recharge without cpap? hdm/breas z2/z2 extended life battery

[qwertyuiop]

I have a z2 small travel cpap from breas/hdm. I need to use it off grid for multiple days, then recharge in one night before using it again if grid for multiple days. I'm considering buying the extended life battery with powershell and two additional batteries. However, this will only work if I can recharge all 3 batteries at the same time. What I've read says that the cpap needs to be inside the powershell in order to charge. Is this true? Any other way to charge 3 of these batteries simultaneously?

Thanks for any help you can offer!

[HoseCrusher]

I don't see any accessories that allow you to charge additional batteries. It looks like you charge the battery in the powercell. Call them and see if they can offer something different.