62 kWh Battery Heater - Quest to Find It!

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knightmb

Well-known member
Joined
Jan 12, 2015
Messages
2,212
Location
Franklin, TN
Just as the subject says, I want to find out how the 62 kWh battery is heating itself in really cold weather. The owners manual is not much help and my technical contacts at Nissan are kind of shoulder shrugging this one, so I am going to design an experiment to try and find out how this actually works.

My first obstacle, I don't live in a cold enough climate. It is rare for it to reach single digit F temperatures for more than a few days and that is not enough to activate the battery warmer regardless. What I do have access to though, is lots of cheap, dry ice. :lol:
So while I don't need to cool the battery to -100F to make this work, it can help cool the battery pack enough to reach the target temperature when it is *suppose* to activate some heating system and then when it does, try to find out how much power it is using and what is it actually doing!

I'm going the simple route, wait till dark, put a thermal bag around the whole bottom of the Leaf to encase the battery, then fill it with dry ice to create a deep freezer right below the battery to *hopefully* cool it down, but not too much. :shock:
Monitor the experiment the whole night, battery temperature, etc. Then when it finally gets close to the target temperature, just watch LeafSpy to see when some "extra" power usage kicks in or maybe a light on the dash will come on if the Leaf is off, I'm not really sure what to expect at this point... :?

If anyone sees an issue with my experiment setup or has some better suggestions, I'm open to "cheap" options. :mrgreen:
 
I suggest that you crowd source this, and have people in cold climates observe their batteries, rather than risk damage to your (or your wife's!) battery. If you do proceed as planned, then I suggest that you only chill your battery when the ambient temp is well below freezing.
 
The HV battery heater controls are pretty well explained in the factory service manual, available here as "EVB" in PDF format:

https://www.nicoclub.com/service-manual?fsm=Leaf%2F2015%2Fevb.pdf

See page EVB-25 for details.
 
The above apears to refer only to the smaller packs with actual battery warmer installed. Knightmb is looking for how the 62kwh pack is heated with no heater installed.
 
LeftieBiker said:
The above apears to refer only to the smaller packs with actual battery warmer installed. Knightmb is looking for how the 62kwh pack is heated with no heater installed.

Yes, because that website has no FSM for newer models. I referenced it in case their are similarities between model years that might provide him with some insights...
 
Knightmb, I would be more interested to know if dry ice on the pack would reduce top end heating during multiple back to back DC sessions? While rapid gate isn't a huge issue, dry ice can be had at many grocery stores now, so for the occasional long road trip would be a possible aid.
 
knightmb said:
Just as the subject says, I want to find out how the 62 kWh battery is heating itself in really cold weather. The owners manual is not much help and my technical contacts at Nissan are kind of shoulder shrugging this one, so I am going to design an experiment to try and find out how this actually works.

My first obstacle, I don't live in a cold enough climate. It is rare for it to reach single digit F temperatures for more than a few days and that is not enough to activate the battery warmer regardless. What I do have access to though, is lots of cheap, dry ice. :lol:
So while I don't need to cool the battery to -100F to make this work, it can help cool the battery pack enough to reach the target temperature when it is *suppose* to activate some heating system and then when it does, try to find out how much power it is using and what is it actually doing!

I'm going the simple route, wait till dark, put a thermal bag around the whole bottom of the Leaf to encase the battery, then fill it with dry ice to create a deep freezer right below the battery to *hopefully* cool it down, but not too much. :shock:
Monitor the experiment the whole night, battery temperature, etc. Then when it finally gets close to the target temperature, just watch LeafSpy to see when some "extra" power usage kicks in or maybe a light on the dash will come on if the Leaf is off, I'm not really sure what to expect at this point... :?

If anyone sees an issue with my experiment setup or has some better suggestions, I'm open to "cheap" options. :mrgreen:

I would just note to ensure that you have adequate ventilation. Otherwise you risk passing out or worse if you raise the CO2 levels too high in your space. CO2 levels don't need to go very high before you will see effects as I understand matters.
 
LeftieBiker said:
I suggest that you crowd source this, and have people in cold climates observe their batteries, rather than risk damage to your (or your wife's!) battery. If you do proceed as planned, then I suggest that you only chill your battery when the ambient temp is well below freezing.

The plan is to just cover the bottom of the Leaf where the battery is and put the dry ice in that. If something goes wrong, like the cooling is too rapid, I can open the blanket and let the cold out. That's the only advantage I see where I am, I can turn the cold on and off. I would love to have someone in Canada do the experiment, but they can't turn off the cold if something goes wrong and I would rather have my battery damaged by my own mistakes than have someone else risk their own (and warranty). :eek:
 
alozzy said:
The HV battery heater controls are pretty well explained in the factory service manual, available here as "EVB" in PDF format:

https://www.nicoclub.com/service-manual?fsm=Leaf%2F2015%2Fevb.pdf

See page EVB-25 for details.

Thanks for the link, I've downloaded the entire manual, will read over for insights into my quest! :)
 
DougWantsALeaf said:
Knightmb, I would be more interested to know if dry ice on the pack would reduce top end heating during multiple back to back DC sessions? While rapid gate isn't a huge issue, dry ice can be had at many grocery stores now, so for the occasional long road trip would be a possible aid.

Being that it is -100F, my guess would be it would be effective if there is a way to deploy it easily and not the "handy man special" setup that I'll be using by just covering the bottom of my Leaf with a thermal blanket and shoving dry ice into it. ;)
 
frontrangeleaf said:
I would just note to ensure that you have adequate ventilation. Otherwise you risk passing out or worse if you raise the CO2 levels too high in your space. CO2 levels don't need to go very high before you will see effects as I understand matters.

It will all be outside, just covering the bottom of the Leaf and using that to sap the heat, I do wonder if the top part of the part is normal temperature if that will have any effect on the experiment or if the Leaf only pays attention to the battery temperature. :?
 
i wouldn't be surprised if it also used the ambient outdoor temperature sensor as an input, but that would require the VCM to be powered up. Maybe it is powered all the time but i don't know.

Since the LBC is always powered up then it can monitor the pack temperature and turn on the heater relay (on the LBC board in previous versions, may be different in yours); it can also send CAN buss message to wake up the VCM and turn on the pack contactors.

Wonder if some of your tech friends down the road there could get you pages out of the FSM to show the LBC and VCM wiring diagrams?

ps There is also the radiator coolant line temperature sensor to consider if it might be used as an input.
 
According to the manual that alozzy shared here (thanks for that! :) ), the battery heater (Or I guess software mode for the 62 kWh) should activate when the internal temperature falls down to -4F/-20C, so I should not have to worry about the rest of the Leaf being warm above, which is good news. Everything seems to be self-contained within the battery pack. So, I will use the same remote sensors I used when doing my gear oil temperature research to monitor the outside temperature of the battery pack on both ends to get an idea of how cold the "environment" is inside the battery pack. I can probably use ACC mode to get some occasional LeafSpy readings to see what temperature it shows inside the battery pack to get an idea of what the delta is between the outside temperature and inside temperature of the battery pack. Knowing that, I should be able to guesstimate when the battery pack should be close to the right temperature to activate... whatever it does... :lol: and observe if I can record a slow increase in pack temperature against the cooling effect of the dry ice.
 
Another approach would be to install a CAN bridge to spoof the temperature reading from the pack. That would have the advantage of being able to monitor the response (which I assume would be over a CAN bus) as well.

On the other hand, that would require a CAN bridge and a quite a bit of coding effort.
 
goldbrick said:
Another approach would be to install a CAN bridge to spoof the temperature reading from the pack. That would have the advantage of being able to monitor the response (which I assume would be over a CAN bus) as well.

On the other hand, that would require a CAN bridge and a quite a bit of coding effort.

That's why I'm going the cheap and "get life experience" route. :lol:

Something that I can setup quickly and still be able to have the hood up and some monitors going to see if it really can heat itself from the inside or if it is going to run some type of external device or power draw. At least with the battery heaters it makes sense, but with the vague "software mode" heating, I mean, are they going to have the BMS divide by zero and make some CPU heat or power up the water pump or OBC to burn energy, it just doesn't really seem logical. I understand that if the pack is so tight that heaters can't fit, find another way to warm up the batteries, but without more info, it really leaves a big information gap. :?

Luckily, if I can see that if the battery isn't warming up and the temperature continues to fall, I can stop the experiment and let the batteries warm back up from ambient air temperature without worrying about long term damage.
 
Snargleblarg said:
Don't you think they're just duty cycling the cell balancing shunts on/off to generate some heat?

10mA of bleed current barely heats up the shunt resistors in the LBC.
 
Is it established that 62kWh packs are only configured for 10mA balancing? Modern BMS chips can support over 100mA balancing. Even at only 10mA, if all shunts are activated on a 400V pack, that's 40W. Not nothing.

This pack uses, what, 6 cells in parallel throughout the stack? So is that 10mA per stack or 10mA per cell? 10mA per cell would mean 240W.
 
Snargleblarg said:
Is it established that 62kWh packs are only configured for 10mA balancing? Modern BMS chips can support over 100mA balancing. Even at only 10mA, if all shunts are activated on a 400V pack, that's 40W. Not nothing.
Not nothing for sure, but no where near enough to keep the larger thermal mass of the pack warm.
This pack uses, what, 6 cells in parallel throughout the stack? So is that 10mA per stack or 10mA per cell? 10mA per cell would mean 240W.
Much better on the power usage, but less than what the 40 kWh packs uses, would it be enough to keep the cells from freezing over though?
I haven't read about any 62 kWh Leaf battery failing in the more extreme weather locations of the world (Canada for example), so something must be working.
If the balancing shunts are the only source of heat, they must have a way to generate more than usual or else it seems like normal operations would create a lot of waste heat (energy) at the top end of charging. If the shunts are really that effective, why does the 40 kWh pack need additional heaters in it?
 
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