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Discussion Starter · #1 ·
Can someone educate me about how the 400V battery system charges or doesn't charge the 12V battery? As long as my 400V battery is charged, will the karma automatically keep the 12V battery charged? Or if the car isn't driven for a while is the 13 V battery in danger of losing its charge, regardless of the charge state of the 400V battery?

Thanks!
 

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Well, there is a DC/DC Converter in the enginebay that is responsible of charging the 12v battery. It will only do so in System Ready, therefore your battery will eventually die much like it would in any conventional car.
 

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As I understood it from the last "Town Hall Meeting" or thereabouts, the high voltage system will only charge the 12v battery when the car is on. And, if the 12v battery is flat as if the car has been sitting for a long time, the systems will not start up and the 12v needs to be charged to turn the car on. Hence the recommendation to use a trickle charger if the car is to be stored for a long time.
 

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Discussion Starter · #4 ·
Thanks Raven and Sigurd; your comments make sense and remind me of the town hall comments.

Two follow-up questions:

1) If I were to disconnect the hard reset plug under the hood, would the 12 V battery still slowly discharge? Or could I leave the car in this disconnected state for months during the winter without risk of discharging the 12 V?

2) How long does it take for the car to charge up the 12V battery while in Ready mode? I realize that using a trickle charger is one solution, but my past experience with these chargers is that some/most cars can be damaged unless the battery is disconnected from the car's electrical systems before charging, and doing so is sometimes not that easy. Also the recommended charging terminals are sometimes located in inconvenient places. Plus having wires running across part of my garage isn't great either (garage power outlets are on two walls only).

In other words, if I wanted to avoid using a trickle charger during the winter, how often would I need to boot up the car and let it sit in ready mode? I assume putting the car in ready mode once every few weeks also has some other advantages as well in keeping the car's systems running during the winter hibernation.
 

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The 12 volt system is just like in any other vehicle, it will discharge eventually. The Converter is quite effective, keeping the car in Ready mode for 15 minutes few times a month should be enough to keep the battery topped.
Using an external charger shouldnt be a problem, just connect it to the car, then to the wall to avoid arcing and youre fine.
 

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Just a small foot note all of you are correct you need to drive the car to charge the 12 volt battery . Simple solution is to buy a trickle charger that you can hook it up and leave it . I just installed one and it is hardwired to the car with a plug pop the hood open plug the charger into the pig tail and your done . A few of our customers leave the car alone for a few weeks and didn't want to have a problem when they get home .
 

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Discussion Starter · #7 ·
Thanks Harleyguy. Can you please provide a link to the installable plug-in-pigtail trickle charger? That sounds like the best solution. Thank you!
 

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what about just putting a timer on the garage lights to turn on for an hour every couple days..

20 watts of lightbulb, efficiently captured, will generate maybe 1 watt of power for the car

:)
 

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drliu said:
Thanks Harleyguy. Can you please provide a link to the installable plug-in-pigtail trickle charger? That sounds like the best solution. Thank you!
I'm not as knowledgeable as Harleyguy about this stuff, however, I do own a boat equipped with a tender boat and two jet skis. We have been using these chargers with great results. They are designed for long term hardwired service, they are reliable, cheap and can tolerate being outside in the salt air for years. I also use one on my Z8 that, unfortunately I don't drive very frequently, especially since I bought my Karma!

The charger got 4.5 Stars with 81 reviews on Amazon as well with virtually everyone raving about them.

http://www.amazon.com/Schumacher-SE-1-12S-Automatic-Onboard-Battery/dp/B0000AXTUY/ref=sr_1_7?ie=UTF8&qid=1339860164&sr=8-7&keywords=plug+in+trickle+charger
 

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I thought the solar panels job was to keep the 12V charged, just like an alternator in an ICE vehicle. Of course it only works if Karma is parked outside on a sunny day, but wasn't that the point of the panels?
 

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Richard Carnes said:
I thought the solar panels job was to keep the 12V charged, just like an alternator in an ICE vehicle. Of course it only works if Karma is parked outside on a sunny day, but wasn't that the point of the panels?
I think the problem is; no one parks their shiny new Karma outside for any extended period of time. I know I certainly don't.
 

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As has been explained elsewhere, the solar panel charges the 12V battery. If the 12V battery is fully charged and it is hot outside, the cabin fans run to exhaust hot interior air and bring in cooler outside air. The solar panel replenishes the energy used to run the cabin fans.
 

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Discussion Starter · #14 ·
Harleyguy,

Can you please post a photo showing exactly where the pigtail terminals should be installed? I received a highly rated Battery Tender Plus trickle charger with pigtail terminals and want to be sure the terminals are installed at the proper locations.

Thank you!

Harleyguy said:
Just a small foot note all of you are correct you need to drive the car to charge the 12 volt battery . Simple solution is to buy a trickle charger that you can hook it up and leave it . I just installed one and it is hardwired to the car with a plug pop the hood open plug the charger into the pig tail and your done . A few of our customers leave the car alone for a few weeks and didn't want to have a problem when they get home .
 

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Harleyguy said:
Just a small foot note all of you are correct you need to drive the car to charge the 12 volt battery . Simple solution is to buy a trickle charger that you can hook it up and leave it . I just installed one and it is hardwired to the car with a plug pop the hood open plug the charger into the pig tail and your done . A few of our customers leave the car alone for a few weeks and didn't want to have a problem when they get home.
Does the car's 12v charge when the 400v 'traction' battery is plugged in and being charged** as well? It works that way on another car I know. **and this means actively charging and not just plugged in.
 

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scottf200 said:
Does the car's 12v charge when the 400v 'traction' battery is plugged in and being charged** as well? It works that way on another car I know. **and this means actively charging and not just plugged in.
The 12V system charges from the high voltage system only when the car is in Ready mode (i.e. turned on and ready for driving, but not necessarily in 'gear'). It does not charge the 12V system when the car is asleep, regardless of whether or not the high voltage battery is plugged in.

If you don't drive your Karma at least occasionally, and this might be as little as 15 minutes every month or so, you might want to consider a battery tender to trickle-charge the 12V system.
 

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LonePalmBJ said:
If you don't drive your Karma at least occasionally, and this might be as little as 15 minutes every month or so, you might want to consider a battery tender to trickle-charge the 12V system.
Got it. I do that for my motorcycle as I've had to replace 1 too many of those batteries.
 

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All: Is it possible to use a trickle charger that plugs into the 12v plug in armrest compartment?
If you use the cigarette lighter in the FRONT center console then yes as it is connected the 12 volt battery at all times (through the fusebox).

The cigarette lighter in the REAR is disabled once the car goes to sleep.
 
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