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Interesting thing I just learned, the engineers at Hyundai have figured out a way to eliminate the 12 Volt battery in the Ioniq EV by tapping off different sections of the main battery. By doing this they eliminate the space, weight and cost of the aux battery and the DC to DC converter. This could also eliminate a major source of problems experienced by EV owners.

Discussion starts about 41 minutes into the link below.

http://www.autoline.tv/journal/?p=48394
 

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The 12v battery was never necessary. It is a safety item.
Perhaps they could get some 'take off' Takata airbags and save even more!
 

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I always understood that it was a safety item required by NHTSA (or whatever gov't body had jurisdiction). The low voltage system controls relays to shut down the high voltage system in an emergency. Sorry if the video explains it, I can't watch a long video right now.
 

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The 12v battery was never necessary. It is a safety item.
Perhaps they could get some 'take off' Takata airbags and save even more!
The stand alone 12 VDC battery is a "back up" and needed for HVDC battery systems. The EV still has the regular devices (including the doors, windows, lights and controls) powered by 12 VDC and can be serviced up to the point of failure, which may not be on the HVDC system. But I still wish to know why the EVs, such as the Chevy Volt, must use a classic lead-acid battery when the loads never need large currents, so a smaller battery or a li-ion replacement can do the same job.

If there are many luxury vehicle carrying two 12 VDC batteries for safety and redundancy (the President "Beast" may have more than two), I also believe that just having power from the HVDC traction battery limits safety and may actually increase cost. The only benefit is a weight savings of thirty pounds (battery and cabling). If GM, Ford, and Toyota (all three are the best hybrid sellers) always have that 12 VDC battery in addition to the HVDC traction battery of their hybrids and EVs, then what Hyundai has done is not as smart as it may seem!
 

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there was talk many years ago about switching cars to 42v and with EVs I am surprised they did not
The 42 VDC was proposed for the use of a "Start-Stop" system, so it can supply all the power needed. But actual vehicles with "start-stop" have two batteries: the regular 12 VDC and the higher voltage for the electric motor. And the suppliers of the accessories and controls would have to redesign all their powered devices to run on 42 VDC, too, so that is a new cost that no manufacturer would absorb. Maybe they could use the 42 VDC to 12 VDC converter and use a single battery, but they are the experienced designers and manufacturers, so they have their valid reasons not to do it. and one of them is redundancy, as I stated in a previous post.
 

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My guess is Hyundai pulls 12 V from part of the main battery by adding a wire between 3 cell modules, easy to do and would be greatly appreciated. You can't go anywhere without that battery anyway. The only problem I see is those cells would see more usage, so I wonder if they have a way to rotate which cells are being used or maybe once the main battery is engaged it provides all the power through a DC to DC converter. Any indication in the video?
 

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The guy from Hyundai was interesting and informative. I just listened to the small part before the discussion of replacing the 12v battery and it included some very interesting observations about battery life in a PHEV. Interesting enough that I'll make an effort to watch the whole episode.

On the desirability of not having a 12v battery, given the percentage of problems attributable to 12v failures for the Volt, I can see the benefits of getting rid of it. On the safety and regulation front, obviously Hyundai has figured out a way to meet the regulations and remove the 12v .... Would be interesting to know how they did it. On the redundancy issue, if you have two systems, and both are required for operation, then it strikes me that you have multiple points of failure rather than redundancy. Redundancy would be where either system would suffice.
 

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Discussion Starter #9
My guess is Hyundai pulls 12 V from part of the main battery by adding a wire between 3 cell modules, easy to do and would be greatly appreciated. You can't go anywhere without that battery anyway. The only problem I see is those cells would see more usage, so I wonder if they have a way to rotate which cells are being used or maybe once the main battery is engaged it provides all the power through a DC to DC converter. Any indication in the video?
He said the 12 V connection is moved to different sections of the battery.
 

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Interesting thing I just learned, the engineers at Hyundai have figured out a way to eliminate the 12 Volt battery in the Ioniq EV by tapping off different sections of the main battery. By doing this they eliminate the space, weight and cost of the aux battery and the DC to DC converter. This could also eliminate a major source of problems experienced by EV owners.

Discussion starts about 41 minutes into the link below.

http://www.autoline.tv/journal/?p=48394
The discussion of the Ioniq Hybrid's 12v battery in the video was a little ambiguous and confusing.

Here's what I wrote for my Ioniq review earlier this year:

http://gm-volt.com/2017/02/24/2017-hyundai-ioniq-review-first-drive/
A unique feature in the Ioniq hybrid is its 12-volt battery. Rather than a traditional lead acid standalone unit, Hyundai uses a lithium-ion design that is electrically separate from – but co-packaged with – a 1.56 kilowatt-hour high voltage hybrid battery under the rear seats. Both batteries are covered under a lifetime failure warranty for original owners.
If the 12-volt battery should ever be temporarily run down too low to start the car it can be revived by the large hybrid battery by pressing a button inside the car. If that fails for some reason the car can still be traditionally jump started.
In other words, they replaced the 12v lead-acid battery with a 12v Lithium ion battery and mechanically co-packaged it with the larger hybrid pack under the rear seats. The part about tapping into the hybrid pack is that if and when the dedicated 12v pack gets run down too low to bootstrap the car there is a button inside the car that will use the hybrid pack to temporarily recharge the 12v pack so you can then normally start the car. The 12v pack is separate from the hybrid pack normally and the 12v pack is individually replaceable independent of the hybrid pack. Because it is Lithium ion it is expected to last longer than a lead-acid battery before needing to be replaced so Hyundai is covering it with a lifetime warranty for original owners only.
 

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Doesn't lead acid have superior temperature tolerance? Might be an argument for keeping it.
When a BEV/EREV's high-voltage lithium battery pack gets so cold that it doesn't work, you can't start or drive it anyway. So it doesn't matter.

I guess it might be possible to run a "regular" hybrid even if its lithium traction battery is too cold to work, assuming that the lead-acid battery cranks the engine. But I'm not sure if that's how modern hybrids work.
 

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Doesn't lead acid have superior temperature tolerance? Might be an argument for keeping it.
Yes, but as mentioned the traction battery needs to be kept warm anyway. Any pure EV will probably have vampire drain in cold weather where the Li-ion self discharges to keep it warm. The Volt doesn't need to do this as it just uses the gas engine in such situations (Deep Cold ERDTT) until it warms the battery enough. Point being is the car will keep the 12V module warm enough to start the high voltage battery. If you leave it for a long time you could have a dead battery (think airport in sub-zero F weather).
 

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It will be interesting to see how it works out, but I have a hunch engineers are not as dumb as some folk think. EV engineers know about the weight reduction that can be had with Li batteries over AGM. Yet, even the newest designs have them using a small AGM instead. Safety, cold temps, cost of replacement, servicing, etc, all have to be considered, and they use Lead.
 
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