I always took it for granted, that the BCM only runs the battery pack over the typical 80%/20% range.
But after trying to discharge the HV battery by using the headlights, and trickle charging the battery back up to full, I have reason to suspect that the 80% part of the equation is mistaken.
Here are the events that leads to this conclusion:
1) Attempt to discharge the battery pack with the car headlights
2) Now the battery needs to be charged to full again
3) Place a 12 volt trickle charger on the 12V battery
4) Put the variac and full wave bridge on the battery pack
5) Turn on the key to the ignition setting without starting the motor. This way the BCM can monitor the charge.
6) Trickle charge at the typical 400 mA until 163 volts are reached. Cut back charge to 200 or so until topped of at 167 volts.
7) At this point the dash shows about 19 bars.
Now here's the strange part. If the BCM only runs the top end of the battery voltage of 167 volts to 80%, shouldn't the bars be topped off at 20 and then some?
The range of the battery, at least based on my voltages should run between:
The fact that the BCM does not do this means that when I let the SOC top off on long downhill sections, that I am putting more heat into the battery pack since it could be "topping off" the battery pack at 10 amps or so, and creating allot of heat in the process.
Unless someone has a good reason not to, I plan on regenning up to about 18 bars or so, and no higher.
Hi Jim,
Interesting observation, you may be correct, but remember that the pack temperature has a big effect on that relationship of SOC and voltage, which is why they do the columb counting.
I have been watching my HV battery voltage for a couple of years with a meter on my auxiliary instrument panel, and have seen the voltage reach over 180V during regen, which will settle back to 165-167 when the regen is stopped. Based on our grid charging experience, this would represent a true 100% SOC.
I also have a indoor outdoor thermometer tucked into the gap between one of the cells and the plastic shroud, so I can see the cell temperature. I do not typically see the sharp temperature rise that we see on the bench when in that 100% SOC condition, which is likely due to the fan being on full speed when the temp gets over 95F, so it seems that the pack can easily dissipate that additional heat.
Except for a long mountain decent, most people do not regen continuously for a full charge.
The charge does limit when nearing the top, fading to no charge when at 20 bars, but that is only on a pack that is behaving normally.
We also know that the SOC guage can be skewed up or down, from the real SOC based on the recalibration issues that we have on some packs, and the fact that cycling the pack fixes the problem.
I have seen charge behavior that seems to change the way regen works after any regen lasting more than 30 seconds. I live on the crest of a 600 foot hill, and every time I descend, I will use regen to control the speed. If I stop full regen after using it for 20-30 seconds, it will limit regen to 5-10A if I re apply full regen, until the system figures out where it is, which is typically after another 20-30 seconds of no regen. At that point I can give it full regen again. This behavior will happen even if I am no where near full SOC.
If the regen is held, the SOC will rise to near full before limiting.
This would indicate that the charge control is more complex than a simple top limit, and we are still making a lot of assumptions, as there can be many modes of control.
Still some mysteries to uncover, but it does appear that the pack may be able to top it self off to 100% SOC under some conditions.
Based on my temperature monitoring, and the charge limiting near the top of charge, the fans should be able to keep up, unless you are driving in hot weather with limited AC cooling the cabin.
Nice observation, and this does change how we should look at that end of the SOC range in my book.
During this time I have purposely drained the battery on the 33 mile home from work.
The last time the battery was drained was about three weeks ago, and I am very conservative on battery usage with MIMA.
A strange thing happened last night on the way home however.
I decided it was again time to drain the battery on the way home and used about 4 bars of assist during various hills and such along the way.
The weird thing was that the SOC dropped from 19 bars to about 16 and then STUCK. It dropped no further even though I had used a consistent amount of assist over the 45 minute drive.
Once assist started limiting, the SOC was still showing 16 bars, and this really threw me.
After getting home, the battery charge showed 150 volts which is a little on the high side. Normally when doing the same thing, it's usually about 142 or so.
It seems that there may be times when a simple voltage measurement is more accurate than relying on the SOC display!
As a former powerwheelchair user I know hte battery indicators are never right. I have driven a chair that read full and soon as I go up a ramp it falls flat on its face and tells me time to recharge. I also have driven on for days when I get the message to recharge or battery low.
As an I2 owner Ive been told the soc display is very inaccurate and slow. I tend to believe it. I also see that a heavy load on the 12 volt side doesnt seem to be accounted for and can trigger a negative recal. Lets say using both defrosters for a few minutes.
Since I have been grid charging and balancing my I2 I see the car sits around 112 volts at 50% on the display. I see 114.5 volts or abouts when its "90%" and 117 volts when its "full". I unplug at 117 volts.
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....After getting home, the battery charge showed 150 volts which is a little on the high side. Normally when doing the same thing, it's usually about 142 or so....
Note: the battery was freshly topped off last night using the Dabrowski grid charger set to 172 volts.
It did the same thing on the way to work this morning.
During the drive I purposely used 4 bars of assist to drain the battery.
Once the battery voltage got to 155 volts, assist stopped.
*** That's when I discovered a strange interaction between the CalpodIMA disable switch and MIMA-CL. ***
With the clutch disable set to OFF, MIMA could again dial in more assist, however the dash did not show any assist but monitoring a voltmeter did indeed show that assist was going on.
Just a heads-up for anyone else in the same situation.
To elaborate further, it seems that heat *may* be an issue as well.
Again it limited to about 152 volts or so, regardless of the clutch switch position on the way home from work.
The outside temperature tonight was 40°F, so the pack was reasonably cold when starting out.
About 10 miles from home the assist as mentioned above, limited itself to about 152 volts.
However I stopped for a chat with a family member about five miles from home and the car sat for two hours.
After making my way the remainder of the trip, the assist again was robust easily giving 4 bars all the way across town with no let up down to 145 volts.
So now I wonder if the pack is getting slightly warm along the hour drive home with 4 bars of assist here and there along the way???
Not to derail the thread, but I'm an Insight newbie, and I'd be interested in as much info about the pack as I can get. In particular -- the nominal capacity in kWh, typical SOC range (I take it, 60%, from 20%-80%?) and typical voltages as either end of the SOC.
Not to derail the thread, but I'm an Insight newbie, and I'd be interested in as much info about the pack as I can get. In particular -- the nominal capacity in kWh, typical SOC range (I take it, 60%, from 20%-80%?) and typical voltages as either end of the SOC.
Sorry again for the derail.
Standard NiMH stuff. 120 cells in series. 144 VDC nominal, 174 or so when fully charged, 120 volts when dead.
Thanks. And pack capacity (kWh) and min/max charge within the DOD?
I'm a newbie also so I have no min/max info other than what others here have posted. The pack capacity is about 1 kW-h, about the same as other hybrids. If 80/20 is accurate, that leaves about 0.6 kW-h useable.
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Does the HV Battery Really Run 80%/20% ?
