On Thursday, September 9, 2021 at 3:57:13 PM UTC-7, gnuarm.del...@gmail.com wrote:> On Thursday, September 9, 2021 at 6:19:52 PM UTC-4, Ed Lee wrote: > > On Thursday, September 9, 2021 at 3:15:16 PM UTC-7, Ed Lee wrote: > > > On Thursday, September 9, 2021 at 2:58:51 PM UTC-7, Cydrome Leader wrote: > > > > Ed Lee <edward....@gmail.com> wrote: > > > > > > > > > > For older model Leaf, there are spacer bars between cells with a cooling air gap. So, forced air from the bottom should help. > > > > Is the spacing for cooling or expansion or explosion/fire mitigation? I > > > Yes, it's allowance for expansion. > > > > haven't torn one apart to see myself. Are there blowers to move air > > > > through these channels? > > > Not currently, but i plan on adding blower pipe from the HV cutoff port (in the middle of the passenger compartment). Someone actually build a 3D model for an adapter for it. But it won't work too well without exhaust holes. > > Here is the link: > > https://www.myminifactory.com/object/3d-print-leaf-battery-cooling-160671 > > > > >> > I did drive the Leaf into a flooded ditch, up to the floor of the car. > > > > >> Sounds clever. > > > > > > > > > > Yes, embarrassingly clever to cool down. The area looks flat off the road, from a distance. > > > > Did you drive into a lake? > > > It was just an open area off the road. It looked like flat area for a quick stop, at least for the surface. > All because he is too cheap to buy an EV that actually manages the battery temperature.It's an opportunity to fix their mistakes 10 years ago. You have to understand that most of these problems were unknown at that time.> This guy is the poster child of how not to drive an EV.I would have driven an ICE into the ditch just as well.
Cooling an electric vehicle battery.
Started by ●September 9, 2021
Reply by ●September 9, 20212021-09-09
Reply by ●September 9, 20212021-09-09
On Thursday, September 9, 2021 at 7:09:31 PM UTC-4, Ed Lee wrote:> On Thursday, September 9, 2021 at 3:57:13 PM UTC-7, gnuarm.del...@gmail.com wrote: > > On Thursday, September 9, 2021 at 6:19:52 PM UTC-4, Ed Lee wrote: > > > On Thursday, September 9, 2021 at 3:15:16 PM UTC-7, Ed Lee wrote: > > > > On Thursday, September 9, 2021 at 2:58:51 PM UTC-7, Cydrome Leader wrote: > > > > > Ed Lee <edward....@gmail.com> wrote: > > > > > > > > > > > > For older model Leaf, there are spacer bars between cells with a cooling air gap. So, forced air from the bottom should help. > > > > > Is the spacing for cooling or expansion or explosion/fire mitigation? I > > > > Yes, it's allowance for expansion. > > > > > haven't torn one apart to see myself. Are there blowers to move air > > > > > through these channels? > > > > Not currently, but i plan on adding blower pipe from the HV cutoff port (in the middle of the passenger compartment). Someone actually build a 3D model for an adapter for it. But it won't work too well without exhaust holes. > > > Here is the link: > > > https://www.myminifactory.com/object/3d-print-leaf-battery-cooling-160671 > > > > > >> > I did drive the Leaf into a flooded ditch, up to the floor of the car. > > > > > >> Sounds clever. > > > > > > > > > > > > Yes, embarrassingly clever to cool down. The area looks flat off the road, from a distance. > > > > > Did you drive into a lake? > > > > It was just an open area off the road. It looked like flat area for a quick stop, at least for the surface. > > All because he is too cheap to buy an EV that actually manages the battery temperature. > It's an opportunity to fix their mistakes 10 years ago. You have to understand that most of these problems were unknown at that time.The same time Tesla knew to control the temperature of their batteries. That is fundamental of not just lithium but all batteries. Batteries are electrochemical and chemical reactions are very temperature dependent.> > This guy is the poster child of how not to drive an EV. > I would have driven an ICE into the ditch just as well.Yes, I have no doubt. That is my point. -- Rick C. -- Get 1,000 miles of free Supercharging -- Tesla referral code - https://ts.la/richard11209
Reply by ●September 9, 20212021-09-09
On Thursday, September 9, 2021 at 4:50:52 PM UTC-7, gnuarm.del...@gmail.com wrote:> On Thursday, September 9, 2021 at 7:09:31 PM UTC-4, Ed Lee wrote: > > On Thursday, September 9, 2021 at 3:57:13 PM UTC-7, gnuarm.del...@gmail.com wrote: > > > On Thursday, September 9, 2021 at 6:19:52 PM UTC-4, Ed Lee wrote: > > > > On Thursday, September 9, 2021 at 3:15:16 PM UTC-7, Ed Lee wrote: > > > > > On Thursday, September 9, 2021 at 2:58:51 PM UTC-7, Cydrome Leader wrote: > > > > > > Ed Lee <edward....@gmail.com> wrote: > > > > > > > > > > > > > > For older model Leaf, there are spacer bars between cells with a cooling air gap. So, forced air from the bottom should help. > > > > > > Is the spacing for cooling or expansion or explosion/fire mitigation? I > > > > > Yes, it's allowance for expansion. > > > > > > haven't torn one apart to see myself. Are there blowers to move air > > > > > > through these channels? > > > > > Not currently, but i plan on adding blower pipe from the HV cutoff port (in the middle of the passenger compartment). Someone actually build a 3D model for an adapter for it. But it won't work too well without exhaust holes. > > > > Here is the link: > > > > https://www.myminifactory.com/object/3d-print-leaf-battery-cooling-160671 > > > > > > >> > I did drive the Leaf into a flooded ditch, up to the floor of the car. > > > > > > >> Sounds clever. > > > > > > > > > > > > > > Yes, embarrassingly clever to cool down. The area looks flat off the road, from a distance. > > > > > > Did you drive into a lake? > > > > > It was just an open area off the road. It looked like flat area for a quick stop, at least for the surface. > > > All because he is too cheap to buy an EV that actually manages the battery temperature. > > It's an opportunity to fix their mistakes 10 years ago. You have to understand that most of these problems were unknown at that time. > The same time Tesla knew to control the temperature of their batteries. That is fundamental of not just lithium but all batteries. Batteries are electrochemical and chemical reactions are very temperature dependent. > > > This guy is the poster child of how not to drive an EV. > > I would have driven an ICE into the ditch just as well. > Yes, I have no doubt. That is my point.At least i don't drive into flashing red and blue with FSD.
Reply by ●September 10, 20212021-09-10
On Friday, September 10, 2021 at 3:08:04 AM UTC+10, gnuarm.del...@gmail.com wrote:> On Thursday, September 9, 2021 at 4:08:09 AM UTC-4, bill....@ieee.org wrote: > > Electric vehicle batteries are about 85% efficient, but the 15% of the energy that you put in that you don't get out has to appear as heat, generated in the battery. > > > > The worst case would presumably be during fast charging. > > I can't say how much of the claimed 15% energy loss is dissipated during charging vs. discharging, but assuming they are even approximately even, the discharge has much higher heat generating potential because the highest power is during discharge. My car can generate 400 kW easily when I mash the pedal. Even though this energy is seldom continuous, it releases significant amounts of heat into the motor and battery.Thermal inertia means that the temperature probably won't go up much.Batteries have got quite a lot of thermal mass.>I normally drive relatively flat terrain, but in mountainous areas I expect such high numbers would be much more protracted. When towing it would be even worse. While most ICE vehicles are designed to dissipate such heat, EVs are typically not designed to dissipate such heat on a continuing basis.ICE vehicles produce a lot more waste heat. Thermal inertia doesn't help nearly as much.> > One has to wonder whether anybody has built a battery with heat-pipe down the middle, sticking into heat-sink extrusions projecting from either end. > ??? Not sure why that design comes to mind. The Tesla batteries have coolant flowing through them. This eliminates the delta T required to push the coolant through the heat pipe and heat sink.The whole point about heat pipes is that heat is transferred as latent heat of evaporation in vapour that has boiled off the hot surface and condenses at the heat sink. The vapour has a lot lower viscosity than any liquid coolant, and flows a great deal faster - the limit seems to be speed of sound in the vapour - and it is transferring an order of magnitude or two more heat in each unit mass of vapour.>The heat transfer is powered by a pump as on nearly every type of vehicle. I don't know a lot about many of the various EVs being designed today, but the Nissan Leaf does much less to control the temperature of the battery with the resultant shortening of the battery life.You could certainly use a pump to transfer liquid back from the heat sink - where it would condense - to the hot spots which is is cooling by evaporating. The small heat sinks used to cool electronic devices don't bother - they just let it wick back along the inner surface of the pipe that carries the stream of vapour in the other direction. You got to keep the heat-pipe vacuum tight - any non-condensible gas in the path slows down the vapour flow rate horribly. Hydrogen and helium have a nasty habit of diffusing in if there is any around, but it doesn't happen fast.> > Nobody seems to do it, so it clearly isn't strictly necessary, but roughly halving the peak temperature inside the battery should make them last longer. > > Nobody does what exactly?Makes a fuss about the mechanisms they use to control battery temperature. Pumping coolant through batteries is an obvious way to do it, but I'd not heard about it. It's also a whole lot messier than a heat pipe. My 1996 paper spells out how I initially made exactly the same mistake in the original design of our thermostat and I'd been away for a few months before Douglas Stewart had the bright idea of cooling our Peltier junction with a heat-pipe assembly rather than circulating water. I would have loved to have come up with the idea, but we'd been busy putting together something that worked rather than making tricky changes that might - and in fact did - make it work better.> It is hard to imagine an EV maker who isn't aware of the need to control the battery temperature. Nissan aside I expect going forward they all provide battery cooling. Are you suggesting your heat pipe idea is a better way to accomplish this?It certainly strikes me that way. -- Bill Sloman, Sydney
Reply by ●September 10, 20212021-09-10
On Friday, September 10, 2021 at 4:52:12 AM UTC+10, Cydrome Leader wrote:> Ed Lee <edward....@gmail.com> wrote: > > On Thursday, September 9, 2021 at 6:54:04 AM UTC-7, bitrex wrote: > >> On 9/9/2021 9:48 AM, bitrex wrote: > >> > On 9/9/2021 9:42 AM, Ed Lee wrote: > >> >> On Thursday, September 9, 2021 at 1:29:02 AM UTC-7, lang...@fonz.dk > >> >> wrote: > >> >>> torsdag den 9. september 2021 kl. 10.08.09 UTC+2 skrev > >> >>> bill....@ieee.org: > >> >>>> Electric vehicle batteries are about 85% efficient, but the 15% of > >> >>>> the energy that you put in that you don't get out has to appear as > >> >>>> heat, generated in the battery. > >> >>>> > >> >>>> The worst case would presumably be during fast charging. > >> >>>> > >> >>>> One has to wonder whether anybody has built a battery with heat-pipe > >> >>>> down the middle, sticking into heat-sink extrusions projecting from > >> >>>> either end. > >> >>>> > >> >>>> Nobody seems to do it, so it clearly isn't strictly necessary, but > >> >>>> roughly halving the peak temperature inside the battery should make > >> >>>> them last longer. > >> >>>> > >> >>> Tesla batteries are liquid cooled (or heated when needed), there's a > >> >>> glykol filled flat tube that zig-zag between the cells > >> >> > >> >> Same for the Bolt, there are heat transfer plates between cells, with > >> >> small pipes zz over the flat plate.<snip>> Batteries are not made of air currents,and conduction is usually able to transfer more heat than convection anyways.Heat pipes transfer heat by evaporating a liquid into a space that contains only the vapour form of that liquid and condensing the vapour somewhere else. That transfers heat a lot faster than conduction or even forced convection (as with liquid being pumped through as system). The latent heat of evaporation of a liquid is a whole lot higher than the heat capacity of the same mass of liquid, and the vapour has a much lower viscosity than the liquid. You can really move a lot of heat really fast that way. <snip> -- Bill Sloman, Sydney
Reply by ●September 10, 20212021-09-10
On Thursday, September 9, 2021 at 1:08:09 AM UTC-7, bill....@ieee.org wrote:> Electric vehicle batteries are about 85% efficient, but the 15% of the energy that you put in that you don't get out has to appear as heat, generated in the battery. > > The worst case would presumably be during fast charging. > > One has to wonder whether anybody has built a battery with heat-pipe down the middle, sticking into heat-sink extrusions projecting from either end. > > Nobody seems to do it, so it clearly isn't strictly necessary, but roughly halving the peak temperature inside the battery should make them last longer. > > -- > SL0WMAN, SydneySL0WMAN doesn't understand batteries or electric vehicles much, that is clear. Most of the energy loss in electric cars is in the electronics, not the battery. For example, charging accounts for up to 25% of energy loss: https://www.smart2zero.com/news/25-energy-loss-when-charging-electric-vehicles-tests-show Energy loss in the battery is the result of its internal resistance, which is, by design, very low. Here is a more intelligent review of the losses (scratch "more'): https://www.fueleconomy.gov/feg/atv-ev.shtml Electric car manufacturers keep battery temperatures down because heat literally destroys the batteries. The Leaf did not do this and suffers from much faster battery degradation than Tesla.
Reply by ●September 10, 20212021-09-10
On Thursday, September 9, 2021 at 9:06:26 PM UTC-7, Flyguy wrote:> On Thursday, September 9, 2021 at 1:08:09 AM UTC-7, bill....@ieee.org wrote: > > Electric vehicle batteries are about 85% efficient, but the 15% of the energy that you put in that you don't get out has to appear as heat, generated in the battery. > > > > The worst case would presumably be during fast charging. > > > > One has to wonder whether anybody has built a battery with heat-pipe down the middle, sticking into heat-sink extrusions projecting from either end. > > > > Nobody seems to do it, so it clearly isn't strictly necessary, but roughly halving the peak temperature inside the battery should make them last longer. > > > > -- > > SL0WMAN, Sydney > > SL0WMAN doesn't understand batteries or electric vehicles much, that is clear. Most of the energy loss in electric cars is in the electronics, not the battery. For example, charging accounts for up to 25% of energy loss: > https://www.smart2zero.com/news/25-energy-loss-when-charging-electric-vehicles-tests-show Energy loss in the battery is the result of its internal resistance, which is, by design, very low. > Here is a more intelligent review of the losses (scratch "more'): > https://www.fueleconomy.gov/feg/atv-ev.shtml > Electric car manufacturers keep battery temperatures down because heat literally destroys the batteries. The Leaf did not do this and suffers from much faster battery degradation than Tesla.It's a matter of how much money you are throwing at the cooling issue. Leaf opted for simplicity and safety and completely sealed the battery. Since it had relatively low incidences of fire, we might be able to relax the safety concern. Namely, opening accesses from the top cover. This guy has the right idea of blowing A/C air into the HV cut-off port, but not going far enough. Modifying or simply removing the top cover would allow cold air to blow in from the center and out of the sides. https://www.myminifactory.com/object/3d-print-leaf-battery-cooling-160671
Reply by ●September 10, 20212021-09-10
On Friday, September 10, 2021 at 2:06:26 PM UTC+10, Flyguy wrote:> On Thursday, September 9, 2021 at 1:08:09 AM UTC-7, bill....@ieee.org wrote: > > > Electric vehicle batteries are about 85% efficient, but the 15% of the energy that you put in that you don't get out has to appear as heat, generated in the battery. > > > > The worst case would presumably be during fast charging. > > > > One has to wonder whether anybody has built a battery with heat-pipe down the middle, sticking into heat-sink extrusions projecting from either end. > > > > Nobody seems to do it, so it clearly isn't strictly necessary, but roughly halving the peak temperature inside the battery should make them last longer. > > Sloman doesn't understand batteries or electric vehicles much, that is clear.Neither does Flyguy, but Flyguy is much too stupid to appreciate how little he understands.> Most of the energy loss in electric cars is in the electronics, not the battery. For example, charging accounts for up to 25% of energy loss: > https://www.smart2zero.com/news/25-energy-loss-when-charging-electric-vehicles-tests-show Energy loss in the battery is the result of its internal resistance, which is, by design, very low. > Here is a more intelligent review of the losses (scratch "more'): > https://www.fueleconomy.gov/feg/atv-ev.shtmlI was talking about the power put into the battery and subsequently taken out again. What the car does with it after it has left the battery didn't come into it - that heat is dissipated elsewhere, and isn't interesting in this particular context (which Flyguy seems to have ignored - that sort of stuff is too complicated for him to follow).> Electric car manufacturers keep battery temperatures down because heat literally destroys the batteries." Roughly halving the peak temperature inside the battery should make them last longer" expresses much the same sentiment, but Flyguy can't understand this. <snip> -- Bill Sloman, Sydney
Reply by ●September 10, 20212021-09-10
On Thursday, September 9, 2021 at 11:42:05 PM UTC-4, bill....@ieee.org wrote:> On Friday, September 10, 2021 at 3:08:04 AM UTC+10, gnuarm.del...@gmail.com wrote: > > On Thursday, September 9, 2021 at 4:08:09 AM UTC-4, bill....@ieee.org wrote: > > > Electric vehicle batteries are about 85% efficient, but the 15% of the energy that you put in that you don't get out has to appear as heat, generated in the battery. > > > > > > The worst case would presumably be during fast charging. > > > > I can't say how much of the claimed 15% energy loss is dissipated during charging vs. discharging, but assuming they are even approximately even, the discharge has much higher heat generating potential because the highest power is during discharge. My car can generate 400 kW easily when I mash the pedal. Even though this energy is seldom continuous, it releases significant amounts of heat into the motor and battery. > Thermal inertia means that the temperature probably won't go up much.Batteries have got quite a lot of thermal mass. > >I normally drive relatively flat terrain, but in mountainous areas I expect such high numbers would be much more protracted. When towing it would be even worse. While most ICE vehicles are designed to dissipate such heat, EVs are typically not designed to dissipate such heat on a continuing basis. > ICE vehicles produce a lot more waste heat. Thermal inertia doesn't help nearly as much.Not sure why you are talking about ICE in a conversation about battery temperature. The point is there are situations where the discharge of the battery causes significant heating of the battery constrained only by the power being used by the vehicle. The thermal mass of the battery won't prevent temperature rise any more than when charging. With a higher discharge rate than is allowed during charging the discharge is the situation that can cause more damage to the battery and sets the requirement for cooling. There are plenty of mountains that tax a vehicle's power capacity, doubly so when towing.> > > One has to wonder whether anybody has built a battery with heat-pipe down the middle, sticking into heat-sink extrusions projecting from either end. > > ??? Not sure why that design comes to mind. The Tesla batteries have coolant flowing through them. This eliminates the delta T required to push the coolant through the heat pipe and heat sink. > The whole point about heat pipes is that heat is transferred as latent heat of evaporation in vapour that has boiled off the hot surface and condenses at the heat sink.Yes, we all know how heat pipes work.> The vapour has a lot lower viscosity than any liquid coolant, and flows a great deal faster - the limit seems to be speed of sound in the vapour - and it is transferring an order of magnitude or two more heat in each unit mass of vapour.So why aren't they using heat pipes in auto batteries? Because the issue you are talking about is not what is important. You don't address the issue of getting the heat from the heat pipes into a cooling system or the environment. The heat pipes in PCs terminate in relatively massive heat sinks that in turn dissipate the heat to air that is blown across large heat sinks. That's not practical in an auto adding increased weight. Instead they would use a water block and end up with a water cooled battery anyway. Heat pipes would not be solving any problems EVs currently have.> >The heat transfer is powered by a pump as on nearly every type of vehicle. I don't know a lot about many of the various EVs being designed today, but the Nissan Leaf does much less to control the temperature of the battery with the resultant shortening of the battery life. > You could certainly use a pump to transfer liquid back from the heat sink - where it would condense - to the hot spots which is is cooling by evaporating.To what end? Where is the advantage?> The small heat sinks used to cool electronic devices don't bother - they just let it wick back along the inner surface of the pipe that carries the stream of vapour in the other direction. You got to keep the heat-pipe vacuum tight - any non-condensible gas in the path slows down the vapour flow rate horribly. Hydrogen and helium have a nasty habit of diffusing in if there is any around, but it doesn't happen fast. > > > Nobody seems to do it, so it clearly isn't strictly necessary, but roughly halving the peak temperature inside the battery should make them last longer. > > > > Nobody does what exactly? > Makes a fuss about the mechanisms they use to control battery temperature. Pumping coolant through batteries is an obvious way to do it, but I'd not heard about it.What are you talking about??? Teslas have water cooled and heated the batteries since day one a decade ago. I guess you've been out of the loop on how they operate.> It's also a whole lot messier than a heat pipe. My 1996 paper spells out how I initially made exactly the same mistake in the original design of our thermostat and I'd been away for a few months before Douglas Stewart had the bright idea of cooling our Peltier junction with a heat-pipe assembly rather than circulating water.Perhaps you aren't aware that every thermal design problem is not identical. In addition to the specific thermal requirements, there are the practical issues involved. I can't say what all the issues might be, but talking about the velocity of vapor in a heat pipe is only one, small issue in this matter.> I would have loved to have come up with the idea, but we'd been busy putting together something that worked rather than making tricky changes that might - and in fact did - make it work better. > > It is hard to imagine an EV maker who isn't aware of the need to control the battery temperature. Nissan aside I expect going forward they all provide battery cooling. Are you suggesting your heat pipe idea is a better way to accomplish this? > It certainly strikes me that way.Can you explain exactly what it would improve on? Is there any reason to think it would be practical in an EV application? -- Rick C. -+ Get 1,000 miles of free Supercharging -+ Tesla referral code - https://ts.la/richard11209
Reply by ●September 10, 20212021-09-10
On Thursday, September 9, 2021 at 11:49:49 PM UTC-4, bill....@ieee.org wrote:> On Friday, September 10, 2021 at 4:52:12 AM UTC+10, Cydrome Leader wrote: > > Ed Lee <edward....@gmail.com> wrote: > > > On Thursday, September 9, 2021 at 6:54:04 AM UTC-7, bitrex wrote: > > >> On 9/9/2021 9:48 AM, bitrex wrote: > > >> > On 9/9/2021 9:42 AM, Ed Lee wrote: > > >> >> On Thursday, September 9, 2021 at 1:29:02 AM UTC-7, lang...@fonz.dk > > >> >> wrote: > > >> >>> torsdag den 9. september 2021 kl. 10.08.09 UTC+2 skrev > > >> >>> bill....@ieee.org: > > >> >>>> Electric vehicle batteries are about 85% efficient, but the 15% of > > >> >>>> the energy that you put in that you don't get out has to appear as > > >> >>>> heat, generated in the battery. > > >> >>>> > > >> >>>> The worst case would presumably be during fast charging. > > >> >>>> > > >> >>>> One has to wonder whether anybody has built a battery with heat-pipe > > >> >>>> down the middle, sticking into heat-sink extrusions projecting from > > >> >>>> either end. > > >> >>>> > > >> >>>> Nobody seems to do it, so it clearly isn't strictly necessary, but > > >> >>>> roughly halving the peak temperature inside the battery should make > > >> >>>> them last longer. > > >> >>>> > > >> >>> Tesla batteries are liquid cooled (or heated when needed), there's a > > >> >>> glykol filled flat tube that zig-zag between the cells > > >> >> > > >> >> Same for the Bolt, there are heat transfer plates between cells, with > > >> >> small pipes zz over the flat plate. > <snip> > > Batteries are not made of air currents,and conduction is usually able to transfer more heat than convection anyways. > Heat pipes transfer heat by evaporating a liquid into a space that contains only the vapour form of that liquid and condensing the vapour somewhere else. > > That transfers heat a lot faster than conduction or even forced convection (as with liquid being pumped through as system). > > The latent heat of evaporation of a liquid is a whole lot higher than the heat capacity of the same mass of liquid, and the vapour has a much lower viscosity than the liquid. You can really move a lot of heat really fast that way.How well does it work at temperatures other than the point of evaporation? Say a battery is optimal at 80°C. How well does the heat pipe work at 0°C when the battery needs to be warmed? -- Rick C. +- Get 1,000 miles of free Supercharging +- Tesla referral code - https://ts.la/richard11209
