This is Just for Safety.....write to the PCM at your own risk
For maximum Safety...
Never write to the pcm without guaranteed power.. Meaning plug in your laptop laptop..and double check the connection to make sure the Laptop is Charging and getting power...a lose connection could mean you are running on your Laptop Battery
If yoy are in a shop.. On the dyno... There is no excuse for not having the laptop plugged in while writing to the PCM/ECM
If you choose to write to a PCM/ECM and are not around any available power sources and are relying on laptop battery.. Be sure all sleep and hibernation is turned off on your laptop
You also may want to set a higher percentage for low battery warning and never write below that level
There is never any reason why you absolutely have to write to a pcm with a low battery
You can always wait till later when you can plug in the laptop for safety
Also Remember that some PCM's/ECM's cannot be recovered by any conventional easy methods if you suddenly loose communication with it.
Thankfully Many newer PCM's/ECM's are designed in a way that they can never be truely "fried" from a mishap....
but lets not risk it...
please play it safe and make sure you have power