Deye Hybrid Installations: A QC Checklist for ESS, Earthing and Caravan Battery Questions

Earlier this week I rejected a handover file because the drawing said ESS and the site had a battery cabinet with no earth conductor connected to the inverter chassis. It wasn't a subtle problem. The file described an energy storage system, but the physical installation did not have the earthing and protections that an ESS needs.

I'm a quality compliance manager at a renewable-energy company. I review roughly 200 project handover files a year before equipment is approved for commissioning. I don't design every electrical detail. I do have to know which missing detail will fail later.

This checklist is for integrators and installers working with Deye hybrid inverters and small storage subsystems. It covers the ESS electrical meaning, Deye 5kW hybrid inverter configuration, Deye hybrid inverter 10kW earthing conductor size, and the caravan/off-grid side where AGM vs LiFePO4 gets misunderstood.

1. Understand the ESS electrical meaning before ordering anything

ESS in electrical documents means Energy Storage System. In a Deye context, that means the whole chain from inverter and battery terminals through communications and metering, isolation, overcurrent protection, and earthing. It is not just another word for the battery cabinet.

Here is a communication failure I've seen more than once. The word 'ESS' was used for weeks. The supplier heard 'battery.' The customer heard 'complete system that can run my overnight load.' They discovered the mismatch when the design arrived with no battery management wiring and no PE terminal.

The drawing should show an ESS boundary box with every component inside it. Once that box is closed, you can see why earthing and protection are not optional.

2. Check what the Deye 5kW hybrid inverter is actually supposed to do

The Deye 5kW hybrid inverter is a popular workhorse in many single-phase storage installations. The common issue in my quality queue is not the inverter hardware. It is the assumption that all 5kW models are interchangeable and that 'hybrid' means the sizing is automatic.

Before approving a Deye 5kW hybrid inverter, I look for the system mode and the battery interface in writing. Is this a grid-tie storage system with backup, or an island installation? Which battery voltage and maximum current are you designing for? Where is the CT or smart meter located? If the bill of materials simply says 'Deye 5kW hybrid inverter' and nothing else, I reject the submittal.

The CT location is almost always an installation problem. The inverter can only manage power flows correctly if the CT is placed on the grid side and orientated with the arrow pointing toward the grid. A reversed CT makes the hybrid charge when it should export and export when it should charge. Photograph the CT before closing the consumer unit and mark the arrow direction on the drawing.

3. Deye hybrid inverter 10kW earthing conductor size: treat it as a calculation, not a guess

Deye hybrid inverter 10kW earthing conductor size is one of the most common technical questions because it is tempting to copy an earthing specification from a smaller inverter. The earth is not just a green wire connected to a chassis screw. It is part of fault protection.

For the 10kW Deye hybrid inverter, the installation documentation I work from specifies a PE conductor that is generally 10mm² copper minimum on TN earthing arrangements. A 6mm² earth conductor is often fine on a smaller inverter, but it is not automatically fine on a 10kW unit. If the phase conductor is larger than 10mm², or if the earthing system is TT, the national wiring regulation and the earth fault loop calculation may require a larger conductor or a different fault-protection method.

I am not a licensed electrical engineer, so I will not tell you to ignore the local calculation. What I can tell you from the quality side is that the Deye manual minimum is only the starting point. I reject systems where the spec writer used a 6mm² generic earth conductor without confirming loop impedance, fault current, and the local regulation. IEC 60364-5-54 is a useful reference for protective conductor sizing, but the current version of your local wiring code is the document that should appear on the drawing.

The PE conductor is not a signal ground and it is not the same as the PV frame bonding conductor. On a Deye hybrid inverter, the PE connection on the AC terminal block is the main protective earth connection to the battery and DC side as well. If that connection is missing, the whole storage system is floating in a way that can turn a simple fault into a dangerous fault.

4. Solar charge controller for caravan: design for the battery profile first

Customers who order a Deye hybrid for the house often ask for a separate solar charge controller for a caravan or outbuilding. The quality mistake is to treat that controller as a low-value accessory. It is a separate charge system with its own failure modes.

With a solar charge controller for caravan installations, the controller type matters less than the battery profile. A small PWM controller can be perfectly acceptable for a small panel and an AGM battery. An MPPT controller makes sense when the panel voltage is significantly higher than the battery voltage, or when you want more yield from a limited roof area. The critical point is not always 'MPPT is better.' It is that the battery type setting on the controller must match the battery chemistry.

5. AGM vs LiFePO4: don't choose before you know the charge source

AGM vs LiFePO4 is not a simple 'new technology beats old technology' decision. It depends on the charge source, the temperature, the load pattern, and the cost of the whole installation.

From my perspective, the first question is not 'which battery has more cycles?' It is: what charge voltage does the controller deliver in absorption and float, and does the battery accept that profile without damage?

AGM remains practical when the charge controller has an AGM or lead-acid profile, you do not cycle the battery deeply, and the location can drop below 0°C without a battery low-temperature protection circuit. AGM batteries also have a lower initial cost and are generally tolerant of cold storage.

LiFePO4 becomes the better total-cost decision when you cycle the battery daily, the controller has a LiFePO4 or user-defined profile, weight matters, and you respect the low-temperature charging limit. For a 12V LiFePO4 battery, a common charge voltage range is 14.2V to 14.6V. Many controllers with an AGM preset go higher and then float continuously. That combination is where good batteries fail early.

Never expected AGM to still be the right answer in some 2025 projects, but it is. A correctly-charged AGM battery is safer than a LiFePO4 battery running on a controller profile designed only for lead-acid.

Final QC routine before energising

Use this before you send the commissioning file:

1. Draw the ESS boundary so everyone knows what is inside the Energy Storage System.
2. Confirm the Deye 5kW hybrid inverter system mode, CT location, battery voltage, and battery current limits in writing.
3. Verify the Deye hybrid inverter 10kW earthing conductor size against the actual manual and local earthing rules. Keep a photo of the PE connection.
4. Set the solar charge controller for the caravan to the exact battery type installed, AGM or LiFePO4.
5. Measure the earth loop resistance and confirm the controller menu before switching on.

I would rather reject a drawing on Tuesday than investigate a failed cable on Friday. That is what prevention means in quality work. Most first-delivery rejections are avoidable. The fix is usually five minutes of verification before the system is energised.