You do not need to change the SEVCON configuration to use a custom battery if the custom battery delivers voltage and power matching the standard operating range and your SEVCON battery protection has not been disabled.
- The SEVCON G48 series can operate with input voltages from 19.3 to 69.6 V. The Twizy SEVCON is by default configured for a range of 39 to 65 V.
- In standard configuration, the Twizy will draw up to ~330 A or 16 kW from the battery, and recuperate at up to ~70 A or 3.5 kW.
If your battery cannot cope with these limits, you can either use the Virtual BMS to lower the limits or modify the SEVCON configuration.
If you need to set the limits regularly below the standards, consider tuning the Twizy down. Triggering the power limiter will result in a sudden power cutback followed by slowly raising power levels until the limit is reached again. This continues over and over leading to an inconvenient pumping effect.
**Note**: SEVCON write access has been limited by Renault on Twizys (SEVCONs) delivered after June 2016. The write protection applies to all power and driving profile tuning registers, and also to the voltage limits. **If you've got a locked Twizy, your battery should match the standard battery parameters.**
A locked SEVCON will respond to register writes with an error. You can also check the software version (`rs 100a 00`): if it's `0712.0003` or higher, the Twizy is locked.
**Example**: to allow voltages down to 35 V, issue…
1.`w 2c02 01 592`
2.`w 2c02 02 560`
**Keep in mind** that the SEVCON derives current levels from allowed power levels (unless configured otherwise, see below). A lower voltage will result in higher currents, take care to lower the power limits as necessary using the `setPowerLimits()` API call when your voltage drops.
## Battery current & power limits
**Note**: these only apply to the driving state, the charger current can be controlled by `setChargeCurrent()` regardless of the SEVCON configuration.
The SEVCON applies these linear cutbacks based on SOC additionally to the BMS power limits allowing for a smooth cutback slope. Default is to cutback drive power below 15% SOC, and leave brake power at BMS control.
These registers need pre-operational mode to allow writes.
**Example**: configure full brake power cutback from 90% to 100% SOC:
Most registers of interest for normal tuning have been documented in the [OVMS Twizy SDO list](https://github.com/openvehicles/Open-Vehicle-Monitoring-System/raw/master/docs/Renault-Twizy/Twizy-SDO-List.ods).
