Showing results for 
Show  only  | Search instead for 
Did you mean: 

Cannot communicate with battery - 7D


Dear Friends,

I am a proud owner of 7D for the past 2.5 yrs and have done many trips and shooting with that.

I am not using any battery grip. Have 2 Canon original battery with me.


Fromyesterday night I am getting an error  "Cannot communicate with battery". It is same described in the below link also :-


I am using Original Canon battery and I have tried with both of them but no result.

As per User Guide ,


If the message "Cannot communicate with battery" is displayed when checking the battery status, select [OK] and continue shooting. Please note that the battery level indicator will appear blank.


My concern is :-

1. If I ignore that and continue shooting , will it create any problem to the Camera functionality ?

2. Wil the battery drain fast due to that ?


I am Ok with not displaying the battery infor as of now ( which I will repair by Canon) but need to confirm that the battery functionality will remain as usual. I will be travelling for a birding trip soon and I due to short time I dont want to send it to repair...


Please guide.


Warm Regards,



Count me in, as well.  I've contacted Canon and a local shop and it looks like I'm going to be out about $300 either way.

I called canon 1-800 phone number.  Spoke to a nice gentleman who said I could continue to use the camera.  When I get the message that says, "Cannot communicate with battery, cancel or OK".  I just have to click OK.  It works fine.  Trouble is I will never know when the battery is dead,  Therefore I'm charging batteries and making sure I have the extra in my pocket.


When and if I choose to send it in, they will tell me what the cost is.  If I say no, they will return it at their expense.  Hmmm.  what should I do?

I will give it a try and see if it works.  Thanks for the feedback.  Like you said, why should we spend $250 when we don't have to?


My 7D is now a few years old, never had a problem with it until now, seemed to be working OK, until

I changed lenses, turned it on, and bingo, the same error message that hundreds of 7D owners are

receiving.  I cleaned the battery contacts, no good, I even tried the freezer thing, didn't do squat.

Removed all batteries, including the coin cell, powered up, same problem.


In a search I found where one person took their camera apart and found  some screws out of place,

one actually floating around in the camera.  Rumor is there may be loose screws and some kind of

connector problem.  If that's true, sounds like a mechanical problem.  By the way, had the same problem

with one of my Canon lenses, the zoom stopped working, I was out of the country and had no choice but

to take the lens apart in an attempt to fix it.  Same problem, a screw came loose and was floating around

inside the lens housing.


I do most of my own camera repairs, I'm about to dig into the camera to find if I have the same problems,

loose screws, loose connector, etc.


I haven't heard a single explaination for the problem that makes sense to me.  With so many complaints

it's got to be a design or manufacturer's flaw.  I haven't contacted Canon, not about to spend more money

on the camera when it seems to be their problem.


I had the same problem with my GL-2 video camera, with the transport.  They wanted several hundred

dollars to replace the tape drive, which they charged many people.  Eventually they would do the repair

for only the labor, kind of like what I've heard on the 7D situation, that's still too much money.


I'm not afraid to take the camera apart, so if anybody has any ideas out there, please share, and I'll

share what I find.  Other than that, the Canon 7D is a great camera, just doesn't work right.



I am afraid to take my camera apart.  But I will try the cleaning of the battery connectors.  At this point the camera still works as long as I say OK to the message that says 'battery cannot communicate with camera'.  It just appears that I have a dead battery.  I make sure I always have an extra and charge them frequently.   AND YES it is very annoying that canon doesn't seem to think they should fix this for free, when it happens all too often to too many people. 


I have spoken to them.  They are very noncommittle and say I should just send it in.  Go figure..........



I've been reading posts from all over the internet about "fixes."  One that I've read so often is to clean the

battery contacts with a pencil eraser.  How many of these people making suggestions have even

seen the contacts?  The contacts on the battery are tiny slits, you can't hardly see them.  They are

"wiping" contacts, that is as the battery is inserted, two knife-like contacts in the camera slice into

the battery contacts.  If there were a tiny amount of oxidation or corrosion on any of the contacts,

the wiping motion cleans them.


If it were a bad battery contact, which I do not believe it is, at least where the battery contacts meet

the camera contacts, the camera would not even work.  The big complaint here is the sensing circuits

in the camera are not getting correct battery readings.


Many devices today, batteries, even print cartridges contain a small memory chip, which keeps track

of usage, number of cycles, amount of ink or charge remaining.  If the circuitry cannot read this chip,

the device thinks the battery is bad.  I've seen this on laptop batteries, where there is nothing at all

wrong with the battery, it is the battery management circuit inside the battery housing that is at fault.

I've never seen a laptop that says "unable to communicate with battery," hit OK to resume, at least

Canon give you that option.


When an after-market manufactures a battery for use in a camera like Canon, they have to install

a chip that mimicks the Canon chip.  I have one no-name battery that does not contain a chip, and

therefore, I would get the message, "cannot communicate with battery" message, so I hit OK.  I

have other batteries made by known companies, Lenar for example that have a Canon-compatible

chip and work fine.


From reading the posts, putting sensible information together, it seems like it is mostly a mechanical

problem, creating an electronic problem.  Circuit boards are held in the camera by tiny screws, and

if the screws aren't tightened properly, they may work loose.  The worse case, they come out entirely,

touching other parts of the circuit board, ultimately shorting traces together.  In other cases, the screws

may come loose, developing a bad connection from the circuit board (PCB) to the camera's frame.

I have a gut feeling that is mostly the case, until the screw actually falls free, causing catastrophic

damage.  There in a built-in electronic flash in the camera, it needs a few hundered volts to discharge

through the xenon flash tube.  It is produced by a dc-dc converter.  The charge is held in a capacitor,

until it discharges through the flash tube.  It can be a lethal voltage, and if a screw should short circuit

between the flash circuit to another part of the circuit, fireworks bigtime.


The only explaination for fixing the camera by cooling it by putting it in the freezer is that cooling causes

contraction, a tiny movement of the parts, which may temporarly be good enough to re-connect loose

connections, which in my opinion, will go bad again.  We have a term, "things that fix themselves,

eventually unfix themselves."


Pulling the main battery and the small coin cell may reset the memory in the camera but is only a

temporary solution, if it even works.  Again, the camera will eventally "unfix itself."


I've seen tare-downs of the 5D and others, where people have changed out the CF memory connector,

and other parts.  One thing I don't want to do, is mess with anything that may change or alter the camera

calibration, because that would mean another trip to Canon, which I'm trying to avoid.

Obtaining a service manual from Canon is about impossible, they

only sell them to their "authorized" service centers.  Once in a while one will leak out and find it's way

to the internet, I've seen them on other cameras but not on the 7D, at least so far.  It's not a matter of

paying for the manual, they just don't let it out.  I've found the parts catalog, but no service manual.

If anybody has such, I'd like a copy, would save some time.


I'm afraid to buy another 7D body because of this problem.  I have not contacted Canon, so I don't

know what their current stand is on this problem.  I mentioned I had problems with my GL-2 with

the tape drive, turns out, Canon was selling cameras with defective tape drives and it took a long

time for them to admit to it, their solution, install a new, free tape drive but charge a moderate labor

charge, which in my opinion, they shouldn't have charged anything.  Then there are the customers

who paid full price for the repairs until Canon admitted there was a problem, they didn't get their

money back.


I've been a photographer for more than 55 years, and an electronic technician for almost 50 years,

I've seen a lot of history take place in the technology world.  As I mentioned, I'm not afraid to take the

camera apart, but I don't want to do a complete tare down, I want to take the camera apart only to

get to the suspected components. Need a schematic or service manual.


Jim - Empirical Technology


This link has a couple of pics of the loose screw, the writing is in Hungarian unfortunately but the pics should assist in fixing the issue if you're brave enough to strip it down.

I have same problem with loosen screw. It's megentted to motor and short to T-line of battery.




This problem on my 7D is not resetting with both batteries removed for a few hours so it looks like I'm gonna have to break into it and fish the loose screw out of there.
Anyone have any idea how to remove the bottom panel to allow access?
Any accompanying pics of which screws to remove and in which order would be great.
I'm more than happy to get in there but if i can go in with a bit of prior knowledge it would be helpful as it doesn't look like Canon are going to offer any help to any 7D owners any time soon!
click here to view the gallery