Everybody is showing here well packaged elegant battery arrangements. But here are just the opposite, hastily thrown together parts and then riding...
Well, you said it, not me
And I'm sure it's great learning experience and the last thing I would want to do is slam anyone curious and energentic to do what you are doing.
But, yes, there is a more elegant solution.
My goal has always been to make using LiPoly as simple and autonomous as possible, to work towards a "Plug and Play" solution.
The first big "breakthough" came several years ago after replacing several RC (Toy) balance chargers due to failures. These were Quality chargers too, they simply don't last for Ebike usage in the long run. By going to "bulk" charging, I was able to stop "breaking" the packs to charge, avoiding accidents. The side benefit to this is the cells stay balanced better when their series connection is not always being interrupted. By using a large capacity pack relative to avg. discharge usage, it's easy to observe to 80% discharge rule, so these thing together means I no longer need to balance the cells(But I always ck. them).
My first attempt at bulk charging was w/ a 2S/3P system using first, Zippy Flightmax and then, the better Turnigy 20C. This required paralleling the balance leads, which turned out to be tricky and messy.
The next "Breakthough" was coming to understand that the best way was to stay @ 2P, which reduced the brick count, allowed me to use 4 Battery Medics and elimiting balance wiring altogether
I did not know that Hobby King has Multistar packs up to 20 000 mAh at a lower price than I had thought. A kilowatthour about 244 eur including local taxes in European Union! Unfortunately, there are no 5S packs, only 6S or 4S . For 36V I have used 5S+5S.
2S + 3S bricks can be series together to create a 5S brick. Of course, their balance taps need to be joined. There are adapters to make it easier. Also 5800 mAh and 6200 mAh 5S brick are avail. in Zippy Compact and Turnigy 20C. If a 11000 mAh or 12000 mAh pack(2S/2P) is not large enough, build 2) 2S/2P packs and keep them apart. Run one down to LVC, then disconnect/connect @ the controller.
As an oldfashioned consumer (and software and electronics hobbyist) I am used to hate solutions, where I have to throw away a product with many good parts instead of repairing it.
When the MultiStars became available and I was able to move up to larger bricks, I had 6S/5000 mAh bricks I wasn't using. I repurposed them into other projects. I now have LiPoly powered lights, heated grips and heated jacket. And a LiPoly car batt. jumper.
E.g. if there are 40 cells in a battery and one cell has gone bad: throw away 39 good cells!? What really happens if I replace the bad cell?
Although it's very rare these days to get a bad cell in a LiPoly brick, it is easy to "jump over" the bad cell. If it the first or last cell, it can be removed(Although it's not neccessary). Of course, this reduces the cell count, which may preclude using it again in a specified system.
Re magic smoke: the damages could be limited during a ride when a person is present all the time and there might be a warning from 'Banggood' cell checkers some seconds (?) before the catastrofe. Cell temperature could be sensed without stopping with one's hand when the battery is open in a basket in front of the handlebar.
"Smoking" a LiPoly while riding is rare and can only happen bricks become shunted due to worn, chafed wiring that gets "Crossed over". Over-discharging or allowing the cells to get way out of balance, while bad for the service life, does not lead to a reaction w/ low-volatile LiPoly like the MultiStar. In 8 years, I have had only one "smoking" event and it was my fault. I accidently pierced a pouch and could smell it right away. I was curious, so I opened the hole to look inside. It was glowing orange like a mini-Mordor and then it starting smoking till the energy was depleted. Rather anticlimatical actually.
Here is an image of 6 packs of Flightmax 5000 mAh, connected 10S3P.They give 540 watthours (= 0.5 kWh, = 15 Ah at 36V) in theory, weight 4.2 kg.
The motor controller ( its display at right) has an undervoltage protection (might be 31.5 V) for the whole battery but not individual cells.You see that SOC display has only 4 states.
The multimeter in the middle (mock up so far, only 5A) could show the amperes being used each moment and thus the power in watts would be roughly the Amperes times 40 Volts. (poor man's power analyzer...).
At the left there is a usual speedometer.
The yellow thing is Hobby King's cell checker, showing voltage in one pack total and 5 cell voltages inside it. 5 more thingies like that will show all the cell voltages (ordered 10 from Banggood, about 17 USD total, with audible alarm).
The shopping basket has thick foam inside.
The LVC of a 36 V controller is a little low for 10S(it's great for 9S), but is better than nothing(This is why 12S is great for Ebikes-a LVC of 42V, means stopping the cells @ 3.65V, perfect). There really is no substitute for a hard and fast LVC in the controller when using LiPoly on an Ebike. I have found that trying to monitor the batteries while riding to not be practical. The small text requires attention that would best be on the road and lacking backlighting means nothing can be seen at night. The biggest deal breaker for me was having to dis-connect all the passive devices to keep the pack from dis-charging when not in use, a major hassle that I did not want to deal w/ every ride.. I use only a LCD Voltmeter that only draws mini-Amps and can be left hooked up all the time.
two shown here, w/ backing switched on.
I will ocassionly ck "sag" under acceleration and knowing what to expect as various states of discharge, any unexpected sag, is all the "red flag" I need while riding. The time to monitor cell health is during the charge cycle, to what degree do the cells stay together, especially after a low-discharge use. If there is a concern, a dis-charge test should be run and I keep a balance charger around for just this purpose.
Bottom line; Big bricks for a brick count of four. Bulk charge using Battery Medics(The good Blue ones, not the blacks).