OVMS User Manual page 40

OVMS: Renault Twizy User Guide
to the actual BMS power limits.
Of course the SEVCON will limit power levels by itself as necessary. But if it does, the effect is
very harsh and abrupt, and it cuts back the power further than necessary. So by adjusting the
DRIVE and RECUP levels you can avoid triggering the SEVCON limiter by keeping your power
levels below the allowed limit at all SOC levels.
Another positive effect is that the battery stress is automatically reduced with the SOC, which can
lead to a better discharge efficiency due to less losses at the battery inner cell resistances.
There's one caveat to mention: only the general power level (DRIVE/RECUP) can be adjusted
while driving, that applies to the power and to the torque. The torque level could be kept high for
launches, as the power level is low in that area. Unfortunately, there is only the general power level.
To accomodate to this, an automatically lowered DRIVE level also enables the kickdown feature,
just like a manually lowered DRIVE level does. The kickdown sets the level back to 100%, so
during a kickdown, the SEVCON limiter may come back.
Auto power adjustment is now based on a reference point defining the maximum electrical battery
power to be expected, and an optional minimum level. You can use the power map calculator to
estimate the electrical power levels needed for your mechanical power output. This is an estimation
because power efficiency is not a constant. You should experiment with slightly higher and lower
reference values to find your personal optimum.
DRIVE and RECUP calculations differ: 100% DRIVE level is assumed to translate to the reference
drive power, while the RECUP levels configured translate to the reference recuperation power.
That's because the RECUP levels normally are tailored to the TSMAP N/B configuration to deliver
maximum recuperation, while the DRIVE level is normally only set below 100% to reduce the
energy use.
You can monitor the auto power adjustment by reading the "
How to determine the reference power level
1. Enter your configuration parameters into the power map calculator.
2. Start with the maximum "auto power ref" values calculated by the sheet.
3. If the limiter still kicks in, raise the reference values.
4. If you think the power adjustment is too early, lower the values.
The reference levels are configured in 100 W resolution. For example, to set normal drive power
level to 100% and activate auto power with reference power level at 17.7 kW, issue:
CFG DRIVE 100 177
To set recuperation levels to neutral 36% and braking 65% with 8.8 kW reference, issue:
CFG RECUP 36 65 88
See command reference for complete parameter explanation.
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