Phantom batteries are a little more than simple lipo batteries...
DJI call them intelligent batteries...
What DJI say about it?
Intelligent ? The board fitted to the DJI batterys ..... mmmmmm ...
Lets look at a DJI battery. I have had a number apart and myself and others as a group have tried various actions ...
a) The cells used are LiPo High Voltage versions that top out at 4.35V per cell. The top 10% of charge acts as HV and then the LiPo follows same pattern as a standard 4.2V per cell LiPo ... this is why standard LiPo cell storage advise works 100% for the HV version as well.
b) The cells do have balance and power leads, but both go to the small circuit board fitted at front of pack inside case.
c) The board reduces the connections to outside to two sets ... main +/- and the secondary smaller +/- contacts.
d) The boards main function is as Charge controller. It replaces what a LiPo charger has and means DJI charger is a plain regulated power brick of 17.5V only. The board monitors charge rate and terminates at the 17.4V total voltage state.
e) Secondary action of the board in terms of battery is to have the setting of when auto discharge is initiated. DJI default is 10 days. This is ok if the P3 is used often .. but is not advised as 10 days is too long. Any damage by having full charge then is accumulative. Better to reduce this to 2 or 3 days maximum. The discharge is ';resistive discharge' - this means energy is dissipated as heat and therefore is slow. Discharge continues at steady rate till below 65%, then slows and continues... well past 50%. Eventually battery reaches a low level of storage and enters Hibernation mode. This then basically cuts off discharge and only physical chemistry takes over.
f) The board has a third function of providing battery data for telemetry based on the balance lead connection. This relays to your display the voltage of each cell ... no load when on ground, loaded when flying. The general display is an average of the 4 cells figures.
OK onto the 'myths' of this 'intelligent' board.
1. It is a total voltage monitor at heart and does not actually correctly balance or even out cells.
2. When charging - once it detects 17.4V regardless of cells inbalance - it terminates charge, unlike a LiPo charger that in final stages balances cells.
3. Deep discharge is not fully monitored or controlled and therefore risks damage to one or more cells. The board terminates at a total voltage figure.
It would be very good if DJI would actually give the information we would all like to have - but they do not and myths get repeated and become accepted fact. Its then very difficult to convince some of the errors.
I will not claim to be 100% correct - but all above has been observed and tested to be as accurate as we can determine.
One of my biggest concerns : is the DJI charger in fact. It is same as your Laptop computer supply .. a regulated power brick. Nothing special, nothing fancy. It will deliver 17.5V till you remove power from it. It has no safety cut-out that we could find. This then means that it relies on the Battery and its Board to cut out when full charged. What happens if there's a fault in the battery or board ?
I prefer using a LiPo charger because I have a second safety back-up .... the LiPo charger will cut out immediately it detects a fault ....
Nigel