Types of Batteries
GEM Energy uses two types of batteries for solar electricity storage: Lead-acid (also called gel or AGM) and Lithium-ion (as well as lithium-ion’s relatively new cousin, lithium-iron-phosphate) technology. When it comes to choosing the right battery for your situation, GEM Energy will take into account a variety of factors. Budget, ambient temperatures, available space, usage patterns and what type of solar panel and inverter you choose are all important considerations when we match up your system’s battery storage. Lithium-ion batteries like Tesla Powerwall tick some important boxes in terms of performance and longevity, yet they are still rather expensive and less proven than traditional lead-acid batteries.
Tesla Powerwall installed at a private residence in May 2017
Modern lead-acid batteries continue to stack up quite well against the new technologies. They are not just a lot cheaper, but also completely recyclable and with a century-long track record of reliable performance. One of the drawbacks for Gel or Lead-Acid battery storage units is that they are only viable for slow cycling, as in being charged steadily during the day and discharged over the full night. The technology required for fast and hard draw is Lithium Ion – this is what makes them popular in Electric Vehicles.
Shipping container with lead-acid batteries for off-grid setup.
The other main benefit of Lithium Ion batteries over Gel or Lead-Acid technologies is the footprint required for the installation. Conventional battery technologies can only be discharged to 40-50% of their total capacity in order to last long enough to yield a good return. This means that you will need a lot more room than with a Lithium Ion bank which can be discharged to 90% and still last 20 years. Gel or Lead-Acid batteries would only typically last 5-7 years when used in a scenario like this. One other important concept that GEM Energy would like to introduce you to, is the Depth of Discharge (DoD) percentage commonly assigned to batteries. In order to gain maximum cycle life (the amount of discharge/recharge cycles over the lifetime of the battery), it is recommended that the battery never gets discharged past about 80 per cent of its capacity – this would be called 80% DoD. The exact figure depends on brand and of course battery chemistry, but DoD describes the degree to which a battery is emptied relative to its total capacity. For example, if you have a battery bank with a nominal capacity of 10 kilowatt-hour (kWh), at 80% DoD, there is 3kWh of charge remaining. All of this means that a battery bank really needs to be properly sized up in order to maximize your system’s performance and cost-effectiveness. GEM Energy has a team of experienced engineers available to support you with this process of choosing the right battery backup system.
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Battery Comparison
| Lead-acid | Lithium-ion (and lithium-iron-phosphate) | |
|---|---|---|
| Performance & Efficiency | - Medium efficiency – a typical lead-acid battery will deliver 75–80 per cent of the energy that was input during charging - Medium tolerance to deep discharging (DoD) - Function best under a clean charge/discharge regime: Withdraw energy steadily, then charge back up steadily | - High efficiency - a typical lithium-ion battery will deliver 95 per cent of the energy that was input during charging - Higher tolerance to deep discharging (DoD) - Ability to ramp up and provide large amounts of power quickly (this makes them popular for Electric Vehicles) |
| Longevity | Can last over ten years under a clean charge/discharge regime | - Long lifetime (measured in charge/discharge cycles) - Can be more regularly discharged without losing capacity |
| Safety | Proven, mature technology | Lower risk of gas explosion as no hydrogen is produced |
| Freight | No freight safety restrictions, so fewer hurdles when importing | Freight restrictions when importing |
| Recycling | Easily recyclable | No standardised recycling program yet |
| Size | Lighter and more compact for the same storage capacity | |
| Temperature | High tolerance to high temperatures | |
| Maintenance | Modern Gel and AGM are maintenance free (no topping up with water or acid) | No maintenance |
| Standards | Highly standardized | Lack of standardization for installation and use (at this time), meaning that batteries must be carefully matched with chargers/inverters |
| Cost | Relatively cheap | Higher upfront costs |
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OUR BATTERY SUPPLIERS
LITHIUM ION / IRON PHOSPHATE BATTERIES
LEAD ACID BATTERIES
What our customers say about us
The work was completed in conjunction with our business needs and everyone from GEM Energy involved with the installation was professional, competent and courteous to the YMCA staff and our patrons.
