NCR18650B - The Future of RC Aircraft Batteries? - Blogs

jadwin edison April 4, 2015 at 9:35pm

can i use 30a Turnigy Plush ESC without any problem with 4 pieace of this Battery ?
or perhaps anyone have any sugested how much battery i can should use with 30a Turnigy Plush Battery.
Thankyou

iskess January 14, 2015 at 9:07pm

Can someone recommend a good source for NCR18650B batteries?

My math shows they have only about 25% more energy density than the HK Multistar batteries.

Check my math:

4s4p Li-ion = 13,600 mAh, at ~800g (48g x16 = 768g + wires, etc)

Multistar 4s 10,000 mAh at 804g

The Li-ion have 26% more capacity at the same weight.

John Campen November 25, 2014 at 11:33pm

" @Tommy and Denny, I also have a hexa around 3kg and I am looking for new 4S batteries. Since your experience is quite different it would be nice if you could provide some details about your setups. Thanks in advance, Thorsten "

Id also be very interested if possible?

steve November 14, 2014 at 1:17pm

is there a video of how to setup this battery pack?

Bosnianbill October 10, 2014 at 10:24am

Quadzimodo & Graham,

Gentlemen, THANK YOU. It appears I have TWO problems instead of just one. First, I will replace the array with the drastically low voltage. As you say, why take chances? It may be only 1 or 2 bad batteries but I'm not willing to risk a multi-thousand dollar quad on it - so they ALL go. The second problem seems to be my charging method. I HAVE been using the LiOn profile on my iCharger instead of the LiPo and keeping the charging current pretty low (1A). Maybe that's why it only charges up to 16.3? I'll switch back to LiPo on the next recharge (after replacing the bad cells) and hopefully it'll get up to 16.8.

Thanks again for your help on this. I was getting pretty....frustrated... with my limited success. My endurance quad draws only 15A on climb and hovers around 8-9A, so I am well withing the C limits of this pack. I will, however, begin to land before 3.2V/cell - appreciate that advice too!

Moderator

Graham Dyer October 10, 2014 at 9:49am

These cells are much more tolerant of low voltages than LiPo's so less damage occurs but there is very little capacity left after 3.2V, enough to keep a plane aloft at low current but maybe not enough for a copter? So as the others have suggested, make a point to land at 3.4V or 3.5V per cell.

There is a test here with lots of data: http://lygte-info.dk/review/batteries2012/Panasonic%20NCR18650B%203...

You'll see on the graphs in the link that 3.2V is generally the minimum usable voltage

Fully charged 4 cell pack should be 16.8V, if you're getting less you're using the wrong chemistry program (should be LiPo not LiOn) or have badly damaged cells.

We have 10 x 6S2P packs in constant use in planes either as 6S2P or 6S4P and have had around 250 logged flights. Flight time is 1hr with 2P and 2 hrs with 4P. We have bought 6S balancing taps for each pack and we do balance charge every time with a Thunderpower TP820CP chargers. Our cells were spot welded but of you know what you're you can solder them.

I have flown 2h17m down to 19V (3.16V per cell) but that's cutting it fine and one must keep current demands very low with no spikes as that will pull the voltage down quickly. Our first packs are still doing well, current draw is around 24A at takeoff and 5-7A during flight, the 2P packs do remarkably well even at nearly 4C during takeoff.

Test of Panasonic NCR18650B 3400mAh (Green)

Quadzimodo October 10, 2014 at 9:11am

Hi Bosnianbill,

I am no expert, nor am I an engineer.

Looking at the total capacity you are getting there of your battery there is no doubt you have a serious problem.

The fact that you end up with 3 paralleled 6P arrays at 3.5V and one at 2.55V when you have finished flying your craft certainly shows that one paralleled array is bad (seems to be about 4P equivalent - or has 2-3 bad cells).

The bad 6P array is 100% depleted long before the other 3 have been able to give up a great portion of their energy - so that is where much of your missing AmpHours are.

You need to dismantle the battery and replace the bad 6P array. All cells in that paralleled 6P array (6 cells in total) should be removed and replaced for new ones for good measure. They may not all be totally bad, and therefore there are likely 3-4 that are salvageable, but they should not be reused in this 24 cell array again.

If there are salvageable cells in the 6P array, then just keep them for another protect. Those few cells may well have been damaged/aged through over discharge when compared to other cells in this battery pack that have not been subject to a deep depth of discharge yet. It is a measure worth taking so that the savaged cells do not negatively impact performance and or service life of the other 18 (virtually new) cells.

Next time you build a $250+ battery, you may want to consider purchasing a spot welder for joining the cells. Go to ebay and search for 'lipo spot welder' for more info.

David Pawlak October 10, 2014 at 8:37am

Yeah Bosniabill.... you discharged to 3.0v per cell. hat is not good for the battery.

You should stop short of the "knee". which is best to be no more than 3.2v per cell.

I had my failsafe trigger set for 3.4, and when the failsafe triggered I had (with luck) 60 second to land.

One time, my FS (failsafe) triggered at 3.4, and started an autoland. I didn't notice and did a manual RTL.

The RTL took it to 1.5 meters from the ground and it died!! A couple of bent landing gear, thankfully no more.

3.4 is too close. Setting it to 3.5 or even 3.45 buys you a bit more time.

Running a battery down to 3.0 volts is only trouble. It's no wonder you last a couple of cells. best you throw those batteries away.

Bosnianbill October 10, 2014 at 7:08am

I could sure use some expert electrical advice...

Using brand new Panasonic 18650B 3400mAh cells I built a 4S6P pack for my endurance quad. I soldered it and was pretty careful with the heat, but can't rule that out as a potential problem. It should have a max capacity of 20,400mAh with 16,320 available (80%).

I'm charging it with a new iCharger 206B and my other chargers give identical numbers. When fully charged it reads 16.3v (unloaded). My calibrated OSD agrees with this number. When on my endurance quad the battery drains at a pretty steady rate until it reaches 12v (loaded). At that point it goes into free fall, depleting to 11v in less than 2 minutes. After several tries, the most I can extract from this pack seems to be 12,400mAh.

Back on the bench I get unloaded reading of around 13v. Here's where it gets squirrely: Three cells read 3.5v and one reads 2.55v - leading me to think something is wrong with that cell.

Could I have overheated one or more of the batteries when I soldered the tabs? Is there a fix for that or do I need to ID and replace that battery? Each of the four cells should be giving up around 4000mAh (for 16Ah), but I'm getting only 12Ah. Could one entire bank of cells be bad? Would one bad battery affect the entire 6-battery cell or is it likely I screwed up worse than that?

Sorry for all the questions but I'm a mechanical engineer and slept through all the electrical courses...

Holger S July 28, 2014 at 12:45am

I use cells without tabs and solder apropiate copper wire directly onto the poles. The 18650 cells are very easy to solder as log as you do not bring to much heat into the cell. To prevent that, I use the following technique:

1. use a large soldering iron (at least 80-100W) and 2mm electronics solder with non-acidic flux

2. glue the cells together (CA glue)

3. pre-tin one of the poles, soldering iron contact required should be less than 2 seconds. Do not be too greedy with solder, but don't splash it around (risk of short circuit)

4. let the cells cool down for half an hour, do same again with the other pole

5. cool down again, connect the cells with 15 AWG pre-tinned copper wire

6. cool down the cells once more, connect balancer leads.

Remember that a xSyP pack is build x from groups of y connected parallel cells, do not parallel y indepenent packs of x serial cells.

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