Warm up the traction battery?

Does your Prius go to EV mode when battery temp is bellow 0c or 32F? Mine doesn’t and it even says it in the user manual that if it has cold soaked for long time in bellow freezing EV is unavailable.

 

This is incorrect information and a common misconception. You will warm the battery more if you use your brake pedal and NOT B Mode. B Mode generates less energy (therefore less heat) by using engine braking to waste energy instead. The idea of B Mode is to take longer to fill the battery by regenerating less, the flip side is that it uses engine braking to compensate. The correct use for B Mode is on long downhill gradient. The way to know if you should use B Mode is if your battery is not full by the time you get to the bottom of a downhill gradient, then you do not need to use B Mode.

 

Just some more helpful info. The two items that I am aware of that affect MPG's before complete utilization of the hybrid system are the catalytic converter and the coolant temperature. Hence, the thermos behind the drivers side headlight. This sucks the coolant out when you turn off the car and tries to keep it as warm as possible. When you start the car, the coolant in the thermos is pushed back in. This helps get the car up to operating temperature more quickly. Another tidbit, you will hear this when you turn off the vehicle. It only takes two or three seconds. When your 12Volt is low, you will hear the sound slow down and take longer. That is when it is a good time to check the health of the 12 volt.

 

FWIW, the Gen III's use a different device to speed up warm-up, in the form of a heat exchanger that warms the coolant from the exhaust.

 

Original question was really for peoples with EV mode button. And especially to Britprius since he told that he can put Prius into EV mode at cold start.

 

The EV button was intentionally left off of the NA version of the Gen II to meet California Emission Standards testing for an ultra-low emissions vehicle.

 

The button EV mode gets disabled for a number of reasons, and is not necessarily an indication that the EV mode *cannot* function under these conditions. For example it also get disabled if the state of charge is too high, yet full electric operation works perfectly well under this condition.

NiMH batteries will still perform well enough for the hybrid system function at temperatures down to well below -20C. Data that I have here for the prius NiMH cells indicate that at -20C the voltage is only reduced by about 4 to 5 percent (compared to room temperature) and the amp hour capacity is temporarily reduced by about 25%. Neither of these factors should significantly hinder the hybrid operation. (BTW, tests on battery aging have shown that the prius can still function reasonably well with the battery capacity reduced by more than 50%.)

What the OP is seeing in terms of the engine running more when the temperature is cold is definitely due to the need for the engine to warm for efficient operation rather than any deficiency in the battery operation. There is absolutely no point in trying to prewarm the battery at the -2C temperatures that the OP is talking about.

 

Many times I have to move my Prius for only something like 20m. I press EV button to stop it from starting ICE. If it’s 1c then no problem. If it’s -1c or colder then EV is disabled. This same thing happens with 4, 5 or 6 bars of charge.

Another thing that I use EV button is to stop ICE from idling if its temperature is something like 50c…60c but its idling cause of heater. Same thing here if battery is colder than 0c then EV is disabled.

Third thing I use EV button is when ICE has reached 70c and I’m driving slowly but not stopping and I don’t want it to idle. Same thing here if battery is colder than 0c then EV is disabled.

I’m sure that all of the situations above are caused by battery temperature and nothing else.

 

Hi valde3, I think you misunderstood what I meant. Yes I TOTALLY believe you that battery temperatures below 0C inhibits button activated EV mode, as do many other conditions.

What I don't believe is that this is because the battery cannot provide the EV power. I suspect that rather it is because it wants to warm the engine as soon as possible.

BTW. Button activated EV mode is inhibited for many different reasons. For me it's inhibited for at least the following reasons, and maybe some others that I don't know about.

- Engine initial warm up (hybrid stage 1)
- Speed > 45 km/hr
- SOC too low (less than 3 bars)
- SOC too high (topped out at 8 bars)
- Battery too hot (about 40C)
- Battery too cold (0C) <--- Haven't personally experienced this. May not apply in all regions.

Personally I never get the battery too cold condition as it's almost always warmer than that here. I very often get the battery too hot inhibited EV mode though. Even when the battery is too hot to allow button activated EV mode (only about 40C btw), it still functions perfectly well in full electric mode (as in activated by the normal method of feathering the accelerator). I'm sure the situation is exactly the same for the 0C lock out.

 

I have no problems engaging EV after standing over night at -10c to stop the engine from starting, and reversing my car out onto the road and rolling down to the bottom of the hill. I do have EV lock out when the battery is fully charged or discharged with a warm engine at any temperature.

John (Britprius)

 

Thanks for the info John. That proves that the batteries still work without any problems at below 0C.

I still believe valde3 however regarding his experiences. The prius software definitely has other regional differences in relation to the EV button, so I wouldn't doubt that the low temperature lockout could be different. For example we have a high speed lock out of only 45 km/hr here with the Australian model. I know for a fact that the gen2 prius in other markets has a higher allowable speed range for button activated EV mode.

 

For force the activity of the HV fan, to cool or in this case to heat the traction battery, I had added these genII hv blower control codes to my pids list.
Codes tested on last torque app should be good for all versions.

"Set Battery Cooling Fan Speed 1","SFS1","30810001","A","0","0","No reply req'd","7E3"
"Set Battery Cooling Fan Speed 2","SFS2","30810002","A","0","0","No reply req'd","7E3"
"Set Battery Cooling Fan Speed 3","SFS3","30810003","A","0","0","No reply req'd","7E3"
"Set Battery Cooling Fan Speed 4","SFS4","30810004","A","0","0","No reply req'd","7E3"
"Set Battery Cooling Fan Speed 5","SFS5","30810005","A","0","0","No reply req'd","7E3"
"Set Battery Cooling Fan Speed 6 (max.)","SFS6","30810006","A","0","0","No reply req'd","7E3"

(Gen2 Prius: Custom PIDs for Torque (Android App) with formulas | Page 24 | PriusChat)


Then I select the fan Speed 2 or 3 PID and put it in the Torque Window so the fan begins to suck from the indoor hot air of the cockpit, with the most rapid increase in the initial low temperature of the battery.

Initially early in the morning, the HV battery is at a temperature of -2 Cº (celsius) after 10 km reaches 13º and slowly it begins to contribute to ICE.


Read more: Gen2 Prius: Custom PIDs for Torque (Android App) with formulas | Page 24 | PriusChat
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