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Re: Scheduling method 2 keep ur 12v battery charged while va

Posted: Thu Jun 21, 2012 2:17 pm
by DarkStar
JeremyW wrote:
DarkStar wrote:I'm seeing about 12.3 volts at rest, which is considered only about 70% charged.


That's concerning if true. Lead acid batteries develop sulfation (lead sulfate crystals on the plates impeding current flow) if they sit too long at a partially discharged state. Lead acids love to sit at 100% all the time. This makes them perfect for the float application and partially why Nissan went with it instead of something newer for the house battery. You can give it a float charge and it will be happy for years.

However, I do ask what kind of multimeter you are using to read the voltage. Some of the no-name brands are notoriously inaccurate. :) I'd check with another meter just to be sure. You should be seeing something around 13.5 to 14.1 during float/charging. My guess is the meter is off by a few hundred millivolts, and the DC/DC is fine.

I purposely didn't check the voltage during float/charging because I wasn't sure if the battery was holding up very well. I just picked up a second multimeter last weekend to perform this test and I'm within a tenth of a volt.

I have a small power backup system for emergencies and I float it at about 13.85 volts (70 degrees F). If I take that battery off and let it rest for an hour or so, it will read 12.8 volts (12.7 volts is considered 100% charged).

I'll have to double-check, but I'm pretty sure I was seeing a voltage of about 14.4 at the battery when the vehicle is powered on. That would be just about right for bulk-charging, but would cause issues once the battery was fully charged (if the voltage doesn't taper).

Re: Scheduling method 2 keep ur 12v battery charged while va

Posted: Thu Jun 21, 2012 2:48 pm
by Ingineer
DarkStar wrote:I'll have to double-check, but I'm pretty sure I was seeing a voltage of about 14.4 at the battery when the vehicle is powered on. That would be just about right for bulk-charging, but would cause issues once the battery was fully charged (if the voltage doesn't taper).
The Leaf does a proper 3-stage charge algorithm, and is even temperature compensated.

-Phil

Re: Scheduling method 2 keep ur 12v battery charged while va

Posted: Thu Jun 21, 2012 4:07 pm
by DarkStar
Ingineer wrote:The Leaf does a proper 3-stage charge algorithm, and is even temperature compensated.

Cool. That's definitely a relief!

Re: Scheduling method 2 keep ur 12v battery charged while va

Posted: Wed Aug 15, 2012 8:23 am
by jpcvb
Something not mentioned it seems to me about the 12V battery when Leaf stays idle : the solar panel. Since I always take long vacation 5/6 weeks away my former Prius used to be dead when I come back since I always forgot to unplug the battery ... didn't want to unplug the 12v battery of the Leaf because I assumed I would have to re-enter all the info already there (may be it's not the case ? if someone has a comment about that ... ?) therefore I decided like everybody said to unplug the car from the EVSE and I didn't park it in my garage but outside under the beautiful South Cal summer sun ... and sure enough, 6 weeks after, I had just to push the start button and ready it was to drive ... all the indicators in the car showing the same amount of juice than when I left (a little bit less for the main battery) no change for the 12v battery !!
So unplug it from the EVSE and let it enjoy the magical sun when you do the same on your exotic island !! it will be ready for you when you return ...posting.php?mode=reply&f=11&t=8970#

Re: Scheduling method 2 keep ur 12v battery charged while va

Posted: Wed Aug 15, 2012 9:21 am
by derkraut
jpcvb wrote:Something not mentioned it seems to me about the 12V battery when Leaf stays idle : the solar panel. Since I always take long vacation 5/6 weeks away my former Prius used to be dead when I come back since I always forgot to unplug the battery ... didn't want to unplug the 12v battery of the Leaf because I assumed I would have to re-enter all the info already there (may be it's not the case ? if someone has a comment about that ... ?) therefore I decided like everybody said to unplug the car from the EVSE and I didn't park it in my garage but outside under the beautiful South Cal summer sun ... and sure enough, 6 weeks after, I had just to push the start button and ready it was to drive ... all the indicators in the car showing the same amount of juice than when I left (a little bit less for the main battery) no change for the 12v battery !!
So unplug it from the EVSE and let it enjoy the magical sun when you do the same on your exotic island !! it will be ready for you when you return ...posting.php?mode=reply&f=11&t=8970#

Might be a good idea---except: Pollution, bird droppings, fading paint, higher temps not good for big battery, vandalism, theft, other security issues, etc. :?

Re: Scheduling method 2 keep ur 12v battery charged while va

Posted: Wed Aug 15, 2012 9:36 am
by TomT
If it really bothers you, just put a trickle charger on the 12V battery... That said, I was gone for five weeks lately and just left the Leaf in the garage unplugged. When I got back, it had lost one bar and everything was just fine. As expected, it stopped communicating via the Telematics after two weeks.

jpcvb wrote:therefore I decided like everybody said to unplug the car from the EVSE

Re: Scheduling method 2 keep ur 12v battery charged while vaca

Posted: Tue Jan 05, 2016 10:43 am
by Arlington
There is no reason to EVER suffer dead 12V in an electric car, except in the case of a catastrophic internal lead-acid failure (in which case a warning might be ok).

But that some system--any system-- would be allowed to old-fashioned drain-until-dead is just STOOPID.

Any time the OBD computer is powered up, the system should make sure that the 12V battery is charged or being charged.

In my specific case, I judge it INSANE that a WiFi dongle plugged into the OBD socket can kill the battery during a week of plugged-in-but-undriven.

That the OBD (or whatever electronic brains are monitoring any system, like battery temp or charging/climate timers) can drain the battery is a violation of the Third Law of Robotics that the computer should work to ensure its own survival, in this case, by checking to make sure that the 12V is charged.

Third Law is literally "A robot must protect its own existence as long as such protection does not conflict with the First or Second Laws."

Before any system is allowed to access the 12V or any current draw on the 12V is detected/permitted, a safety system or computer should "ask" is the 12V charged or being charged.

Re: Scheduling method 2 keep ur 12v battery charged while vaca

Posted: Tue May 24, 2016 12:00 pm
by powersurge
Wow, we went from worrying about charging a battery while on vacation to the laws of robotics!!

Very simple. If you are away on vacation, or wont use the car for weeks, or more, then connect a plug-in "Battery Tender" that can keep the 12v battery charged indefinitely. end of problem.

Also, if you are so worried, then disconnect the 12 volt battery and leave it to the side. Connect it when you get back.. And I don't want to hear anyone say the YOU MUST keep the 12v powering the computer of the car. You are going to have to disconnect it when you change the battery anyway...