the RESUs is IP55 which means they are protected against both dust and water. But if dust and water combined their powers to make mud, well, it would be protected against that also. According it its rating it can handle being sprayed with water under moderate pressure from any direction but not immersion. So if you are going to use it on a submarine, try to remember to install it on the inside.
Like most new battery storage systems, apart from keeping them reasonably clean, RESU require no maintenance.
Round Trip Efficiency
LG Chem gives the round trip efficiency of the 48 volt RESUs as greater than 95%, but states this is only under good conditions. In real life I would expect its round trip efficiency to be a little under 95%, especially if it is installed outdoors and often exposed to temperatures above 30 degrees or below 15 degrees.
Operating Temperature is -10 to 45 Degrees Celsius
One important piece of information missing from the above tables is its operating temperature. RESUs can function at ambient temperatures from -10 to 45 degrees Celsius. Ambient simply means the air temperature in the immediate surroundings. It is possible that some day we may know why battery manufacturers don’t just say, “local air temperature”.
The lower limit is not likely to be a problem for Australians, but it is possible for it to shut down during a severe heatwave. To prevent it conking out from heat exhaustion, installing RESUs out of direct sunlight is a very good idea. LG Chem gives its recommended operating temperature as 15-30 degrees, so placing it indoors is probably a good idea and will help improve its efficiency and extend its battery life.
The RESUs have no cooling fan and rely on natural convection from its metal case for cooling. This means they are very quiet, which is useful for indoor installation.