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Disconnecting the High Voltage Battery?


Taiwwa
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I would only trust an independent mechanic with non-hybrid stuff such as brakes or filter changes or bulb changes etc.    Do you really want a mechanic messing around in there when they have indicated a lack of confidence?

 

As much as a object to dealership service prices, they are getting regular bulletins and updates from Ford.

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Took my Cmax hybrid to an independent mechanic. They didn't want to do some work on it because they were afraid of the liability from the battery. How tough is it to disconnect the batteries?

Not sure about the hybrid, but there is a disconnect behind the right rear passenger seat on the Energi. But so long as they stay away from the HVB and transmission, it should be no trouble.

 

However, I also only service mine at ford, except for tires. The vehicle is too complex, and it is all computerized.

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Took my Cmax hybrid to an independent mechanic. They didn't want to do some work on it because they were afraid of the liability from the battery. How tough is it to disconnect the batteries?

What work wouldn't they do???  Like stevedebi says there's a disconnect on the Hybrid also.  See this link and page 12 for the disconnect for the Hybrid.

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I took my Prius to an independent garage once and I didn't realize it at the time but the 12V battery was weak so they couldn't get it started.  I eventually got the car started under its own power but the look on the mechanics' faces as they tried to find the battery to jump start the car under the hood was enough to make me never take it back there again.  At least they are telling you they don't want to work on it, There are multiple computers in that car and they are all easy to fry if you introduce voltage the wrong way.

 

Having said that I did give someone a jump start one time and never had a problem, I guess I was lucky that my friend didn't gun the engine and cause a bunch of current to come back through the other way.

 

I actually had small issues with the Toyota service manager too, they were trying to save me money by using multi-spec ATF fluid but Toyota has a TSB about using very specific fluid in the Prius.  Save $20 in ATF fluid in order to pay $3K for a new transaxle later when the insulation on the motor windings shorts out.

 

So far the Ford techs seem to be doing okay with the C-MAX, then again for being such an "unreliable" car the only time mine sees the garage is for oil changes and tires.

Edited by jestevens
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I've got mixed feelings on this one...  Off the top of my head:

 

-I trust my independent  mechanic across the street WAY more than I do my "Ev Certified" Ford dealer.  This was true with Toyota dealers as well.  I finally called around to about a dozen and found ONE that actually instilled confidence in me.  But I'd still only go there if I had to.  The majority of my experience with dealers in sales, service and parts is that they know less than I do yet talk like they know it all and are happy to charge $120 an hour.

 

-Most independents definitely do seem a bit more nervous around hybrids.  Mine said they wouldn't touch the hybrid system, but had no trouble doing any of the few repairs I needed on my Prius over 6 or so years.  

 

-I'll agree there there should be respect for the HV components, but I think a lot of the concerns are less founded.  If the car isn't "ON" then there's no HV outside of the battery itself.  Otherwise they could do away with the entire 12V battery, etc.  The ONLY purpose that the little 12V has is to Boot up computers that verify it's OK to turn on the HV Relay.  It would be a much more efficient, reliable operation to just not have a 12V battery and instead leave the HV battery connected.  But in the interest of safety we've basically got a 40lb battery that amounts to the same purpose as a switch.

 

-Sure, there are lots of computers in the car, and theoretically you could fry them, but just how would one go about introducing voltage to do that?  I mean do we think someone's going to accidentally have the car running, and then cut through the large orange HV cable and then run a jumper wire to the 12V side of things?  or just connect the 12V cables on backwards?  Again, now we're back to stupid stuff anyone can do on any car and screw things up...

 

 

Now, if your battery pack dies and your buddy Joe has never even wired up an electrical outlet but tells you he's going to take apart the battery and take a look, I'd be concerned.  but otherwise I'll much prefer my competent independent mechanic to look at things instead of the dealer.

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...  The majority of my experience with dealers in sales, service and parts is that they know less than I do yet talk like they know it all and are happy to charge $120 an hour.

 

-Most independents definitely do seem a bit more nervous around hybrids.  Mine said they wouldn't touch the hybrid system, but had no trouble doing any of the few repairs I needed on my Prius over 6 or so years.  

 

...  The ONLY purpose that the little 12V has is to Boot up computers that verify it's OK to turn on the HV Relay. ...

 

I have that same feeling with my dealer.  Creepy.

 

I wonder what kind of 12volt battery we have.  Since it doesn't have to turn the engine, is it more like a wheelchair battery, steady low amperage over a long period of time.

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I wonder what kind of 12volt battery we have.  Since it doesn't have to turn the engine, is it more like a wheelchair battery, steady low amperage over a long period of time.

 

http://www.fordparts.com/Commerce/PartDetail.aspx?n=6YLiDeXwiM6gbahIM7SREg%3d%3d&id=388654604&m=44&search=true&year=2013&make=Ford&model=C-Max

 

So the C-Max battery does not appear to be a deep cycle battery (wheelchair type battery).  Looking at the picture it seems to have 390 cold cracking amps which assuming the HVB starts a C-Max is not necessary.  My Dad's electric scooter battery is about that size and 35 amps but it runs a scooter a really really long time.  A battery about that size that starts a riding mower runs a scooter for about 45 seconds though it has lots more amps (cold cracking amps).  

 

There may be advantages to using a deep cycle battery in the C-Max.

 

Having jumped my car when the battery had been dead, I do believe the car is started with the HVB.  (Though this implies that if the HVB is dead, the car will not start.  But will charging the 12V battery charge the HVB ? )

 

(By the way, it is around 30 lbs.)

Edited by obob
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-I'll agree there there should be respect for the HV components, but I think a lot of the concerns are less founded.  If the car isn't "ON" then there's no HV outside of the battery itself.  Otherwise they could do away with the entire 12V battery, etc.  The ONLY purpose that the little 12V has is to Boot up computers that verify it's OK to turn on the HV Relay.  It would be a much more efficient, reliable operation to just not have a 12V battery and instead leave the HV battery connected.  But in the interest of safety we've basically got a 40lb battery that amounts to the same purpose as a switch.

 

I'm really interested to see how the Hyundai Ioniq and Kia Niro do, without the 12V battery. 

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My experience has different with Ford Service because I found a smaller dealer in a rural area.  The reason I trust the service department there is because they were able to reprogram the BCM to turn off my DRLs.  It's a small thing but they could have easily said, "We can't figure it out".  But they listened to my concern and it was no problem for their service manager.  They also did 3-4 recalls (including airbag replacement) and an oil change in one day for me.

 

I once needed to make an appointment at later hours so I scheduled service with one of their high volume dealerships (5 time Presidential award winner or something) and had a terrible experience.  I had inspection, oil change, tires replaced and an alignment done, waited quite a while and they never showed me any paperwork from the alignment, the notes didn't record the tire wear,,.  I don't think the advisor was being untruthful but it would have been nice to see -something- for the $90 cost of that alignment which he first said would be free with the tires.

 

If you find an independent mechanic who specializes in the car that's one thing but I'll never forget the look of bewildered amazement on the face of those guys when they lifted the hood of the Prius and were trying to find where the battery terminals were..

Edited by jestevens
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http://www.fordparts.com/Commerce/PartDetail.aspx?n=6YLiDeXwiM6gbahIM7SREg%3d%3d&id=388654604&m=44&search=true&year=2013&make=Ford&model=C-Max

 

So the C-Max battery does not appear to be a deep cycle battery (wheelchair type battery).  Looking at the picture it seems to have 390 cold cracking amps which assuming the HVB starts a C-Max is not necessary.  My Dad's electric scooter battery is about that size and 35 amps but it runs a scooter a really really long time.  A battery about that size that starts a riding mower runs a scooter for about 45 seconds though it has lots more amps (cold cracking amps).  

 

There may be advantages to using a deep cycle battery in the C-Max.

 

Having jumped my car when the battery had been dead, I do believe the car is started with the HVB.  (Though this implies that if the HVB is dead, the car will not start.  But will charging the 12V battery charge the HVB ? )

 

(By the way, it is around 30 lbs.)

 

There's 2 ways of looking at what you want for the 12V battery... One is smaller and lighter weight.  I recall a post somewhere of someone who built LI-ION batteries at work and he made a custom one for his C-Max.

The other is if you're going to leave it sitting for longer periods of time or otherwise leave it in any state that's just using up the 12V battery.  In that case the little battery does not hold up very long and I agree, not being deep cycle it really doesn't like it.

 

I'm not sure of the exact needs of the C-Max but with the Prius, the biggest load on the battery was the pump for the brakes.  Estimates were around 30 amps for a few seconds or so while it built up pressure, but that was about the most it ever had to deal with.

 

 

-If you manage to kill your HVB and actually have zero voltage in it, then yeah your car is well and truly dead as far as motive power.  There's nothing to start the ICE with at that point and even if you got the ICE started, you still need the HV side of things to run the MG's to make your planetary transmission work to get power to the road.

I'd guess there are some safeguards in place to prevent the HVB from ever getting drained that far.  If you do manage it I'd guess it's similar to the Prius in that you need a special charger from Ford, or else you'd have to find someone handy with such things to get it charged for you.

 

No, charging the 12V will do nothing for the HVB.

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My experience has different with Ford Service because I found a smaller dealer in a rural area.  The reason I trust the service department there is because they were able to reprogram the BCM to turn off my DRLs.  It's a small thing but they could have easily said, "We can't figure it out".  But they listened to my concern and it was no problem for their service manager.  They also did 3-4 recalls (including airbag replacement) and an oil change in one day for me.

 

I once needed to make an appointment at later hours so I scheduled service with one of their high volume dealerships (5 time Presidential award winner or something) and had a terrible experience.  I had inspection, oil change, tires replaced and an alignment done, waited quite a while and they never showed me any paperwork from the alignment, the notes didn't record the tire wear,,.  I don't think the advisor was being untruthful but it would have been nice to see -something- for the $90 cost of that alignment which he first said would be free with the tires.

 

If you find an independent mechanic who specializes in the car that's one thing but I'll never forget the look of bewildered amazement on the face of those guys when they lifted the hood of the Prius and were trying to find where the battery terminals were..

 

Feels about like the opposite around here.  I'm in the rural area.  My EV certifed Ford dealer certainly didn't seem overly busy but they:

-had online appointments that they never responded to

-only took down my info on a sticky note

-I told them my problems like 5 times to several different people over the course of a couple days(not that they ever bothered to call me and give me an update)

-The responses I got were things like

-"Oh"

-"Nope, doesn't work for us either. Maybe try contacting someone at Ford on the website."

-"There is no problem with your GPS(Cause mine was showing it off by several blocks at various times).  But if you wanted us to troubleshoot further, the first thing you would need to do is buy a $189 map update.  It's just like your phone, you have to do that every year."(Never mind that my roads haven't changed in over 50 years).

 

-I've since fixed the GPS myself by updating the GPS module.  Apparently the 10 minutes it would have taken them to do that was too much work or some such thing.

 

 

The better dealers I've found are up near the larger cities.  Not saying that they are all good, but the single ones I've found are there.

 

Also not going to tell you that all independent dealers are great. There are some lousy ones and there are some that are great but just haven't seen a hybrid yet.  But I get the impression you might see the same look of surprise in a lot of Ford dealer garages as well depending on when and where you are...

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