6A minimum charge current per phase

[PETVK]

Hi,

The minimum charge current for the car per phase cant be set lower then 6A. My car (MG4) accepts 6A total (3 phase), and 2A per phase. To charge my car purely on solar energy it would be beneficial if the setting could be set at 2A

Thanks in advance,

Peter

[mstegen]

Unfortunately the standard does not allow the charge current to be set lower then 6A.

[arpiecodes]

If you goal is to consume all your solar generated power 'as seen from the meter' (so not the 'actual' power), then you could theoretically switch over to single phase charging and apply a 6A current limit. It does require some extra steps and considerations, though. May want to check out the serkri fork (https://github.com/serkri/SmartEVSE-3) which has more features and also has a description on how to implement the single/three phase differentiation.

[PETVK]

Its a bummer that the standard doesn't allow lower than 6A but the proposal of arpiecodes fixes the issue, thanks!

[uhi22]

Just to make it more clear: The solution still is according to the 6A minimum current. It does not go below the 6A. The "trick" is just to have 1 phase with 6A, which is 230V6A = 1380 Watts, instead of the 3-phases which are 3 230V 6A = 4.1kW. Did I understand this right? Or is there (for certain cars) the possibility, to apply a non-standard PWM below* 6A, to convince it to draw less current?

[arpiecodes]

Just to make it more clear: The solution still is according to the 6A minimum current. It does not go below the 6A. The "trick" is just to have 1 phase with 6A, which is 230V6A = 1380 Watts, instead of the 3-phases which are 3 230V * 6A = 4.1kW. Did I understand this right? Or is there (for certain cars) the possibility, to apply a non-standard PWM below 6A, to convince it to draw less current?

That's correct. The car and charger can only communicate a single amperage limit and so it applies to all of the phases in use. So by forcing single phase charging, it would effectively limit the total current to 6A. On three phase households, one could accomplish the same by using two contactors (relays) - One 4p 'main' contactor and another 2p contactor to switch the extra phases on/off.

Of course switching has to be done with care (and to prevent unsafe situations, the 2p contactor is chained behind the 4p one so if the 'extra phases' contactor gets stuck, it cannot result in two phases remaining energised within the plug). There is another consideration though; some cars would 'bridge' the internal phases together (e.g. to achieve larger charger capacity on single phase charging) which could cause problems if the 2p contactor is switched late for whatever reason. The workaround is definitely not perfect, but it works.

The standard itself does not allow going below 6A for current limiting. At least not through the PWM signal/control method and proper implementation of it in the PEV side. But maybe it would allow going lower in the DIN/ISO spec? As that could in theory give the possibility to simply send any integer to the car, including the amount of phases to use (still have to be careful with the extra phases potentially being bridged internally in the car, though).

IIRC it should be noted however that efficiency drops pretty fast when going below XX amperes of charging current.

[dingo35]

There are some users (if I remember correctly especially Tesla-users) that have been able to lower the minimum charging current to 3A; we would like to stick to the standards, BUT I have made a compiling option, so people can make their own firmware.bin on their own risk: if you compile the firmware with option -DMIN_CURRENT=X, X will be the MinCurrent value (in Ampères) that will be used in the firmware.

[bobosch]

I can reduce the charging current with the Tesla App to 5 A ... but not with the PWM signal :-(

[dingo35]

https://github.com/dingo35/SmartEVSE-3.5/issues/51