When is the 12 volt battery being charged?

[davideos]

...consider a deep cycle RV/Marine battery.

That actually seems like a pretty good idea. However, it makes me wonder why they put in the battery they did...likely because it is the cheapest battery available to them due to high volume. It would be interesting to get a charge / discharge profile and match that to the battery specs and the useage. My thought is if the current battery is going dead, there is still an issue of more discharge vs the amount of charge and therefore, even a deep discharge battery will go dead after awhile...granted without the amount of damage as a regular battery.

Might be worth a monthly or bi-monthly maintenance routine to actually measure the battery voltage with the car off and not plugged in. If the voltage gets to 11.5V or so, it might be worth topping it off with a battery charger.

I've heard that Optima batteries are really good...and also 3x the price. Might be worth looking into.
OPTIMA® Batteries 8040-218 D35 YELLOWTOP $239 retail. (assuming a regular focus uses the same battery)...
http://www.optimabatteries.com/us/en/find-a-battery/?year=2012&make=Ford&model=Focus&engine=&find_button=Search

 

[WattsUp]

it makes me wonder why they put in the battery they did...

It's probably just the same one that goes into the ICE version.

 

[davideos]

...I also noticed my charge voltage is only about 12.66v on the level 2 charger, so I must be having charging system issues as well.

Measure your battery voltage after the car has been plugged in awhile as well as before you start charging.

Before I started charging my car this afternoon, I took the following measurements....
12.03V unplugged with car off
12.8V plugged in 120V with car off

An hour and a half later, I read...
13.33V plugged in 120V with car off.

The car charger is likely feeding in a constant current source. As the battery charges, the voltage will increase. If voltage were constant, then the voltage would be fixed and the current would vary....high at lower battery voltage and lower as the internal battery voltage increases.

I believe with a bad 12V battery, the internal resistance of the battery is high, so it doesn't take much current to make the voltage increase to the max charger voltage. So If you measure your battery with the car off and not plugged in and then measure it again with the car plugged in, if your voltages are pretty much the same, then I would suspect your charger is bad. But if your pre-charge voltage is 12.0V and your charge voltage is 12.66, then I would think the charger is ok.

The one thing I don't know yet, is if the 12V charging continues when the High Voltage battery is done charging. I think I've read here that it doesn't; however, I will know this evening when the car is done charging.

 

[davideos]

With the car done charging now, the battery measured:
12.34V plugged...and unplugged. The value was 12.03V before I started.

Anyway, bottom line, if you don't get much run-time to charge the battery to compensate for the power consumed while not running and not charging, you could be deficient on keeping the 12V battery charged. Simply being plugged in will not charge the 12V battery....it will only charge if the High Voltage battery is being charged as well.

 

[Gatorman82]

Well, I just looked into replacing my battery myself, and they make it VERY hard to remove the 12V battery. Since I'm under warranty, I've decided to have it taken to the local Ford dealer. I am going to request that they upgrade the battery, though - even if I have to pay for it.

 

[davideos]

If you let your battery sit for one day without charging, what is the voltage? If you are around 12V or more, your battery might be fine and the problem might just be the parasitic draw of the car.

However, your battery may have degraded since according to your Ford Manual, you should be able to go 30 days without running the car. Ford suggests disconnecting the 12V battery only if "storing" the car for more than 30 days.

If you do upgrade the battery, make sure the capacity is more...and/or the quality. A higher quality battery may let you go longer without having to disconnect the 12V battery....but that is hard to say exactly how much you will get.

If you frequently don't use the car for several weeks, a trickle charger might be a good investment. It would have to be connected directly to the 12V battery since the car disconnects the accessory power adapter a few minutes after the car is turned off.

 

[Astrand1]

The other thing to keep in mind. Since we know the 12v battery gets a charge while the HV battery is charging it stands to reason that those using level 1 charging should have a better charged 12v battery simply because it's charging so much longer than level 2. At the studio my car is parked at now only has level 1 so it took 7 hrs to charge, so I figure the 12v battery got the same 7 hr charge as apposed to level 2 that would have taken like 1-2 hrs. Just another thought.

 

[LJinLACA]

Hey all:

Took the FFE into the dealer today, and they replaced the battery no problem. I have the service advisor looking into what the proper float charge should be when plugged into 120 or 240v. It has to be higher than 12.66v. When the car is on, the DC to DC converter is putting 14.65v on the system. I was only able to see the low float voltage due to the battery being well below voltage - otherwise a healthy battery would be masking the low float voltage itself.

Since the DC to DC converter is providing ample current to charge the accessory battery, they have this tiny reserve battery because it really doesn't do much work. Keeping the car alive during unplugged status is it's main function, and when plugged in it is being float charged so we don't need a massive battery. The biggest concern I have is the quality of the battery. The good news is a simple booster battery will get you up and running to the shop absent a completely shorted system, with a simple jump to get the DC to DC converter online. Then you are good until you shut the car off. I told the dealer not to shut it off until they got it to the stall. As soon as they turned it off, I received low battery text messages.

Replaced Defective Battery.

I also received a reprogramming of the IPC module - instrument panel cluster...

Hope this helps.

LJ

 

[jeffand]

For the 12volt battery to charge it must have a voltage over 13 volts, or charging will not be afffective. The vehical plugged in you should see 13.5 volts. Then the car is switched on the battery should be about 14.5 volts. Note: These readings are taken after the values had time to stablize. With only 12.5 volts on the battery when the car is charging will result in the battery never being fully charged. Lead acid batteries age faster when they are left in a discharged state.
Level 1, or 2 charging resulted in same voltage being applied to the 12 volt battery.

 

[davideos]

The charging circuit appears to be more dynamic than I originally thought. I've been monitoring it the last couple of days. Here's a few more oddities:
When I first turned the car on this morning, the accessory plug goes up from 12.01V up to 14.35V. After a few miles, I looked at my meter again and noticed the voltage had dropped to a range of about 13.5V. I had originally though constant votage at 14.35V, but this suggests that the circuit adapts; likely it realizes the battery is full. When I got to work, I turned the car off and back on again and the voltage jumped back up to 14.35V. I didn't wait around long enough to see if it dropped.

Next I also reported that the charge voltage when plugged in was in the neighborhood 12.8V at the start. Agreeing with jeffand that a charge voltage less than 13.5 is likely inaffective, the charger probably starts low and works its way up.

Anyway, it is fun to speculate. Now I need to get a chart recorder and a current meter.

 

[jmueller065]

Adding another piece of data to this thread:
I just returned from a 10 day vacation. Before leaving I set up a test go time with the climate control off. During the active 20 minutes or so of the go time the voltage at the cigarette lighter read 13.5V--enough to hold a charge.

So for the 10 days my FFE would sit in the garage plugged in to my Level 2 EVSE I setup two go times roughly evenly spaced that would just "start" the car and not turn on the climate control. When I got home the 12V battery was just fine and the FFE drove normally.

Granted this solution won't work if you can't get the go times to work properly.

 

[jeffand]

Wow, this is a simple method of keeping the 12 volt car battery charged. I would recommend doing this if car is parked for more than 10 days. If you do park your car for more then 4 weeks you will likely have a dead battery if you do nothing. You could also buy a battery maintainer. It charges the battery to a voltage then shuts off. When the voltage drops below a certain level it switches back on.

For this to work the car must be plugged in.
Turn off the climate control and all assessories.
Turn the headlight switch to the off position.
Then program a go time for every day.

The car will power up for every go time and charge the battery for 20 minutes.

 

[Astrand1]

Another easy and free way to keep the 12v battery topped off is to get one of those 12v solar panels and put it on the dash and plug into the 12v outlet. Those are always hot so it would trickle charge the battery while the car sits. Of course that's if it's outside.

 

[jeffand]

I thought the 12 volt power outlet is switched off when the car is powered down. So this may not work.

 

[unplugged]

I thought the 12 volt power outlet is switched off when the car is powered down. So this may not work.

No, interestingly on Ford products, the 12v outlet is always on. (I use it to charge my video recorder battery while I am at a game and might need to recharge the battery. Same thing for your phone.)

 

[WattsUp]

I thought the 12 volt power outlet is switched off when the car is powered down. So this may not work.

No, interestingly on Ford products, the 12v outlet is always on. (I use it to charge my video recorder battery while I am at a game and might need to recharge the battery. Same thing for your phone.)

Right, I had a Honda for years... the 12V jack is only powered when the key is in the "accessory" or "on" position. I assume there are some other auto makes that behave the same way.

But, yup, in my FFE, the 12V jack is powered all the time.