Solar Batteries – Rentech Solutions

Solar Batteries

Solar batteries are designed to offer exceptional energy storage capacity and cycle life for off-the-grid energy sustainability.

Solar batteries form part of a solar system and are charged with energy captured by solar panels or from the grid. The sun’s energy is converted to Direct Current (DC) energy which is then converted to useable Alternating Current (AC) energy through inverter technology. The AC energy is distributed throughout homes, buildings and work areas with any excess energy stored in the solar batteries for future use.

Solar batteries are available in different technologies and capacities. Lithium-ion batteries with a built-in battery management system and high cycle life are increasingly becoming popular and affordable. With the battery being the heart of any back-up power system, choosing the correct solar battery technology and capacity is an important step in the design of a solar or back-up power system to meet the customer’s requirements.

A complete solar system with solar batteries sized for the customer’s requirements provides both security of supply during load shedding and grid failures, as well as electricity cost savings from own energy generation through solar panels. It is advantageous, empowering and an excellent long-term investment.

Benefits of Solar Batteries

Clean energy source

Noise reduction comparing to generators

Cost savings

Uninterrupted electricity supply

Considerations in Choosing Solar Batteries

A battery’s capacity is the total amount of energy it can store, measured in kilowatt-hours (kWh). The power rating is the amount of electricity that a battery can deliver at one time, measured in kilowatts (kW). A battery with high capacity and low power rating will deliver a low amount of electricity for a long time. A battery with low capacity and high power rating can run an entire home or larger operation, but only for a few hours.



Most solar batteries need to retain some charge at all times due to their chemical composition and to prolong their lifespan. The DoD refers to the maximum amount of a battery’s capacity that should be used. For example, sealed lead-acid solar batteries are usually operated at ≤50% DoD to achieve a reasonable cycle life, while lithium-ion batteries can operate at 80% DOD, 8kWh from a 10kWh battery, and still provide 5 years or more cycle life.


Round-trip efficiency represents the amount of energy that can be used as a percentage of the amount of energy required to fully charge a battery. For example, if a 5kWh capacity battery, which delivers 4 kWh electricity, would typically require 110% to 120% times the 4kWh to be fully recharged. The battery has 80% to 90% in round-trip efficiency. One should, however, remember that the battery is part of the total system, and the system also has inefficiencies and energy losses.


A battery’s ability to hold a charge gradually decreases the more it is used. For example, a battery might be warrantied for 5 000 cycles or 10 years at 70% of its original capacity. This means that at the end of the warranty, the battery will have lost no more than 30% of its original ability to store energy.

Solar batteries come with warranties that guarantee a certain number of cycles and/or years of useful life.

Rentech Solar Batteries


Lead-acid batteries feature tested technology that has been used in off-the-grid energy systems for decades.

While AGM and GEL batteries have a relatively short lifespan and lower Depth of Discharge (DoD) than other battery types, it is one of the least expensive options in energy storage. For off-grid solar systems where large battery banks are required, 2V tubular flooded lead-acid cells (PzS) or 2V tubular GEL cells (PzV) can be the preferred option, providing long life expectancy as well. Rentech offers a range of lead-carbon batteries at 12V, from 100 Ah up to 250 Ah. These batteries have a long cycle of life and excellent deep cycle discharge ability. They also provide an impressive charge acceptance ability and reliable performance under both hot and cold conditions. Lead-carbon batteries have a 2-year warranty.


The majority of new energy storage technologies use some form of lithium-ion chemical composition.

Lithium-ion batteries are lighter and more compact than lead acid batteries. They also have a higher DoD and longer lifespan when compared with lead-acid batteries. Although lithium-ion batteries are more expensive than their lead-acid counterparts, it offers lower life cycle and energy costs over the long run.

Rentech provides Lithium-ion batteries with proven Lithium Iron Phosphate (LifePO4) chemical composition and the range includes both 24V and 48V batteries, up to 7.68kWh. These batteries are designed for rack installation, and each battery has an integrated Battery Management System to provide high reliability and safety and for parallel installation of up to 15 batteries. These batteries have a long lifespan of 6 000 cycles at 80% DoD at 25°C and ≤0.3C charge/discharge rate. This product has a 5 year warranty with a 10-year warranty option.

Technical Assistance & Advice

Rentech provides technical assistance and advice to customers to help you choose the most appropriate solar batteries. Regular maintenance and the protection of batteries against extreme conditions are also important.


A number of factors determine the exact lifespan of solar batteries:

  • How much energy does a household or a workspace consume on a daily basis?
  • What are the capacity and power ratings for the solar batteries?
  • What is the storage capacity of the solar batteries in the system?
  • Is the entire solar system connected to the electricity grid?
  • What is the size of the solar array?
  • How and to what depth the batteries are cycled (discharged/charged) during the day and night?
  • What the partial state of charge usage versus fully charged and fully discharged usage is?
  • If the batteries are regularly fully charged with good charge absorption time.

Determining the lifespan of solar batteries needs a complete assessment of the solar installation. Regular maintenance and proper protection of batteries against extreme heat and cold is also important as this has a significant impact on the solar batteries’ lifespan.

Selection Table & Technical Documentation Downloads

Product Description Datasheets Manuals
Features: Built-in BMS. Parallel up to 15. Warranty: 5 years, 3500 cycles*; 10 year option 6000 cycles*. (* T&Cs apply).
BTESF24V100-R 25.6V 100Ah Lithium Iron Phosphate Rentech 24V Rack Mounted Li-ion Battery.pdf Manual - BTESF series LFP batteries Rentech.pdf
BTESF24V200-R 25.6V 200Ah Lithium Iron Phosphate
BTESF48V50-R 51.2V 50Ah Lithium Iron Phosphate Rentech 48V Rack Mounted Li-ion Battery.pdf LFP Batteries Quick Start Quide.pdf
BTESF48V100-R 51.2V 100Ah Lithium Iron Phosphate
BTESF48V150-R 51.2V 150Ah Lithium Iron Phosphate
Lead-Carbon sealed batteries
Features: Better partial state of charge tolerance for cyclic applications
JPC 12-100 12V 100AH Lead Carbon Rentech Lead Carbon 100Ah 12V.pdf
JPC 12-120 12V 120AH Lead Carbon Rentech Lead Carbon 120Ah 12V.pdf
JPC 12-150 12V 150AH Lead Carbon Rentech Lead Carbon 150Ah 12V.pdf
JPC 12-200 12V 200AH Lead Carbon Rentech Lead Carbon 200Ah 12V.pdf
JPC 12-250 12V 250AH Lead Carbon Rentech Lead Carbon 250Ah 12V.pdf
Inverter Settings for Lead-Acid Batteries
Deep Cycle Lead-acid batteries General purpose deep cycle Contact us for details
Flooded Lead-acid Batteries (PzS) 2V flooded lead-acid cells Contact us for details
Tubular Gel Lead-acid batteries (PzV) 2V tubular gel lead-acid cells Contact us for details