There is nothing wrong with your battery temp. You can also check you CPU temp (nope, maybe you will have scared
)... Fortunately you didn't saw your CPU temp during your 4 Antutu runs...
The temperature (CPU or battery) depends of your room temperature and your current use. You said yourself with 4 Antutu runs the temperature increase, nothing abnormal even for the battery..., same thing after browsing for 20 minutes even in wifi.
A guy had 24°C battery temp in idle and 34°C max, well, what was the room temperature? Nothing running in background? What he was doing?
I mean even in idle, screen off, your phone can do a lot of things especially if you have a rogue app keeping the CPU busy so there could be a little more heat.
In any case there is a thermal protection (thermal throttling) to prevent damages in case of "overheating" for both CPU and battery the CPU freq decrease according to the temp. Even the screen brightness can be automatically lowered. In last case the phone shutdown if a high temperature is reached (about 100 °C for the CPU). The max battery temp should be about 50°C, I don't remember exactly.
Don't worry, as you reported there is nothing wrong with your tempetatures... Same thing if you take a look at your CPU temp, can be arround 70°C in heavy use, even a bit more in really heavy use.
We have a quadcore device running at 2.26 Ghz, all is enclosed without thermal cooling... it's normal to have "heat" with all the components.
Use your phone and profit, no need to monitoring each minutes your temperatures. You confused yourself by only reading the °C, not how or why it is compared to the other posts you read. Each user have different room temperature, use, settings, etc... you can't have the same temperature as xx user. An average yes, I agree and here you are in the good average...
Sent from my LG-D802 using xda premium