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Does anyone know how the 12 volt battery gets charged? The dealer told me that if the car is going to sit for an extended period of time that I need to trickle charge the 12v and plug in the drive battery. That leads me to believe that the 12v does not charge when the car in plugged in.

I know the solar roof charges it some. But, does it charge off the ICE? Is there an alternator somewhere that runs off the drive motors?
 

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There is a module referred to as the APM that convertes the near 400v HV system down to the 12v LV system for the control modules and maintanes the 12V battery state of charge. the 12V battery is needed to power up the modules that unlock the HV system. Any time the car is in READY mode, the 12v battery gets monitored and charged by the APM, however since the HV system is not active in ACC, it does not in ACC. IF the 12v battery state of charge gets below 10v, the car has a REALLY hard time entering Ready mode (that current draw is about 200 Amps!) and can not charge it self further. Additionally the On-Board Charge Module (OBCM) requires the 12v system to unlock the HV battery for charging, and since it runs off 12v it self, plugging in the car to 110/220V will not power that module if the cars 12V system is down. Additionally once the OBCM shuts down because charge is full and the HV system is locked off, the APM can not charge the 12v because it lacks the HV needed to do so.

For storage of a few weeks at a time: attach a 12v battery tender/maintaner/trickle charger and you should be good.
 

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Discussion Starter · #4 ·
Nimisys said:
There is a module referred to as the APM that convertes the near 400v HV system down to the 12v LV system for the control modules and maintanes the 12V battery state of charge. the 12V battery is needed to power up the modules that unlock the HV system. Any time the car is in READY mode, the 12v battery gets monitored and charged by the APM, however since the HV system is not active in ACC, it does not in ACC. IF the 12v battery state of charge gets below 10v, the car has a REALLY hard time entering Ready mode (that current draw is about 200 Amps!) and can not charge it self further. Additionally the On-Board Charge Module (OBCM) requires the 12v system to unlock the HV battery for charging, and since it runs off 12v it self, plugging in the car to 110/220V will not power that module if the cars 12V system is down. Additionally once the OBCM shuts down because charge is full and the HV system is locked off, the APM can not charge the 12v because it lacks the HV needed to do so.

For storage of a few weeks at a time: attach a 12v battery tender/maintaner/trickle charger and you should be good.
Thank you Nimisys! This is very helpful. Does this explain the advertised 200 mile/year range off the solar roof? If the 12v gets charged from the High Voltage battery, then anything that charges the 12v from other than the HV battery will save charge in that HV battery?
 

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Sparky168 said:
Nimisys, it sounds like that it needs a charging path from the AC plug-in to the 12V battery when the 12V battery is low. Once the 12V is charged up, then it can unlock the OBCM module, which in turns allow the main battery to be charged.
That point was brought up during technical training last July, as most peoples reactions to a dead 12v battery will be to plug in the 110v charger. Unfortunitly, i suspect the OBCM lacks the circuitry to energize the 12v DC control circuits off of the 110v/220v plug, as after a few phone calls between engineers, it was confirmed that the 12v side would not be powered by the 110v/220v connector. There may be some SAE/NHTSA restrictions as well on the HV side that come into play. Perhaps in a few years, or with NINA.
 

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Nimisys said:
Sparky168 said:
Nimisys, it sounds like that it needs a charging path from the AC plug-in to the 12V battery when the 12V battery is low. Once the 12V is charged up, then it can unlock the OBCM module, which in turns allow the main battery to be charged.
That point was brought up during technical training last July, as most peoples reactions to a dead 12v battery will be to plug in the 110v charger. Unfortunitly, i suspect the OBCM lacks the circuitry to energize the 12v DC control circuits off of the 110v/220v plug, as after a few phone calls between engineers, it was confirmed that the 12v side would not be powered by the 110v/220v connector. There may be some SAE/NHTSA restrictions as well on the HV side that come into play. Perhaps in a few years, or with NINA.
Is it possible to use an external 12V Battery to energize the 12V circuits to allow the system to power up? The same process used to jump start an ICE, but in this case the goal would be to unlock the HV and energize the system, not to start the engine.
 

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Fabulist said:
Is it possible to use an external 12V Battery to energize the 12V circuits to allow the system to power up? The same process used to jump start an ICE, but in this case the goal would be to unlock the HV and energize the system, not to start the engine.

Yes, which is why i would recommend a trickle charger or tender for weeks between use, otherwise a convential jumper box (or jumper cables and a second vehicle) is needed (again the current draw) to power everything up. However, once in Ready mode, the 12v battery charges back up fairly quickly (15 minutes is normally enough).
 

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on the driver side where the APM is, the positive terminal is behind the red cap, however the case is grounded, so you have to be careful not to short it. the perfered positive post is under the fuse cover by the left headlamp
 

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My Karma is in the Garage. Not working. After one week Holiday with an other car. it was not plugged in. 400V battery was full.

Do you think i can load the 12V Batterie if i connect it like on the Picture?

 

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Thanks for this Smoothoperator! I have done this when my Karma sat for 4 weeks. I was told that if you were hesitant about leaving a trickle charge on the car, just have someone run the car for 15 minutes once a week to maintain the 12 volt battery which has a slight draw from the electronics in the infrastructure.
 

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Thanks for this Smoothoperator! I have done this when my Karma sat for 4 weeks. I was told that if you were hesitant about leaving a trickle charge on the car, just have someone run the car for 15 minutes once a week to maintain the 12 volt battery which has a slight draw from the electronics in the infrastructure.
You could also park your car outside for a few hours every week (if its sunny). Would have been cool if FA made an outside car cover that leaves the solar roof portion open so that it can still trickle charge the battery when not driven for long periods of time. The other option is to pull the 12v cable connector in the engine bay as this will preserve the battery.
 

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Thanks for this Smoothoperator! I have done this when my Karma sat for 4 weeks. I was told that if you were hesitant about leaving a trickle charge on the car, just have someone run the car for 15 minutes once a week to maintain the 12 volt battery which has a slight draw from the electronics in the infrastructure.
Every two weeks should be more than enough. I uploaded the recommended storage guide on here somewhere in another 12 volt battery thread. It has some more tips but that is the biggest one to follow.

If the 12 volt battery does drain completely and someone were to jump start the car (which is ok), the car should be left in ON in Ready mode for at least 30 minutes before actually driving. After 30 minutes the 12 volt should be fully charged.

If one were to drive it immediately after getting a jump start and on the off chance that you needed to make an evasive braking/steering maneuver; you could put yourself at risk since both system draw very high amperage and can cause the vehicle to stall.
 

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I've updated your picture with a red line. Connect the positive cable to the red spot on the left, and the negative cable to the point on the right. Ignore your pink/purple line completely.


 
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