ElectricMotorcycleForum.com
General Category => General Discussion => Topic started by: NEW2elec on October 31, 2016, 10:07:11 PM
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Georgia used to have a 20% tax credit for EVs. Leasing a Leaf ended up being little to nothing.
As a result we have a lot of Leafs for sale 2nd hand pretty cheap.
I started researching them and they don't blow you away like a Tesla but at the right price could be a mile sponge for around town.
Two big things stood out to me in the reviews and specs for the car.
First it has a "longer battery life" charging mode. Basically it stops charging when the battery is at 80% SOC. I've heard some of our big battery guys on the forum talk about how 100% SOC stresses the battery so that makes sense but what about cell balancing? Can the BMS balance the cells to a uniform 80% SOC, or just cut off when some or most or one of the cells hits 80% ?
Member have discussed this double edged sword of leaving Zeros plugged in when not in use.
The 100% SOC stresses the cells but left unplugged too long could hurt the balancing.
Second Leaf disclaimer was about fast charging and battery life.
Basically stating that if you only fast charge (with the fast charge option) it would speed up the loss of total battery capacity by 10 to 20% over slow charging.
The standard Leaf is only 84 miles est. so there is not much room for loss of capacity once you factor in highway speeds, hills, and headwinds.
So what effect would it have on Zeros? I know they use different cells but are at least similar in there make up.
I haven't heard anyone talk about loss of capacity on Zeros so far although it would be very hard to test it out as conditions vary greatly but is anyone testing the effects of fast charging on the batteries?
For some fast charging is the best or only realistic option for their needs but for others it would be nice to know what your getting into by fast charging just for convenience.
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There is an extensive summary on the wiki of what experts have said about Zero batteries on the forum:
http://zeromanual.com/index.php/Unofficial_Service_Manual#Battery (http://zeromanual.com/index.php/Unofficial_Service_Manual#Battery)
Terry recently made comments about fast charging specifically that I'll cite here:
http://electricmotorcycleforum.com/boards/index.php?topic=6363.msg49256#msg49256 (http://electricmotorcycleforum.com/boards/index.php?topic=6363.msg49256#msg49256)
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I've heard some of our big battery guys on the forum talk about how 100% SOC stresses the battery so that makes sense but what about cell balancing? Can the BMS balance the cells to a uniform 80% SOC, or just cut off when some or most or one of the cells hits 80% ?
Just an FYI.. your zero does not fill the battery to 4.20v for each cell.. it stops at 4.15v for that reason, and tells the end user its 100% All EVs do this. The leaf caught a bad wrap because they had some early issues.. mostly didnt put any cell cooling into the design, used a thermally sensitive chemistry, and so this 80% is a band-aid fix for that so some users can feel better about it.
As far as the Leaf BMS goes, it is always balancing. each module is 2S2P and each 2P "cell" is constantly monitored and balanced via a tiny 1206 size 430 ohm resistor... its only 10mA of current so it takes FOREVER to balance, but since they are never far off, its not a problem. They're stable and reliable cells, just heat sensitive. While I like their module layout, its horribly space inefficient and lacks cooling. Something like what Chevy does is much nicer.. long stacks of cooling plate->cell->cooling plate->cell... with the plates thermally connected to liquid coolant.
Im actually playing with a leaf BMS right now based off the info gleaned from here: http://www.wolftronix.com/E10_LithiumUpgrade/index.html (http://www.wolftronix.com/E10_LithiumUpgrade/index.html)
I have a leaf module pack I am putting on a gokart for fun.. so I figured I would mess with the leaf BMS too... mostly im using the circuit board and the BMS chips on it, since I cant really source them elsewhere and WolfTronix already showed us how to talk to the chips.
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Thanks for the input guys, helps explain some of the differences and reasons.
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There's evidence that fast charging is good for battery life.
https://electrek.co/2016/11/01/tesla-battery-degradation/ (https://electrek.co/2016/11/01/tesla-battery-degradation/)
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There's evidence that fast charging is good for battery life.
https://electrek.co/2016/11/01/tesla-battery-degradation/ (https://electrek.co/2016/11/01/tesla-battery-degradation/)
When you look at the chemistry, as long as you stay "in bounds" its always better to bring it back up from low to wherever the chemistry is happy as quickly as possible.