12V Battery Replacement

Discussion in 'Ford Hybrids' started by GaryG, Oct 1, 2007.

  1. GaryG

    GaryG Well-Known Member

    My Hybrid Tech stated that he had to use the built-in Jump-Start Procedure 3 times before my HV battery would start the ICE. He said it was getting near 3yrs old and the heat here in Florida takes a toll on it so I should consider replacing it.

    Suggestions have been around that our standard car battery should be replaced with a deep cycle battery. After thinking about that for a while, I decided I would stay with a battery that met the specs of the original OEM. I have been noticing a drop in my battery SoC even while my generator was charging my HV battery. I thought the 12V battery was taking a big adjustment from the DC/DC converter to top it off when I seen those drops in the SoC. It seems that this is happening more often now. For all of the reasons above, I've been looking for a replacement. After all, if replacing a 12V battery may improve my mileage by holding a charge longer, it may be worth it.

    At first, I thought just go to Sears and get one of their best Diehard batteries. Sunday I was in Costco and thought I'd take a look at the replacement they recommend from their line. Costco listed a 96R, 500 CCA for a replacement, but they had none in stock. Today, I called Sears and they said they only had a Diehard Gold that would fit. When I ask for the specs, they gave me a 40R, 590 CCA. I told them that Costco's book said I needed a 96R, 500 CCA, but he said Ford recommended their 40R battery as a replacement.

    At this point, I did some research to find out what the difference was, and looked at the battery in my FEH for the specs and measurements. I found that the 40R and the 96R had to do with the measurements and CCA ratings. The stock Motorcraft battery was a BXT - 96R, 500 CCA. I've always thought the stock Motorcraft batteries were junk and I would never replace one with another.

    After digging into warranty and size, I found the Sears battery would not fit, and I had the same problem in a Ford Focus I own a while back. I was not about to cram a big battery in the holder again. The generic 96R was very close to the stock replacement size, but I would still not have a perfect fit in my stock battery holder as the stock Motorcraft battery.

    Both the Costco and the Sears batteries had a 3yrs replacement and 100 month prorated warranty. The Sears wouldn't fit and the Costco 96R was not in stock, so I did some research on Motorcraft batteries.

    The higher end Motorcraft battery offered the same warranty as the Sears and Costco battery. At this point, I called the dealership and ask if they carried the higher end "MAX" Motorcraft battery. They told me no, but they had the stock BXT - 96R that was the stock battery for the '05 FEH for $85 which was $2 less than the Sears that didn't fit. Then, I found out that the BXT - 96R Motorcraft battery had the same warranty as the Sears and Costco battery, which was 3yrs full replacement, 100 month prorated coverages.

    I had no idea I have 6 months of full replacement value on my stock battery. Any recommendations or ideas of what I should do?

  2. MyPart

    MyPart Well-Known Member

    I would talk to the Hybrid Tech again and see if he has any pull with the dealer (or Motorcraft) to get a warranty replacement. He should work with you since it was his recommendation in the first place and he's seen the issue first hand.

    It's my understanding that the jump-start function on the FEH uses power from the HV to quick-charge the non-HV battery. If the non-HV battery can't take a quick charge then it's probably on it's way out.

    You can also go by any local auto parts store and have them check the standard battery with a load tester. They are usually quick to point out an under-performing battery. Take this recommendation with you when you try to get the Motorcraft warranty replacement.

    Heat will kill batteries: I recently moved from MA to SC and the heat killed the battery in two separate cars. One was a <2 year old Gold series battery. The other was <1.5 years. Both replaced for free under warranty. (thanks to Autozone and my retention of receipts)

    What factory warranties came with your '05 FEH? I thought that there was a 3yr/36,000 Bumper to Bumper that covered just about anything and then the 8yr hybrid warranty for drivetrain/emissions.

    Did the '05 have the 5yr/50,000 roadside assistance program? If so, wouldn't your tow for the previously mentioned relay issue have been covered by it?
  3. GaryG

    GaryG Well-Known Member

    Good points about going back to the dealership and also getting a load test for documentation. Carl also suggested monitoring the voltage with the SG also and I'm going to do that as well.

    The 12V battery does not spin the engine for start-up, but it's needed to supply 12V systems power to start the engine such as spark, fuel pressure and modules. The 12V battery boost the HV battery with the jump start procedure, not the other way around as you stated.

    I only have the 3yr/36,000 mile warranty and the roadside assistance is only covered during that time. However, if the problem was my HV battery or eCVT which is still covered, my SA said the tow would be covered also.


  4. hobbit

    hobbit He who posts articles

    I would closely question then as to what the hybrid battery
    SOC was before they went to jump it. There should seldom be
    *any* need to do that under normal operation...
  5. GaryG

    GaryG Well-Known Member

    The problem keeps coming back and I'm left with a no start if I let the FEH sit for two days. Last week it would not start again so I when to the dealership in my other car and talked to the Hybrid Tech again. He told me a little more about finding both batteries low. I had tried the jump start procedure several times with no luck and he again said Ford was telling him it had to be a problem with the low voltage system.

    I went a head and bought a new OEM 12V battery hoping to save a tow fee ($131) and installed the new battery in my driveway. It still would not start so I did a few more Jump start procedures again. At this point, with the old battery and a portable jump start box and a new battery I had done about 7 jump start procedures. No luck so I called for a tow for the next morning to the dealership. I left the keys on the console for the tow guy when I took my wife to work. The tow guy got to my house and it started for him. He drove it up on the ramp and took it to the dealership. It started again when he got there.

    The Tech told me he had to reset a bunch of codes having to do with low voltage to all the modules, but everything was checking out good. He said he contacted Ford again and they told him again it was a low voltage problem that must have reset itself over night.

    Well, yesterday I had the same problem, so I've used the Jump Start procedure and recharged my new battery with no luck. I've disconnected the 12V battery and put it on the charger for the night and will try again tomorrow.

    Any ideas folks? Back to the dealer again I guess.

  6. brick

    brick Answers to "that guy."

    I'd be interested to know how much current the car is drawing on stand-by. It sounds to me like you've got some kind of parasitic load or else there's an intermittent fault between the battery and the 12V system. If you can check current draw, maybe start with that. The next thing I would do is spend some time with my head in the engine bay looking for bad connections, especially bad chassis grounds. That kind of thing isn't exactly expected on something as recent as '05 but not unheard of either.

    Even simpler than messing with an ammeter, have you just put a volt meter to the battery terminals to see if it's really down? Especially the new battery? That'll tell you if it's being drained (or not charged.)
  7. CarlD

    CarlD Well-Known Member

    If it's not starting with a charger attached to the 12V battery, then it must be either SoC too low or the HV contactors not closing. Do you have the xgauge firmware yet? If so there are many,many things to look at with regards to the battery.

    I would guess something more than a power sustain relay was bad last time...

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