WHICH IS THE BEST BATTERY TYPE?
IT ALL COMES DOWN TO HOW YOU ARE GOING TO USE IT...
Different battery types will have different performance parameters depending on their chemistry and construction.
The first thing to work out is - what battery type best suits your use? The information aims to give you a more informed decision.
OFF-GRID or ON-GRID HYBRID or "BACK UP / U.P.S?
Off-grid and on-grid refers to the mains electricity grid and whether your house has an existing connection.
Either way you can have a solar-battery system which provides you with the electricity you produce and store yourself.
OFF GRID USE
Larger battery bank (often 3-4 days autonomy) , with shallow daily discharge
People who are in rural areas may only be 200m away from the power lines but still be charge large sums of money to have their houses connected. In this situation an off-grid system is a great alternative, possibly costing the equivalent or less than the grid connection fee. After the initial outlay you’re providing your own free-power.
The ideal battery types for this off-grid situation have the following properties :
Quality of construction, materials and chemistry – Purity of plates, Acid density, plate separation, oxygen combination and container quality all matter when you investing in a long lasting, solar system specific application.
High Cyclic life –Cyclic life which is a great indicator of a batteries true life expectancy. A cycle is each time a battery discharged (to a certain level) and re-charged, which in an off-grid may occur nightly. A good battery with a high cyclic life should last from 8 – 15 years.
Deep cycle – In an off-grid situation your batteries have to get you through bad weather periods (days autonomy) where no solar is recharging the batteries but users still require power. Deep cycle batteries can handle this occasional low depth of discharge. Please note - this does not mean deep cycle batteries are to be cycled to a low depth of discharge frequently.
Maintenance free – A good off-grid should be seamless and foolproof. Batteries are also often in remote locations or out of sight, out of mind. A battery that doesn’t need to be toped up with fluids ensure the batteries don’t run dry which is the best way to damage your batteries.
Safe to store and transport – Being sealed and spill proof batteries can be laid down in rack mounted battery enclosures or during transport without leaking corrosive electrolyte or effecting operation. This also reduces freight cost for people in rural or remote area’s as batteries or not classified as a dangerous good. Special vent valve design ensures they only gas under high charge/discharge rates.
Solar Series Absorbed Glass Mat (AGM)
Our Solar Series AGM batteries are extremely good value for money with a great price and a 10 year cyclic life. The construction makes them maintenance free, cuts out spill hazards while reducing gassing and stratification. They are well made, deep cycle batteries with good resistance to high and irregular charge/discharge rates. Perfect for off-grid applications.
All quality construction purpose built for off-grid solar applications .High purity raw material gives less gassing, high corrosion-resistant, low self-discharge. Durable copper and stainless steel terminals for high electric conductivity.
The unique plate group configuration, high quality AGM separator and battery management system ensure battery with a longer service life. With a cyclic life of 3500 life cycles @ 20% DOD, translating to a 10 year cyclic life. Great value for money.
All of our Solar Series AGM’s are made with high density, specialized lead past formula and alloy sheeting for deep cycle application.
Maintenance-free high strength ABS or PP case & cover and valve-regulated construction.
No loss of performance or chance of electrolyte spill when used vertically or horizontally in a rack mount situation. Classified as “Non-Spill Battery” for transportation. Exclusive electrolyte formula and separator protects the electrolyte density from stratification.
OPZV Tubular Plate Gel
Tubular gel technology give the highest performance of all Valve Regulated Lead Acid (VRLA) batteries. Our Tubular Gel batteries have superior 20 years cyclic life and extremely good deep cycle ability. Maximum charge/discharge rates are also superior to most technologies. They are sealed, maintenance free, cut out spill hazards and stratification all together. This is a step up from any AGM technology.
The quality construction and advanced technology makes these ultra-high performance Tubular Gel batteries the best valve regulated lead acid batteries on the market. This technology means extremely low self-discharge, higher temperature resistants and no internal short circuits are possible.
The tubular die cast plates and true gel chemistry these batteries result in a highly reliable, stable, long life battery. With 5500 life cycles @ 30% DOD these batteries can give a 20 year cyclic life. This is a superior cycle life and with a 5 year warranty you won’t find better for your money.
Superior deep cycle ability and deep discharge protected these batteries have a cyclic life of 10 years @ 50% DOD or 5 years @ 80% DOD. Tubular Gel have a great deep discharge recovery.
Maintenance-free, high strength, flame retardant ABS case & cover. Valve-regulated construction and flame arrestors.
No loss of performance or chance of electrolyte spill when used vertically or horizontally in a rack mount situation. Classified as “Non-Spill Battery” for transportation. No acid stratification, so no equalizing charge necessary and less losses during gassing.
ON GRID USE
Smaller battery bank, less than 1 day autonomy, very deep daily discharge.
Many people currently have or are think of investing in grid connected solar panels. In the past good feed in rates for grid connected systems made it worthwhile to feed the solar power back into the grid.
Currently with low feed in tariffs people are looking to store any unused solar power in batteries and use it of a night. The demands on these battery storage systems differ from batteries previously discussed. Batteries ideal for the situation must have the following properties -
Long cyclic life and low depth of discharge- In a grid connect battery backup system the battery storage is designed to just get your through the night time until the solar input returns the next day.
You always have grid connection for bad weather so day’s autonomy is not required. A small battery bank that can be used to a low depth of discharge is essential.
With the correct battery you can use close to your batteries full capacity night after night continuously and still get a 10 year battery life.
High discharge and charge ability – In relation to their size batteries in these systems are usually supplying considerable loads over short periods. Grid connected users often have electric hot water elements, electric ovens/cooktop and air conditions.
Also as you are using the batteries full capacity each night it needs to be charged quickly the next day from your solar array.
This means large charge and discharge demands on a battery. If you wanted good battery life this type of performance was unattainable in older battery technology. Luckily due to advances in technology and availability the battery described below tick all the boxes.
Safe – Due to demands described above and the fact that there is usually less room to house on-grid battery storage, safety is paramount. Good Battery Management Systems (BMS) or using none flammable chemistry is a must.
Lithium ION (LiFePO4)
Lithium ION batteries are an immense breakthrough in battery technology that leaves last centuries technology behind. Half the weight of lead-acid batteries they can be used to their full capacity and still have a long life. There far superior charge and discharge rates are perfectly suited to supplying the majority of their capacity to house hold loads, all in a few hours of a night.
Lithium ION have revolutionary cyclic life at deep discharge rates. LiFePO4 batteries can supply 4000 life cycles at 80% DOD, that’s a 10 year battery life using close to the batteries full capacity every night. This figures that far exceed any old technology on the market.
Our Lithium batteries have incredible charge and discharge rates, defying Puekert’s Law.
LiFePO4 chemistry offers the highest and safest power to weight ratio of any Lithium Ion battery on the market. Our Fusion Lithium range is constructed with a built in state of the art BMS that controls cell balancing, over/under voltage protection and short circuit protection.
WHAT SIZE BATTERY
Correct battery size is one of, if not the most crucial thing to your off-grid system and how it aligns to your expectations.
To size your battery bank to ensure you have a system that works, designers follow a process:
Estimate your power usage
The most accurate method to estimate your power consumption will depend on your circumstance. Assessing your current power bill, energy audits and power consumption meters are all ways to get the best idea on when and how much power you will use. Looking at the appliances use, especially big consumers like electric hot-water etc. and the amount of hours they run per day, is usually the first step.
Battery Voltage required
Some off-grid customers require a certain battery bank/system voltage. To have the safest, most efficient system, the size of the off-grid system and your power consumption should dictate the battery/system voltage.
Power = Voltage x Current. A battery bank that has a total capacity of 10.5 kWh would require a 12 Volt 880Ah battery bank. A 24 Volt 440Ah battery bank would have the same capacity - 10.5 kWh. You don’t save yourself money buying using a smaller battery voltage, in fact can increase the strain and requirements.
Building in days autonomy and Depth of Discharge.
Once you have an estimated daily (24hr) power consumption, you can calculate the battery storage required to keep you running, even during bad weather periods. The rule of thumb in off-grid design is 3 days before reaching a 70% depth of discharge (DOD), meaning the batteries can keep your house running as normal for 3 days with no solar or generator input whatsoever. Three days autonomy may equate to over a week of bad weather before your batteries need to be recharged.
Ensuring you have battery storage for bad weather periods is crucial to having a system that will work all year round. There is no use spending money on a system, only to run a generator every time you have bad weather.
Sizing to have day’s autonomy also builds in the correct battery depth of discharge (DOD) during your good weather periods. How far you cycle your batteries during average conditions directly relates to your battery life. The heavier you cycle your battery each day the less life it will have, the effect of DOD on a battery is dramatic. To get the best life batteries should only cycle on the top 20%-30% during your average conditions. If you use this 20% each day, even after 3 days of no solar/gen input your batteries will only be at 60% - 70% depth of discharge.
Our certified Stand Alone Power Supply (SAPS) designers and installers are always available to help you with sizing your batteries, ensuring you receive what you expect from your new off-grid system. You can always reach us via email or call 1300 883 847.
THE 5 MOST IMPORTANT THINGS...
What to consider when making the move to off grid power.
When considering off-grid as a viable option to power you residence, we must assess you daily power consumption. When calculating how much power you may use in a new property you must consider 5 important things and how they relate to reducing your systems requirements, possibly saving your thousands of dollars in system costs.
Energy intensive appliances are those that heat or cool a space, be it air, water or an element. We ask all our customer to contemplate:
1. Gas or Solar Hot water – An average hot water system for a 3 or 4 person house may easily consume 4 kWh per day alone if it is powered from your new off-grid system. Gas or Solar Hot water is a great way to simply and drastically reduce you power consumption, in-turn saving you big $$$.
2. Gas Cooking – Electric cook tops and ovens are another big requirement for an off-grid system to supply. All though running ovens and elements from your off-grid system is definitely achievable you may find going with gas will save you allot of money.
3. Wood fire heating – Electric Bar heaters are massive consumers and when run for long periods don’t really fit-in with an off-grid situation. Wood fire heating is an options taken up by many of our customers. Nice warm ambient temperature of a wood fire stove can also be harnessed to heat up living spaces
4. Efficient appliances – If you are buying a new property a lot of customers take the opportunity to ensure they get the most efficient appliances to reduce their off-grid systems requirements. Energy star ratings are now present on most appliances along with a yearly kWh usage. This can be used to select the most efficient appliances for your budget. LED lighting are now a very efficient option and give off good light. As numerous lights are usually on for at-least a few hours a day a more efficient light can add up to big savings.
5. Change your behaviours - It’s simple when the sun is out use your bigger consuming appliances. Do your washing and vacuuming during the day, this way the electricity is in-effect supplied directly from you panels and not discharging your batteries. For smaller systems you may want to load-share, which means stagger the use of your high draw appliances such as toasters, microwaves and kettles etc. This will reduce the requirement for a large off-grid inverter which will save you even more money on system cost.