In an attempt to consolidate some of the BATTERY threads.....

[Adair]

We have closed 6 of them and provided links to 2 of the main ones....

 

This one is a general *Battery problem* thread

 

 

http://fordcmaxhybridforum.com/topic/361-battery-dead/page-20?hl=%2Bbattery+%2Bdead&do=findComment&comment=11225

 

This one is a Poll....with specific questions/categories.

 

http://fordcmaxhybridforum.com/topic/1294-for-those-who-have-had-12v-battery-problems/?hl=%2Bbattery+%2Bdead&do=findComment&comment=11661

 

Please read both and jump in where ever you find a fit.

 

~~~Staff

[T Thomas]

Hello. New to forum. We've had our C Max Energi about a month, and had one inexplicable dead 12 v battery, which was easily recharged (jumper cables from AAA). In searching this forum, and the web in general, I've come across a variety of proposed causes and potential fixes. However, I remain unclear about the cause (bad battery, bad console software, inadvertently leaving the EV motor running, leaving in accessory mode, etc)

 

All of this has revealed that I am quite ignorant about the basic electronics of the car-e.g. do the 12v and HV batteries share any tasks? Is the 12 v battery used only to start the car and run the instrument panel, while the HV used only for HVAC and power train? Is the 12 v recharged solely by the HV battery? Does not the engine participate in charging the 12v (traditional alternator)? The owner's Manuel provided almost no help with these questions...

 

So, can anyone provide a reference which provides a general overview of the two batteries in the C-max hybrid/Energi? Thanks!

[Bill-N]

Hello. New to forum. We've had our C Max Energi about a month, and had one inexplicable dead 12 v battery, which was easily recharged (jumper cables from AAA). In searching this forum, and the web in general, I've come across a variety of proposed causes and potential fixes. However, I remain unclear about the cause (bad battery, bad console software, inadvertently leaving the EV motor running, leaving in accessory mode, etc)

 

All of this has revealed that I am quite ignorant about the basic electronics of the car-e.g. do the 12v and HV batteries share any tasks? Is the 12 v battery used only to start the car and run the instrument panel, while the HV used only for HVAC and power train? Is the 12 v recharged solely by the HV battery? Does not the engine participate in charging the 12v (traditional alternator)? The owner's Manuel provided almost no help with these questions...

 

So, can anyone provide a reference which provides a general overview of the two batteries in the C-max hybrid/Energi? Thanks!

 

I can shed some light on this, although no reference to a general overview.

 

• "do the 12v and HV batteries share any tasks?"  Not really.
• "Is the 12 v battery used only to start the car and run the instrument panel, while the HV used only for HVAC and power train?"  Generally correct, but with one big exception:  starting the engine is done by the HV battery.
• "Is the 12 v recharged solely by the HV battery?"  Yes.
• "Does not the engine participate in charging the 12v (traditional alternator)?"  No.  The engine recharges the HV battery which, in turn, recharges the 12V battery via a DC/DC converter.

 

 

Hope this helps.  Others will add/correct any (mis)information.   :)   And, some of the above may differ with the Energi.

 

 

Cheers.

[T Thomas]

Thanks so much. Very helpful. However, this leads me to question, If only the 12v is dead (and not the HV), why would the car not start? I'm guessing it is because the instrument panel is necessary? Seems weird that the HV battery could start the engine, which could then (via braking etc) regenerate the HV battery, but that neither the engine nor the HV battery could recharge the 12v battery. I must be missing something fundamental.

[Bill-N]

Thanks so much. Very helpful. However, this leads me to question, If only the 12v is dead (and not the HV), why would the car not start? I'm guessing it is because the instrument panel is necessary? Seems weird that the HV battery could start the engine, which could then (via braking etc) regenerate the HV battery, but that neither the engine nor the HV battery could recharge the 12v battery. I must be missing something fundamental.

 

Effectively, all the electrical controls are 12V.  No 12V, no way to tell the HV what to do.

 

Note that there are several possibilities as to the cause of the dead battery.  My take is that there are actually multiple causes which is why the "problem" is so hard to diagnose and resolve.

 

 

Cheers.

Edited July 24, 2013 by Bill-N

[Noah Harbinger]

Thanks so much. Very helpful. However, this leads me to question, If only the 12v is dead (and not the HV), why would the car not start? I'm guessing it is because the instrument panel is necessary? Seems weird that the HV battery could start the engine, which could then (via braking etc) regenerate the HV battery, but that neither the engine nor the HV battery could recharge the 12v battery. I must be missing something fundamental.

 

The high-voltage battery is physically disconnected from the car by a relay when the engine is not on, and the car is not in accessory mode. The 12-volt relay controls the circuitry necessary to reconnect the high-voltage battery when you want to begin driving. 

 

I believe this is done for safety reasons - if someone needed to work on the car, the high-voltage connection would be insanely lethal if connected.

[GaryM]

From what I have read, it sounds like all that is needed is a fairly small amount of 12 volt power to wake up the computers. I think I will have to try my amp probe and see how much current it pulls from the 12 volt battery when you "start" the car. Once the system is powered up, the DC-DC converter should take over and supply all the 12 volt power needed from the HV battery. I have a jump starter pack with a 17 AH gel pack in it. That can start a conventional engine without a problem, it is probably total overkill for "starting" a C-Max hybrid with a dead 12 volt battery. The 7 AH gel packs used in a computer UPS unit will probably be enough to fire up the electronics. They are much smaller and lighter to carry around. It could even be setup to charge off the accessory power socket with isolation so it won't be sucked down when the car is off.