Choosing the best batteries for your RV: AGM vs Lithium

With lithium batteries becoming a more common option in RV solar, it can cause information overload for both dealers and customers alike. Do they go with the traditional Absorbed Glass Mat (AGM) or move to lithium? Here are a few tips to weigh the benefits of each battery type for your customer and help them make a more informed decision.

Lifespan and Costs

Budgets play a huge role in deciding which battery to get. With lithium batteries being more expensive to begin with, it can seem like a no-brainer to go with an AGM. But what causes this difference? AGM batteries remain less expensive because the materials used to make them are inexpensive and widely available. Lithium batteries, on the other hand, use more expensive materials with some being harder to come by (i.e. lithium).

Another part of the decision-making process to consider is the lifespan of these batteries. This is where the initial cost of the lithium could be offset. The following points highlight the differences between lithium and AGM:

AGM batteries are sensitive to depth of discharge. This means the deeper the battery is discharged, the fewer cycles it has.
AGM batteries are generally recommended to only be discharged to 50% of their capacity to maximize their cycle life. This limited depth of discharge (DOD) of 50% means that more batteries are required to achieve the desired capacity. This means more upfront costs, and more space needed to store them.
A lithium (LiFePO4) battery, on the other hand, is not affected much by depth of discharge so it boasts a much longer cycle life. Its DOD of 80-90% means fewer batteries are required to achieve the desired capacity. Fewer batteries mean less space needed to store them. More on discharge depths later.

Initial Cost Per Capacity ($/kWh)

AGM – 221; Lithium – 530
Initial Cost Per Life Cycle ($/kWh):
AGM – 0.71; Lithium – 0.19

AGM

NOT BAD

Lithium

GREAT

Technology

While lithium batteries may have advantages, AGMs still have proven time-tested technology as they have been around much longer. AGM’s also have the upper hand when it comes to charging in freezing (below zero degrees Celsius) temperatures – albeit, with a bit of a hit to its efficiency. Unlike AGM’s, lithium batteries require temperature regulation for use in below-freezing temperatures.

AGM

GREAT

Lithium

GREAT

Size and Weight

Lithium batteries have the added bonus of not containing the heavier lead-acid found in AGM’s, therefore, are much lighter. Since their DOD is 80-90%, lithium a battery bank generally occupies less space. (Less batteries are required for a desired capacity.) Because of this, lithium batteries can save quite a bit of volume and weight in comparison to the traditional AGM’s.

AGM

NOT BAD

Lithium

GREAT

Discharge

The depth of discharge of a battery refers to the percentage of the battery that has been discharged (used) relative to its overall capacity within a charge cycle. A lithium battery with an overall capacity of 100Ah (amp hours) will give you 80Ah-90Ah (or discharge to 80%-90%), while AGM’s offer 50Ah (or discharge of 50%) before needing to recharge.

Based on these numbers, AGM’s are the better option for those who use their RV only a few months at a time, and lithium batteries are preferable for those who are off-grid all the time.

AGM

NOT BAD

Lithium

GREAT

*Keep in mind which application you are using it for. It can be great for intermittent RV’ers.

Maintenance

As both the Go Power! lithium and AGM batteries are sealed, they are considered maintenance free.

AGM

GREAT

Lithium

GREAT

*Keep in mind which application you are using it for. It can be great for intermittent RV’ers.

Summary

AGM – While it may seem like lithium is the better option, AGMs are still a good consideration for some. Here’s why:

Can be used as starting batteries (most lithium batteries cannot)
Perform better in colder conditions
Time-tested technology
Can be wired in series
Less expensive initially
A good starting point for most amateur installers

Lithium – A fairly new entrance into the RV battery market compared to the AGM, the lithium battery is an efficient powerhouse. Its benefits are as follows: