Ok just thought I'd share my experience trying this. I built a 4S3P out of real Panasonic 18650 3400mah batteries for use on the hexa (really just to play). Well did not go so well. My two Turnigy 5000 mah managed to keep the 680 Pro up for 20 minutes. The new test battery failed within the first few minutes see graph below. Maybe would be better on a single engine plane that doesn't pull so many amps. I'm no expert what do you all think. I can say this config did not work on this copter. :(
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Hi Chris,
My hexa680 with sunnysky 3508, 380kv, esc spider 30A, propeller 1355, fc Pixhawk. 9tatal 3kgs include gimbal, cam)
I using lipo 4s 5400 can fly 5 minute.
when I using 4s 3p 18650 battery Samsung 30Q
(Specification:
So it can't take of.
I think with 3S are 45A discharge, It can take off, is it right ?
regards
Reed Noel.
chris wilson said:
Me too, so I using 4s3p 18650 Samsung 30R, so ít ca't take off.
Reed.
Try with GEB8043125 Cells.
you wont be disappointed
Hi Tipu,
I sent to you a friend request, i think you can help me in a question. Thank you!
Yes your battery pack was just too small. If your copter pulls let's say 20 amp at hover, to have best results with NCRs you need about 4S 20.000mAh battery eg. keep nominal discharge rate around 1C or max at 1.5C (1.5 = 14.000mAh).
So how many battery cells that is then?
4S/20.000mAh is 24 batteries in total, 4 series / 6 parallel, weight about 1.2kg
4S/14.000mAh is 16 batteries in total, 4 series / 4 parallel, weight about 750gr
I would personally go on 20Ah battery if weight is not an issue
With 4S3P your nominal discharge rate with 20Amp hover would be about 2C which is a bit too much for NCRs, they die rather fast with 2C.
Also make sure you are using NCR18650E models and not NCR18650BE models and BE can only give 0.5C discharge rates..
Hi Dale, Increase your voltage to lower amperage, but you must lower the KV of your motors to match. This brings the total amps within the range of the batteries. I few a Quanum 680 pro (same as the tarot) with the Multistar Elite 3508 268KV motors with 13 inch props on 8s for 1hr 20 min. The amp draw in hover per motor in on 8s is 1.2A totle was 8~9A. I was using a custom 2c GEB cell battery. but the same will work on the panasonics.
3P will be over drawn, its probably around 30C. You need 4S10P to be around 2C OVERALL with those cells. The more parallel packs you add, you reduce the current drawn across the other packs. Play around with it in ecalc.ch paid version has those cells. It is possible to use these cells and you will get a 25% weight reduction vs lipo, however the pack needs to be large enough to spread the load out.
also, you might have damaged the cells you have by over current draw. Do a charge/discharge logging peak voltage mAh test.
and, in your calculations consider the the NCR18650b is really a 1C battery, but you can peak draw it at 2C without damage for 15 seconds according to the white paper. So, your hover is around 50% throttle which is roughly half the total power load, so design your pack for 2C and when you are hovering around its using 1C, This over course assumes that you wont go above 50% throttle for very long.
good luck, and feel free to ask questions
Thanks I will look into them. I should do more research first but I just like to try. I have enough battery power now to probably power all my "other" devices. They may make for some good secondary power sources for video etc.
Panasonic ncr 18650b (wether genuine or not) are not suitable for anything other than a super light machine, like Forrests amazing endurance quad for example. Simply put, they cannot supply enough amps for most copters. Check out this thread if you have not already, it discusses pretty much everything!
http://diydrones.com/group/arducopterusergroup/forum/topics/lipo-ba...