@h00ligan Most hobbyists and RC use LiPo 2s & 3s which are 2 or 3 cells in series, and use a special balance charger to charge them, I have one for my Darwin Mods squonker which has a 2s LiPo.
If the mod is made by an expert then anything that uses 2 batteries in parallel should in theory drain both batteries equally at the same time, unfortunately that is not always the case, and quite often one battery will become depleted before the other triggering the mod to say low power, you then take them out, put them in a charger to find that one battery still has quite a bit of power in it. That is why it is
advisable to marry them, and swap them around each time you use them, some people think that is not necessary.
Now with batteries in series the first battery always gets used first with the second one topping up the first as it depletes, if my understanding is correct, therefore both batteries should be the same when mod says low power. All the forums I have been on state that the batteries
must be married and should be swapped around each time you use them, so that each battery has a fair share at being the primary battery.
Myself, I prefer to keep any dual batteries together and swap them, that way I do not have to worry about whether the mod is parallel or series and would advise anyone to do the same, apart from the one parallel mod I mentioned before when I had the 1 battery empty 1 battery 3/4 full problem which cured itself after the first recharge/swap, I have never had any problems using my preferred method.
I have also noted in the forums that they say that if you split a married pair then they should only be used a a single battery afterwards.
We had a high of about 29C today, but think your heat is probably drier than ours, we tend to swelter, steam and sweat and most homes don't have full aircon, SM might not have anywhere close to you, but they probably have a few resellers in the states that could sell to you over the Internet and that way you would know they were genuine and save on the shipping from Germany.