Hi!
I wrote this response to the yahoo group and thought it might be interesting in general:
The IMA charge/assist gauge has some life of it's own. It appears to be more of a software-driven indicator to provide feedback to the driver than a direct gauge running off one of the current sensors.
The Insight has several current sensors:
-DC battery current
-DC IMA current
-individual phase currents in the AC cable to the motor
I have a meter rigged to read the output of the battery current sensor. Here is what I know of that relationship with the IMA gauge:
Cruising: If the battery management determines that there is no need for charging the battery, the battery current is exactly zero. So the DC-DC converter appears to be driven off of the IMA motor/generator directly. The generator is controlled such that it delivers the exact amount of power needed for the DC-DC converter. I call it the alternator-emulation mode.
It is this observation that makes me think a dead 12V battery should have little to no effect on the 144V battery, except things like lost computer power (what Geoff mentioned).
Assist: The assist bars will reliably light a few bars every time there is any current drawn from the battery to feed the IMA motor. No bars lit mean there is no assist current flowing. Bars lit mean there is at least some assist current. More bars will light for more current. There is, however, no direct relationship between the number of bars lit and the actual current. (i.e. you couldn't say 10 bars = 20 Amps). For example, flooring the gas in second gear yields 90 Amps initially (full assist shown). After a few seconds, assist drops to 50 Amps, but the gauge still shows full assist! In most gears, full assist is 45 Amps to 50 Amps depending on battery voltage.
Charge: Here, it gets hairy.
When green bars are lit, you know there is some charge current flowing. Again, more bars more current. However, no bars doesn't necessarily mean no current! Many times (especially with the lights or AC an), the car decides to charge during cruising. In this case, the green bars will only light if the SOC gauge is less than about 2/3. E.g. if my car is charging recovering from a recal, there may be 8 Amps charge current and four green bars while I cruise on the highway. Once the SOC hits 2/3, the green bars turn off, but the current stays exactly the same! I call this the hidden-charging mode. So if no bars are lit you cannot tell if the car is charging or not.
There is a strange situation when the car is cruise-charging with a few bars lit: If I step on the gas gently enough, the charge current will gradually reduce (before dropping out of lean burn). If it get's to 1 or 2 Amps, the green bars will start to flicker on and off. I guess, it's not sure if it's charging or not. Great effect to use to maximise lean-burn power!
I wrote this response to the yahoo group and thought it might be interesting in general:
The IMA charge/assist gauge has some life of it's own. It appears to be more of a software-driven indicator to provide feedback to the driver than a direct gauge running off one of the current sensors.
The Insight has several current sensors:
-DC battery current
-DC IMA current
-individual phase currents in the AC cable to the motor
I have a meter rigged to read the output of the battery current sensor. Here is what I know of that relationship with the IMA gauge:
Cruising: If the battery management determines that there is no need for charging the battery, the battery current is exactly zero. So the DC-DC converter appears to be driven off of the IMA motor/generator directly. The generator is controlled such that it delivers the exact amount of power needed for the DC-DC converter. I call it the alternator-emulation mode.
It is this observation that makes me think a dead 12V battery should have little to no effect on the 144V battery, except things like lost computer power (what Geoff mentioned).
Assist: The assist bars will reliably light a few bars every time there is any current drawn from the battery to feed the IMA motor. No bars lit mean there is no assist current flowing. Bars lit mean there is at least some assist current. More bars will light for more current. There is, however, no direct relationship between the number of bars lit and the actual current. (i.e. you couldn't say 10 bars = 20 Amps). For example, flooring the gas in second gear yields 90 Amps initially (full assist shown). After a few seconds, assist drops to 50 Amps, but the gauge still shows full assist! In most gears, full assist is 45 Amps to 50 Amps depending on battery voltage.
Charge: Here, it gets hairy.
When green bars are lit, you know there is some charge current flowing. Again, more bars more current. However, no bars doesn't necessarily mean no current! Many times (especially with the lights or AC an), the car decides to charge during cruising. In this case, the green bars will only light if the SOC gauge is less than about 2/3. E.g. if my car is charging recovering from a recal, there may be 8 Amps charge current and four green bars while I cruise on the highway. Once the SOC hits 2/3, the green bars turn off, but the current stays exactly the same! I call this the hidden-charging mode. So if no bars are lit you cannot tell if the car is charging or not.
There is a strange situation when the car is cruise-charging with a few bars lit: If I step on the gas gently enough, the charge current will gradually reduce (before dropping out of lean burn). If it get's to 1 or 2 Amps, the green bars will start to flicker on and off. I guess, it's not sure if it's charging or not. Great effect to use to maximise lean-burn power!
