I'm late to this thread as I just joined and wanted to share my experience/setup here. Reading through this thread I realize very much I simply 'got lucky' with the combination of batteries and bags I went with - thanks for the tips about better protecting the insides of the bags against wear and such!
The batteries I carry are Bionx 11.6Ah which weigh a little under 9lbs each. I built up a Giant Toughroad SLR 2 last year with Jones Bars, a Bionx D500 motor (the first one I every bought on a cheap bike in 2017) and for bags I went with the easy to use Ibera rack, top bag and panniers:
Rack:
http://www.ibera.info/products_detail.php?cID=2&Key=31
Top Bag:
http://www.ibera.info/products_detail.php?cID=1&Key=4
Panniers:
http://www.ibera.info/products_detail.php?cID=1&Key=19
*everything was available at least last year on Amazon.
For my 'longer' rides my setup is to carry water bottles and food in the top bag and 5 batteries total - 1 on the downtube and 2 in each pannier. The panniers are rated for 25lbs each I believe so the 18lbs of batteries I put in has been fine and since the Bionx batteries are 'rounded corners' along with riding only on roads - I haven't seen any wear in the panniers - but! I will look to add a bit of padding to the bottom now that I read this thread (thank you).
Here's a photo of my bike setup with 5 batteries and 6 water bottles (4 in the top bag, 2 on the mounts) for a typical long day out:
And yes, with that much weight on the bike, and no where to install a mounted kickstand - I love the Click Stand I found and use anytime I don't have something easy to lean the bike up against.
Last year I did get adventurous and did 2 rides with all 7 of my batteries. I put the final two in the top bag for a total of 6 (54lbs) of batteries on the rear rack. Don't forget I'm a 270lb rider on top of the seat as well, lol.
It worked...but at that weight the front wheel would get loose and wobble above 30kmph, causing me to have to stand up and lean over the front to give it more weight (only happened on downhills thankfully). With that issue aside, I managed to a 150km and 163km ride out with over 1,200m of elevation thanks to all the batteries I had with me.
This year I'm both building a new bike that I will share with once complete with extra battery capacity and until then riding this bike but with a new setup. The new setup is to better carry multiple batteries and also other gear with me, grocery store runs, camping gear for weekends away (hopefully campgrounds open soon) - all done by going with a Burley CoHo trailer that I can use with most of my bikes simply by upgrading to the 'Burley Ballz' (love that name, lol) for the attachment point.
The trailer rolls along at 40kmph without problem, even with the larger 3" 'fatty' tire installed and the spring suspension works great for protecting the load inside the trailer. I will try out the skinnier 'road' tire that it came with originally as well but with the 3" tire working well on road it also means it will be ready to go for dirt/single track riding when I hook on to my other bikes.
Above I was out with 4 batteries in the trailer and all my water bottles in the top bag. I could have added the panniers but simply did not need them for this day - I did 85kms riding between towns with battery life to spare.
My goal is to pick campgrounds 100-120km away (lots of them within that range from my place I have learned) and pack up with tent, batteries, food/water and chargers for a weekend and to out, enjoy the time outdoors and ride back.
Thanks again for the tips shared in this thread. Hope I helped with what I have shared as well.
Cheers