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The ideal temp. for the HV battery is 28C (82F) with a desired range of 25C (77F) to 38C (100F). I notice performance issues with the HV battery during cold starts in the 50F's.

The HV battery is an air cooled unit with no heating method. Near the left (driver) rear cargo area is a access plate to the HV battery filter. Remove it and there is cap that also needs to be remove to slide out the battery filter. This is the only access to the air cooled battery housing from inside the cabin of vehicle.

Blocking the outside vent with something (insulation) would force cabin air to be used if this filter and access panel was removed. Your most likely going to regulate the cabin temp with the cabin heater that uses the engine coolant (no extra energy). If the battery fans come on, they would only pull warm air from the cabin which will keep the battery temp warm enough to maintain near ideal conditions. Also, if the outside vent is plugged, the battery will not be as cold in the AM. I would most likely use an insulating material to block the outside vent. You could place a filter material between the openning and the cabin to keep the battery and components clean also.

There is no physical air duct connecting the auxiliary climate control system for the HV battery to the cabin as some people believe. There is a supply and return duct that directs air flow across the battery cells which Ford has patented. There really is no exsisting way to close off the vent to the outside with an automatic door. The air flow mode door actuator allow air to circulate in and out of the battery housing through the evaporator. This appears to be the only "DOOR" in the duct system. There are only two things separating the outside supply vent from the battery housing, which are the filter and the auxiliary evaporator. Therefore the battery has a constant openning to the outside cold or hot temp. This would be like the vent mode in the cabin with no fan speed. In other words, if it's cold outside, you would close the outside vent to the cabin and turn the heater on. This is the same idea I've come up with for the HV battery.

When the battery get hots, the door opens to allow air to circulate at a predetermined temp. The variable speed fans control cooling with outside vent air combine with recir air, but if the TBCM request further cooling, the PCM answers by activating the compressor. Outside air is still provided by the outside vent, just like normal AC without recir. mode.

In most cases, the inside cabin temp in cold climates is never over 82F, so if the battery starts to get hot, the cabin temp will cool it down with my suggestion before the need for the A/C compressor. You still have the A/C if it gets warmer during the day if needed.

This past summer and winter has taught me the importance of EV and battery temp. See page 412-03B-11 of volume 2 of the workshop manual for a drawing of the duct, door actuator, and evaporator placement if you have concerns.

This idea needs testing, and my location does not get that cold. Any thought?

GaryG

I could see blocking and unblocking the vent overnight to help maintain temperature; although I do not think that using cabin air to cool the battery would be advantageous over outside, colder air. I would think the thermal mass of the batteries is going to be much greater than the air, and cooling would be a straight function of the temperature difference, all things (air flow rate, etc.) being equal.

If the controller is good enough, the temperature should be maintained in the same temperature range, regardless of the source of the air.

If the batteries are not generating a lot of heat, then the passenger compartment air would be the way to go, as you could probably get the batteries warmer, quicker -- although I think the Ford Engineers would have added a little ducting if that were going to be a big issue.

Now, an old time engine block heater -- hooked up to the battery compartment, to keep it at 25C, could be another alternative.

Hi Gary:

___Very detailed write up of what you have discovered. Without some kind of temp probe(s) back there to monitor ambient in the pack compartment, I would be a little leery. Not that I have taken non-monitored mod risks with great results myself but a $3,000 + OEM Pack is not something to be toyed with.

___My question has to do with the ECU inputs for how the pack, emissions control and the ICE itself work together for maximum FE. Do you see Closed loop ops even with a sub 50 degree F pack compartment? I would assume you would but your EV capabilities may be hampered somewhat? Does a cold pack force a trickle like charge to warm it up and can you see the FE hit? The Insight on sub 0 degree F mornings would force charge from 19 to 20 of 20 bars and I have to assume Honda programmed the Insight this way to bring pack temp up somewhat even if I barely touched it. What is the performance capability of the pack in sub 50 degree temps? ¾ the range in EV vs. 70 +? ½ the distance? Tighter SoC band? I do not know these parameters at various bracketed temps (0 - 30, 30 - 50, 50 - 70, and 70 - 90 as examples) and that is why I am asking …

___I will assume a pack temp of 75 degrees F would provide optimum performance but optimum means what exactly?

___On a different topic, I spoke with Eric Powers ~ 3 weeks ago about his chance drive in an 07 FEH. He said it would drop into EV a lot easier then the 05 he tested last. No LGA or double tap in particular needed if I remember our discussion correctly? Much more Prius like. If this is so, maybe Ford is finally starting to listen to those like yourself who push tanks and how to make the FEH even better! Driving into EV without all the stunts would be a boon for the average FEH/MMH driver in my book as they would not have to learn but simply drive conservatively ;)

___Good Luck

___Wayne

Thanks Hamilton and Wayne

Wayne, you are correct that Ford is making adjustments in their programming, and the average driver will benifit. The '06 FEH has less of a run-up in RPM's to burn off energy the HV battery will not except. Already I'm seeing better than average MPG out of the '06 and even better in the '07's. However, one thing I feel would reduce my ability for the super high MPG is the reduction in regen to reduce run-up. I'm one who now knows how to control battery temp and take advantage of the fake shift in "L" for a quick HV battery charge for extended EV driving.

Back to warming the battery. There is now no manual control in keeping the HV battery at ideal temps in cold climates for EV driving. As I stated, I see problems at 50F. When I try to build up a low charge with regen in "L", regen is cancelled by the TBCM because the battery is too cold to accept the charge. How do I know this? There is no regen braking as in warm weather. I need that battery charge.

Returning control of heating and cooling of the battery to a driver in cold climates is my suggestion. Many do not care to take control and can live with below performance and that's a choice. Controling battery temp will prolong the life of the battery while charging and discharging IMO.

Wayne, I really don't think there would be any possibility of damage to to the battery with the TBCM requesting the A/C compressor if needed. If I heard to compressor kick in, I would let the windows down for cooler air in the cabin. This is the control you can have in cold climates.

As far as the engine running at max FE with the CAT, Those are issues with the other half of the propulsion and not addressed untill they become a problem. The radiator block maybe the answer to that problem in cold climates, I just don't know.

GaryG

man this tech stuff is getting to me, can't i keep it simple and put a blanket over the battery for those cold nightS!?!

man this tech stuff is getting to me, can't i keep it simple and put a blanket over the battery for those cold nightS!?!

LOL! Now, there's a thought - a block heater for the engine & an electric blanket for the HV battery!:D :D

Seriously, I'm reading this discussion with interest, as my FE is starting to take a hit from the dropping temps, but I'm afraid of doing something that might turn out to cause problems or interfere with my warrantee.

Sorry Debbie

GPSman found something not shown in the Helms workshop manual I was looking at. There is already a door between the outside vent filter and the battery housing. You can still do the trick blocking the vent and openning the filter to the cabin, but I don't think it will help that much.

As I responded on GH, you guys might benifit with the heating blanket idea before you start out on a cold day, just don't get the battery to hot. The more you use EV, the longer the battery will stay warm. If my battery is cold from the start, it will not accept a fake shift in "L" to build the battery SoC.

It was just brought up on GH, that Ford did install block heaters in the FEH in your State and a few others and Canada with cold climates. Enjoy!

GaryG

Here's a thread on this general topic at PriusOnline:
http://www.priusonline.com/viewtopic.php?t=9303

In particular, if anyone has any thoughts on implementation of the heater I discuss in my posts I'd love to hear more.

Hi Efusco

I read that thread and I would be against that heater fan idea for the FEH. Maybe in the AM when things are real cold to get me going, but only on house current. What chemical effect would the dirrect blowing of dry heat have on the cells is another question.

Our ideal battery temp is 82F, but I tend to stay off the freeway where the battery would not be used to stay warm in cold climates. In cold weather here in So. FL (40F), I still overheat my battery with heavy charging in city driving. My problem is bad FE while getting the battery warm for EV use on a cold start. If I lived in a real cold climate and had to drive some highway, I would find a way to bypass the outside closed vent door and supply cabin air (maybe with one of those small DC fans) like I originally talked about in this thread.

This is the second day of 70F - 80F weather here, and I can see almost a 10mpg jump in FE because of great battery temp while still getting the CAT warm pretty quick for EV. My battery is still kicking on the A/C compressor those two days, but not everytime the ICE comes on. My last tank was 44.6mpg, but it can only get better from here till next summer.

Scangauge 1

Tank Average - 44.6mpg

Average Speed - 22mph

Hours To Empty - 4

Miles To Empty - 89.0 (based of a 15 gallon tank)

Trip or Miles - 580

Gallons To Empty - 2

Gallons Used - 13.0


Nav Sys. and Dash Gauges

OD Reading - 30,140

Trip OD - 586.1

Nav Sys Average - 47.2mpg

Miles To Empty - minus 26 miles from 0 reading

Miles To Empty After Fill - 665 miles

Gallons pumped - 13.0

GaryG

Nothing to be sorry about, Gary - thanks for looking into this for us poor, cold Northerners;)

The block heater seems to be doing its job nicely. My husband laughs at me for plugging it in overnight already, but that's because he's thinking of it in terms of something to help starting in the AM. We've been having temps in the 30's at night (it was 31F when I got to work this morning), & I was afraid my FE for this tank was going to stay below 40mpg, but with the block heater, the engine kicks off in about half the time it would if I hadn't plugged it in the night before:) As of this morning, with ~100mi. on the trip-meter, my FE display stands at 38.3mpg, up from 36.? yesterday.

I may be speaking too soon, but I have hopes of passing 40mpg before I have to fill up again. :)

Hi Efusco

I read that thread and I would be against that heater fan idea for the FEH. Maybe in the AM when things are real cold to get me going, but only on house current. What chemical effect would the dirrect blowing of dry heat have on the cells is another question.

Our ideal battery temp is 82F, but I tend to stay off the freeway where the battery would not be used to stay warm in cold climates. In cold weather here in So. FL (40F), I still overheat my battery with heavy charging in city driving. My problem is bad FE while getting the battery warm for EV use on a cold start. If I lived in a real cold climate and had to drive some highway, I would find a way to bypass the outside closed vent door and supply cabin air (maybe with one of those small DC fans) like I originally talked about in this thread.

This is the second day of 70F - 80F weather here, and I can see almost a 10mpg jump in FE because of great battery temp while still getting the CAT warm pretty quick for EV. My battery is still kicking on the A/C compressor those two days, but not everytime the ICE comes on. My last tank was 44.6mpg, but it can only get better from here till next summer.

Scangauge 1

Tank Average - 44.6mpg

Average Speed - 22mph

Hours To Empty - 4

Miles To Empty - 89.0 (based of a 15 gallon tank)

Trip or Miles - 580

Gallons To Empty - 2

Gallons Used - 13.0


Nav Sys. and Dash Gauges

OD Reading - 30,140

Trip OD - 586.1

Nav Sys Average - 47.2mpg

Miles To Empty - minus 26 miles from 0 reading

Miles To Empty After Fill - 665 miles

Gallons pumped - 13.0

GaryG
Gary,
Thanks for your thoughts. It seems, however, that I need to clarify a few things that perhaps were not as clear as I would have intended.

1)I'm driving a Prius II ('04)--the intake vent for cooling (and warming?) the HV battery is inside the cabin already so I have no concerns about bypassing the outside vent.

2)The fan/heater would be on only when plugged in to AC power at home and at work, not while the car was driving. The intent would be to keep the battery at its peak operational temperture before start up.

3)The HV battery still has a significant roll to play even in highway driving. I think it was in that linked thread that I told my story about the 48 hour sub-20 degree cold soak I put my Prius through this past winter. Start up battery temp, per CAN-View, was only ~21 degrees. Even after almost 2.5 hours of freeway driving (albeit iced roads at 45-50mph mostly) the temp had only risen to ~40 degrees despite cabin heat being on. Clearly well outside it's peak operating temp and my power and FE paid the price for that. It's just a very dense mass of battery and it takes a long time to get to temp.

4)I'm only aiming for a target start-up temp of around 60 degrees for the HV battery with this low wattage heater. I have no concerns about overheating the battery at all, I've only experienced the cooling fan come on for my Prius battery a handful of times and always after the car had "green-housed" in the summer sun and start-up temps for the HV battery were above 110 degrees. Normal city battery temps, even in the summer, rarely exceed 98 degrees. In winter it's very rare to see it over 80 degrees.

5)I can't see how there could be any concern about the battery chemistry if I'm slowly warming the battery to 60 degrees...I guess I'll need you to clarify your concerns there.

Debbie, any time you can warm that block before a startup is going to improve how soon the CAT will reach EV temp and the sooner you will get to KAM long term fuel trim and close loop. Be as consistance as you can with plug-in so your KAM long term fuel trim learns and keeps a good RPM and engine load memory during cold weather.

What I have found in real hot weather, I can go EV in one mile with no stops. In colder weather, add another 1/4 to 1/2 mile to go EV. My battery is aways at the bottom of the SoC when I start out in the morning, and I may have half SOC in that one mile to go EV. If you can leave with a warm block and a ~warm battery in cold weather, the cold weather will help the battery maintain a fast charge without overheating. In other words, leave with a low ~warm battery, use the Fake Shift in "L" tow or three times to maintain a warm battery, let the small generator work the ICE to heat things up for better FE sooner and get to KAM long term fuel trim ASAP.

The way I judge my FE on cold starts is how fast in the shortest distance I can get my SG Current Trip reading. If I'm at a 35mpg average in two miles, I'm off to a good start. During hot weather, if I'm at a 35mpg average in 4 miles, I'm off to a good start because the A/C is running. In cooler weather, I can get to a 44-45mpg average in 6 miles, but in hot weather, I'm good if that same distance is at a 40mpg average. This is how I compare how I'm handling my conditions. If I make changes in my techniques, I can see if is better or worse fairly soon. Headwinds will always play a part in those figures also.

If I were you, I would see how long it takes to reach max block temp with the block heater, give yourself a little extra time for temps that may very, and put the system on a timer. The energy is going to cost you, so maybe overnight is a bit much.

GaryG

Gary,

I did as you suggested & put a timer on the outlet where I plug my block heater in, so now it's only on for 3 1/2-4 hours. I'm *very* pleased with the result - until the last couple of mornings, when the temperature was below 30, I would be able to go EV in half the time/distance that I had previously needed in this cooler (not colder yet, this *is* WI after all!) weather :) :) Now I just have to block off the front grille to keep more of that heat in the engine compartment.

It does seem that the HV battery is a little reluctant to charge up with the lower temps, so I've been bringing some warmth into the cabin with the fan, sort of on the same premise as your suggestion about using the A/C last summer to help keep the HV battery cooler. It seems to be helping, but that may be just my imagination/wishful thinking :rolleyes: (I guess one of the advantages to being a woman in my 50's:eek: is that normally I don't need to draw heat off the engine to keep *myself* warm:p, but I'll do it to keep those mpg's up!)

At this point, in spite of AM temps in the high 20's/low 30's, I'm still hanging onto my high 30's mpg...

I'm also working on getting the hang of your more active method of HV battery management - I'm nowhere near as good at it as you are, but I'm finally able to add *some* charge to the battery without losing it in getting back up to speed. Any further details you're willing to throw my way would be appreciated!

I'm also thinking that I may be ready to graduate from just my NAV displays of FE & SoC to a ScanGuage - the biggest problem will be explaining to my husband why I need *another* gadget to watch instead of the road :rolleyes:

Debbie and All

Just posted this on GH, but thought it may be something to think about for you snow birds:

I read some articles about the effects of wide open throttle (WOT) efficiency compared to the increase vacuum of partial throttle efficiency. Engineers agreed that the reason for better fuel efficiency in partial throttle was due to the warming of the outside air in the intake system. WOT was worst because of the faster rate colder air made it to the combustion chamber. Many intake designs draw air channeled directly from the front of the vehicle and not through the engine compartment. Perhapes if you could use the air which passes through the radiator during winter, FE would get better. Also, maintaining as low RPM you can would also give more time for outside air to warm in the intake sytem.

Just my thinking on the matter.

GaryG