okay cool! il look into that, the batteries are around 3,5€, so for a 6S4P thats around 85€, what is a good BMS, i have no experience with that 
You in the states? If no nkon.nl is a good source for batteries. 2,90€ for a q30 and they legit About bms I can’t say so much Look bestech here in the forum Maybe there is a group buy at the moment If no you can find them on Alibaba.com
im from belgium, and yes i have got 18650 from nkon before (vape) what should be the rates for a BMS, you maybe wanna chat private, thats a bit easier 
If you stay 6s, I think HK Graphene 65c will be good for you. Or if you stay with the blue packs, put them in parallel, 6s2p. You’ll need to be more consious if you go 2p though. Some rules of thumb to make them last:
- charge to 4.1/cell. This will increase cycle life by like 50-100%.
- try to figure out how much energy you spend per mile. charge to 4.1/cell, ride for a set distance, like 3 miles, then charge, and take note of how much watt-hours your charger puts back in. Divide by the distance, and you’ll see watt-hours per mile.
- don’t discharge more than say 60%, based on above. This will give lots of safety margin and your packs will be less stressed. The bottom 30% of a pack is usually not so great anyway, lots of sag, etc.
- try to store the cells around 50% charge
I think, hobby lipos are expected to do about 50 cycles. 150 cycles if you treat them real nice. If you treat them like I said above, I would not be surprised to get 300 or more cycles.
The HK Graphenes seem to do a lot better, like 1000 fairly abusive cycles. So they cost more but are way cheaper in the long run (unless you get unlucky or make a mistake).
the graphenes are like 65$ for a 3S 5000mah 75C, thats kinda expencive is 18650 not a better solution? also for charging and using?
You won’t match the high current capabilities of lipo with 18650 without going really big on p groups. And assembly is a lot more involved and fraught with danger. But generally they’re a lot more tolerant of abuse and have longer cycle life (HK Graphene kind of changes the cycle life picture). Also some people have had bad luck with Graphene packs. It may vary batch-to-batch…
Above 8s it gets hard to charge with hobby chargers, but with 6s you can do interesting creative one-plug charging tricks using hobby chargers.
The 75c are new and more $$. The ideal thing is to catch a sale on 5000mah+ 65c+ packs.
18650 and lipos are both good though. Just different pros and cons.
Can’t always trust what you read on teh interweebs!
12? Damn dude, you got me there! I’ve only destroyed two… maybe I got lucky?
I take no disrespect, no worries! I agree, caution first for sure, we’ve seen way too many fires recently. I think part of the problem is also cheap cells from unknown Chinese sources.
Although I would never advocate harassing @psychotiller, he seems like a stand up guy! 
Since you asked: MSEE and currently PhD student. Several start ups and contract work doing embedded systems, electromagnetics, etc.
Back on topic: being conservative is always a good idea, I tend to design in at least a 3:1 safety margin. Not much I can add here, you guys covered it pretty well. I would say, if you KNOW what you’re doing you can push these limits but for newbies or even those not 100% confident in their battery knowledge, stay conservative. I cutoff at 3V, but I “know” what I’m doing… 
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I flew almost daily 
so the abuse of high amp draws at low voltage & loads of charge cycles made it rather easy to kill them.
‘‘Luckily’’, esk8 replaced that hobby almost entirely. Now I only kill 4 lipos per year 
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Yeah that’ll do it! Haven’t had a battery blow up on me yet, knock on wood!