Hey all, been lurking for some time now and gathering tons of useful information...just joined up in the hopes of getting some input on an interesting situation that I have on my P2 (non-vision).
Long story short (somewhat), I have had issues with my P2 picking up satellites from day 1 when I received the unit back in mid-december. Sometimes it seemed to work fine and others I couldn't seem to pick up any sats no matter how long I waited (I have now figured out why).  Here is the conclusion that I have come to with a little guidance and a lot of tedious troubleshooting:

The battery on my GPS module appears to be discharging very fast...not sure if it is due to a dead battery or a short somewhere causing battery drain.  I have verified by measuring voltage with a multimeter that it gets down to 0.0 to 0.2 volts after a full day of sitting.  If the P2 has been powered off for 20 mins or more, the P2 will not pick up satellites no matter how long I leave it on.  I have left it on for as long as 30 mins and it will pick up zero satellites in an area with good view of sky and sats verified via phone app.  Now...if I turn the P2 off and back on again, it will pick up sats like normal within a minute or two at most.  

From further testing, I have verified that if it has been left powered off for an extended period of time (an hour or more) and if:

-  I power it on for 5 mins and then power cycle it, it will still not pick up satellites.

-  I power it on for ~10 mins and power cycle it, it will pick up satellites but take a little longer...maybe a couple mins.  

-  I power it on for 15+ mins, it will pick up sats within a minute of being powered on.

Based on input from others, it seems that the GPS is starting up with no memory since there is no battery backup and takes longer to pick up sats.  In the meantime, it seems as if the P2 is timing out on waiting for a GPS signal from the GPS module (or is the module timing out on sending a GPS signal to the P2??).  Either of these scenarios would explain why on a cold start (if P2 hasn't been powered on for more than 10 mins within the last 20 mins) the P2 does not pick up any satellites no matter how long I wait.

Has anyone run into a similar issue before.  I have searched high and low and can't find anything other than maybe a couple of other posts about someone seeming to have a similar issue but not figuring out why.

Any suggestions on options moving forward?  If its just a bad battery, it seems replacing the battery should be an easy fix.  Not sure how the battery is installed, but it seems to be held in there quite firmly and I don't want to use excessive force at this point to remove and risk slipping and damaging anything.  Let me know if anyone has replaced a battery on the GPS before.

My ideal scenario is to get a replacement GPS and I am communicating slowly with DJI right now.  Don't think they fully understand my scenario and just want me to send it in for repairs.  I'm trying to avoid having to ship it off for a few weeks it if it is as simple as swapping on the GPS module or replacing the battery.  

There is a little more background to the story if anyone is interested, but I have already rambled too long.  Any input is much appreciated!

Brian

Hi Brian,

welcome to the forum. Firstly, your trouble shooting is awsome! I wish more would go through a great effort finding the fault on their own first or at least have a good look into the issue.

I have also never heard of a problem like you are explaining yours. I do suppose that the battery might not be charging properly and may be causing your issue, or like you say, the GPS module itself might be faulty. Changing the battery should be your first attempt. The GPS module will cost you well over 100 $ and a battery approx 1$. I have never removed mine, but I suppose you could just lift the hatch with a screwdriver and slide the battery out, I know it can be done without causing any damage. I wouldn't send mine in for repaire either (at least not before I tried my best first).

Hope you get it fixed.

Markus

Thanks for the reply markus.  I attempted to lift the hatch with a moderate amount of force and it wasn't budging...didn't want to try any harder and risk damaging something at this point.  

Here's a little more background to the story:

Purchased in mid-december and spent a lot of time reading on the forums and DJI manuals to learn as much as I could while i was waiting for the delivery truck.  Set mine up with H3-3D, iOSD mini, and immersionrc 600mw tx.  Started off flying in Phantom mode but shortly after switched to NAZA mode only as I realized the benefits.  Became fairly proficient at flying and took the P2 to our property.  

Had 65% battery left on my second battery and wanted to do one more flight before we headed home.  Flew from an open field to over some timber and within a minute and a half upon powering up the P2 began returning to me on its own and then stopped and began descending straight down into the timber.  Caught some limbs on the way down and had quite the fall, but damage wasn't too bad.  Battery had dropped to 7% within that brief flight.  H3-3D brackets were severely bent and a couple of broken props.  Contacted DJI and was very pleased with customer service.  I sent the H3-3D in for repairs and also sent the P2 for a "post crash inspection".  DJI repaired the H3-3D at no charge and turned it around in about 3 weeks.  They indicated the crash was due to a 'possible' bad cell and replaced the battery an no charge. Note that after the crash, I could still fly the P2 with no issue and still had GPS lock (although finicky as described above).

Seemingly, DJI was having the same issue that I have been having with the GPS.  Here is their exact response:
"We have tested both batteries and replaced 1 due to a 'possible' bad cell. We also replaced the center board due to no GPS output on the Phantom. "

I replied and indicated that I was able to fly with GPS after the crash the same as I could before, but I have had issues since day 1.  DJI's reply was as follows:

"When we first test flew your Phantom to drain both batteries to find the flaw that would auto descend, we could not get a GPS lock no matter how long in was in the air, even after replacing the GPS module it still had the same GPS problem. The center board was at fault, even though it registered the GPS firmware and loader in the Phantom assistant software. - Possibly damaged after the crash."

So sounds like they replaced the main board and the GPS module.  I can't say with 100% certainty that I am having the exact same issues now that I was before sending it in, because I hadn't yet diagnosed the issue, but knowing what I know now it seems it was the same.  I would try flying at my backyard and would leave it powered on for 20 mins with no satellite lock.  Then would drive a mile down the road to a park and would pick up sats within a minute.  Upon returning home I could pick up satellites.  

So it sounds as if DJI replaced both my main board and GPS module (unless they tried new GPS module and it didn't work so they switched back to the original) and I am still having the same issues.  I have re-opened the ticket with them in an effort to get this fixed without sending it in.  Really hoping they will send me a replacement GPS module that I can swap out and confirm if working, then return my GPS.  

I think I am being reasonable in asking DJI to send a GPS module at no charge since this is unresolved from when I just sent it in.  I have done all of the diagnostics and troubleshooting thus far and provided a very detailed description of my issues for them to confirm my logic.  All that I get is a reply saying that I have to send the unit in for repairs.  

Let me know if anyone can find any loopholes in my logic.  Is it possible for anything outside the GPS module (or battery) to cause the issues I am having?  Any other recommendations appreciated.

See those three dots on top of the battery bit? Its spot welded to the battery. Im sure you can break the welds with a bit of care but not sure how secure it would be after replacing battery...

Phantom2Flyer Posted at 2015-2-16 09:21
See those three dots on top of the battery bit? Its spot welded to the battery. Im sure you can brea ...

Thanks for confirming that.  It almost appears to be soldered at the base also, although I didn't look too hard when I had it opened up a few days ago.  Either way, the tack welds explain why I found it to be so rigidly placed in there.  Don't think I'll mess with it at this point, not worth the risk.

Shortly after I got my Phantom as a Christmas present I was flying it in my backyard one night. I was low to the ground and I hit our bird bath. I had prop guards on and it wasn't a hard hit. The was no physical damage, bit it would no longer pick up any GPS sats.
I opened it up and checked all the connections and they were fine. I went to a hobby shop that sells and services drones and I got to talking to a tech and told him I crashed and was having issues with my GPS. The 1st thing he ask me was if I recal'ed the IMU. I hadn't. When I got home I recal'ed the IMU and the GPS worked. The only downside was after the IMU cal now the yaw drifts a little.

Don't know why it worked because the GPS is connected to the motherboard and not directly to the IMU, but it did.

JATO Posted at 2015-2-16 11:09
Shortly after I got my Phantom as a Christmas present I was flying it in my backyard one night. I wa ...

I've calibrated IMU multiple times with no change in GPS issues.  Compass also.  Thanks for sharing your experience though.

brianh Posted at 2015-2-15 18:47
Thanks for confirming that.  It almost appears to be soldered at the base also, although I didn't look too hard when I had it opened up a few days ago.  Either way, the tack welds explain why I found it to be so rigidly placed in there.  Don't think I'll mess with it at this point, not worth the risk.

Same slow GPS lock issues here.. Just checked the GPS Battery in my P2V+ v3 and it's at 1.1volts. I'd really like to replace it. Any ideas as to what type of battery it is? VERY tiny, can't possibly hold much energy!

I'm reasonably certain I could splice-in a slightly larger 3.0 volt button cell