Futurehome Charge - why does it charge so slow?

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There are several factors that affect the charging speed, and in most cases you will not reach the theoretical maximum. If you struggle with slow charging speed and you are not sure why, please check the steps below.

Imagine a river that flows through gates. On the way there are 8 gates, and for you to take advantage of the full potential, all the gates need to be fully open. If one of them is slightly closed, this limited speed will be your “new” maximum.

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Electrical limitations

1. Grid type to your home.
In Norway we have IT and TT, which are practically very similar, and TN. If you have IT or TT, you will not charge faster than 7,4 kW.
Check the label on your fusebox.

Grid

Phase

Breaker

Max current

TN/IT/TT

1 phase

16A

3,7 kW

TN/IT/TT

1 phase

32A

7,4 kW

IT/TT

3 phase

32A

7,4 kW*

TN

3 phase

16A

11 kW

TN

3 phase

32A

22 kW

*Note that Futurehome Charge does not support 3 phase charging on IT/TT grid. This is due to safety reasons, and you can read more about that in the article linked here.

 

2. Households main breaker.
If your main breaker is too smal, the electrician installing the Charge will limit the maximum current.
Many households got a main breaker with rating of e.g. 40 amps. In that case the electrician will most likely not install a 32 amp breaker on the Charge circuit, since that can lead to tripping the main fuse when other appliances are turned on.
Check the label on your main breaker in the fusebox.

 

3. Charge circuit breaker.
Due to laws and regulations, Charge need a separate breaker. The size of this breaker is a possible limitation for the speed. This breaker is installed and configured by the electrician, and shall not be changed by uncertified personal.
This is related to the point above, households main breaker.
Check the label on your specified circuit breaker in the fusebox.

 

4. Configured maximum speed.
When the electrician installs Charge, they must set a maximum limit - with a safety margin - in accordance to the circuit breaker. If the circuit breaker is rated 32 A, you’ll often find the maximum configured to 28 A. You can not change this value if you are not a certified installer.
Check point number 7. The maximum available current there, is the value set by the installer.

 

5. Charging cable.
All charging cables are rated for different charging speeds. Check that your cable allows for the speed you want and have configured. 
Note: We have a know issue with 20A rated cables. By Charge, these are read as 16A, leading to slower charging speed. 
Check the labelling on your charging cable.

 

6. Car limit.
Check your car settings and maximum charging speed allowed by your car. Most hybrid cars have significantly lower maximum speed than EVs.
Check the charging settings in your car.

Futurehome software

 

7. Charging current limit.
In your chargers settings, you will find a limit. This is a value between 6 ampere, as the lowest, and the value from point 3 above, the breaker size of Charge’s circuit. You can safely set “Charging current limit” in the chargers setting at maximum, since the electrician has set a hard limit on the circuit breaker configuration.
Check “Charging current limit” under your chargers settings in the app. Read more here.

 

8. Power manager - dynamic load balancing.
If your charger is activated in load balancing, the charging speed will be affected by the power usage in your household. This functionality is used to prevent the main breaker from tripping. Do not change this value, as you will risk tripping your main breaker.
Check the usage in your household and try turning other appliances off.

 

9. Power manager - energy threshold.
Due to the grid tariffs, we have a function to limit the energy usage on an hourly basis, kWh pr. hour. If you set your limit to 10 kWh/h, you can have a load of 10 kW turned on for 1 hour. If you use 20 kW, you can have that turned on for half an hour.
Check the timeline in the app. If Power manager is scaling down, there will be an event here.

Example

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  1. We have a IT 1-phase grid. On this grid type, the maximum charging current is 7,4 kW.

    The formula is 230v * 32 ampere = 7360 watts.

    32 A is the maximum supported ampere.

  2. The main fuse in the household is 40 A. In a regular household, this is more than enough, but if you add a charger with 32 A to this, the remaining capacity is 8 A. (For reference that equals 2 panel ovens).

  3. Due to the smaller main breaker, the electrician installed a 25 A circuit breaker, as a safety measure. This leaves 15 A to the household when the charger is running at full capacity.

  4. A rule of thumb is to add an extra layer of safety by setting up chargers with 10% safety margin. This will allow the charger to charge at 22 A maximum. (25-10% = 22,5 ~ 22 A).

  5. The cable has a rating of 32 A, but since the charger only delivers 22A, this is still the maximum current.

  6. There are big differences in the on-board chargers in electric cars. This can be the bottleneck in many cases. In this example the car limit is 1 phase - 32 A (7,4 kW), but since the charger only supplies 22 A, this will be the final Charging speed.

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