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### Re: Battery Upgrades are very possible

Posted: Wed Aug 05, 2020 1:24 pm
After going through this, any thoughts about how to improve the air cooling?

### Re: Battery Upgrades are very possible

Posted: Wed Aug 05, 2020 5:56 pm
SageBrush2 wrote:
Wed Aug 05, 2020 7:15 am

My inclination would be to measure the battery temp in the early evening and then in the am. If I know the average ambient then I presume a simple calc to tease out the heat transfer coefficient could then be used for measures that reduce ambient temperature. Since I leave our LEAF outside for ventilation and I live in a dry climate, I've been toying with the idea of soaking the ground under the battery after a long drive. I think that would give me a ~ 10C increase in temperature delta. If the battery is 38C and

K = kelvin

18C = 290K
28C = 300K
38C = 310K

Then the temp delta would increase from 10K to 20K, implying a 50% increase in heat transfer initially.
By the time the battery reaches 28C the cooled ground would still have a 10K temp gradient, implying an average gradient of 15K instead of 5K with no cooling.

Sound ballpark ? Is the physics correct ?

I'll go back and find the calcs, but they were strickly theoretical using a significant overall delta T ( requiring plate refrigeration), with estimated film coefficients of still air at the surface of the cold plate and the suface of the battery case itself. The "resistance" to heat transfer is so great at these thin films that I ignored all other heat transfer limitations a negligable - including the air itself, and the inside battery case to LI cells (likely not negligable - but would make it worse). I ignored the radiant heat transfer - that would need to be checked actually as it could be significant?? With just those simplified assumptions, the actual heat transfered was very low - definitely not worth refrigerating a garage floor as an example.

I do like your idea of a cold wet ground (in your area, not mine - humidity at 90%+) that is outside where some air movement could up the limiting transfer coefficients of the battery "skin" itself (thin film resistance is much lower with increased air velocity), However, between the protector plate and battery case will likely be an extreme limitation (again stagnant thin films of air) unless you put some heat transfer stuff between the two or temporarily remove the skid plate. Since it would be quite simple to moniter with a infared heat gun, why not give it a try? Back calculating at different temperatures would likely be more accurate than any "theoretical" calcs. At the least you would have a good idea of the actual cooling capability that the "cold ground" can impart to the hot battery. An accurate calculation of actual overall heat transfer coefficients is quite difficult due to so many variables.

### Re: Battery Upgrades are very possible

Posted: Wed Aug 05, 2020 8:03 pm
I think the best case scenario would be to remove the amount of heat required for the state change of the water evaporating off the ground from the battery pack. Even if 100% of that energy was removed from the battery pack (and it would be nowhere near that) it doesn't seem to me like it would make much of a difference. This is obviously a qualitative argument but even if the ground was kept continuously wet, the evaporation of the water just doesn't seem like it would absorb much energy, and most of that would probably just come from the ground.

### Re: Battery Upgrades are very possible

Posted: Wed Aug 05, 2020 10:27 pm
It's very unlikely to do much. You've got in the order of megajoules in heat energy to remove at a distance - more really, because it's not just the battery that'll feel the 'cold', the rest of the car is probably at a similar temperature on the exterior.

### Re: Battery Upgrades are very possible

Posted: Thu Aug 06, 2020 7:01 am
howardg wrote:
Wed Aug 05, 2020 11:21 am
Hi,

I think the photos of the can bridge wiring can be accessed with the url below. If the link works, it should show that the mod isn't that complicated. The can bridge itself is a small electronic box that is tucked into the fuseboard cavity and about the size of a small matchbox.

https://ibb.co/album/48TJf2

The actual battery swap was just a bit of hard slog with jacks, timber levers, wedges and a hand winch. Helped to have a 6ft 23 year old son to do some of the hard work.

The stupid bits I struggled with were the plastic rivets that hold the battery cover on and the battery heat connection that requires a plastic wedge sliding out. I couldn't find any online content that explains either of these.
Thanks for the pics! I didn't realize the CAN bridge/converter was so small: kind of makes me think I could handle that part (I'm an EE). Now the battery swap is a different story (and why I'm in talks with a local garage to do it). I just need to get "hooked up" with the knowledge sources (I think there are a couple in North America).

### Re: Battery Upgrades are very possible

Posted: Thu Aug 06, 2020 11:44 pm
Hi, if you are an electrical engineer its definitely do-able.

I did speak to a local garage about doing the battery swap who quoted £180 and a local auto-electrician quoted £48 for the wiring, so Its perfectly feasible to get the swap done without so much as picking up a spanner.

I just fancied having a go.

### Re: Battery Upgrades are very possible

Posted: Tue Aug 18, 2020 12:16 am
Recently had a remote-customer in Sweden perform a 24->40kWh upgrade on an eNV200. Here are some pics: https://www.flickr.com/photos/magnus_jo ... 5487665596

Initially we placed the CAN bridge to far up the EV-CAN, which resulted in some error codes. But we then moved the bridge to where the EV-CAN enters the chassis, and all error codes went away. Quite capable customer!

### Re: Battery Upgrades are very possible

Posted: Tue Aug 18, 2020 11:20 am
Dala wrote:
Tue Aug 18, 2020 12:16 am
Recently had a remote-customer in Sweden perform a 24->40kWh upgrade on an eNV200. Here are some pics: https://www.flickr.com/photos/magnus_jo ... 5487665596

Initially we placed the CAN bridge to far up the EV-CAN, which resulted in some error codes. But we then moved the bridge to where the EV-CAN enters the chassis, and all error codes went away. Quite capable customer!
Nice !

### Re: Battery Upgrades are very possible

Posted: Wed Sep 09, 2020 1:14 pm
FYI, Advance Auto Salvage in TN near the assembly plant has several 2019 62kwh packs available currently. They're asking 6995, + 500 core (bring in an old empty shell with rocks in it?), plus sales tax unless you say you have a business, and \$800 if you want it shipped to you. They are at 615-896-7700. Something to watch for on car-part.com, or probably could pre-order one for the future maybe. This is the salvage yard I got mine from, and they are part of the disassembly / scrapping process for vehicles from the plant, test vehicles.

### Re: Battery Upgrades are very possible

Posted: Wed Sep 09, 2020 2:37 pm
Daklein wrote:
Wed Sep 09, 2020 1:14 pm
FYI, Advance Auto Salvage in TN near the assembly plant has several 2019 62kwh packs available currently. They're asking 6995, + 500 core (bring in an old empty shell with rocks in it?), plus sales tax unless you say you have a business, and \$800 if you want it shipped to you. They are at 615-896-7700. Something to watch for on car-part.com, or probably could pre-order one for the future maybe. This is the salvage yard I got mine from, and they are part of the disassembly / scrapping process for vehicles from the plant, test vehicles.
I know someone here in TN that can do these, he runs his own shop plus an expert in electronics & auto. He is interested in doing these, he is just waiting for me to send him more info about how/what needs to be done, this is a good start to know where to get some packs to test with, thanks for sharing!