cFos Charging Manager - Formulas

The cFos Charging Manager allows the dynamic evaluation of formulas. This functionality is available for a meter of the type "Expression" and for charging rules of the type "Formula".

You can therefore set up meters that calculate values from other meters or EVSEs and keep them ready and display them. The charging rules can also use formulas to dynamically calculate the charging current and also access meters and EVSEs (including meters of the "Expression" type).

The following operations are possible with the formulas:

+ - * / %Addition, subtraction, multiplication, division, modulus
& |bitwise AND and OR
^Power calculation, e.g. 10^2 = 100
min(x,y)Minimum of x and y, more than 2 arguments possible
max(x,y)Maximum of x and y, more than 2 arguments possible
abs(x)Absolute value of x, e.g. abs(-2) = 2
clamp(x,min,max)Value x = min (if x < min), x = max (if x > max), otherwise keep x
round(x)Round x to whole number. Example: Rounding to 1 decimal place: round(10*x)/10.
sqrt(x)Square root of x
exists(x)true if the variable x exists, otherwise false

Furthermore, the following logical expressions are possible:

== (equal), != (unequal), < (less), <= (less-equal), > (greater), >= (greater-equal), ! (not), || (logical Or), && (logical And), ? (conditional operator, e.g. x ? y : z, returns y if x is true, otherwise z)

This allows, for example, the current to be switched off depending on conditions: M1.current >= 6500 ? M1.current : 0 returns the current of M1 if it is greater than 6.5A and 0 otherwise, which pauses the charging. For such conditions, it is also possible to query inputs (see below)

The following names are possible:

MxMeter with unit ID x, e.g. M1
ExEVSE with device ID x, e.g. E1

It is also possible to access virtual meters, such as solar surplus, grid draw or "Power avail. for EVSEs" (power available for wallboxes), by setting up the meter and then using the corresponding device ID in the formula.

You can then access individual values of the units by means of the point. These are called as follows:

current_l1Current of phase 1 in mA
current_l2Current of phase 2 in mA
current_l3Current of phase 3 in mA
currentCurrent of the current phase in mA (for charging rules, the Charging Manager queries all phases one after the other; for meters of the type "Expression", the respective phase to which the formula refers applies. If you have specified a formula for "Current L1", you can omit the fields for Current L2 and L3. Then the formula for current L1 is used)
power_wCurrent active power in watts
offeredWallbox: Current offered in mA
import_whEnergy drawn in Wh
export_whInjected energy in Wh
dtThe time that has elapsed since the last past update (in seconds)
inputNInput number N of the unit, 1 = active, 0 = inactive
socSOC, charge level in percent (meter/storage)
idDevice Id, Modbus ID
txn_durationDuration of the current transaction in seconds (EVSE)
charging_durActual charging time of the current transaction in seconds (Wallbox)
txn_energyCharged energy of the current transaction in Wh (EVSE)
min_currentMinimum charging current in mA (EVSE)
max_currentMaximum charging current in mA (EVSE)
stateStatus: 1 waiting, 2 plugged in, 3 charging, 4 charging with ventilation, 5 error, 6 offline (EVSE)
cphasesNumber of charging phases (0-3)
pphasesNumber of predicted charging phases (0-3)
surplus_pcurPV excess current per (predicted) phase in mA
surplus_wanted1, if a PV surplus rule has already been applied, otherwise 0
budgetKWh or minutes in the current budget
budget_amountMaximum kWh or minutes on the current budget
budget_usedKWh or minutes used on the current budget
com_err1, if there is a COM error, otherwise 0
com_err21, if a COM error is present for longer than 12 sec, otherwise 0
reactive_powerReactive power specification in watts (if supported by the device), positive values: Inductive, negative values: Capacitive

M1.current_l1Current of meter M1, phase 1
E2.import_whConsumed Wh of the EVSE E2
E3.power_wCurrent charging power of E3 in watts

If you use the formulas for a meter of type "Expression", you can also omit the device ID. Then the field names refer to this meter, e.g. 'power_w' is then the power of this meter in watts. By means of 'dt' you can realise a few extended functions, e.g. in a meter of the type "Expression":

  • As a formula for 'import_wh': import_wh + M1.power_w * dt / 3600 updates the sourced energy based on the power during the past update time
  • As a formula for 'power_w': (power_w * (20 - dt) + M1.power_w * dt) / 20 smoothes the power over the last 20 seconds.

Global variables


date.yearCurrent year
date.monthMonth from 0..11
date.dayDay from 1..31
date.weekdayWeekday SO=0, Mon=1, Tue=2, ... Sat=6
date.yeardayDay in the year from 0..366
date.hourHour from 0..23
date.minuteMinute from 0..60
date.secondSecond from 0..60
date.daysecondSecond of this day from 0..86399
date.dayminuteMinute of this day from 0..1439
date.dst0 = winter time, 1 = summer time

PB (nur cFos Power Brain)

PB.input1S0 Input 1, 1 = active, 0 = inactive
PB.input2S0 Input 2, 1 = active, 0 = inactive

CM Charging Manager Variables

These variables can be set by the admin under 'Configuration'. For example, if the admin sets the variable 'var_x' to 1.5, CM.var_x returns the value 1.5.

Predefined variables:
_num_charging: Number of wallboxes currently charging
_num_charging1: Number of currently charging wallboxes, 1 if none is charging
_max_total_current: Maximum current of the house connection in mA per phase
_max_total_evse_current: Maximum current for wallboxes in mA per phase
_price: Current electricity price
_price_level: Current electricity price level, -2=very expensive, -3=expensive, -4=normal, -5=cheap, -6=very cheap
_surplus: Current solar surplus in watts
_org_surplus: Solar surplus as would have been calculated by the Charging Manager independently of its own formulas
_storage_home_max_capacity: Total capacity of the storage, home, if specified in the meter configuration, in Wh
_storage_home_capacity: Current capacity of the storage, home, if specified in the meter configuration, in Wh
_storage_all_max_capacity: Total capacity of the storage, All, if specified in the counter configuration, in Wh
_storage_all_capacity: Current capacity of the storage, All, if specified in the counter configuration, in Wh
_max_total_current_prc: Percentage of the available maximum total charging current. This variable can also be written (by counter definitions and Charging Manager variables)

Use of the global objects:
charge 8A starting at 8:00am: date.dayminute >= 480 ? 8000 : 0
charge 16A on Saturday and Sunday: date.weekday == 5 || date.weekday == 6 ? 16000 : 0
charge 6A if input 2 active: PB.input2 ? 6000 : 0 charge 6A if CM variable non-zero: cm.var1 ? 6000 : 0
Under Custom Counters you will also find instructions on how to use formulas with global Charging Manager variables and outputs.

GM Global counters

GM.grid_demandMains reference
GM.consumed_evseConsumption e-cars
GM.available_evseAvailable power
GM.surplusPV surplus
GM.storage_homeMemory Home
GM.storage_allMemory Everything
GM.errorPerformance through error

Use of the global counters
Jeder Zähler hat die Felder power_w, current, current_l1, current_l2, current_l3, import_wh und export_wh,
z.B. GM.prod_pwr.current_l1 oder GM.cons_pwr.power_w
. Bei 'current' wird der Strom der gerade betrachteten Phase ausgewertet. Ströme werden in mA geliefert, Leistung in W, Energie in Wh.

Application example

You want to additionally limit the charging current with regard to a consumption meter of a flat. To do this, you can set up a charging rule with the formula 16000 - M1.current.
M1 is the meter that measures the consumption of the flat. The load management of the cFos Charging Manager first tries to provide the EVSE with the maximum current in relation to the house connection power, but then limits this to 16A minus the consumption of the flat.