The Charger
The build in On-Board Charger (OBC, 7.2kW) is manufactured by Delta Electronics, Taiwan. This kind is used by multiple automotive manufactureres and was intensively examined by the U.S. Department of Energy (in the bi-directional version): Project Summary 2015, Project Summary 2016.
It consists of two internal 3.6kW chargers capable of delivering up to 7.2kW DC power for the HV battery.
| Power,in / kW | Rail 1 / kW | Rail 2 / kW | Remark |
|---|---|---|---|
| ≤ 3.6 | ≤ 3.6 | 0 | The carger will pick one rail |
| ≤ 3.6 | 0 | ≤ 3.6 | and will choose the other one for wear leveling during the next charge. |
| > 3.6 | > 1.8 | > 1.8 | Load balancing the two rails. |
Using Gallium Nitride (GaN) power switches the chargers are very efficient and probably uses a combined LLC for the converter stage (Efficiency data measured at about 350V):
| Mains: Current,in | Mains: Power,in | Charger: Power,out | Battery: Power,chg | OBC Eff. % | Charging Eff. % |
|---|---|---|---|---|---|
| 6 | 1329.02 | 1199.78 | 901.81 | 90.28 | 67.86 |
| 8 | 1735.10 | 1597.58 | 1355.41 | 92.07 | 78.12 |
| 10 | 2116.42 | 1968.52 | 1776.88 | 93.01 | 83.96 |
| 12 | 2642.12 | 2510.75 | 2287.39 | 95.03 | 86.57 |
| 16 | 3597.92 | 3450.50 | 3181.81 | 95.90 | 88.43 |
| 20 | 4506.15 | 4285.27 | 4100.51 | 95.10 | 91.00 |
| 25 | 5623.10 | 5398.61 | 5198.44 | 96.01 | 92.45 |
| 32 | 7074.79 | 6816.74 | 6533.23 | 96.35 | 92.35 |
Fraunhofer IISB, Erlangen also developed a similar subsystem (for 7.4kW):
Conference Paper: Modular Design for 22kW Charger and 3.7kW Module Specifications
