Short answer: this is a plain-language glossary of the words used when planning, buying and running a DC fast charging station in India, from CCS2 and kVA to LT, HT and OCPP. Each term is one or two sentences, written for a site owner rather than an engineer. The guides on this site link here whenever they use one of these words.
Missing a word you met in a proposal or a DISCOM letter? Write to us and we will add it.
Plugs and charging
- AC charging
- The grid's alternating current goes into the car, and the car's own onboard charger turns it into direct current for the battery. The onboard charger sets the speed, which is why AC charging tops out at 22 kW and is the norm at home.
- DC charging
- The charger itself turns grid power into direct current and feeds the battery directly, bypassing the onboard charger. That is what allows tens or hundreds of kilowatts. Also called fast charging.
- CCS2
- Combined Charging System, type 2: the DC plug used by almost every electric car sold in India today. The top of the socket is the Type 2 AC plug and two large DC pins sit below it. Every Zevpoint DC charger uses CCS2.
- Type 2
- The seven-pin AC plug used for home and workplace charging in India and Europe. Most cars in India have a Type 2 socket for AC and a CCS2 socket that builds on it for DC.
- Bharat DC-001
- An older Indian low-power DC standard. A few early cars and commercial vehicles used it; new cars use CCS2.
- Gun
- Charging-industry slang for the plug and handle at the end of a charger's cable. A dual-gun charger has two.
Power and battery
- kW (kilowatt)
- A rate: how fast energy flows. A charger's rating and a car's charging limit are both in kW.
- kWh (kilowatt-hour)
- An amount of energy: a battery's size, or what a session delivered. A 50 kWh battery charged at 50 kW for an hour would gain 50 kWh, if the rate held, which it does not.
- Peak power
- The highest rate a car will accept, usually only in the middle of the battery and only when the battery is at a comfortable temperature. Brochures quote the peak.
- Taper
- The drop in charging rate as the battery fills. Above about 80% every car cuts the current hard to protect the cells.
- 10 to 80%
- The window makers use to quote DC charging times, because it avoids the slow start and the slow finish.
- SoC (state of charge)
- How full the battery is, as a percentage.
- BMS (battery management system)
- The car's controller that watches every cell and tells the charger how much current to send. It, not the charger, decides the rate.
- C-rate
- Charging rate relative to battery size. 1C on a 40 kWh battery is 40 kW; 1.5C is 60 kW. Some makers quote their DC charging in C instead of kW.
- Preconditioning
- Warming or cooling the battery on the way to a charger so it accepts a higher rate on arrival. Some cars do it when a charger is set as the destination in the car's own navigation.
The grid connection
- DISCOM
- The distribution company: the utility that supplies electricity to your site and sanctions your load. Each state has one or more.
- Sanctioned load
- The power a connection is approved to draw, printed on the electricity bill. Drawing above it brings penalties; raising it is an application to the DISCOM.
- kVA (kilovolt-ampere)
- The apparent power a connection or charger draws from the grid. It is a little higher than the kW the charger delivers, because of losses and power factor. DISCOMs often sanction load in kVA.
- Power factor
- The ratio of useful power (kW) to apparent power (kVA). A good DC charger runs close to 1.
- Maximum demand
- The highest load a site actually drew in a billing period, as recorded by the meter. Some states key their rules to it rather than to the sanctioned load.
- LT (low tension)
- Supply at 415 V three-phase straight from the DISCOM's transformer. Simple and quick to connect, up to a ceiling the state sets.
- HT (high tension)
- Supply at 11 kV or above, with a transformer the consumer owns. Required above the state's LT ceiling.
- LT ceiling
- The largest load a DISCOM will supply at LT. It differs by state, roughly four-fold between the strictest and the most generous.
- Electrical inspector
- The state officer who inspects and approves electrical installations above set limits before they are energised, typically HT installations.
- Earthing
- The connection of the charger's metal parts to the ground through earth pits, so a fault current has a safe path. Chargers monitor it and stop on a fault.
Chargers and sites
- Dual gun
- A charger with two guns sharing one power unit. Its rating is what the two deliver together.
- Load sharing
- Dividing a charger's or a site's power between cars. Dynamic load sharing moves power as each car's needs change.
- Charge point
- One charger. A charging station or site may have several.
- IP rating
- Protection against dust and water. IP54 means protected against dust and splashing water from any direction.
- IK rating
- Protection against impact. IK10 is the highest grade on the common scale.
- Utilisation
- The share of time a charger is actually charging a car. The single biggest driver of a public charger's earnings.
- Uptime
- The share of time a charger is working and available. Below a high uptime, a public site loses its drivers.
Software and business
- OCPP
- Open Charge Point Protocol: the open standard a charger uses to talk to its management software. An OCPP charger can be moved to other software without replacing the hardware. Zevpoint DC chargers use OCPP 1.6.
- OCPI
- Open Charge Point Interface: the standard networks use to share chargers with each other and with map apps, so a driver can find a charger on someone else's app.
- CMS
- Charge point management system: the software that runs chargers, sets tariffs, starts sessions and collects payments. Ours is Zev Connect.
- CPO (charge point operator)
- The business that runs public chargers and sells charging to drivers. An owner who runs their own station is their own CPO.
- Franchise model
- A network brands and runs the station, usually for a joining fee and a share of every session, and the site owner hosts it.
- Tariff
- The price a driver pays, usually per kWh, sometimes with time-based or idle charges. The owner sets it in the CMS.
- Idle fee
- A charge for staying plugged in after the session ends, to free the bay for the next car.
- RFID
- A card or tag a driver taps on the charger to start a session against their account.
- AMC (annual maintenance contract)
- A yearly service agreement that continues support after the warranty ends.
Where to go next
Start with what each car takes from a DC charger and how much power a DC station can get, or see every DC guide.
Frequently asked questions
What is the difference between kW and kWh?
kW is a rate, how fast energy flows; a charger's rating is in kW. kWh is an amount of energy, such as a battery's size or what a session delivered.
What is the difference between kW and kVA?
kW is the useful power a charger delivers; kVA is the apparent power it draws from the grid, slightly higher because of losses and power factor. DISCOMs often sanction load in kVA.
What is CCS2?
Combined Charging System type 2, the DC plug used by almost every electric car sold in India. It adds two large DC pins below the Type 2 AC plug.
What is OCPP and why does it matter?
Open Charge Point Protocol, the open standard a charger uses to talk to its management software. It lets an owner change software without replacing the charger.
