OBD II Data for HVB

[larryh]

The BECM is supposed to manage the HVB so that no damage occurs.  There have been many times that I have looked at the SOC of the HVB and found it to be below 10% after a trip and the car had rested a while.  The HVB still works fine.

Edited June 26, 2015 at 12:46 AM by larryh

[Hybridbear]

After the car charged for a few hours we ran an errand. The HVB temp had increased to 95.0 during charging. The outside temp was about 82. We used AC during the entire 5.2 mile trip each way. The HVB cooled from 95.0 to 91.4 during our drive. Now there are no spaces available near outlets so the car will sit unplugged overnight. The HVB SOC is about 20% according to MFM. Hopefully I will be able to find a space tomorrow to plug in so that it can charge. We don't expect to use the car tomorrow at all since we can get everywhere we need to go on foot.

[larryh]

So basically charging heats up the battery until a certain threshold where the fan can hold the temp from rising further.  If temp is too high it fan is able to cool the battery to a certain point where charging stops any further drops.

 

Maybe over the weekend you can run some tests to see if 120v charging makes a difference in the steady state temp of the battery, while hopefully the outside temp is in the 70's as you stated above.  I'd be interested to know what's the difference because cooling is the same but slower charging 1/3 the rate of 240 should technically generate less heat.  You may find under similar tests that the steady state temp of the battery might be 86 instead of 90 if the tests are done accurately.

 

-=>Raja.

 

The 90 F is a very rough estimate--it is not very accurate.  It depends on how aggressively the car is attempting to cool the HVB, which varies quite a bit.  Equilibrium temperature is achieved when the amount of heat generated by charging equals the HVB heat loss due to cooling.  The warmer the HVB, the more heat will be lost due to cooling.  It can be shown that the equilibrium temperature above the ambient temperature is proportional to the power used to charge the HVB.  Since the 120 V charger provides 1/3 the power of the 240 V charger for charging, the equilibrium temperature above the ambient temperature for the 120 V charger will be 1/3 of that for the 240 V charger.  If the 240 V charger equilibrium temperature is 21 F degrees above the ambient temperature, the 120 V charger would raise it 7 F degrees above the ambient temperature (all else being equal).

 

If you wish to cool the HVB after a trip, the HVB may cool down faster using the 120 V charger than just letting the car sit.  Last night, the HVB was 102 F and the outside temperature was 81 F.  Using the 120 V charger, the battery cooled down at a rate of 1.5 F degrees per hour. 

 

I have previously observed that the HVB cools down 5.4 F degrees over a six hour period when the HVB temperature was 15 F degrees above the ambient temperature.  That would imply that if I had just let the car sit, the HVB would have cooled down 5.4 / 6 / 15 * (102 -81) = 1.3 F degrees per hour.   So using the charger probably cooled down the HVB slightly faster than just letting the car sit.  This is only true when the HVB is relatively warm. 

Edited June 26, 2015 at 10:31 AM by larryh

[rbort]

Cooling 0.2 degrees more per hour isn't a whole heck of alot of difference.

 

In the past you used to say there is no difference between charging with 240 vs 120v in regards to temp rise.  Are you noticing something different now?

 

-=>Raja.

Edited June 26, 2015 at 02:38 PM by rbort

[larryh]

If the HVB temperature is below the equilibrium temperature of post 228 for the 120 V charger, there is not much difference.  The 240 V charger will raise the temperature by about 4 F in 2 hours while the 120 V charger takes 5.5 hours to do it.  This is the normal case.  I charge at 3:00 am in the morning after the HVB has cooled off. 

 

However, there are differences when the HVB is warm after a trip, i.e. the temperature is above the 120 V equilibrium temperature.  For the 120 V charger, the temperature will fall/rise to the 120 V equilibrium temperature.  For the 240 V Charger, the temperature will fall/rise to the 240 V equilibrium temperature.  The 240 V charger equilibrium temperature is higher than the 120 V charger equilibrium temperature.  I normally charge the battery for a short time when the HVB is hot to raise the SOC above 25%.  There is not much HVB temperature change when charging for such a short time.  So unless you fully charge a warm HVB, there is not much difference in the rise in temperature using the 240 V vs. the 120 V charger. 

Edited June 26, 2015 at 03:05 PM by larryh

[rbort]

Sounds like you're going to end up at a higher temperature charging with the 240v vs the 120v because of the higher equilibrium temperature.  Even if it takes more hours to charge with 120v, the heat insertion into the battery from charging is less so it might take 5.5 hours to reach its peak, but that peak temp will be lower that what you would reach with 240v.  And if its hotter from driving, 120v might cool it down some while charging where 240v will probably hold it steady.  If there is an option, its best to charge with the 120v (unless you're in a rush to recharge or are on the road at a public level II charger).

 

-=>Raja.

Edited June 26, 2015 at 03:29 PM by rbort

[larryh]

It is not going to make much difference which charger you use with regard to HVB degradation.  The temperature is only going to rise at most 4 F degrees. 

 

For the 240 V charger, the rise occurs in 2 hours and then the temperature begins to fall by maybe 1 F degree per hour.  The average temperature has increased by 2 F over a 6 hour period. 

 

For the 120 V charger, it rises 4 F degrees over 5 hours, and then begins to fall.  The average temperature has increased by 2.5 F degrees over a 6 hour period.

 

The battery is warmer longer for the 120 V charger simply because it takes longer to charge.  With the 240 V charger, it may warm up the battery more, but the battery also has a longer time to cool.

 

The only time there would be a significant difference is if the HVB is hot.  The 120 V charger might cool it down whereas the 240 V charger may continue to warm it up.  That would occur if you charged immediately after returning from a trip.

 

Use whichever charger pleases you.

Edited June 26, 2015 at 03:52 PM by larryh

[rbort]

Something is not making sense Larry.  Maybe you can explain it differently...the way I'm thinking:

 

Think of the 240v charger as a 3000w heater on the battery with a cooling fan.   The temp is going to rise quicker to the peak until the cooling fan is able to hold it steady thereafter.

 

In the case of the 120v charger, its a 1000w heater on the battery with the same cooling fan.  The temp is going to rise slower but it will not rise as much as there is less heat input and the fan is going to hold it steady thereafter.

 

This logic sort of jives with what you said above, so if 240v brings the temp up by 4 degrees say within an hour and then holds +4 degrees for the next hour, then 120v may only bring the temp up by 2 degrees, and due to the lower heat input will take 3 hours to get there, then it will hold +2 degrees for the next 3 hours before charging is finished.

 

Does this make any sense?  Next time I have an opportunity I'll try to check battery temp with an IR gun to see if I can get a sense of what the rise is while charging.  May take me a while to compile enough data to make a determination.

 

-=>Raja.

Edited June 26, 2015 at 04:01 PM by rbort

[larryh]

The battery is about 97% efficient when charging.  Only 3% of the energy is wasted as heat.  That means the HVB is heated at a rate of 90 watts for the 240 V charger and 30 watts for the 120 V charger. 

 

If the heat capacity of the HVB is around 10 watt-hour/F degree, then charging the HVB for one hour with the 240 V charger will raise the temperature by 90 watts * 1 hour / 10 watt-hour/F degree = 9 F degrees.  It is not going to go up by that amount because of cooling.   The rate of cooling of the HVB is proportional to the temperature difference between the HVB and the ambient temperature.  Suppose that constant is 0.22.   If the HVB temperature is 102 F and the ambient temperature is 81 F, then the rate of cooling is (102 - 81) * 0.22 = 4.6 F degrees / hour.  The net increase in the HVB temperature in 1 hour is thus 9 - 4.6 = 4.4 F degrees.  For the 120 V charger, the net increase in HVB temperature would be (30 * 1 / 10 - 4.6) = -1.6 F degrees / hour.

 

The equilibrium temperatures are not going to be reached when charging the HVB unless the HVB is already hot.  It takes hours to reach the equilibrium temperature.  At the beginning, there will be very little cooling.  The temperature difference between the HVB temperature and the ambient temperature is small--the rate the HVB cooling is proportional to this difference. 

 

The 120 V charger and 240 V charger are going to apply the same amount of energy to the HVB and the temperature will rise exactly the same amount (if we disregard cooling).  It doesn't matter what rate you apply the energy.  The temperature rise will be exactly the same.  You just get there faster with the 240 V charger.

 

So the only difference in charging with the 120 V charger and the 240 V charger is the cooling.  With the 240 V charger there is going to be slightly more cooling because the HVB temperature rises faster and there is thus a greater difference between the HVB temperature and the ambient temperature.  If the HVB starts at ambient temperature, you will have more cooling with the 240 V charger for the first two hours.  But then you get additional cooling with the 120 V charger for the next three hours that you don't get with the 240 V charger since the fans stop when charging stops.  The HVB still cools when the fans are not running, just not quite as fast.  So you get slightly more cooling during the first 2 hours and slightly less cooling for the next 3 hours with the 240 V charger vs. the 120 V charger.  This cooling difference is what is responsible for the different HVB temperatures between the two chargers.  So to determine the HVB temperature rises more with one charger vs. the other, one would need to determine which charger results in more cooling.  It probably runs the fans faster with the 240 V charger for a shorter period of time, but slower with the 120 V charger for a longer period of time. 

 

I don't think it is going to work measuring the HVB temperature using IR.  You will be measuring the combined heat from all the electronics, the charger itself (which gets very hot), and the HVB.  You will not be measuring the HVB temperature. 

Edited June 26, 2015 at 05:51 PM by larryh

[rbort]

Larry, so imagine this.  A 10 watt resistor on 1 heat sink with a cpu fan blowing on it.

 

You turn on the resistor and the fan, and in about 15 to 20 minutes if that thing is in a wind tunnel the air coming out the other side might be 100F.

 

Now the same setup, but 3 10 watt resistors.  You turn them on, and in less than 15 to 20 minutes the temp is going to surpass 100F and go up to 150F by the time everything is heated up.

 

3 times more heat, warmer air circulating off the battery in the car.  I'll check with the IR gun the temp inside the cavity after the car has been charging for some time to see what it is and make note of the temps.  Today I'm going now but its sunny out, would rather do it in the evening but I'll gather some data.

 

-=>Raja.

[larryh]

That is not a correct analogy.  The same amount of energy goes into the HVB whether you use the 240 V charger or the 120 V charger.  The amount of energy that goes in the HVB determines how much it heats up.  The fans and ambient temperature then determine how much it cools down.  In your analogy, you have three times the energy being consumed for the one case vs. the other.   You can only run the second case for 1/3 the time of the first case for the two cases to use the same energy.  Now the same amount of heat is generated in both cases.

Edited June 26, 2015 at 07:32 PM by larryh

[rbort]

Okay so I'm at the big Y. The outside temperature is 76°, the car has been charging for 46 minutes. I just took the temperature inside the cavity with the high-voltage disconnect is and it was 110 Fahrenheit. The windows were cracked about 1 inch to 2 inches each I just rolled them all the way down. It is partly cloudy partly sunny today.

 

I will have to compare this temperature inside the battery compartment during the night when the sun is not a factor and also in my garage with the 110 V charger to see if there's any difference .

 

-=>Raja.

[larryh]

Today I'm going now but its sunny out, would rather do it in the evening but I'll gather some data.

 

-=>Raja.

 

The Sun warms up the HVB far more than any charger would.  Leaving the car out in the Sun for two hours will quickly warm up the HVB from 89.6 F to 93.2 F, i.e. 4 F degrees.

Edited June 26, 2015 at 08:42 PM by larryh

[rbort]

I checked 15 minutes later and the highest temperature I saw was 112, then when the car was at 99% charge level the temperature was down to 110f. Now that the charge is complete the fan is no longer running I checked the same spot it shows 93° but if i check on the ceiling of that cavity where metal is it shows 99°F.

 

It's not that hot outside it's in the 70s, my watch shows 73f.

 

I will check this again sometime when there's no sun.

 

-=>Raja.

[rbort]

Need the car tomorrow morning so after that full charge I drove about 6 miles and the charge level was down to 86%.  I plugged the car in about an hour ago, garage temp still showing 76F and after an addition of 10% to the battery (96%) about 30 to 40 minute charging I checked the temp and it was at 89F.  When the car reached 99%, I checked the battery again and its down to 87F, so its been dropping though there isn't enough charge time on 120v to make a good judgement.

 

Tomorrow I'll be using the car for about 60 miles EV, so after I get home it should be pretty close to empty.  I'll wait until Sunday and plug it in during the day to see how much the temp will rise after 2 to 3 hours on the 120v charger.  Granted what I'm checking is the hot air that is circulating around not the battery itself, but whatever I find there will be relative to the battery temp and certainly if I check that same spot all the time I can tell a temp difference between charging with 120v vs 240v over time.

 

That aside, what a wonderful range on this car!

 

-=>Raja.

Edited June 27, 2015 at 01:34 AM by rbort

[rbort]

Charging after a 25 mile 204mpge trip in maynard. Temp today is 68f under cloudy skies, pocket temp hot air showing 106f.

 

-=^Raja.

[rbort]

After a 6 mile round-trip from the charging station in Maynard, I recharged once more because it was dark and raining from 80% back up to 99%. I drove 25 miles home and got home with half a hybrid battery left.

 

Once home I plug the car in right away with value charging on. I went to take a shower and came back to the car 40 minutes later. I took the temperature inside the battery cavity and it was at 72°F, the outside temperature on the drive home was 58°. Apparently the battery didn't get that hot on the drive home. Just before going to bed now I decided to unplug the car because I figured burning 60 W of energy overnight continuously was not going to be worth it tonight. The car is 0% charge level now. I will plug it in the morning and charge it back up to 60%. About three hours into the charge I will check the temperature to see with the peak is, the battery should be as hot as it's going to get by then.

 

 

By the way Larry the car did not charge the battery at all, it went to value charge and is still at 0% as expected.

 

-=>Raja.

Edited June 28, 2015 at 05:53 AM by rbort

[rbort]

This morning I powered up the car to check the HVB charge level.  It had dropped from 1/2 a hybrid battery last night to about 25% hybrid battery, really typical as when the battery cools down from driving the voltage could certainly drop and what I've seen in the past, in other words, pulling in with 2 miles range to eat at Panera Bread before going to a charger 2 miles away and then when getting back in the car finding out the 2 miles range is gone and I only have a partial hybrid battery and now I can't make it to the charger -- should have just kept going there I would have made it.

 

Anyway, I plugged the car in 2 hours ago now.  Charge level is back up to 32% now.  The temp of the hot air inside the cavity is 88F.  The fan seems to be running at a constant medium speed.  When I charge with 240v I notice the fan races up to high and back down to medium speeds, its alternating between the two.  The current temp in the garage is 68F.

 

Edit:

 

3 hours into the charge the cavity temperature is now 91F and the battery is at 53% charge level now.

 

Last update, 3 hours 50 minutes into the charge, temp now 92F and the battery is at 68% charge level.  The fan is now alternating between high and medium speeds. High for a few seconds then medium for a longer time period and repeat.

 

I unplugged the car as I don't want to charge it any further than this at this time.

 

-=>Raja.

Edited June 28, 2015 at 05:35 PM by rbort

[Hybridbear]

I unplugged the car as I don't want to charge it any further than this at this time.

Do you work from home that you're able to do all this plugging in & unplugging of your car?

[Hybridbear]

Coming home last night we used up all of the HVB again. We started with a reported ETE of 7.105 and arrived home with the ETE showing 1.107 kWh. I plugged the car in immediately upon arriving home. The HVB temp started at 71.6 F and rose to 86.0 F on the drive home. The car did not begin charging immediately upon being plugged in, but rather showed that it would wait to charge until 3:00 am until 5:48 am. This was the longest predicted charging time I have ever seen on a 240V connection. I expected the ETE to drop as the HVB sat and thus I wanted it to do some immediate charging. When it still had not done any charging 30 mins after we got home, I set a Go Time to get it to start charging. I let it charge for about 30 minutes and then deleted the Go Time. It finished charging overnight at its normally scheduled time. MFM shows 5.9 kWh used for this trip. We used 1.30 gallons coming home and 1.37 gallons going south including the extra 0.05 burned due to the drop in ETE while the car was off.

[Hybridbear]

I would add one additional item to the list.  Avoid over-stressing the HVB.  This means, while in EV mode, avoid excessive acceleration, driving at high speeds on the freeway, or ascending a steep hill rapidly.  Also, avoid hybrid mode until the end of a trip. 

 

The following chart plots HVB power (red line) and SOC (green line) vs. time for a 60 mile commute.  The blue indicates the voltage variation between cells, which is a proxy for stress on the HVB.  When there is significant voltage variation between the cells, the weaker cells are doing a disproportionate amount of the work making them even weaker.   Weak cells impact HVB performance.  To function correctly, all the cells need to be the same strength. 

 

While the SOC is above 22.5%, i.e. the car is not in Hybrid mode, the blue line is generally well below 20 mV.  It spikes above 20 mV when the HVB outputs more than 20 kW of power (about 2 bars on the empower screen).  When in Hybrid mode, as the SOC continues to fall at the end of the trip, the blue line rises to about 40 mV.   The increases in variation indicate the greater stress on the HVB when it outputs high power or when the SOC is low. 

I thought I would reply to this here as it seems to fit better than in the other thread. I have not yet started monitoring cell voltage variation in the Fusion but I can in the Focus Electric with FORScan. At a full charge each cell is about 4.06 V. The variation is measured in hundredths of a volt and is 0.01 when at rest. When HVB power (positive or negative) exceeds ~ 17.5 kW the variation goes up to 0.02. When HVB power exceeds ~ 35 kW the variation goes up to 0.03 volts. When HVB power exceeds 52.5 kW the variation goes up to 0.04-0.05 volts. I rarely exceed 50 kW of power during acceleration or deceleration (max charge rate is 60 kW and max discharge is 110 kW). At full throttle with a nearly fully charged HVB the cell voltage variation is around 0.08 volts. As the HVB discharges the cell voltage variation increases at all power levels. When the HVB is nearly depleted (under 10 miles of range remaining) the cell voltage variation at rest was around 0.05-0.07 volts. When the HVB is discharged this low the voltage variation doesn't increase as much as the power demand increases.

Edited July 1, 2015 at 07:31 PM by Hybridbear

[rbort]

Bear, I have my own business so the answer to that would be yes.  

 

Also, if you want the car to charge right away, its alot easier than setting up a go time, just change the value charge to "charge now" either from the car's MFT screen when you get home or from your cell phone or from MFM.  When you had enough charge, change it back and the car will wait to charge until 3am in your case.

 

You and I are in the same boat, our cars don't recharge the HVB in value charge even if it is very low.  Larry got something wrong going on at his end...

 

When you were charging the battery, did the temp go up higher than 86F?  I would expect that it did especially with the 240v.

 

-=>Raja.

[Hybridbear]

Bear, I have my own business so the answer to that would be yes.  

 

Also, if you want the car to charge right away, its alot easier than setting up a go time, just change the value charge to "charge now" either from the car's MFT screen when you get home or from your cell phone or from MFM.  When you had enough charge, change it back and the car will wait to charge until 3am in your case.

 

You and I are in the same boat, our cars don't recharge the HVB in value charge even if it is very low.  Larry got something wrong going on at his end...

 

When you were charging the battery, did the temp go up higher than 86F?  I would expect that it did especially with the 240v.

 

-=>Raja.

I did not check the temperature. This morning my wife drove the Fusion & I took the Focus Electric since I will be driving more miles than the Fusion could do without the ICE today. I normally do change it to charge now, but since we had been charging away from home I could not see home in the cell phone app under Value Charge profiles. The MFM app only shows the two most recent Value Charge Profiles used. Since we charged at two different locations in Rochester using Value Charging I could not see my home profile even though the car was plugged in at home. Thus it was easier to set a Go Time. Using a Go Time also should have triggered the car to stop charging once the Go Time passed even though it wasn't fully charged, but I didn't wait to test that out.

[rbort]

I had another opportunity to charge again on level 2 today.  I waited until evening until the sun was not a factor any more and plugged the car in at 6:45pm.  By 7:15pm the temp in the cavity had risen to 99 degrees, and 1 hour and 10 minutes into the charge (7:55pm) at 95% charge level I checked the battery temp once more and it had risen to 107F.  I'm talking the hot air circulating around the battery.  I unplugged the car and drove home.

 

It is my findings that level 2 charging raises the air temp in the cavity along with other parts in there (metal shield, etc) quicker than 110v and even higher as well.  Level 1 charging takes about 3 hours before the fan starts to turn up to high and charging 1/2 with level one back to storage mode and then the 2nd half before departure is probably the best practice if you have time to spare.

 

Level 2 is good only if you need it quick, if you don't, level one would be a little bit easier on the battery.

 

Tomorrow I drive to Natick to meet my brother for lunch, I have 86% left now enough to get there I won't charge again.  I'll be using level 1 at the mall to bring my car back up to 100% (or close to it) while I'm there.

 

-=>Raja.

Edited July 2, 2015 at 01:24 AM by rbort

[rbort]

Going back and looking at my posts, looks like level 2 typically raises the pocket air temp to 106-107 degrees with or without long distance driving -- last week I drove 25 miles and charged up, today I drove 3 miles and charged up - about the same temperature.

 

In the heat of the sun, it went up to 112F, but in that case I would contribute that to "baking in the sun" even though it wasn't that "hot" and partly sunny that day.  Could have been worse with a hotter day and full sun.

 

Level 1 charging seems to be cooler, and takes longer to warm up the battery enough to require the cooling fan on high speed.

 

This is what I see here with my Cmax.

 

-=>Raja.