Fox ESS EQS2900 2.88kWh Slave Battery

Fox ESS EQS2900 2.88kWh slave battery

The Fox ESS EQS2900 is the expansion battery for the EQ2900 high-voltage storage system. It is used to add capacity to a compatible battery stack and is designed to work alongside the matching master module within the same range. For customers familiar with previous Fox ESS part codes, EQS2900 is the updated replacement for older ECS2900 references that may still appear in historic paperwork, older websites or existing installation records.

That change in naming is worth making clear because many buyers still search by the older ECS code. On a product page, this helps connect older search habits with the current Fox ESS range while keeping the listing accurate to today’s product naming. It is also important to highlight that current EQS2900 modules use Type A connectors, so older systems should be checked carefully before any additional batteries are ordered.

What EQS2900 is used for

EQS2900 is used when a Fox ESS EQ2900 battery system needs more storage capacity. It is the support or slave battery in the stack, which means it adds extra usable storage but does not replace the role of the master module. If a project needs the main battery in the system, the correct product would be the EQM2900 master battery instead.

This makes EQS2900 suitable for planned battery expansion, storage upgrades and projects where a modular approach is preferred. Rather than replacing the whole battery setup, installers can increase capacity using matching modules from the same Fox ESS family.

Main features

• 2.88kWh nominal capacity
• Slave battery for the EQ2900 range
• 90% depth of discharge
• CAN communication
• Scalable system capacity up to 20.16kWh
• Supplied in Type A connector format

The 2.88kWh module size makes it easy to expand storage in manageable steps. That is useful for projects where the original installation has been sized around current needs but may need extra battery capacity later. It also helps customers build storage gradually rather than committing to a much larger setup from the start.

Fox ESS also states 90% depth of discharge for the EQ2900 platform, supporting strong usable energy from the installed battery capacity. Together with CAN communication and the modular design of the range, EQS2900 offers a straightforward route to storage expansion within supported Fox ESS systems.

Understanding the slave battery role

One of the most important things to understand about EQS2900 is that it is not the master battery. It is the add-on battery used to increase capacity once the correct master module is already in place. In simple terms, this is the battery for expansion, not the battery that starts the stack.

That distinction matters because it helps avoid ordering mistakes. If a customer is building a new EQ2900 system or replacing the master battery, they should be looking at EQM2900. If they are adding more capacity to an existing compatible stack, EQS2900 is the correct battery to consider.

Installation and compatibility

Fox ESS describes the EQ range as a plug-and-play battery solution, helping installers work within a modular and recognisable system design. For battery expansion projects, that is a practical advantage because it keeps the installation within the same product family and supports cleaner future upgrades.

As with any battery expansion work, compatibility checks are essential before ordering. Installers should confirm the existing system layout, supported battery configuration and connector format before mixing new and older components. This is especially important here because current EQS2900 stock is supplied with Type A connectors, while older ECS-series installations may not always match.

Replacement for older ECS2900 references

If you have searched for ECS2900, this is the updated Fox ESS model you are most likely looking for. EQS2900 is the current replacement reference for the older 2.88kWh slave battery, making it easier for buyers to move from older stock codes to the latest naming used in the EQ range.

That is helpful both for trade buyers and for website search visibility. Many customers continue to use the part codes they already know, so clear replacement wording helps them find the correct current product without confusion.

Why buy Fox ESS EQS2900 from Evergy

At Evergy, we know that battery expansion products need to be clearly described so customers can order with confidence. The Fox ESS EQS2900 is a sensible choice for projects that need extra storage within the EQ2900 high-voltage battery range, whether for a new design that allows future growth or an existing system being expanded carefully.

It is a strong fit for buyers who want to stay within the Fox ESS battery platform, use the current replacement for older ECS2900 codes, and add capacity without changing to a completely different storage system.

Related ranges

You can also browse our wider solar batteries range or explore more Fox ESS products to compare compatible storage options.

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