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apresher
User Rank
Blogger
48V Safety
apresher   8/2/2013 8:38:15 AM
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Mirox,  Thanks for the additional info on safety of these systems.

MIROX
User Rank
Platinum
Re: Safety a Concern
MIROX   8/1/2013 11:23:34 PM
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FMVSS #305 

This standard applies
to passenger cars, and to multipurpose
passenger vehicles, trucks and buses
with a GVWR of 4536 kg or less, that
use more than 48 nominal volts of electricity
as propulsion power and whose
speed attainable in 1.6 km on a paved
level surface is more than 40 km/h.

 

SO 48V "nominal" is not a safety issue as far as NHTSA/DOT is concerned.

apresher
User Rank
Blogger
Safety a Concern
apresher   8/1/2013 9:52:38 PM
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Still wondering if safety is an issue to overcome.  My understanding is that voltages this high could be lethal if not handled correctly. Anyone know if that is true for these systems?

Charles Murray
User Rank
Blogger
Re: 48 V - my vote is YES !!!
Charles Murray   8/1/2013 7:23:50 PM
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That's great information. Thanks, Mirox!

MIROX
User Rank
Platinum
Re: 48 V - my vote is YES !!!
MIROX   8/1/2013 2:12:11 AM
@Charles Murray 

With about 10 years of experience with NEV (limited to 25 MPH by federal law, but allowed to go up to 35 MPH in few states) we have actual proof that when it comes to effective regenerative braking, weight actualy does not matter in EV or Hybrid as the energy gets recouped rather well from the "extra" weight.

in ICE ONLY vehicle it DEFINITELY matters, but not in EV !!!

Pd-acid sealed batteries (gell or AGM) can especially take huge current pulses over few seconds of braking with no problem or special battery management, not so for Li-ion there you need $$$ in BMS just to protect the batteries, or MUST add super caps to store the energy.

2kWh pack in Pb-acid is about 160 lbs, but 4kWh pack that is double the weight gives 260% better range, by "theoretical" calculations it should only be 180% due to extra weight on car that starts at 1520 lbs.

So the "extra" weight actually assists in energy regeneration, especially on down hill, the "lighter car" will generate lot less energy and will freewheel by gravity at lower terminal speed on the same downhill.

This is REAL LIFE experience, that actually surprised us.

Of course at some point you reach point of no "gain" but not sure where that is for car with conventional tires and same Cdx.

We only tested the same vehicle to 1850 lbs as adding more batteries was not possible due to space limitations, but more weight (even 4 passengers versus just one driver) actually DOES NOT reduce the range, and usually increases it !

a.saji
User Rank
Silver
Re: Miraculous EU Marketplace
a.saji   7/31/2013 10:49:56 PM
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@William: I think the price range is high isn't it ? Per gallon that much ?  

Charles Murray
User Rank
Blogger
Re: 48 V - my vote is YES !!!
Charles Murray   7/31/2013 6:16:32 PM
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Great points, Mirox, especially about air conditioning applications. Regarding the choice of li-ion over lead-acid: Again you are correct, lead-acid will give a big cost advantage. The reason some automakers are looking at li-ion for these applications is volume and weight. A 48V lithium-ion battery can replace three 12V lead-acid batteries, so automotive engineers get a packaging advantage, as well as a weight advantage. Weight becomes especially important with automakers facing 54.5-mpg CAFE standards in 2025. Every little advantage counts. But as you accurately point out, they will have to bite the bullet on cost if they do that. Great comments.

MIROX
User Rank
Platinum
48 V - my vote is YES !!!
MIROX   7/31/2013 4:00:40 PM
We make NEV that uses 48V DC to power 3 phase 32 to 36 V AC motor, and regenerative braking is a big plus in comparison to 48 V DC Serial Motor.

But the BIG plus for mild hybrid or even ICE car is that you can run Air Conditioning, Water and Oil pumps from 48 V (actually as much as 56 V on fully charged battery pack) with lot less current, for which MOSFET are already available at low costs.

40A DC or AC motor for Air Conditioning is no issue to control with 48V, but up that AMP to 160 A for equivalent power at 12 to 14 V and it is problematic and very expensive.

Of course this is IN addition to normal 12 V DC Automotive system, but then STARTER, ALTERNATOR are eliminated and regenerative braking via power train as well as FREE START STOP is part of the deal.

4kWH battery pack is quite adequate and Sealed Pb-acid technology at 1/4 the price of Li-ion will do just fine with up to 7 years or service life per battery that will cost about $1,200 retail to replace.

The biggest POSITIVE from consumer research is that Air Conditioning can be run in recycle mode when vehicle is parked for up to about 45 minutes and keep the car cool inside even at 120 F in direct sunlight, something that is great for TAXI and LIMO services in places like Phoenix and Las Vegas.

 

 

Jack.L
User Rank
Silver
Re: Am I missing something here?
Jack.L   7/31/2013 1:49:21 PM
This is not about pushing 48V electronics which would only happen if the costs demanded it.

 

What this is is a method to bring mild-hybrd to the market at far less cost than existing proprietary lower volume but arguably better hybrid systems.

48V can lend some advantages to ICE in terms of electrically actuated valves which work better when you can drive them harder.

The 48V section will be contained to keep wiring costs lower so I am not too worried about CAN not being able to take a hit as the likelihook of that is pretty low. Sure there will be some missteps but that is what progress takes .. failure.

 

The goal is to have this on the majority of vehicles especially those that spend a lot of time in the city, which many cars do in much of the world.

 

Gas prices are not likely to go down as no matter how cheap we can pull oil out of the ground in North America, prices will still be set by the world market and demand does not seem to be going down.

 

 

OcelotZ3
User Rank
Silver
Coercion...
OcelotZ3   7/31/2013 1:46:37 PM
Folks say that the Europeans are being "coerced" by higher gas prices.  If our prices reflected all the government puts into the oil industry (military interventions, subsidizing advertising for the oil industry, etc.), our price/gal would be much higher than it is now.  Personally, I would support this.  (After removing government subsidies for the oil industry).

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