12 volt Battery recharge in Roadster

[Botbldr45]

Does anybody know when the roadster 12 volt battery recharges? What voltage triggers a recharge and what is end voltage on battery after recharge?

 

[Earl]

The Roadster 1.5s don't even have 12v battery.
They have a DC-DC converter hanging directly off of the High Voltage traction battery that powers accessories.
I don't know if later Roadsters had a 12v battery

 

[gregd]

From my research during my replacing the 12v battery in my 2.0 car, the charging is done whenever the car is "Awake". 13.8 volts at a couple of amps; I forget the exact current. It's a single stage charging to the float level. When the car is asleep there's a much lower current (under 100ma?) 13.8v supply to the battery, to keep it at the float level, so the net is that the battery is basically just sitting there at 13.8v regardless of what you're doing.

Note that the battery is NOT used to run things when the car is asleep, as it is on the newer cars. Under normal conditions, the only time the battery is discharged is when the Unlock button is pressed on the key fob, and this regardless if the car is already unlocked. At this time, the car apparently does a "load test" on the battery, pulling a bunch of current (more than 10 amps) for a second or two, and watching the voltage drop. If it falls too far and/or doesn't recover, the "12v battery needs replacing" alert is generated. I'm assuming that this is to assure that the battery is available to run the critical safety items in the event of a main pack or other power system failure.

 

[gregd]

From my research during my replacing the 12v battery in my 2.0 car, the charging is done whenever the car is "Awake". 13.8 volts at a couple of amps; I forget the exact current. It's a single stage charging to the float level. When the car is asleep there's a much lower current (under 100ma?) 13.8v supply to the battery, to keep it at the float level, so the net is that the battery is basically just sitting there at 13.8v regardless of what you're doing.

Note that the battery is NOT used to run things when the car is asleep, as it is on the newer cars. Under normal conditions, the only time the battery is discharged is when the Unlock button is pressed on the key fob, and this regardless if the car is already unlocked. At this time, the car apparently does a "load test" on the battery, pulling a bunch of current (more than 10 amps) for a second or two, and watching the voltage drop. If it falls too far and/or doesn't recover, the "12v battery needs replacing" alert is generated. I'm assuming that this is to assure that the battery is available to run the critical safety items in the event of a main pack or other power system failure.

Here's the thread with my research: 12v battery time (sigh)

 

[Botbldr45]

That is outstanding…… thank you Greg