[!CAUTION] Working with high voltage is dangerous. Always follow local laws and regulations regarding high voltage work. If you are unsure about the rules in your country, consult a licensed electrician for more information.

Installation guidelines

This section will guide you towards making a safer installation of the battery. Please start by familiarizing yourself with your local regulations regarding solar inverters and stationary storage requirements. Make sure the inverter selection is approved by your grid operator before ordering parts. Finally, make sure the person installing the hardware has a valid electrical safety & installation training.

[!CAUTION] At the end of the day, you alone are responsible for the system.

Battery placement

The most important decision to make is battery placement. Any used EV pack should always be operated in an area where a potential fire would not be of risk for human life. Almost all salvage batteries come from crashed vehicles, with an unknown history. While the Battery-Emulator and your solar inverter performs several safety checks, note that almost all checks rely on communication data, so a physical error (damaged cell casings, ruptured/leaking cells, corrosion etc.) wont be easily detectable via software.

Due to all this, it is recommended to only install batteries in the following places:

• Outside
• Detached garage
• Tool-shed
• Underground
• Shipping container

Regardless of placement, great care must be taken to avoid water getting into the battery. While most EV batteries are splash proof, they cannot cope with large amounts of water/rain. If you are installing a battery outside, construct a roof to keep the battery dry.

[!TIP] Batteries can often be tilted, and installed on the side of a wall to save space

Keeping the temperature in check

Lithium batteries are like humans, they perform best at 20°C. Many installs will have the batteries outside or in basic sheds/shelters. This means the battery might be subject to extreme temperatures, which will affect the battery performance. Depending on your climate, this might mean -40°C, or +40°C, both being bad for battery performance/longevity.

Hot tips :hot_face: Many lithium battery chemistries stop taking charge/discharge at >50°C. Having the battery in direct sunlight in a hot climate like Australia can cause high temperature shutdown. This can be avoided by placing the battery in a shaded area, and/or utilizing the coolant loops found on some battery packs like Tesla batteries. For temperate climates this is usually not required at all. In the event that temperature cannot be maintained below 50°C, the Battery Emulator will automatically stop power transfer and raise an overheated fault event.

Cold tips :snowflake: The same is true for the other side of the thermometer, at low temperatures it is not possible to charge/discharge lithium batteries. This lower temperature limit depends on what chemistry is used. LFP batteries start to struggle already at <0°C, while other cells such LMO and NMC can still perform at -20°C. Simply using the battery by charging and discharging it will generate heat, and by putting the battery in an isolated space, this self-generated heat can be enough to keep the battery performing thru winter. Simply keeping the contactors engaged in a battery will consume between 10-20Watts, which is excellent for keeping some heat in it. Some batteries also contain heating elements, which will automatically turn on when it gets too cold. An example of this is the Nissan LEAF battery, which has internal heating elements that turn on at < -17°C. Other batteries like Tesla S/3/X/Y has coolant loops, which you can run a heated loop thru in order to keep the battery warm during the winter. A simple space heater can also be used to keep a battery shed heated during the winter. If the battery gets too cold, <-25°C ,the Battery Emulator will automatically stop power transfer and raise a battery frozen fault event.

Examples of battery placement

Example: Detached garage, vertical placement

Example: Wallmounted, with extra roofing

Example: Outside, vertical placement with waterproofing

Example: Underground concrete sarcophagus

Example: Shipping container

Wires and fuses

DC wire sizing is a very important part of planning your battery build. Most inverters accept 6mm² or 10mm²(check your inverter manual for more inf), but most EV packs are 50mm². This creates a small problem, you will need to step down this wire size. When stepping down, it's a good idea to install fuses directly near the battery, to protect your wiring.

• When selecting the hardware (wires,fuses,switches), make sure they are rated for the voltages in your system. Hardware designed for solar will often work great with EV batteries. Do note that if you are using an 800V battery, you need to buy hardware that is capable of 1000VDC, it is not enough to go with 500VDC certification.

• Also keep in mind that longer DC cabling will cause larger voltage drops. Try to keep the DC wiring run as short as possible. 20-30meter is doable, but if you start to go longer distances (80m?), you will need to have a much larger diameter wire to avoid voltage drop. For instance 10-25mm² might be required when going longer distances. Use a voltage drop cabling calculator suited for your country to see how large diameter you need for a specific distance.

  • 12V control/signal wire has the same limitations, increase cable area to be able to go longer distances. Use a calculator.
  • CAN communication at 500kbps is good for 100meter max!

• DC cabling should also be installed in a conduit, to avoid any external factors damaging the insulation around the wires. The conduit material can either be plastic or aluminium, depends on what's typical in your region.

• Avoid installing communication wires next to high voltage wiring, in order to avoid signal interference

[!CAUTION] Verify polarity of HV system before wiring it to the inverter. Many EV batteries don't have markings which side is +/-, so doing a test run without the inverter connected is a good idea to ensure polarity. Incorrect polarity will destroy your system

Example, 50mm² cable stepped down to 10mm², and at the same time fused off with a 25A solar DC ceramic fuse

Example, two EV battery inputs stepped down to 10mm² using DC fuses

If you just want to step down the wire size, you can use a terminal block such as this one

How large fuse do I need?

Sizing your fuses depends on your target kW and battery voltage. You will generally want to have a 20% overhead to allow for the fuse to work at high temperatures (full load). Use the lowest voltage your battery will see for the calculation.

Example calculation, 5kW inverter with a Nissan LEAF battery (300-400VDC).
I=P/U - 5000W/300V=16.6A , *120% = **20A fuse required**

Fuses can either be DC Ceramic, or DC DIN-mounted fuses. Make sure the fuse you are purchasing is certified for DC and for the voltage range of your battery. A tip would be to look at what Solar DC fuses are usually used in your country. These are rated for high voltages, and work great with DC battery setups.

Disconnect switches

Some countries have legislation that dictate a need for DC disconnect switches (also known as DC isolation switch). The idea behind this is that these switches will be installed in a place where first responders and firefighters can easily turn off your solar/battery combination. Check your local legislation to see if this is required in your area

Protective earth

The battery case needs to be connected to protective earth (PE). This is required for a few technical and safety reasons;

• Signal integrity. Having the battery case sit at earth potential avoids any ground loops thru communication shield wires.
• CAN transceiver longevity. Failure to attach PE to battery case can damage CAN bus systems from ground loops thru shield wires
• Isolation testing. Your inverter will periodically test how safe the high voltage system is by measuring insulation resistance between HV+/- to PE. If the battery case is left freefloating and not connected to PE, any HV leaks might go unnoticed.
• If you are in a country that requires a residual current device in your electrical panel (GFCI/RCD), these also need to be able to accurately measure any DC leakage to PE and trip

[!CAUTION] Failure to connect battery case to protective earth can lead to dangerous situations where high voltage leaks are not detected

Example, Nissan LEAF battery case connected to PE

Optional stuff!

[!TIP]
You can also add an equipment stop button to the Battery-Emulator, to make it easier to stop the system