1. Various concepts in the battery world
2.0 Concepts of Sirius
Various concepts in the battery world

2. Training Overview Introduction to Greenfox Core Concepts of Sirius
Different Sirius models
Market Segments and Applications
Sizing for solar applications
Module Operation & Specifications

3. Ideal Storage The concept of ideal storage
There is currently no defined description for ideal energy storage. So here is my view of ideal storage.
“Ideal storage is the ability to store energy, delivered at any rate in order to access this energy later, again at any rate without losses, and no degradation to the storage medium”
Supercapacitors are not ideal storage, but they get us a lot closer than any other technology currently.
We have had the benefit of static storage since Ewald and Pieter developed the Leyden Jar in It has taken scientists 270 years to develop this concept to the point where it is economically and practically viable to power everyday appliances. Let’s be fair to the scientists though… the first 235 years there were no appliances to power, so not much use for storage.

4. Challenges Static vs Chemical Storage
In order to fully understand the benefits that static storage offers, one has to understand the shortcomings of the other forms of energy storage.
Chemical storage converts electric energy into chemical energy, and back when required. This has been the main form of storage for decades. The problem with converting energy between different states are the losses and permanent damage, the conversion process generates losses in the form of heat. Temperature is a chemical battery’s nemeses. Chemical batteries have limited cycles, due to deterioration of the components. At higher temperatures the deterioration to the components accelerate exponentially. To prevent chemical batteries from generating their own heat they are typically oversized by a large factor. This term is labelled “C-Rate”, this is the charge/discharge rate of a unit, and a chemical battery’s abilities are represented on a C-rate matrix sheet.
Concepts required to understand chemical storage
Temperature effect
C-Rates
Depth of Discharge & Cycle life
Round Trip Efficiency
Disclaimer… It is very important to state clearly, this document is in no way used to degrade any other form of storage, I simply go through each of the concepts so that you can understand clearly why Sirius get sized the way it is in applications. If the correct sizing methodology is applied to Sirius your solutions will be significantly more cost effective. But if you apply the shortcomings of chemical storage to Sirius, you will no longer be more cost effective.
Chemical batteries will still be around for a long time, and in certain applications chemical batteries may offer a sound solution to fulfil a clients needs.

5. Temperature Effect
Temperature is one of the major factors to consider when dealing with chemical batteries. Chemical batteries are not only affected by ambient temperature, but generate their own heat internally through losses.
Some manufacturers void warranties if the battery temperature exceeds 25°C. Other than warranty issues, chemical batteries have roughly a 50% reduction in cycles for every 8°C over 25°C. The same applies to the standby life of most chemical batteries.
For this reason, battery temperature should be controlled very closely. To add to this problem, chemical batteries are not 100% efficient. Losses are converted to heat during the chemical process of charging and discharging. The more inefficient the operating of a battery the more heat will be generated and the shorter the life. This is one of the most significant factors as to why lead batteries need at least days autonomy. At faster charge rates like C5 or C1 up to 50% of the energy stored converts to heat loss.
Figure 1.1 – DoD vs cycle life of OPzS lead acid at various temperatures
Sirius can efficiently operate at temperatures between -25°C up to 75°C with NO DEGRADATION. As such, no air conditioning is required and “free cooling” (exchange of air from inside the battery room with ambient air outside the room) is sufficient for Supercap storage. Supercaps are 99.1% efficient and do not generate heat internally - even at very high charge/discharge rates.

6. C- Rates
Charge/Discharge rates have three factors working against each other, energy absorption or round trip efficiency, speed of charge and temperature of batteries. For chemical batteries a slower charging process is more efficient, and the higher the C-rate the more energy a chemical battery will store. Faster charge and discharge means lower efficiency, which results in heat, and therefore decreased cycle and standby life. The only way to get around this fact is to install a larger storage bank. By increasing the bank size you are dispersing the load over more batteries. This however increases the capex requirement. When comparing various chemical technologies the same problem simply looks a bit different for each. Lithium maintains higher efficiency at faster charge and discharge rates, but are three to four times the cost of lead acid technologies. As such, the same result could be achieved by installing three to four times more lead.
Many clients and system designers think that weather is the main reason for autonomy. Autonomy is actually determined by the storage technology that you use, weather has very little to do with Autonomy.
C-rates are a good platform to introduce the two different Sirius models. There is the “standard” model and the “fast charge” model. Models in between these can be manufactured, but to simplify training we will stick to these two for now.
The “standard models” operate between 1C and 2C. This is mainly used for solar/standby/general etc. This means 30min to 1hour C-rate, already 10-20times faster than lead, and 3-6 times faster than Lithium.
The “fast charge model” is capable of operating at 112.5C (32 Second charge/discharge), this feature is useful in the transportation space. Internally there are major differences between the two models and they also differ in costing.
Figure 1.2 – C2 charge of a 7.1kW.h Sirius Supercap

7. Average DOD and Cycle Life
Chemical batteries cannot be fully discharged without permanent damage. Depending on the construction of the battery, acceptable DoD varies between 40% and 80% for most chemistries, and DoD plays an important role in cycle life. The type of battery used in a specific application will determine the expected service life of a battery bank and is used to calculate the R/kW.h cycle cost of a battery in an application.
The biggest drawback to a battery aging is the loss of capacity “degradation”. This means as you cycle your batteries their capacity reduces. This is a major hurdle for chemical batteries. Once the capacity reduces, the degradation then accelerates, as with each cycle you now use a larger portion of the remaining capacity of the battery.
Degradation combined with C-rates are the two main reasons for oversizing batteries. It is for this reason that the terminology “autonomy” became solar lingo. In order to size a lead acid bank properly so that cycle life and standby life more or less match up - you need about 3 days autonomy. This means you should only have a 15% daily draw out of your batteries. Supercap, on the other hand, can be discharged 100% multiple times per day with no degradation. It is therefore possible to size this battery to the exact power requirement of the application. At 1 Million cycles the capacitors will likely outlive the rest of the equipment.
Figure 1.3 – 12V Lead Acid DoD vs Cycles at 25°C

8. Round Trip Efficiency
Chemical batteries experience losses converting electrical energy to chemical and back. The conversion process efficiency gets affected by speed as well as construction and chemical composition. As mentioned earlier, heat is a by-product of the chemical process of converting electricity to chemical storage and determines/impacts inefficiencies. The slower the charge process the less heat is generated, resulting in higher efficiencies. Another factor to consider, where applicable, is the absorption period. Lead batteries need to be maintained at “absorption voltage” for a fixed period, often 1-2hours during which the battery in this state does not absorb much energy at all, but rather stabilizes the cell voltages. Not taking a lead acid battery through absorption will result in the battery operating at charge states lower than 85%, which will drastically impact expected life. Lead batteries should ideally be absorbed daily and equalized every 14-28days.
Standby lead acid batteries have a round trip efficiency of around 40%-60% on pure energy in and out, not taking generator or other inefficiencies into account, if they operate at C-rates higher than 10 hours. Lithium has a round trip of around 90% if operating at C rates higher than 4 hours.
Supercap has a round trip efficiency of 99.1%, even at very low C-rates like 1 hour (with very little heat generation and almost no losses). Supercap does not need to go through absorption or equalization like other batteries. Not charging a Supercap battery to 100% will have no adverse effect on expected life.
Figure 1.4 – Round trip efficiency of a Sirius Supercap

9. Core concepts and Sirius
Core concepts relevant to Sirius
Sirius does not play by any of the rules that chemical batteries have to conform to.
Chemical batteries need to be oversized by a large factor. Sirius do not need to be oversized.
Chemical batteries need to be cooled if the ambient is not suitable, Sirius can handle the temperature.
Chemical batteries lose capacity as they age, Sirius is the same at day 1 as any day in year 45.
The energy that Sirius receives, it will give back less 1%.

10. Summary
In order to satisfy the requirements of cyclic battery applications, in practical terms “ideal storage” is required. The Sirius Supercap battery comes the closest to ideal storage of any technology out there currently. Chemical batteries have many shortcomings and although Capex is slightly less than Supercap, OPEX soon catches up.
The main advantages of Supercap are:
The “slow charge” Sirius Supercapacitor achieves 1.35C, resulting in a charge and discharge time of 45 minutes.
The “fast charge” Sirius Supercapacitor achieves 112.5C, resulting in a charge and discharge time of 32 seconds.
The round trip efficiency is 99.1% if one were to discard the cable losses connecting the battery.
Operating temperature range is -25°C up to 75°C with no damage to the unit.
Expected lifespan 1 Million cycles for capacitors.
No degradation expected during lifespan.
Expected operational life of 45 years.
10-year warranty.
No change in capacity at different charge rates.
Safeties that protect the battery from overvoltage, under-voltage and short circuit.