Headlights run off of traction or accessory battery?

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8thMan

New member
Joined
Apr 30, 2015
Messages
4
In my manic quest to nurse a few more miles of range out of my Spark, I am considering replacing the halogen headlights with LEDs. It is not clear to me however if the headlights run off the traction battery or if they use the 12V accessory battery. Any information on this would be helpful.

Thanks.
 
So is the accessory battery being charged from the traction battery the whole time the vehicle is being driven, or only when the accessory battery has dropped below a certain charge threshold? I ask this because the panel display appears to indicate no additional current draw when the headlights are turned on.
 
8thMan said:
So is the accessory battery being charged from the traction battery the whole time the vehicle is being driven, or only when the accessory battery has dropped below a certain charge threshold? I ask this because the panel display appears to indicate no additional current draw when the headlights are turned on.

You likely don't see a change on the in dash power usage display because the headlights use on the order of 100W (0.1kW). This is well below the display threshold of 1kW.
 
I don't know for sure, but I'd assume the DCDC comes on with the ignition and stays on. You'd really need a more accurate meter to register the draw off the high voltage pack. I mean it's 360v. At 100w, that's only .28a (compared to the 100's of amps it's scaled to measure when driving). White noise.
 
ExtensionCord said:
... White noise.

As is the difference between LED's and halogen. Halogens are something like 55 Watts (each) on high beam, what's the wattage of the LED's?

Drive for 2 hours and the headlights on high consume 220 Wh. I get 4.7 miles per KWh so that 220 Wh equates to 1.034 miles range loss compared with NO headlights. LED's will therefore add less than that compared to the halogens...
 
That's the equation I was looking for. LED lights run around 10W each, so as you say, the improvement would negligible. Thanks for your help.
 
8thMan said:
So is the accessory battery being charged from the traction battery the whole time the vehicle is being driven, or only when the accessory battery has dropped below a certain charge threshold? I ask this because the panel display appears to indicate no additional current draw when the headlights are turned on.

Chevy does actually claim to do this. The amount of charge will not be very much maybe 100-200Wh. I.e. equivalent to about maybe 1 mile.

Even when you put the lights on they will only consume ~100-150W so it would not show on the display with 1kW resolution.

kevin
 
8thMan said:
In my manic quest to nurse a few more miles of range out of my Spark, I am considering replacing the halogen headlights with LEDs. It is not clear to me however if the headlights run off the traction battery or if they use the 12V accessory battery. Any information on this would be helpful.

Thanks.

Hi. I am curious about the LEDs that you are looking to use to replace the Halogen lights. Can you please share what LEDs you have chosen?

thanks
 
The Spark is designed to partially discharge its 12V battery until it is being recharged from a wall, thereby using the Lead-Acid battery as a form of power storage as well as the Li-ion.

GM obsessively went over the Spark with a fine tooth come to minimize 12V electricity use as well. Most of the electrical circuitry completely shuts off when not in use to eliminate ANY unnecessary energy loss.

An SAE article broke down how much energy they believed each step would save, but I can't remember the figures.
 
Quaman26 said:
8thMan said:
In my manic quest to nurse a few more miles of range out of my Spark, I am considering replacing the halogen headlights with LEDs. It is not clear to me however if the headlights run off the traction battery or if they use the 12V accessory battery. Any information on this would be helpful.

Thanks.

Hi. I am curious about the LEDs that you are looking to use to replace the Halogen lights. Can you please share what LEDs you have chosen?

thanks

Here they are: http://www.autoanything.com/lights/plasmaglow-igniters-led-headlight-bulb-conversion-kit
 
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