High voltage battery not holding a charge? (Hybrid city mpg dropping)

[Qwahzi]

Hello all!

I have ~3000 miles on my hybrid XLT, and over the last 2 tanks I've noticed that my city mpg has dropped significantly (from 35-45 to 18-25), even though weather conditions & driving style haven't changed much (90+ hot weather, tire pressure the same ~37 psi, city driving at ~45 mph or less, eco mode, etc).

Highway mpg seems unchanged (~33), but it feels like the Maverick no longer starts with any battery charge, and when it finally (after 1-5 minutes of driving) switches to battery, it lasts for less than 30 seconds before switching back to the engine (the size of the blue battery bar keeps shrinking until the truck switches), even if I let my speed drop to stay in electric mode

Any ideas before I reach out to the dealership?


EDIT:
Per Mach 1's suggestion, I attached a battery tender yesterday evening and it was still charging after a few hours, so I left it overnight. Woke up with the charging done, so I took the Maverick for a short city drive, and I was seeing much better battery performance, even with the AC on max. 14:48 drive time, 37.4 mpg, 7.4 miles total, 3.9 of which were electric. That's about what I was getting before the recent issues that dropped me down to 18-25 on almost the exact same route

I'll keep an eye on it for the next few days and see if it lasts

EDIT 2:
As the temperatures have dropped a little bit, the mpg has continued to climb back up towards previous levels. I'm currently sitting at ~34 mpg, which sounds about right for the type of driving/idling I've done recently. Also found this article:

"The Environmental Protection Agency and Department of Energy says running your AC in high heat can reduce your fuel economy by as much as 25%.​

...​

For a car that typically gets 30 miles to the gallon, that's like losing seven and a half miles."​

​

https://www.kens5.com/article/news/...think/89-b44ada20-bb6f-41ad-b447-af4fe6f7fb46

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[Scupking]

Probably because you have the AC on since it's been hot out. Just a guess.

 

[Qwahzi]

Does AC have that much of an impact? I used to get 35-45 mpg around the neighborhood pretty easily, but now even when I turn the AC and radio off I get 28 if I'm lucky. Combined mpg since my last fillup is sitting at 19, and that's non-highway miles at <50mph

 

[Mach 1]

Wow..that much of a drop off? 106 here today, still pulling downrun mine at 75-77, and that still cold in truck with vents right on us.
Might check air pressure again just to be sure. Battery charge after starting is dependent on the charge before shutting off, if you use the emode to drive home before shutting off, there will be little in battery charge. Mine will usually only have a small charge to cool Mav and get rolling before the ICE kicks in.
Thats a pretty good drop off, depends on your speed as well, i do 55-60mph and get 45mpg is the worse i can get.

18-25mpg is really bad drop off, i cant imagine that bad. Does the engine have a miss? Bad fuel?

Notice any shake of engine, power loss?

 

[Mach 1]

Theorize here..with all these battery cable issues going on with the hybrid, i could see the 12v battery not having a good charge/connection, could possibly be effecting the operation of the HVB?

 

[Qwahzi]

Wow..that much of a drop off? 106 here today, still pulling downrun mine at 75-77, and that still cold in truck with vents right on us.
Might check air pressure again just to be sure. Battery charge after starting is dependent on the charge before shutting off, if you use the emode to drive home before shutting off, there will be little in battery charge. Mine will usually only have a small charge to cool Mav and get rolling before the ICE kicks in.
Thats a pretty good drop off, depends on your speed as well, i do 55-60mph and get 45mpg is the worse i can get.

18-25mpg is really bad drop off, i cant imagine that bad. Does the engine have a miss? Bad fuel?

Notice any shake of engine, power loss?

No shaking, no weird noises, no performance impact, highway mpg is still consistent, and this has persisted through at least 2 different gas stations so far. It just seems like the HV battery is getting discharged much more quickly than before, so "battery time" has dropped significantly (impacting city mpg)

 

[Qwahzi]

Theorize here..with all these battery cable issues going on with the hybrid, i could see the 12v battery not having a good charge/connection, could possibly be effecting the operation of the HVB?

Hmm, not a bad theory (bad 12v battery/connection draining the HV battery?). I'll try jumping it and/or changing the battery to see if it makes a difference

 

[wax87]

Does AC have that much of an impact? I used to get 35-45 mpg around the neighborhood pretty easily, but now even when I turn the AC and radio off I get 28 if I'm lucky. Combined mpg since my last fillup is sitting at 19, and that's non-highway miles at <50mph

No the AC is not the issue

 

[Mach 1]

Q..read up on the battery cable issue on the hybrid..i just thru that out there..a bad connection..causes voltage variations that do crazy things to electronics..this would be my first place to go..its just the connection of the 12v at the frame? Good luck..keep us in the mix..

 

[Eagle11]

Hello all!

I have ~3000 miles on my hybrid XLT, and over the last 2 tanks I've noticed that my city mpg has dropped significantly (from 35-45 to 18-25), even though weather conditions & driving style haven't changed (90+ hot weather, tire pressure the same ~37 psi, city driving at ~45 mph or less, eco mode, etc).

Highway mpg seems unchanged (~33), but it feels like the Maverick no longer starts with any battery charge, and when it finally (after 1-5 minutes of driving) switches to battery, it lasts for less than 30 seconds before switching back to the engine (the size of the blue battery bar keeps shrinking until the truck switches), even if I let my speed drop to stay in electric mode

Any ideas before I reach out to the dealership?

Why the dramatic subject heading?

If you are running the AC on MAX, it will affect the MPG, but not as much as you say has effect yours. If the battery was failing you would get a engine light on.

 

[Eagle11]

No the AC is not the issue

Do you have hard data to back this up? I have data to disprove you..... BTW is was 114 here in PHX..

 

[fbov]

Any ideas before I reach out to the dealership?

No, go to the dealer, explain what you see and ask for them to interrogate diagnostics for any codes. My dealer will do that for free.

Do you have hard data to back this up? I have data to disprove you.

Love to see data from a hybrid with electric AC showing any mileage impact. I can't find it in my driving. My highest mileage is in the hottest months, but then, we call three 90-degree days a heatwave. You call it a weekend.

 

[Qwahzi]

Theorize here..with all these battery cable issues going on with the hybrid, i could see the 12v battery not having a good charge/connection, could possibly be effecting the operation of the HVB?

I attached a battery tender yesterday evening and it was still charging after a few hours, so I left it overnight. Woke up with the charging done, so I took the Maverick for a short city drive, and I was seeing much better battery performance, even with the AC on max. 14:48 drive time, 37.4 mpg, 7.4 miles total, 3.9 of which were electric. That's about what I was getting before the recent issues that dropped me down to 18-25 on almost the exact same route

I'll keep an eye on it for the next few days and see if it lasts

 

[LGA737]

AC takes a small fraction of the power that moving a 2 ton vehicle around does. Running it will definitely reduce mpg, but I would be surprised if it were more than 2 or 3 mpg.

I have a Tesla and when I’m heavily using the AC, my watthours/mile goes up by about 10%.

Andy

 

[Mach 1]

Q, sounds like you are on to something. Although you are starting out with a fully charged HVB. Yes you will be getting better mileage, i would think a DMM will help you further now. Start looking at that 12v battery voltage. To see if your problem is the charging of the 12v.

I started watching mine and i saw 12.35VDC the other day and that was the first time i took a reading, i am trying to figure a more permanent 12v gauge. Where i can keep record at a glance, instead of tilting rear seat and opening battery box and connecting leds. Hope this helps.

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