Tech Question - DC-DC Converter?

Tech Question - DC-DC Converter?

Curious question, in the Model S, the DC-DC Converter for the 12 volt battery. How much current could it handle for aftermarket accessories?

Bob W | September 15, 2013

Can't answer that question, but the maximum current you can draw from the 12V socket is 15A since that's how it's fused. That's 180W max. You probably knew that already.

I don't think the DC-DC Converter runs continuously. I think it only activates when needed to recharge the 12V battery.

I guess you're trying to figure out how to power a 500W stereo or something. You could drain the 12V battery pretty quickly.

There are posts that the DC-to-DC converter is "undersized" but I couldn't find any source for that claim.

nickjhowe | September 15, 2013

There's a YouTube video from user 'kmanauto' where he measures the current on the 12 V posts behind the nose. It shows a constant draw/charge even when the car is off. Can't remember the current, but was about 13.8V

chrisdl | September 15, 2013

Current is measured in Amperes.
Kmanauto was indeed measuring Voltage. I remember he thought it was high and would be bad for the 12V battery, although I didn't share that opinion. About 13.8V, yes.

mrrjm | September 15, 2013

If someone has the answer to this that would be great. On my Volt I can draw 190 amps off the 12 volt accessory power module. This is great if you every need to use the car as a stationary power source such as in a power outage along with and inverter. Yes is does void the warranty. Does anyone know where this module is located on the car?

nickjhowe | September 15, 2013

I meant to say "Can't remember the current, but the voltage was about 13.8V"

jat | September 15, 2013

In an ICE, the laternator normally keeps the 12V circuit at a bit under 14V, so it is no different in the Model S.

Bob W | September 18, 2013

mrrjm wrote: "On my Volt I can draw 190 amps off the 12 volt accessory power module."

Uh, I think you meant 190 Watts, about the same as model S.

EVino | November 9, 2014

I am resurrecting this post since I could not find a definitive answer after many searches.

Does anyone know if the DC-to-DC converter is continually charging the 12V battery, even when the car is on Park? If there's a draw on the 12V battery during Park will the car allow it to drain or does the DC-to-DC Converter detect the low voltage and activate charging?

jeff | January 6, 2016

Another user took a picture of the DC to DC converter and it shows as 2500 watts.

If you add up everything that is potentially on the 12V rails, it could be quite a lot. Consider the following:

1) Upgraded sound system playing at a loud volume
2) Passneger and Driver seat heaters on max
3) Rear seat heater on
4) Max brightness on both screens
5) Streaming internet radio
6) Autopilot engaged
7) Two devices charging from USB ports
8) 12 volt accessory drawing 180 watts
9) headlights and fog lights on max brightness
10) windshield wipers running and using washer nozzle heaters

I could easily see this setup drawing 1000-1500 watts, and a dead 12v battery would likely cause serious problems with the electric system, so 2500 watts is plausible for the DC-DC converter.