How to choose battery for solar trailer, GEL or LFP?

Batteries, as one of the most important components of solar trailers, are crucial for the stable and reliable operation of monitoring or lighting systems. Therefore, selecting the appropriate battery type is very important. At BIGLUX, we typically offer two types of batteries for selection. If cost is not a concern, we highly recommend using LFP (lithium) batteries; however, due to market competition and other factors, many customers also opt for Gel batteries.

An additional reason why we currently prefer Gel batteries on our mobile trailers is because they tend operate better under sub optimal conditions and are less prone to accidental damage or damage due to adverse environmental conditions. Let's analyze and understand the different types of batteries and their advantages and disadvantages.

Understanding LFP Batteries

A LFP battery is a type of lithium ion battery. It is rechargeable and useful in a variety of applications. It is also known as LiFePO4. LiFePO4 is the short form for "lithium iron phosphate." This name implies its composition.

The active material is an intercalated lithium compound. It also contains phosphate, iron, and oxygen. It uses lithium iron phosphate (LiFePO4) as the cathode material. And for the anode, it utilizes a graphitic carbon electrode with a metallic backing.

Key Characteristics of LFP Batteries

Voltage and Capacity
Voltage is the measure of electrical energy a battery has stored. It rises as the battery charges and falls as it discharges. LiFePO4 batteries have a fast charging rate. They also have 80% depth of discharge. Hence, they usually have high voltage and high capacity.

Energy Density
This refers to the amount of energy stored in a given space. LiFePO4 batteries have a high energy density. Hence, it will store more energy for any given size and give higher power output.

Cycle Life
A battery's cycle life is the number of charge and discharge cycles it can complete before losing performance. LiFePO4 batteries have a long expected cycle life of 2000 - 10000 cycles. 

Safety Features
LiFePO4 batteries do not contain lead and acid. Hence, they are less hazardous and do not cause contamination. They are eco-friendly.

Understanding GEL Batteries

A gel battery is a type of lead-acid battery. It is similar in composition to a typical lead acid battery. The only difference is that it uses a silica based gel. The gel is produced by mixing the electrolyte with silica and sulphuric acid. It does not use liquid electrolytes. And all the acids are suspended in a solid matrix. This composition makes it spill-free. It is also maintenance-free and supports deeper discharges.

Key Characteristics of GEL Batteries

Voltage and Capacity
Earlier, we established that the charging rate of a battery affects its voltage and capacity. GEL batteries charge slowly. Hence, they have low voltage values.

Energy Density
GEL batteries have low energy density. This means that gel batteries will require a heftier design for their storage capacity.

Cycle Life
When compared with other lead acid batteries, gel batteries have a greater cycle life. This is because they are sealed. Also, they do not require any maintenance like refilling water levels or cleaning plates.

Safety Features
GEL batteries contain lead and acid. These components cause environmental hazards. But they release less hydrogen gas, thereby reducing the damage it can cause.

LFP Batteries VS GEL Batteries

So which is better? LiFePO4 or Gel Batteries? I will analyze it in detail for you based on various indicators:

Depth of Discharge

When you start discharging a battery beyond a specific limit, it begins to suffer damage. Depth of discharge measures the percentage of the initial charge that can safely be discharged without causing harm.

LFP Batteries: Modern lithium-ion batteries have a depth of discharge of 98%. So you can discharge almost the entire charge without damaging the unit. This provides optimal conditions for use with most of the stored power available.

GEL Batteries: Like other lead-acid batteries, the depth of discharge is about 80% when new and 50% when older. This makes them less competitive compared to lithium-ion batteries.

Winner: Lithium-ion batteries have the highest depth of discharge and a longer operating time.

Lifespan

Regardless of type, a gradual decrease in performance occurs over a battery's lifespan. There is a point in time when the battery will become useless.

LFP Batteries: LFP technology is known for its superior durability, typically degrading by less than 1% per year and providing about a 10,000 charge cycle life.

Gel Batteries: Gel Batteries providing a useful lifespan of about 2000-3000 charge/discharge cycles.

Winner: A lithium-ion battery has a considerably longer lifespan, typically about five times longer than an Gel battery.

Size and Weight

Size is a key concern for people working with limited space. LFP batteries weigh approximately 50% less than  GEL batteries for the same energy capacity.

LFP Batteries: Lithium-ion batteries weigh less due to the absence of any liquid acid. Additionally, since they have a higher depth of discharge, a smaller lithium-ion battery can provide the same power as a larger lead acid battery.

Gel Batteries: GEL batteries contain a gel-like sulfuric acid liquid, which adds weight. Additionally, a low depth of discharge means that you need a high-capacity (big) battery for any given application.

Winner: Lithium batteries are the better choice in terms of weight and size.

Charge Time and Efficiency

LFP Batteries: Due to their higher efficiency, smaller lithium batteries can do the same job as larger GEL batteries. They also charge faster.

GEL Batteries: Although they charge considerably faster than wet lead-acid batteries, GEL batteries still charge much slower when we compare them with lithium-ion batteries.

Winner: LiFePO4 batteries charge faster than GEL batteries and over four times faster than general lead-acid batteries.

Operating Temperature Range

LFP Batteries: LFP batteries have a limited operating temperature range and the ranges must be strictly observed or irreversible damage will occur.

Charge Range: 32 F to 114 F

Discharge Range: -4 F to 130 F

GEL Batteries:While all batteries benefit from optimal operating temperatures, GEL batteries are a bit more resistant to damage at extreme temperatures. When temps dip below -4 F and above 110 F you will get a reduction in capacity by anywhere from 20-30%.

Winner: Gel Batteries are a better choice when it comes to extreme operating environments. Especially for application that require placing the batteries in a non climate controlled enclosure during summer and winter months, we find that this is currently the biggest factor in using GEL batteries.

Initial Cost

Cost is one of the most important factors when deciding between two battery types. There are two cost factors to consider – the initial cost and the cost per kWh. Here we will discuss the initial cost of each option.

LFP batteries require a higher upfront cost. Although lithium-ion batteries outperform GEL batteries when considering all other parameters, the initial cost is much higher.

Winner: GEL batteries win when you compare the initial cost. Over a longer time frame LiFePo4 may have a lower cost.

Choosing between LFP Batteries and GEL Batteries can be a daunting task. However, the above information should simplify your decision. If you have decided which battery to choose for your solar trailer and would like to know more about the products, please contact us.