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kenneal - lagger
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Joined: 20 Sep 2006
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Location: Newbury, Berkshire
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 Posted: Sun Mar 25, 2018 3:49 pm Post subject: |
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| vtsnowedin wrote: | | I expect that they will make considerable progress in both the construction and operation of battery packs to greatly reduce the number of rouge or dead cells. The whole pack will age together gracefully and be of little use once it can no longer move the car. |
It's not a case of being able to move the car its the distance it can move it. Once that starts to drop there comes a point where it is "economic" (hate that word) to replace the battery.
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Pepperman
Joined: 10 Oct 2010
Posts: 768
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| Posted: Sun Mar 25, 2018 5:21 pm Post subject: |
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| Mr. Fox wrote: | I guess he's getting them wherever he can - the Tesla model S used 18650s.
As I understand it, the Teslas (and other EVs) using Li-Ion cells don't incorporate balanced charging of the cells in the design... My own experience - mainly with electric bike batteries - is that a pack can fail because half a dozen of the cells are bad, whilst the rest are perfectly serviceable.
I had a recent 24v 10Ah pack, (35 x 18650s, 5P/7S) all but 5 cells tested held >90% of their rated capacity (of 2000mAh)... again, no balancing. Considering the manufacturer charge ~£400 per pack, I thought this was a bit tight of them, but if it lasts beyond the warranty period, I guess they don't really care. Good news for us 'recyclers', though. 
(I reckon I'm going to need a low-voltage spot welder soon, so I'm keeping my eyes peeled for a scrap microwave).
No idea where you'd get hold of big 2nd hand EV batteries in the UK, though - with only ~13,500 new registrations of plugin EVs last year, I guess it's not a 'mature market'... yet! |
EVs will all have a BMS. I don't think it's possible to safely charge large lithium-ion batteries without them. |
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vtsnowedin
Joined: 07 Jan 2011
Posts: 4603
Location: New England ,Chelsea Vermont
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| Posted: Sun Mar 25, 2018 5:22 pm Post subject: |
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| kenneal - lagger wrote: | | vtsnowedin wrote: | | I expect that they will make considerable progress in both the construction and operation of battery packs to greatly reduce the number of rouge or dead cells. The whole pack will age together gracefully and be of little use once it can no longer move the car. |
It's not a case of being able to move the car its the distance it can move it. Once that starts to drop there comes a point where it is "economic" (hate that word) to replace the battery. |
I was being a bit taciturn in omitting satisfactory or properly after" move the car". If it can't complete the whole trip then a shorter movement would be of no use. |
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Potemkin Villager
Joined: 14 Mar 2006
Posts: 917
Location: Narnia
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| Posted: Sun Mar 25, 2018 7:31 pm Post subject: |
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| PS_RalphW wrote: | | Cold weather performance improves in models like the Hyundai ioniq which has active battery teperature control. |
Just spotted this.
"Active battery temperature control" 
To me this sounds like something straight out of a sales brochure!
Is any clue given to where the energy comes from to power this active battery temperature control I wonder?
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"Test to destruction: engineers like to do that. Only with a test to destruction can you find the outer limits of a system's strength".Kim Stanley Robinson |
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Mr. Fox
Joined: 24 Nov 2005
Posts: 615
Location: In the Dark - looking for my socks
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| Posted: Sun Mar 25, 2018 9:25 pm Post subject: |
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| Pepperman wrote: | | EVs will all have a BMS. I don't think it's possible to safely charge large lithium-ion batteries without them. |
Yes, very true all have a Battery Management System, but not all BMSs do charge balancing - many (most) simply monitor individual cells or parallel cell group voltages and cut charging/draining for the whole pack when one cell or group is full/empty. All things (cells) being equal, this is OK... it's when they aren't that the fun starts.
I read this on the Tesla forum:
| Quote: | We can not "balance" our battery packs! Balancing is done cell by cell. The battery management system in the Tesla is not set up cell by cell. All that happens when we "fully charge" and "full discharge" is we reset the counter that estimates the level of charge. That's right we don't really know how much charge is in the battery. We can only measure how much is put in and taken out. The algorithm makes little mistake over time because of short charging...
( Anthony J. Parisio | April 3, 2015) |
https://forums.tesla.com/forum/forums/full-battery-vs-balancing-pack
The bike batteries I've been working with certainly don't have a BMS capable of balanced charging... exactly how much this impacts the useful life of the pack is something I'd be keen to see any real-world data on.
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"Active battery temperature control" sounds like "doesn't deliver as much current when the battery's getting hot" - hence the "improved cold weather performance"...
Engineer: "Shit. It slows down in hot weather!"
Sales team: "Heh... I know..!"  |
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Potemkin Villager
Joined: 14 Mar 2006
Posts: 917
Location: Narnia
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| Posted: Sun Mar 25, 2018 9:46 pm Post subject: |
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| Mr. Fox wrote: | be keen to see any real-world data on.
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"Active battery temperature control" sounds like "doesn't deliver as much current when the battery's getting hot" - hence the "improved cold weather performance"...
Engineer: "Shit. It slows down in hot weather!"
Sales team: "Heh... I know..!" |
Mr Fox ye sound an even bigger marketing cynic than me,
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"Test to destruction: engineers like to do that. Only with a test to destruction can you find the outer limits of a system's strength".Kim Stanley Robinson |
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Pepperman
Joined: 10 Oct 2010
Posts: 768
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| Posted: Tue Mar 27, 2018 10:55 am Post subject: |
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| Interesting. |
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Potemkin Villager
Joined: 14 Mar 2006
Posts: 917
Location: Narnia
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| Posted: Thu Mar 29, 2018 8:54 pm Post subject: |
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Then there is the issue of where the materials for the batteries comes from.
https://www.amnesty.org/en/latest/news/2017/09/the-dark-side-of-electric-cars-exploitative-labor-practices/
" A key component of the rechargeable lithium-ion batteries on which electric cars run is cobalt. More than half of the world’s cobalt comes from the Democratic Republic of Congo (DRC). Despite its mineral riches, the DRC is one of the poorest countries in the world, and has suffered from decades of war and corrupt leaders. With so few formal jobs in the country, hundreds of thousands of Congolese men, women and children, have been driven to dig their own mines to earn their livelihoods."
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"Test to destruction: engineers like to do that. Only with a test to destruction can you find the outer limits of a system's strength".Kim Stanley Robinson |
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Potemkin Villager
Joined: 14 Mar 2006
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Location: Narnia
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adam2
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Joined: 02 Jul 2007
Posts: 6467
Location: North Somerset
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| Posted: Wed Apr 04, 2018 10:02 pm Post subject: |
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| Potemkin Villager wrote: | | PS_RalphW wrote: | | Cold weather performance improves in models like the Hyundai ioniq which has active battery teperature control. |
Just spotted this.
"Active battery temperature control"
To me this sounds like something straight out of a sales brochure!
Is any clue given to where the energy comes from to power this active battery temperature control I wonder? |
IME, "active temperature control" is not that sophisticated and uses very little energy.
When the battery is being charged it will become warmer due to the losses in the battery. When it is about to become warmer than it should, then a fan forces air between the battery cells to cool them. Sometimes an anti-freeze solution is used and cooled by passing through a radiator.
The only energy used is for fans and maybe a pump.
In some climates a fully charged battery may become too cold if left charged but unused for a few days, in these circumstances, electricity from the charging supply is used to keep the battery warm. This is only needed in climates so cold that FF vehicles parked in the open need engine block heaters.
When the battery is being discharged, heat is again produced, and a thermostatically controlled fan or liquid cooling system removes the excess heat so as to keep the battery at an optimum temperature.
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