Brice,
I believe you are pretty accurate on this. From what I have read current generations of Li ion batteries are pretty good providing they are operated within certain parameters. The parameters are a function of their chemistry and not subject to change by any one manufacturer.
Specifically they should not be charged to more than 70% of full charge nor discharged to less than 40% of full charge.
Exceeding these limits adversely affects battery life. To quantify battery life I am referring to the total number of charge/discharge cycles the battery will survive. Thus a good Li ion battery drill will just stop drilling when the battery drops to 40% charge. I understand that Festool and Protool drills behave in this fashion. As you might imagine there is a fair amount of research going on about getting access to the other 70% of charge!
With regard to the drills mentioned by Wood_Junkie....
The loss of battery life may be different for discharging beyond 40% compared to charging above 70% i.e. non linear. So having no discharge protection circuitry would give access to 70% of the charge but may reduce battery life by say 15% while also extending the working life of the drill. This could be a win for the customer and Ryobi as they then only have to stock one line of batteries and are seen to be actively supporting their customer base.
The discharge electronics may be in the battery.
This is just idle speculation on my part, however, as I have not seen the drills in question nor talked to Ryobi nor their sales people. My comments should not be seen as negative to Ryobi either, they are not meant to be. I did own a Ryobi sander that gave excellent life and would still be in use if the local agents had been easier to order parts through.
I am sure that Ryobi would have covered off all the issues related to this, with regard to the market niche of the tools in question.
Nor, by the way am I an expert in battery technology , so i would be more than happy to hear the views of anyone who really does know about Li ion batteries.
Cheers
The Beryl Bloke