SyncUp & Drive kills batteries/alternator

I recently added the SyncUP & Drive device to my account - we are long-time T-Mobile customers and have not had any problems whatsoever besides this to date. My son was getting his license and I wanted to be able to monitor his driving. The SyncUP device worked like a charm for the first week or two, until the battery started dying nearly every night. This battery had been replaced less than 6 months prior, so there should not have been an issue. I was going on a trip, so I decided to let him drive my SUV while I was out of town since he was having problems with the battery and I wanted him in a more reliable vehicle. I also have a new battery in my vehicle, about one year old and also had my alternator replaced between 2-3 years ago. Well, when I was on my trip my battery started dying and then after a couple of days my son had the vehicle completely stall on him while driving. This device not only killed my battery, but my alternator! Fortunately, the batteries were both still under warranty but my alternator cost me a pretty penny. These devices sound absolutely amazing for teen drivers but they are most definitely too good to be true!


Best answer by tmo_amanda 22 June 2018, 19:38

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Userlevel 3

Hey, @hjchase1​! 

Welcome to our Support Community! Gosh, that's not a great first experience for your son especially since he's just getting on the road. It doesn't put your family in a great position either with this happening to two vehicles from the sounds of it. I listed next steps in a different thread you commented on: SyncUp Issues​. Please follow those steps to get a ticket filed so our Engineers can figure out why this is happening.

Userlevel 4

Hey there!

Just wanted to check in and see if you were able to fine a ticket like Amanda suggested!


Userlevel 4

Just checking in again on the ticket possibility! 😊


I just added a syncup drive to my 2017 Honda CRV two weeks ago.  Car is less than a year old.  It has worked with no issue for the past two weeks, but last night it killed the battery in my car.  Prior to this, there was an anomolie seen where the device kept saying it was offline and then the battery went dead.  after the anomolie, the care did start and I was able to drive to my next destination, but after two hours of being stopped at that desitnation, the car was dead, but the syncup drive was actually online again.

I believe the dead battery was caused by either the unit staying on, or it causing something else in the car to stay on.

I have removed the syncup drive and the battery has been fine..

I also got the sync up Drive and it was put in my vehicle on Monday so it's been less than a week and I noticed the lights flickering on my dashboard in my speedometer needle and RPM needle. I assumed it was the sync up system trying to check my car system, I'm not sure? It didn't happen all the time but periodically while I'm driving and woke up this morning and there's absolutely nothing working on my car no lights absolutely nothing it's the completely dead my battery is less than a year old so now I have to try to tow the vehicle and I attempted to use the synced up roadside assistance after 3 phone calls and two of them being hung up on what they found is that the device doesn't start with the normal numbers and they can't find me in their system either so now I have to figure out how to get my car towed and figure out what's going on with it the device is still attached but it says it's offline. I'm not sure what's going on but I'm not really thrilled. I love the idea of the fact that the device lets me see what's going on with my car but these other problems are less than ideal and couldn't come at a worse time.

I picked up a SyncUp on 12/21/18 and plugged it into my 2007 Chevy Silverado.  It connected no problem and appeared to be working fine.  Later that day the red battery light stayed on after the truck was started.  Voltage gauge showed the alternator was not charging.  I removed the SyncUp but the problem persisted.  I took the truck home and disconnected the negative battery terminal to reset the OBD2 system.  Two hours later when I started the truck, the red battery light went out and the charging system was working fine.  I repeated the scenario again today with the same result.  For some reason the SyncUp shuts down the charging system of the vehicle.  Obviously I am reluctant to plug it into another vehicle for fear of damage to that vehicle's charging system. 

Perhaps I have a defective unit or is there a problem with the programing of the unit?

Does T-Mobile have any idea of what the problem is ?

Hmm, interesting. My car has been done recently and we've been at a loss for why it's been doing this. I've been having other small issues with the device saying a trip has ended, but it hasn't. I'm unplugging device and calling t mobile tomorrow about it.

I too, had issue with this device.  This device killed my battery.  My car stalled on the freeway and i was lucky to be able to pull to the shoulder.  Very scary.  This device is NOT safe and should NOT be promoted by TMobile.

We had the same issue. I got the Sync-up when they first came out. Had minor issues all along but didn’t make the connection that it was this device. My husband was driving my daughters car when it completely shut down on him while driving. He managed to get to the dealership and they told us to never use it, that they cause tons of issues. We didn’t use it for 4-months but am trying it again til we find something similar (she doesn’t drive far so we feel “okay” using It for the short, local drives).

Good morning,

I am currently posting on this thread due to the fact that, I have purchased two sync drive devices in the past year. I added them to my BMW and Honda, Originally my concern was the notifications of disturbances were really slow. Then this past year soon after i connected the device to my BMW my vehicle died on me and would not turn on, my alternator and battery died, i did not think anything of it. I traded my BMW in for a Toyota highlander that same week of the malfunction. At this point friends and family suggested it might be the Sync drive, I looked past the comments. Sure enough this past December my Honda civic began to have electrical problems starting my vehicle, battery was recently new, and i also had to replace my alternator and starter at the same time. I have been maintaining my vehicle well, and this was unfortunate. The reason why i am writing this comment due to the fact that my vehicle needs to be inspected by today, and sure enough when i take it to the Inspection location they are unable to initiate the inspection due to my car not being able to turn on unless the Sync drive is connected. I contacted the T mobile support number and no one has answers for me, at this point I have lost my patience and am frustrated being that i have been paying for this service and devices and both of my cars that i utilized these devices on, have had issues that are in fact costly. I really need answers, I looked past all the trouble shooting aspects of the device being that i can live with minor, but having my second vehicle die on me this is outrageous and i refused to let this go without any answered or clarity.  

Why is there no reply from tmobile? I too had big electrical problems and I am scared to let my 16 year old daughter drive with something that is not tested enough. If I don't get an answer from tmobile I will raise hell on social media.

I have been thinking of getting some thing like this for my truck. Reading these responses brings back memory of a PANIC I had, the truck had lost the belt at night (the alt., power steering, water pump belt). After the belt was replaced, there was little charging, noted as the voltage was at the nominal 12.8V. So there was a nail biting trip back 230 miles worth. With some research, I found that the vehicle was smarter than the driver, there is a charge control on the negative cable, to extend battery life.  So during the day time driving the voltage is kept about the 12.8V, but most of the time at night (or with headlights on) voltage does go up to 14V, presumably for the 14V headlights, or when the battery is cool and needs charging.

Now for the 'kills the battery' it would be possible to drain a battery through that connection, but it would take some time.  The OBDII line that powers the plug has a 15A fuse, so current high enough to over power a 150A alternator, that does not figure.

This fact finding will apply to most all GM vehicles. 

did anyone got help from tmoible? i am having the similiar issue with my battery. The syncup drive shows offline and the battery dies more often in my nissan rouge. I never had this problem. My car even starts acting weird while driving. I am scared to drive car in this condition.  but reading this thread, i came to know it is because of the syncup drive. i unplugged the syncup drive, after coming here and seeing other people had the same issues. How can we make tmobile pay for this damage? 

I’ve had this problem twice but not with T-Mobile, it was with the Verizon Hum. I figured out what the fix is. After you drive your vehicle, make sure to TURN WIFI OFF from the app!! The wifi staying on constantly will slowly kill your battery. It’s fine driving with the wifi on, but if you know your vehicle will be parked for over an hour or two, just turn off wifi to be on the safe side. Once I did that with the Hum, I didn’t have anymore problems. I just got my Syncup today and I’m following that same rule as I did with the Hum. Hope this helps. 

It's December 2021 and this is apparently an ongoing issue.  I received to back to back low battery warning just now and the first about 12 hours ago.  I'm pulling it out of the car and returning it and canceling service on the device.  It should have been fixed 2 years ago when these reports started coming in. 

I just purchased  the syncup drive is it safe to use I have a new car 2021 kia forte can someone please give me some information on it

At your own risk and don't trust what t mobile says.  My mechanic says it almost fried my cars power management system.  I ripped mine out.  Plus you'll get very anoid at the constant notices when someone is using the car and it dawned on us we were now open to having our car hacked.  if you're in your 14 days, get rid of it while you can. It's a gimmick and dosnt do anything your phone in your pocket can't do except kill your car battery and power management for me a $1200 part.  RUN AWAY!

Rodgerinmichigan how do I contact t-mobile to send it back I'm new to this I just received the syncup yesterday and do I get my money back. 

Call customer service to lock in your intent to return.  You'll likely have quicker service if you can get to a t mobile store.  If not, good luck on waiting for a mailer.  We've already several mailers behind and waiting over 6 months on a mail return.  I recommend changing providers.  That's what we are getting ready to do.

I don't have phone service with them just got internet service with them..

Roderinmichigan t-mobile full of bs I called the nearest store told me I had to call customer service to return the device back

I just received this in the mail and will be returning it promptly. Not only does it seem to wreak havoc on cars, t-mobile seems to continue to ignore this issue over the past couple of years.

I will definitely be returning it today after 10 times calling tmobile finally got someone to send me the return package to my email what did the syncup device do to your vehicle..


I too, had issue with this device.  This device killed my battery.  My car stalled on the freeway and i was lucky to be able to pull to the shoulder.  Very scary.  This device is NOT safe and should NOT be promoted by TMobile.

would this have anything to do with the car recall airbags etc.  that's strange

My battery has died twice since I got this device within a week. Coincidence? Don’t think so, the battery is less than a year old. Today, the car started losing power on the highway, and eventually died on the exit ramp while showing the battery warning light. Luckily, it turned back on and the battery light disappeared; but the car had little power. Called AAA, they said the battery was fine and that it was the alternator (aside from the battery not receiving a good charge and trying to provide power to make up for the failing alternator). Car is now at Audi and it sounds like this darn device is going to cost me around a $1,000 in repairs. To make it worse, and I’ll admit it’s pretty funny, the device says my battery is healthy and shows good amps even when the battery died a few days ago and I had to get it jump started, and today when the battery icon turned on and the car was clearly struggling. T-Mobile probably won’t care, I’ll call in the morning; but if you don’t want to risk damaging your car do not get one of these. Just suck it up and pay the premium for your car’s built in wireless service or use your phone as a hotspot. If you want to spy on your teen driver (not why I got this) just stick an AirTag or Tile into the car, or have a pro install a good dashcam (some offer 4G/LTE, not aware of 5G).