zappi has four modes to help optimise the charging of your EV.  As zappi is designed to optimise the use of local renewable generation these modes can be a bit confusing - particular if you don't have any PV panels or a micro wind turbine.

Hopefully these notes will help

• FAST Mode
• ECO Mode
• ECO+ Mode
  • Minimum Green Level (MGL)
• STOP Mode
• Using zappi if you don't have local generation (PV or wind)

FAST

In FAST mode, zappi will allow the EV to charge as quickly as it can - limited only by the rating of the EV's onboard charger or any limits that might be set (i.e. the device limit or the grid limit).  

As soon as the EV is plugged in it will start charging (provided there are no timers set in the EV).

The maximum current that can be supplied is 32A, which for a single phase zappi is a charging power of ~7.4kW.   For a three phase zappi the maximum charging power is ~22kW

ECO

ECO mode is a special zappi mode that tries to match the power used to charge the car to any spare local generation you may have.   Zappi continually tells the car how much power it can use to keep export (and import) as close to zero as possible.

Unfortunately it's not that simple.   According to the EV charging standard, the minimum charging current is 6A (which is ~1.4kW for a single phase EV charge) so if you have less than  1.4kW of surplus generation the extra power has to be taken from the mains.   

For a three phase EV, then then the standard requires 6A per phase, so the EV needs 4.2kW of power to charge so the local generation will be topped up from the main is there is there is less than 4.2kW available.

In ECO mode the EV should start charging as soon as it is plugged in and will continue charging at 1.4kW (or more if there is spare generation) until the EV is unplugged or the battery is full.

ECO mode and Boosts

If you set a boost in ECO mode (Scheduled Boost, Manual Boost and Smart Boost) then zappi will tell the car to charge at full power while the boost is active.

ECO+

ECO+ mode goes one better than ECO and will stop the charge if you don't have enough surplus generation.    

As the spare generation will vary during the day, zappi has a countdown timer which has to time out before a charge starts or stops.  This prevents the contactors opening and closing too often (although they are rated for several million operations so shouldn't wear out!) 

When you plug your EV in zappi will first say "Waiting for Surplus".   If there is enough surplus generation (nominally 1.4kW for single phased zappi or 4.2kW for a three phase zappi) to start the charge then the time will count down and the charge will start, tracking the surplus generation to keep the grid import / export as close to zero as possible.

ECO+ mode and Boosts

If you set a boost in ECO+ mode (Scheduled Boost, Manual Boost and Smart Boost) then zappi will tell the car to charge at full power while the boost is active.

ECO+ mode and Minimum Green Level (MGL)

On a cloudy day you might want the charge to start even if there is less than 6A (~1.4kW) available as surplus from the local generation.   That's where the Minimum Green Level (MGL) comes in.

With MGL at 100% then zappi will stop the charge is the surplus generation drops below 1.4kW.

By reducing MGL, zappi will allow some power to be drawn from the grid to top up the generation if needed.  For example, with MGL at 50% zappi will keep charging the EV until the surplus generation drops below 700W.  

At MGL = 1% the charge will continue until there is less than 14W of surplus generation.  In practice this means zappi will only stop charging if all local generation has stopped.

STOP

In STOP mode zappi will not allow your EV to charge even if you have a Scheduled Boost set or try a Manual Boost.

Using zappi if you don't have PV panels or a wind turbine

If you don't have any local generation then it's best to leave zappi in the ECO+ mode and then use boosts to charge your EV as needed.

Scheduled Boost

To set a time when you want the EV charged - for example to charge overnight on an economy tariff

Manual Boost

To charge the EV straight away with a set amount of energy

Of course you can also switch zappi to FAST mode if you want to completely charge your EV straight away but don't forget to change the mode back to ECO+ when the charge is finished.

Alternatively you could simply set a Manual Boost with a target power that is greater than the EV battery capacity