My intention is to replace drone controller batteries with a 5v power bank. So I can charge my phone and use the drone controller with the power bank rechargeable batterys.
My question is can I hook up 2 batteries in series to get the 7.2v needed to power the drone controller without damaging the power bank? Also will the the power bank charge the 2 batteries in series fully?

 

Welcome to AAC!

My question is can I hook up 2 batteries in series to get the 7.2v needed to power the drone controller without damaging the power bank?

It depends. The weakest cell in the 2 batteries will rundown first and be forced into polarity reversal. A relatively small reverse current to kill a battery.

BTW, this can happen in any multi-cell battery. Battery pack manufacturers match the batteries to get better performance in a pack.

 

Also will the the power bank charge the 2 batteries in series fully?

How can a 5V power pack charge a 2S battery (7.2V nominal)?
Charging cells in series requires a dedicated balanced charger. Lithium batteries are dangerous if not charged/discharged properly.

 

Each cell in a 2S pack can be charged separately from 5V by bringing out a 3rd wire. You may want to balance from that. Since you don't describe anything about the chemistry of your batteries, I am assuming you mean lithium batteries.

 

If you are going to use a 2s battery pack to charge your phone you need a 7.2V to 5V buck convertor and to charge the two batteries you need a 2s charger, see below:

https://www.aliexpress.com/item/328...chweb0_0,searchweb201602_4,searchweb201603_52
https://www.aliexpress.com/item/400...chweb0_0,searchweb201602_4,searchweb201603_52