Installation guidelines
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.
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.
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
Example: Detached garage, vertical placement
Example: Wallmounted, with extra roofing
Example: Outside, vertical placement with waterproofing
Example: Underground concrete sarcophagus
Example: Shipping container
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.
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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.
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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 (100m?), you will need to have a larger diameter wire to avoid voltage drop.
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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.
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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
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).
Example calculation, 5kW inverter with a Nissan LEAF battery (400VDC).
I=P/U - 5000W/400V=12.5A , *120% = **15A 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
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
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
Tip
You can also add an equipment stop button to the Battery-Emulator, to make it easier to stop the system