Ultra Fit USB 3.0: Excessive Heat

I’ve got mine, a 64 GB Sandisk Ultra Fit 3.0 yesterday (SDCZ43).

Completely agree with others that this USB stick runs too hot! I also noticed that the performance dropped when it gets too hot and resume after several seconds passed.

I share the same concerns like others that this USB stick might somehow damage my USB 3.0 port.

I had the 16 GB Sandisk Cruzer Fit 2.0 and this one runs much cooler. Is it anything I can do to get rid of the heat issue rather than return it?

same here, i bought 64 GB SanDisk Ultra Dual USB Drive 3.0, i just plugged-in only (both PC and my Android phone), not doing anything, then it gets very hot. Do you solution for this, @dromedary? i am afraid that i bought defect product. Can we get replacement for it? If you have, please share your solution.

thank you and best regards,
Gunawan Agung

In addition, I measured the current drawn by the Ultra Fit USB 3.0, it is more than 4x higher than the current drawn by the Cruzer Fit USB 2.0.

Ultra Fit USB 3.0 = 896 mA

Cruzer Fit USB 2.0 = 200 mA

Could this be the reason of the overheat, considering the physical size is not much larger while the power has increased 4 times.


The first answer from “Sandisk” is critisism towards a Sandisk user.

I plugged the drive in my computer and it got hot.

It got hot before I transfered anything to or from the drive.

The longest that I can touch the plugged in drive is 4 seconds before I have to pull my hand away.

I get the same result from USB2.0 ports, USB3 ports, and my MP3 player.

The flashdrive has a 5year garantee, but I assume that does not cover the equipment the dirve is plugged into…

SanDisk… your responses are aphauling, grabbing at anything the users say to shift the blame?

Cruser fit 8GB

The first answer from “Sandisk” is critisism towards a Sandisk user.

Can you provide a link to the “first answer” your referring to?  Cause the first answer I see is mine and I don’t see any critisism. 

And BTW this is a users forum, posters are people who use SanDisk products just like you do.

Hi There,

Just to let you know, I have found that this disk overheats, and found many threads about it like this one, that’s why I registered

My Cheap no-name USB 3.0 sustained 20MB/s with my test copying a movie file and a folder full of photos.

The SanDisk UltraFit starts at 90MB/s then all of a sudden drops to about 20MB/s for the rest of the transfer. I note if I pause the transfer for 10 seconds and then resume the speed ramps back up to 90MB/s and again drops off. I did this test many times, even trying different ports.

Really disappointed that my cheap USB stick is better overall than SanDisk. I was expecting that SanDisk was high quality but I am concerned that frequent use may end up doing some damage due to the heat problem. So after paying about 5 times the price of my cheapo USB I now have a dud product. Why should I have to wait for the SanDisk to cool down, I bought it for high speeds so I can get things done faster.

I’m sure many of you have seen this on their website:

So Small You Hardly Know It’s There. So Fast You Barely Have to Wait.

This ultra-small, low profile drive stays put for extra storage, or moves media super-fast between devices. Enjoy performance speeds up to ten times faster than USB 2.0 drives, transfer a full-length movie in less than 40 seconds.

ripped off

Do the excessive heat posters use the drive’s SecureAccess app on it?  I could see encrypting & decrypting large or many files on the drive being a load that could cause excessive heat.

I did not use any encryption appl. Only a plain disk, formatted normally and written with normal copy from either Windows Explorer and Linux.

Even worse, without copying anything, the flashdisk also becomes hot by itself.

formatted normally

So you are not using the USB drive with the factory format?  How did you reformat it and to what format?

Nope. I never trust the factory format as they do mass production and it is understandable that some may be formatted not perfectly. I always reformat on my own computer to let the flashdisk formatted structure matches the computer format.

Format normally = insert the flashdisk to USB port, wait until it is recognized by Windows Explorer (i.e. assigned a drive letter). Then right-click the drive letter and select Format.

The goal of the factory format is as a Super Floppy and is designed to maximize the efficiency of the drive.  Windows format does not support the Super Floppy format and may not even care if the drive is removable.  It’s just not a goal of Windows format function.

So did you format it as NTFS or exFAT?

It is very possible the overheating problem is a self inflected problem.

Doesn’t matter whether NTFS or exFAT, both runs extremely hot.

So what is the “factory format” standard and how can I do this?

@chin wrote:


So what is the “factory format” standard and how can I do this?


You can’t. You already burned that bridge when you re-formatted it because you didn’t trust the factory format.

So what is the “factory format” standard

For drives less than 64GB FAT32, for drives 64GB and larger exFAT., but all in superfloppy mode with the drive as a single partition. No partition table, no MBR.  And neither format has journaling which NTFS has that adds overhead to a drive.

@Tapeworm: if what you claimed is true, does Sandisk make this clear to the consumer? I do not see any notes neither guidance re. this factory format in the packaging.

@Ed_P: as I informed earlier, using exFAT does not help to reduce the heat either.

Is it anyone from Sandisk in this forum to help to explain this?

it’s a basic engineering problem. as you put more functional stuff into a smaller space, you get more excess heat. there are workarounds to deal with overheating, but the problem is always present (unless there’s a radical change in technology). this is why computers and game consoles have built-in fans, they would overheat and shut down otherwise.

I’ve had the same issue with my 128gb sandisk ultrafit. the metal gets burning hot when I transfer gigabytes, and even when I leave it in without doing anything, it’s hot right after ejecting. it makes sense actually, because they maximized efficiency - with as much speed and memory in as small a space as possible, there has to be a tradeoff: excess heat.

I’ll assume on good faith that sandisk is aware of this, and that QC determined that the excess heat is not enough to cause damage to hardware. But naturally it’s alarming to the end-user, and I wish they’d been more up-front about this.

In the meantime, I’ll still use it, but I’ll limit my usage to be on the safe side. It seems to especially heat up in my laptop. I’d think adding ventilation holes would’ve helped but there could be design reasons I’m not aware of.

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“I’ll assume on good faith that sandisk is aware of this, and that QC determined that the excess heat is not enough to cause damage to hardware.”

Have you seen the photos joeydee posted?


@xcalibur: you said “the metal gets burning hot when I transfer gigabytes, and even when I leave it in without doing anything, it’s hot right after ejecting” — I agree if it gets hot when there is data transfer, but when it is idle doing nothing, what makes it get hot?

In my logic, if it gets hot when idle, it will be no surprise if it overheat and fail when it is “in action” (i.e. huge data transfer). One thing to clarify, did you copy files into it straight away “out of the box” or did you reformat it before transferring anything into it?

My primary concern (which I guess others’ too) is whether this excessive heat will damage our laptop (i.e. USB port or burn/melt the palmrest area where the USB port is located)?

Sandisk does provide warranty but only on the stick (which makes sense), not our laptop neither USB port. Therefore I guess many would rather not to use, or at least use with high caution.

@Ed_P - those pics didn’t show up until I clicked the link. that is a serious malfunction for sure, but I haven’t had issues like that yet. you can’t rule out the possibility that it was defective and that the heat issue wasn’t at fault.

@Chin - it heats up while idle because it’s still running. there’s much more heat during data transfers.

I didn’t reformat.

it hasn’t caused any problems for my USB port yet, even though I did big transfers the other day. while I’m assuming the best, I’m still going to use it economically. for more routine data transfers I’ll probably use the 16gb flashdrives.

Thanks for the clarification xcalibur. This rules out the factor that the heat issue is caused by reformatting the stick (as explained earlier in this topic).