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Jack.L
User Rank
Silver
Re: Why not just be rid of the 12v battery altogether?
Jack.L   7/31/2013 10:52:10 AM
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I was not suggesting removal of the 12v battery. I fully see the advantage of this architecture. To your point, legacy 12V support when it does not need to start the vehicle is quite easy and less expensive.

 

Jack.L
User Rank
Silver
Re: Why not just be rid of the 12v battery altogether?
Jack.L   7/31/2013 10:49:07 AM
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It is not the issue of the weight /energy density of a 48V lead acid versus a 12V lead acid, it is the weight/energy (and power) density versus the equivalent lithium battery.

There is work on mild-hybrid using lead-acid-carbon batteries that have far longer life, good power density, but worse energy density versus standard lead-acid.

Dom
User Rank
Iron
Re: Why not just be rid of the 12v battery altogether?
Dom   7/31/2013 10:48:29 AM
Jack getting rid of the 12V battey in this case no interest at all : imagine putting DC/DC converter on every single consumer that works under 12V! better centralize with one DC/DC converter + 12V battery which in this case become very small since no need to compromize like today between energy(consumer feeding) and power (starter motor powering) but only energy in this case battery are half the size and the cost not a pb.
the real interest of this architecture is the combination with downsizing like 2 cylinder ICE (1000cc) and 6kW electric machine that's the good fit and very good FE

ltron
User Rank
Gold
Re: 48V on board cars
ltron   7/31/2013 10:22:45 AM
I'm not sure why we don't dump the 12V Lead Acid battery entirely. They could easily use 48V for any high power loads and provide a 12V step down converter for legacy 12V low power loads.

It would be an easy 50lbs savings.

 

Jim_E
User Rank
Platinum
Re: Compressor
Jim_E   7/31/2013 10:13:41 AM
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I believe you, but it's a real mess having the belt driven compressor, condensor, piping, evaporator, etc. under the hood of the car!  I've love for there to be some other technology which would offer equivalent cooling ability, but be powered by electricity without the need for all of that junk.  I just want a box that attaches to the firewall with some wires that go into it.  :)

 

Jack.L
User Rank
Silver
Re: Incremental is good
Jack.L   7/31/2013 10:13:20 AM
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Because fuel price shock has not completely set in for consumers. They don't see yet that they may be paying $5000 - $10000 more over the life of the vehicle for additional fuel versus what they could be paying.  I am still surprised to see people use pickup trucks as mainly commuting vehicles. Over a 120,000 mile life of the vehicle they could be easily paying $10,000 more in fuel versus a mid-sized sedan.

I do get the whole tow vehicle thing. The market has not really addressed the efficient tow vehicle yet. Part of the problem, in N.A. at least is outrageous power requirements. There is an expectation of car like performance even while towing it seems.

cgosnell
User Rank
Silver
Nothing comes for free...
cgosnell   7/31/2013 10:07:18 AM
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In several of the posts, I heard claims that the 48V accessories will take load off the engine and improve efficiency.  

While I agree that some increased efficiency will be had by using an electric power steering assist vs. hydraulic due to the idling losses in the hydraulic system, I don't see a big improvement for the A/C system as A/C compressors already have clutches to remove their load from the engine when not used and when under hard acceleration.

I agree that recovering regen braking energy and then using it for peak loads may be a good idea, but for extended driving periods the A/C system will use up any (all) of the regen stored energy requiring makeup by the Alternator.

Will the Alternators have dual 12V-48V outputs, or will they just run at 48V and be stepped down to 12V using the recharging electronics?  

Given the losses involved with electric driven A/C, wouldn't it be more efficient just to leave the A/C compressors as-is?

Just my $.02

Ken E.
User Rank
Gold
Re: Why not just be rid of the 12v battery altogether?
Ken E.   7/31/2013 10:07:04 AM
NO RATINGS
Jack,I don't understand why the weight/energy density of a lead acid would change significantly for 12v vs 48v.  Seems there whould be more cells, but smaller, (1/4 the amps required) for roughly the same energy density. 

Jack.L
User Rank
Silver
Re: 48 Volts
Jack.L   7/31/2013 10:05:35 AM
NO RATINGS
The lowly compressor is significantly more efficient than even the best peltier cooling devices.

Jack.L
User Rank
Silver
Re: 48 Volts
Jack.L   7/31/2013 10:02:40 AM
NO RATINGS
Jim_E,

 

There are numerous battery compositions that fall under the heading of Lithium-Ion. These range from the dangerous if treated poorly but very common LiCo02 batteries that are in our laptops, to quite benign LiFeP04 with a range of options in between. LiFeP04 has much better high temp characteristics versus lead-acid. I would not have any concerns with this type of battery in my car. We also need to be realistic. We are already sitting on a large capacity of highly flammable liquid and we do that without thinking.

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