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Find reviews of the best Solar Products, SMA Sunny Boy, Aurora Power-One, Growatt, SunPower, SolaX, QCells, Trina Solar, Jinko, Selectronic, Tesla Powerwall, ABB, SMA Sunny Island, Hybrid inverters, battery sizing, Lithium-ion, lead-acid batteries, off-grid, on-grid, stand-alone power systems

Complete Solar Battery Review

Jason Svarc

solar battery review LG RESU Tesla Powerwall 2

Jason Svarc

  • UPDATE 1 - May 2016 - price reductions and specification changes
  • UPDATE 2 - July 2016 - Powerwall specification changes.
  • UPDATE 3 - Aug 2016 - Powerwall warranty and LG chem spec update. Cost per kWh comparison now includes battery efficiency.
  • UPDATE 4 - Oct 2016 - New LG chem RESU battery range, new pricing and warranty. Updated Pylon Tech battery and warranty details.
  • UPDATE 5 - Nov 2016 - Tesla Powerwall 2 announced, double the capacity with integrated back-up inverter and huge price reduction.
  • UPDATE 6 - Feb 2017 - Powerwall 2 pricing and specifications for DC version, AC version coming Q3 2017
  • UPDATE 7 - Mar 2017 - Powerwall 2 available as AC only - No DC version! PylonTech new battery model US2000B, was Extra2000

Background

Home battery storage systems combined with solar are being touted as an energy revolution, a game changer, a renewable energy saviour, or simply as a way for people who are sick of paying high electricity prices to lower their bills. In countries like Australia there is a great incentive to store solar energy as the feed-in tariff has been reduced to as little as 5c per kWh or less, while the cost to purchase electricity is an average of 28c per kWh and rising. This has become a driving force and great incentive to store solar energy rather than send it to the power grid for little return.

Batteries for energy storage in buildings have been around for a long time in both stand-alone (off-grid) and commercial back-up (UPS) power systems, however over the last few years domestic energy storage in the form of hybrid solar systems have started to gain momentum, even with the relatively high cost of batteries. The other main driving force for battery storage is energy security. With the increase in severe weather events due to climate change causing regular blackouts in some locations, a battery system can provide instant back-up power for your home or business. Residential battery storage systems also enable energy independance and provides a means to generate and store your own clean renewable energy.

Home battery storage - Want to know which solar battery is best suited to your home? See our guide to Selecting and sizing a home solar hybrid system.

 

The Battery Lineup

  • Tesla Powerwall (Gen 1 & 2) – Lithium NMC

  • LG Chem RESU (Gen 2) – Lithium NMC

  • Pylon Tech US2000B – Lithium-Ion (LFP)

  • Aquion Hybrid Ion – Sodium-Ion

  • Narada – Lead-Carbon

  • BAE – Gel Lead-Acid

 

Battery storage cost per kWh over cycle life efficiency

Results summary chart - See conclusion for full details:

 

Battery Types available

Many hybrid and off-grid solar installations still use the traditional (gel or AGM) deep cycle lead-acid batteries, however over the last 2 years lithium batteries have really started to take hold with many large companies such as LG and Samsung releasing lithium based battery systems. Of course the biggest boost in interest came with the announcement of the Tesla Powerwall, this was when the mainstream population became aware of the possibility of home energy storage. But will the Tesla Powerwall or new Powerwall 2 be able to meet these high expectations, especially with growing competition from well established companies such as GCL and Narada in China, LG Chem, BAE in Germany and newer technologies such as the Redox flow battery from Redflow?

Update: Unfortunatley Aquion Energy voluntarily filed for bankruptcy in March 2017, most likely due to the huge competion and price reductions from lithium battery manufacturers such as LG & Tesla.

In this article we will try to compare both new and traditional battery technologies using a number of criteria. A direct comparison is not as easy as it sounds as each battery chemistry behaves differently under different conditions which can either prolong or decrease the life of the battery. The primary aim is to compare each of the batteries storage capacity measured in kWh (kilowatt hour) over the cycle life of the battery, but we will also try to highlight the key advantages and disadvantages of the various types available. We will not be looking at unsealed (flooded) lead-acid batteries, as these require high levels of maintenance and any cost savings can be outweighed by regular maintenance work required throughout the life of the battery.

To do an accurate comparison we compared the Powerwall (both 1 & 2) with the recently released LG Chem lithium battery which is considered the leading competitor to the Powerwall in Australia, together with the better known and widely used lithium iron phosphate (LiFePO4 or LFP) battery modules by the large Chinese manufacture Pylon Technologies.

The Redflow Zinc bromide battery

The Redflow Zinc bromide battery

Two innovative companies which have managed to manufacture completely new battery chemistries at a competitive price are Aquion Energy and Redflow

The newer lithium based batteries are also lined up against the leading gel lead-acid based batteries from BAE and the advanced lead-carbon battery recently released by Narada. There are also many new batteries technologies currently being developed but few are suitable for residential applications or have moved to the high-volume production level required to become price competitive. One innovative company which managed to manufacture a new battery chemistry at a competitive price is Aquion Energy. For this reason the sodium-ion based ‘Aqueous Hybrid Ion’ battery system was also added to the list, however unfortunately Aquion has recently filed for bankruptcy in the US. The Redflow (Zinc bromide) flow battery also appears to be a very promising and unique new battery technology developed in Australia with many benifits but will not be included in this comparison until a later release.

Deep cycle battery options

Advanced tubular gel deep cycle batteries are a proven technology with 15+ year design life. There are many well established companies manufacturing high quality tubular gel lead-acid batteries (VRLA), such as Sonnenschein, Hoppecke and TAB but we selected the well known German BAE solar PVV battery to represent the sealed lead-acid batteries.

Common single cell 2v deep cycle sealed gel lead-acid batteries are avilable in sizes from 200Ah up to 4500Ah

Common single cell 2v deep cycle sealed gel lead-acid batteries are avilable in sizes from 200Ah up to 4500Ah

To accurately compare all the leading battery technologies currently available we have selected several key criteria listed in order of importance below (when comparing smaller capacity home/hybrid systems).

Comparison Criteria:

1.  Price per kWh (upfront cost)

2.  Depth of discharge (DOD) – usable energy

3.  Cycle life – Number of charge cycles

4.  Power output – Max continuous and peak output

5.  Round trip efficiency – Charge/discharge losses

6.  Size and Weight – Energy density

 

1. The first key criteria is price per kWh, since upfront cost and payback time is one of the most important aspects for many consumers.

2 -3. The second and third criteria really go hand in hand as battery life is almost always directly proportional to the depth of discharge (DOD). This means that the further a battery is discharged the shorter the battery life. The available energy or DOD on a daily cycle (charged and discharged every day) is usually specified by the manufacturer and the cycle life in years is based on this DOD value. However, the end of life (EOL) of a battery is not always clear as a battery doesn't just suddenly stop working after a certain number of cycles.  Almost all battery technologies new and old slowly loose capacity over time and the industry standard for Lead-acid is to determine the EOL once battery capacity has dropped to 80%. However more recent lithium manufacturers such as LG and Tesla are warranting their batteries to lower EOL values of 60 or 70%. Remember the battery is still usable after this, it just doesn't hold as much energy. To complicate this further in a real world there are many variables including temperature, rate of discharge and incomplete charge (partial state of charge) so the performance and life of a battery system can be significantly altered. As a general guide the newer lithium and sodium based batteries are designed to be discharged up to 70-90% total capacity while the traditional lead-acid (gel & AGM) batteries are generally not discharged lower than 40-50% unless in emergency backup situations. For those in the industry this is a relatively standard assumption. See our battery article for more specific information.

4. Following this we have the continuous and peak power output. This can be very important depending on the type of inverter you are using and the application, for example off-grid installations will usually require a higher peak power output as you do not have the grid available to assist in high load (high power draw) situations.

5. Next is round trip efficiency, this is the charging and discharging efficiency or losses during cycle use. Unfortunately, due to the laws of physics the transfer of energy from one form to another (in the case of batteries from electrical to chemical energy) will always result in some losses. Generally, charge/discharge losses from a lead-acid based battery is close to 20% while most new lithium based batteries are closer to 10%.

6. You may be surprised but I have put weight or energy density last. This is simply because I consider it rather irrelevant in a stationary situation, however if this comparison was for electric vehicles it would probably be on top of the list.

Sustainability - Environmental impact

Of course there are other important factors which should be considered such as recyclability, temperature tolerance and safety. As more and more battery systems are installed recyclability will become a major issue which I have discussed in a new section at the end of this review.

The Battery Details

Note: The cost per kWh figures are based on the price of the battery from various distributors. Due to variable Australian dollar we have used the standard US dollar. More importantly the estimated prices do not include the cost of the solar array, inverter, installation and other associated costs such as rewiring switchboards or solar array circuits.

 

Tesla Powerwall (1 & 2)

        Powerwall 1               Powerwall 2

        Powerwall 1               Powerwall 2

The Powerwall 1 was available as a 6.4 kWh unit (previously listed as 7kWh).  The 10kWh 'backup only' model was not released due to low sales. The Powerwall 2 will have double the 'usable' capacity at 13.2kWh and now comes with an integrated 5kW DC-AC inverter with the AC version. (DC version no longer available). The integrated inverter will make installation simplier but will still require a solar inverter to function with a solar array, plus an additional gateway box will be required to enable backup power (UPS) during a grid outage.

The Powerwall (1 & 2) uses a lithium nickel-manganese-cobalt (NMC) cell chemistry developed in collaboration with Panasonic. The battery cells are similar to the batteries used in the Tesla electric vehicles. The unit features an integrated battery management systems (BMS), liquid thermal management, DC to DC converter for Powerwall 1 and AC inverter in the Powerwall 2. The new Powerwall 2 will have the capability to work in parallel with up to 9 units for homes/businesses with greater energy storage requirements. Interestingly the first Powerwall was designed to be connected between the solar array and the inverter and so accepts a high DC voltage input of 350-450V which is unusual for a battery storage system but does slightly improve efficiency. The Powerwall 2 will only be available as an AC unit but this will enable it to work with an existing grid-tie solar installation no matter the age or type.

See the full Powerwall 2 review here

Warranty Controversy (Powerwall 1):

The original warranty was 10 years but only under certain conditions such as 5.4kWh usable for the first 740 discharge cycles or 2 years and reduced capacity for the remainder of the 10 year warranty.  This was replaced with " this Limited Warranty does not cover normal degradation of your Powerwall’s energy capacity over time" See updated Warranty certificate for Powerwall 1.

Warranty for the Powerwall 2 is 10 years with unlimited cycles. End of life capacity after 10 years is expected to be 70% but it will depend on a number of factors including total cycles, shallow cycles and average depth of discharge per cycle. See complete warranty details in the full review here

POWERWALL 1

COST: US$3000 - After shipping from the US, import duty, taxes and distributor mark-up the cost increased significantly to around AU$6500.

  • 5.4kWh usable (85%) for 3650 cycles - estimated
  • Power output (DC) – Continuous = 3.3kW, Maximum Peak= 3.3kW
  • Round trip efficiency (claimed) = 92.5%
  • Powerwall = US$3500 (AU$6500*) – Cost per usable kWh = US$864

POWERWALL 2

COST: US$5500 - Australian listed price AU$8000 inc GST

  • 13.2kWh usable for 3700 cycles - estimated
  • DC-AC Inverter included
  • Power output (AC) – Continuous = 5.0kW, Maximum Peak= 7.0kW
  • Round trip efficiency (claimed) = 89%
  • Powerwall = US$5500 (AU$8000) – Cost per usable kWh = US$482

 

LG Chem RESU

LG chem RESU battery review vs Powerwall

UPDATE: LG Chem have released an updated, much larger range of RESU (Residential Energy Storage Unit) batteries in various sizes from 3.3kWh up to 9.8kWh. Previously just the single 6.4kWh RESU6.4EX lithium battery was available. The new range includes RESU3.3, RESU6.5 and RESU10 units with an option to combine different units using a new adapter for up to 19.6kWh of total storage. More about the new range of new RESU batteries here.

LG chem use lithium nickel-manganese-cobalt (NMC) cell chemistry (as per the Powerwall). The new range of batteries are housed in compact weather rated (IP55) enclosures with integrated BMS and are now warranted to 10 years life. However this is to minimum 60% retained capacity (EOL) but is expected to be in the range of 60-80%. The battery module operates at the nominal voltage of 51.8V and can provide a relatively high continuous power output of 4.2kW although this may reduce battery life. The peak output is now also 4.2kW (was previously 5.0kW).

Compatibility

An important note: the new LG chem RESU batteries are compatible with almost all leading hybrid & off-grid inverter, this gives LG a huge advantage and great flexibility for different homes and business. The growing list of compatible inverters include: Selectronic, Solax, SMA, SolarEdge, Sungrow, Schneider, Ingeteam, GoodWe, Redback and Victron Energy.

Warranty is 10 years - See warranty certificate for more details.

  •  5.2 kWh usable (80%) for 4000cycles to min 60% retained capacity (EOL) - estimated
  • Power output – Continuous @ 48V bank = 2.5kW recommended, Maximum Peak = 4.2kW
  • Round trip efficiency (claimed) = 95%
  • New 6.5kWh LG RESU = US$3000 (AU$4300) – Cost per usable kWh = US$631

 

PylonTech

The Pylon Technology lithium iron phosphate (LiFePO4 or LFP) batteries were some of the first modular lithium based batteries available which enclosed both the lithium cells and battery management/control system in a simple rack mounted unit. The Extra2000 has now been replaced by the US2000B and Phantom-S series (pictured) which has a more aesthetic enclosure and more robust battery cable connections. Available in the same standard size 2.4kWh modules (previously with a touch screen interface) allows easy setup and monitoring together with connections for multiple units in parallel. Now also available in high voltage modules for commerical applications.

The pylontech battery modules are often re-branded and used by several large solar manufactures and distributors including SolaX, Canadian Solar and Redback Technologies.

Lithium ferrous phosphate (LFP) is generally considered the most stable of all the lithium battery chemistries especially at elevated temperatures above 40 degC (common in Australia) which is highlighted by the high battery cut-off temperature of 50 degC. Cycle life is also quite high at a claimed 6,000 cycles at 80% depth of discharge, although it is unknown what the end of life (EOL) retained capacity is after this number of cycles?

The warranty is for 5 years and specifies 80% EOL capacity or 70% EOL capacity with the extented 7 year warranty. Also the previous warranty states that not more than 360 cycles per year. Based on this the new battery performance will remain the same and we can assume 3,000 cycles at 80% DOD. The battery module operates at the nominal voltage of 48V and now has a higher peak power output of 5kW (previous model was 2.2kW) over a short discharge duration of 60 sec. The updated US2000B battery retails at the same price as the previous Extra2000.

Extra2000 - Warranty: 5 years - See warranty certificate for more details.

  •  1.92kWh usable for 2500 cycles to 80% retained capacity (EOL)
  • Power output – Continuous @ 48V bank = 2.0kW, Maximum Peak 5.0kW
  • Round trip efficiency (claimed) = 92% - estimated
  • Extra2000 = US$1100 (AU$1520) – Cost per usable kWh = US$594

US2000B - Warranty: 7 years (after online registration)

  •  1.92kWh (80%) usable for 3000 cycles to 70% retained capacity (EOL)
  • Power output – Continuous @ 48V bank = 2.0kW, Maximum Peak 5.1kW
  • Round trip efficiency (claimed) = 92% - estimated
  • Extra2000 = US$1100 (AU$1500) – Cost per usable kWh = US$590

 

Aquion_battery_review

 

Aquion Energy*

* Unfortunatley Aquion Energy voluntarily filed for bankruptcy in March 2017. 

Aquion Energy started mass manufacturing an advanced sodium-ion (saltwater) battery system early in 2014. Aquion developed the solution now patented Aqueous Hybrid Ion (AHI™) chemistry using abundant, nontoxic materials and modern low cost manufacturing techniques. They are the first battery manufacturer to have met all the stringent criteria to obtain cradle-to-cradle certification which means that they are possibility the most environmentally friendly batteries currently available.

In addition, unlike many other battery technologies Aquion claims the AHI battery system is very tolerant to abuse with the ability to stand at a partial state of charge with minimal or no degradation. The Aquion battery is also the only battery we have seen which is able to be discharged to 100% without any detrimental effects on the life of the battery or loss of capacity. However, one major drawback as the full capacity can only be obtained at a slow discharge rate of 20 hours (C20) which is not optimal for all hybrid situations with a full discharge more likely to be over 10 hours or less. The batteries are available in individual stacks of 2.2kWh with a nominal voltage of 48V. The claimed life is 3000 cycles to 70% retained capacity (EOL). Warranty TBA. If we assume a faster discharge and round trip efficiency of 75%, using these specifications we can assume:

  • 1.7kWh usable for 2500cycles to 80% retained capacity (EOL)
  • Power output – Continuous = 0.45kW (4 x stacks = 1.8kW), Maximum Peak = 0.96kW per stack
  • Round trip efficiency (estimated) = 70% (based on 12 hour discharge rate - C12)
  • 2.2kWh module = US$1150 (AU$1550) – Cost per usable kWh = US$665

 

Narada Lead-Carbon

ZHEJIANG Narada Power Source Co. is a Chinese based company primarily focused on power system and energy storage solutions. The REXC series Lead-Carbon based battery technology uses a nano carbon material with high capacitance and highly conductivity on the negative electrode. The company claims this combines the advantages of both lead acid batteries and super capacitors to enable faster recharge. The lead carbon battery technology provides not only a higher energy density, but also high power, rapid charge and discharge, and longer cycle life than traditional lead-acid batteries. However, the batteries are only currently available in large 6V and 12V modules so multiple strings of batteries would be required for usable capacities above 6kWh which is not ideal for large system but suitable for most domestic hybrid setups. Also the rated capacity can only be obtained at a very slow discharge rate of 100 hours (C100) which is not optimal for a hybrid situation with full discharge more likely to be over 12 hours or less.  Although the claimed cycle life of 3000 cycles can be obtained at high temperature of 40degC so in theory they should last longer at lower temperatures. Warranty 2 years

  • 48V bank = 4 x 12V 200Ah (C12) = 4.0kWh usable for 3000cycles to 80% retained capacity (EOL)
  • Power output – Continuous @ 48V bank = 5.0kW, Peak up to 10kW
  • Round trip efficiency (estimated) = 80% (based on 12 hour discharge rate - C12)*
  • 4 x 12V 200Ah batteries = US$2600 (AU$3600) – Cost per usable kWh = US$650

 

BAE_Secura_PVV_battery_review.jpg

BAE Gel Lead-acid

BAE Gel Secura batteries are high quality German made lead-acid based batteries designed specifically for off-grid and hybrid installations. BAE manufacture a wide range of batteries of various sizes and voltage configurations but for this review we will focus on the Gel Secura PVV solar (tubular Gel) range. BAE have been manufacturing lead-acid based batteries for more than 100 years and the latest Gel Secura PVV battery design uses an advanced tubular-plate electrode with woven polyester gauntlet and solid grids in a corrosion-resistant lead-calcium alloy.  The fully sealed maintenance free battery design utilizes the VRLA technology and have been proven to perform in harsh conditions and elevated temperatures. The Secura PVV batteries are single 2V cells therefore require battery configurations of either 12 or 24 batteries in series to create a battery bank nominal voltage of 24V and 48V respectively, refer to our battery article for more information. The secura range like most VRLA batteries are available in a vast range of sizes ranging from 140Ah up to a massive 4940Ah which in turn enables a wide variety of battery bank capacities up to a 235kWh or higher, however we selected the smaller 770Ah (C25) battery for the comparison (610Ah @ C10). BAE batteries are capable of deep discharges to a maximum of 80% total capacity but for the purpose of this article we will use a DOD of 50% which according the specifications will provide 3000 cycles to end of life (EOL). Warranty: 5 years

  • 48V bank = 24 x 2V 610Ah = 14.6kWh usable for 3000cycles to 80% retained capacity (EOL)
  • Power output – Continuous @ 48V bank = 5.0kW, Peak up to 9kW or higher**
  • Round trip efficiency (estimated) = 80% (based on 10 hour discharge rate - C10)
  • 24 x 2V 350Ah batteries = US$9300 (AU$12800) – Cost per usable kWh = US$635

**Unlike Lithium based batteries Continuous and Peak power output of a lead-acid battery bank depends on battery capacity chosen, up to (235kWh @ 48V) and so power output could be rated as high as 100kW.

 

Results

Upfront Cost per kWh - usable energy

(prices based on Australian distributor prices, not US RRP)

Solar Battery Comparison upfront cost Powerwall 2 LG Chem PylonTech review.jpg
  • Tesla Powerwall 1 - US$864 per kWh (10 year life) – 85% DoD
  • Tesla Powerwall 2 - US$482 per kWh (10 year life) – 85% DoD**
  • LG Chem RESU 2 – US$631 per kWh (10 year life) – 80% DoD
  • PylonTech Extra2000 - US$594 per kWh (8 year life) – 80% DoD
  • Auqion Energy - US$675 per kWh (8 year life) – 100% DoD
  • Narada REXC - US$650 per kWh (8 year life) – 50% DoD
  • BAE Secura PVV - US$635 per kWh (8 year life) – 50% DoD

** Not available until Q1 2017

 

Cost per kWh per year over battery life *

* Including battery efficiency factor - the round trip efficiency of the battery during charging and discharging in which some energy is lost.

* Including battery efficiency factor - the round trip efficiency of the battery during charging and discharging in which some energy is lost.

Conclusion

With the release of the Powerwall 2 and new generation RESU series from LG chem a comparison based on cost per kWh over battery life shows the new Powerwall 2 as the best value with the LG batteries close behind. It is important to note there are several assumptions used and true performance in real world conditions may vary. Also this comparison is focused on smaller capacity (hybrid) systems used for residential applications less than 20kWh. For larger capacity applications lead based batteries would be much more competitive.

The Powerwall 2 (AC version) also includes a 5kW battery inverter and so will be the best value for money but it's worth noting that it doesn't incorporate a solar inverter or back-up capability so like the other battery options additional equipment will be required. The Powerwall's are the only systems which incorporate a liquid temperature management system which may prove to prolong battery life over time. The new LG chem RESU batteries may have a slightly higher up-front cost but due to above average efficiency and huge range of battery sizes to choose from end up as one of the two best options, especially if you have an older system and want to move from lead-acid batteries to lithium.

Battery Size

LG batteries are the lightest and most compact coming in at close to half the size and weight of the Powerwall, and the new range are able to be expanded up to 19.6kWh capacity. If a smaller system is required (less than 10kWh) and space is an issue then the LG chem or Pylon Tech batteries would be the best option.

Lithium Battery Power output comparison LG Powerwall Pylon Tech

Power Output

Continuous power output of the lithium batteries can be limited as highlighted in the above chart, although in some cases multiple battery modules can be linked together in parallel to provide greater power output. However if a high capacity, above 20kWh or a high power output system above 5kW is required then Gel lead-acid from BAE, Narada or any of the other well known manufacturers would generally be the perfered option.

Gel VRLA battery Sonnenschein

Note: Other well known, high quality, tubular Gel battery manufactuers include:

  • Sonnenschein
  • TAB
  • Hoppecke

Compatibility

Besides the cost per kWh figure there are many important factors to consider when selecting a battery storage system such as compatibility with the hybrid or interactive inverter and adaptibility with your existing solar setup (if installed). The Powerwall 1 was somewhat limited in this regard and can only be used with the SolarEdge inverter for single phase and Fronius inverter for 3 phase, it was also unable to operate as a back-up power supply without additional equipment. Tesla have learned from this and the Powerwall 2 (AC version) will have an integrated inverter but it is not yet know how it will provide back-up power or operate off-grid. In contrast the LG chem batteries are compatible with all leading hybrid and high-end interactive/off-grid inverters so this gives much greater system flexibility. PylonTech are also compatible with most leading hybrid inverters.

Based on a typical charge cycle (as per batt specs) and discharge duration of 8 hours.

Based on a typical charge cycle (as per batt specs) and discharge duration of 8 hours.

Another important consideration is some hybrid and off-grid inverters are optimised for charging lead-acid batteries and some lack the compatible communications to charge/monitor a lithium battery management system (BMS). As mentioned the new LG chem RESU batteries are compatible with almost all the leading solar hybrid & off-grid inverter brands (48V). The list now includes SMA, Selectronic, Solax, Sungrow, Schneider Electric, Ingeteam, GoodWe, Redback and Victron Energy.

The communications used by the Pylon Tech batteries are not compatible with many off-grid inverters but can be used with the popular Redback and Solax hybrid inverters. See here for full hybrid/off-grid inverter details and reviews.  For this reason it is recommended that you purchase a hybrid kit (battery and inverter combo) which is known to be compatible. Some examples are:

There are also many all-in-one systems with built-in battery storage such as Alpha ESS, Solax-Box, Enphase, Sonnen Eco and Samsung ESS.

 

Going Off-grid?

Whilst the lithium batteries seem to be the most cost effective solution and excellent for most smaller hybrid applications if you are setting up an off-grid system then high quality gel or carbon lead-acid batteries are still the most trusted option. Lead-acid batteries are a well proven technology and still advancing. In most cases with a correctly designed system you can expect a life of 10-15 years. Also most lithium batteries are not able to be linked up to provide adequate storage capacity for larger off-grid systems above 20kWh, where as lead-acid cells in series can provide energy storage of 500kWh or higher.

Off-grid system Review - Selectronic SP PRO multi-mode inverter and 48kWh Gel battery bank

For information about designing a solar powered home refer to the building off-grid guide on our other site. You don't have to build an 'earth ship' made from recycled materials to have a solar powered off-grid home. Although looking at the newer housing developments we definitely need more unconventional and intelligent/passive home designs.

How much does it cost to go off-grid?

To learn more about selecting an off-grid or hybrid solar system for your home and the costs involved see our guide to selecting a home solar battery system.

 

Battery Recycling and Sustainability

With an ever increasing number of battery installations around the world comes the inevitable problem of recycling the batteries once they have reached the end of their usable life. In the case of lead-acid based batteries this is not an issue as the infrastructure and recycling collection centres are already in place in most countries, enabling the Lead, plastic and electrolyte to be extracted and recycled relatively easily. In fact approximately 96% of all lead-acid batteries are recycled.

The Aquion Sodium-ion (salt water) battery system is possibly the only battery which has been designed with sustainability in mind. With a unique non-toxic chemistry they are the first battery manufacturer to have met all the stringent criteria to obtain cradle-to-cradle certification for sustainability. Also since Aquion batteries are manufactured using abundant materials they are not be likely to suffer any material shortages due to high demand.

Lithium batteries on the other hand are the obvious achilles heel with many manufacturers not yet fully capable of recycling the lithium cells. However there have been several breakthroughs in recent months by independent groups which are developing advanced recycling techniques specifically for complex lithium based batteries.

Since almost all lithium batteries are still in use there is no real push on recycling until the batteries reach their end of life. The recycling difficulties lie in the complex lithium chemistries being manufactured of which there are several variations. Some cells are in powder form, others coated onto metal foil, all of which must be separated. At present the safest Lithium combination is lithium iron phosphate (LiFePO4 or LFP for short) which is also one of the lithium batteries which can be recycled. Lithium cells are also much smaller and often incorporate electronic management systems and thermal sensors which will also need to be disassembled. There is abundant quantities of lithium minerals but it is a finite resource so this will eventually lead to greater incentives to develop more ways to recycle lithium batteries as the raw material cost will no doubt rise as demand increases.

 

FURTHER INFORMATION AND REVIEWS:

For more information to help you understand hybrid inverter technology and select the appropriate inverter or battery for your installation, see our introduction to solar & hybrid inverters

For more reviews on hybrid solar - Hybrid inverters and energy storage systems