Bidirectional Charging

Bidirectional charging means, that the car is able to provide power to the outside world, via the charge port.

Tags: bidi, inverse charging, vehicle-to-load, V2L, vehicle-to-home, V2H, vehicle-to-grid, V2G

Forum discussions related to bidirectional charging:

https://openinverter.org/forum/viewtopic.php?t=5090

https://openinverter.org/forum/viewtopic.php?t=3551

Bidirectional Charging via AC

Some OEM on-board-chargers are able to create AC voltage. Todo: any reverse-engineering ongoing for such chargers? E.g. for Hyundai/Kia E-GMP?

Bidirectional Charging via CHAdeMO

The CHAdeMO standard was planned for supporting bidirectional power transfer from the beginning. Todo: Any open-source projects in this direction?

Bidirectional Charging via CCS

The CCS standard did not plan bidirectional power transfer. This means, depending on the implementation details of the cars charge controller, the car may or may not allow to draw energy out of the CCS port. Later versions of the CCS standard, ISO15118 (2020?), are defining special communication procedures for bidirectional power transfer. But it will take some time until this standard is widely adapted.

In the open-source world, however, we do not need to wait until OEMs and charger manufacturers implement the latest ISO15118. We can support bidirectional charging even with the "old" DIN spec. The strategy is: Even if the car is requesting to be charged, it also accepts discharging, without terminating the charging session. It may terminate if the SOC falls below a certain, configurable level, to prevent an empty battery. The car announces the allowed charge current, and the same value, just in opposite direction, can be used as a discharge current limit, too.

Practical implementation with parts list

First prototype

One way to DIY an bidirectional charger is the use of a hybrid PV inverter with high voltage battery input. The advantage is that these are mass-produced (thus cheap) and conform to the various legal requirements. The inverter then handles power transfer and optionally smart functions such as zero grid import/export and we only need to supply the surrounding logic and electrics.

Second version

This component list is just an example that has proven to work. It is preliminary and has not been tested with OEM cars yet, so it will likely be extended. As always, you are working with high voltage and especially grid voltage. Make sure you are qualified otherwise ask for help.

Item	Approximate cost	Link/Source	Remarks
Sungrow SH5.0RT (or more powerful variant)	850€	Sungrow	Pick an inverter that is supported by Battery Emulator
CCS Connector	90€	AliExpress	Plain connector without cable
BeagleBone Green	45€	Mouser
BeagleBone COMCPE	40€	Mouser	RS485, CAN comm and 2x relay driver
TPLink TL-PA4010	15€		Powerline modem
4x4mm flexible cable	4€/m	Local hardware store	Sufficient for 25A charging current and carrying CP signal
2 Fuse blocks	6€ each	Mouser
2 25A fuses	8€ each	Mouser	400V AC rated from your local hardware store suffices as it's 2 in series
12V 2A DIN rail supply	18€	Mouser	In case relays are needed later on, otherwise 5V model makes things easier
12V to 5V step-down converter	5€	ebay or ali	Needed if you chose 12V supply
DIN rail cabinet	20€	Local hardware store
MC4 connector set	5€

Collection of documents related to bidirectional charging

todo

References

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