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Re: Battery Upgrades are very possible

Posted: Fri Jun 26, 2020 5:37 am
by Marktm
mux wrote:
Wed Jun 24, 2020 10:20 pm
You're blowing ever so slightly colder air over a battery case with poor thermal conductivity. There's not enough delta-T and not enough thermal conductivity to get much heat out of the battery that way. During a QC session the battery is producing between 1-2.5kW of heat, and the best you can do with 10C colder air is remove in the order of 100W or so. It's going to delay thermal throttling a little bit, but not much.
Did some grosso modo calculations on flat plate cooling using a cold plate directly below the battery case - with heat transfer material between the bottom battery case and the protector plate. BY NO MEANS AN EXACT CALCULATION. However as the film heat transfer coefficients are so low on the three limiting air surfaces, that - as mux points out - the cooling is extremely limited. It appears using a refrigerated cold plate below the battery - say on a garage floor that is 40 degrees Fahrenheit below the battery temp would only cool by a few oF over an entire night. I'm sure blowing air and adding radiation "cooling" to the calcs might add accuracy, but not likely change results - internal cooling is the realistic answer.

I am sure open to alternative proof of something that might work - I have a garage to experiment with and live in a very hot climate!

Re: Battery Upgrades are very possible

Posted: Mon Jul 13, 2020 5:21 pm
by coleafrado
Marktm wrote:
Fri Jun 26, 2020 5:37 am
Did some grosso modo calculations on flat plate cooling using a cold plate directly below the battery case - with heat transfer material between the bottom battery case and the protector plate. BY NO MEANS AN EXACT CALCULATION. However as the film heat transfer coefficients are so low on the three limiting air surfaces, that - as mux points out - the cooling is extremely limited. It appears using a refrigerated cold plate below the battery - say on a garage floor that is 40 degrees Fahrenheit below the battery temp would only cool by a few oF over an entire night. I'm sure blowing air and adding radiation "cooling" to the calcs might add accuracy, but not likely change results - internal cooling is the realistic answer.

I am sure open to alternative proof of something that might work - I have a garage to experiment with and live in a very hot climate!
The steel plate is definitely the limiting factor here. Its k-value is way too high!

Re: Battery Upgrades are very possible

Posted: Tue Aug 04, 2020 6:28 am
by howardg
Hi, I've just fitted a 40kw battery to my 2015 Leaf using a can bus bridge that was supplied by Dala EV repairs. This required me to use the android beta version of Leaf Spy to identify my battery ID.

This was emailed to Daniel at EV repairs who sent out the can bridge pre configured with the firmware loaded.

With the 12v battery disconnected, had to wire the can bridge into the wiring behind the passenger footwell plastic cover using a crimping tool and use a piggy back fuse from the internal light fuse on the board to the side of the passenger dashboard. I also had to earth it using a screw just above the board.

With the new battery fitted and the 12v battery reconnected and with all fingers and toes crossed the car came back to life with a new range of around 160 miles.

I have no expertise in car repairs, but with the help of Daniel and Calvin from EV Breakers, the work was relatively straight forward.

The 40 kw battery cost £5k and the can bridge with software was £450. My old 24kw battery had covered 82,000miles and was on 11 bars and SOH of 85%. I've been offered 2k for the old battery.

If the new battery degrades at the same rate as the original I'm hoping it will give the car another 5 years life with a consistent range more than 130 miles.

I took a chance on the replacment as the cost of buying a replacement with the same sort of range would have been far more expensive.

Re: Battery Upgrades are very possible

Posted: Tue Aug 04, 2020 10:10 am
by ginetto
wonderful report, thanks! do you have also fotos?
howardg wrote:
Tue Aug 04, 2020 6:28 am
Hi, I've just fitted a 40kw battery to my 2015 Leaf using a can bus bridge that was supplied by Dala EV repairs. This required me to use the android beta version of Leaf Spy to identify my battery ID.

This was emailed to Daniel at EV repairs who sent out the can bridge pre configured with the firmware loaded.

With the 12v battery disconnected, had to wire the can bridge into the wiring behind the passenger footwell plastic cover using a crimping tool and use a piggy back fuse from the internal light fuse on the board to the side of the passenger dashboard. I also had to earth it using a screw just above the board.

With the new battery fitted and the 12v battery reconnected and with all fingers and toes crossed the car came back to life with a new range of around 160 miles.

I have no expertise in car repairs, but with the help of Daniel and Calvin from EV Breakers, the work was relatively straight forward.

The 40 kw battery cost £5k and the can bridge with software was £450. My old 24kw battery had covered 82,000miles and was on 11 bars and SOH of 85%. I've been offered 2k for the old battery.

If the new battery degrades at the same rate as the original I'm hoping it will give the car another 5 years life with a consistent range more than 130 miles.

I took a chance on the replacment as the cost of buying a replacement with the same sort of range would have been far more expensive.

Re: Battery Upgrades are very possible

Posted: Wed Aug 05, 2020 3:05 am
by hgarde
Hi,

Yes, I have photos, but not sure how to post them on the forum.

Re: Battery Upgrades are very possible

Posted: Wed Aug 05, 2020 3:23 am
by LeftieBiker
You have to use an image hosting service like IMGUR, and then link them here.

Re: Battery Upgrades are very possible

Posted: Wed Aug 05, 2020 6:31 am
by Stanton
howardg wrote:
Tue Aug 04, 2020 6:28 am
Hi, I've just fitted a 40kw battery to my 2015 Leaf using a can bus bridge that was supplied by Dala EV repairs. This required me to use the android beta version of Leaf Spy to identify my battery ID.
Great story: thanks for sharing!
Obviously you live in the EU. I need something like this a bit closer to home (Texas)...and not so much DIY.

Re: Battery Upgrades are very possible

Posted: Wed Aug 05, 2020 7:15 am
by SageBrush2
Marktm wrote:
Fri Jun 26, 2020 5:37 am
mux wrote:
Wed Jun 24, 2020 10:20 pm
You're blowing ever so slightly colder air over a battery case with poor thermal conductivity. There's not enough delta-T and not enough thermal conductivity to get much heat out of the battery that way. During a QC session the battery is producing between 1-2.5kW of heat, and the best you can do with 10C colder air is remove in the order of 100W or so. It's going to delay thermal throttling a little bit, but not much.
Did some grosso modo calculations on flat plate cooling using a cold plate directly below the battery case - with heat transfer material between the bottom battery case and the protector plate. BY NO MEANS AN EXACT CALCULATION. However as the film heat transfer coefficients are so low on the three limiting air surfaces, that - as mux points out - the cooling is extremely limited. It appears using a refrigerated cold plate below the battery - say on a garage floor that is 40 degrees Fahrenheit below the battery temp would only cool by a few oF over an entire night. I'm sure blowing air and adding radiation "cooling" to the calcs might add accuracy, but not likely change results - internal cooling is the realistic answer.

I am sure open to alternative proof of something that might work - I have a garage to experiment with and live in a very hot climate!
I'm interested in the calc method.

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

C = centigrade
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 ?

Re: Battery Upgrades are very possible

Posted: Wed Aug 05, 2020 7:23 am
by SageBrush2
hgarde wrote:
Wed Aug 05, 2020 3:05 am
Hi,

Yes, I have photos, but not sure how to post them on the forum.
I'm jealous ! Sounds like a tremendous upgrade
How did you handle the uber heavy battery ?

Your old battery is easily worth 2,000 as a home storage battery.

Do you use Google Drive ? You can link to the photos from the drive. A little tinkering with the URL is required, feel free to PM me for details

Re: Battery Upgrades are very possible

Posted: Wed Aug 05, 2020 11:21 am
by howardg
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.