Should I be concerned?

[Genzeka]

So I just went to charge my Mavic batteries. I have a total of 5 batteries. I pulled the batteries out of this case (pic below) & noticed they were warm, one warmer then the next. I check the battery that was in the Mavic & it was cool. I checked my 5th battery in a separate battery case & that was cool. Why would my 3 batteries in the Mavic case be warm?

 

[Simmo]

Because they are self discharging mate. The number of days before discharge commences is in the app.

 

[MAvic_South_Oz]

If you tested the two cool batteries anytime after the others, or completed a charge on them under 10 days, then that over rides the discharge.
You probably had the 3 warm batteries unused for 10 days by the sounds of it, and flew then charged 1 and 5 last time out.

Leaving the batteries fully charged is not good for the LIPO batteries, that's why they discharge automatically.

If using the Mavic regularly, you can leave them charged, but always best to check batteries before heading out for a flight and top off any needed.
If not planning a flight for a week or so, I will just end flights at 30% or so charge (1 solid and 2nd led flashing) and not bother charging until ready to head out again.

You can set discharge time down to 5 days i the app settings for the battery (or 9, 8, 7, or 6 days).

 

[Montypaks]

I just ordered the same case but I only have 4 batteries.

You could get the battery terminal covers if you're worried the case material might be slightly conductive

 

[GerdS]

covers if you're worried the case material might be slightly conductive

The battery contacts are hidden deeply within the connector and so they are safe against short circuits made by accident. There is no risk.