Last week I did some bench testing on the NCR18650B Lithium Ion cells, and the results were very promising, showing twice the energy density as a LiPo. This week I wanted to get the packs out of the lab and in the air on the Raptor 100 for some real life testing.
First I tested what the take off and cruise throttle was for the Raptor100, and then used a watt meter to determine the watts at those throttle settings. I found the same throttle setting for those same watts on the Li-Ion pack to ensure all was tested equal. The throttle % was lower for the Li-Ion cells as they operate at a higher voltage, and I was able to match the same watt rate at about 4A, just over 1C for takeoff.
The plane flew just fine on the Li-Ion packs. I did some full throttles and hard climbs and this single 4S1P pack performed perfectly. The Raptor100 flew faster than it ever has before due to the higher voltage, and was easily traveling 100kph.
Now I'm off to build 6 more packs and put them on the Raptor140 for over 2 hours of flight time!
See you next week!
-Trent
Lithium-Ion Packs
RTF Li-Ion Packs: http://store.mygeekshow.com/product-p/3.3a-4s-2c-battery.htm
Li-Ion Kits: http://store.mygeekshow.com/product-p/ncr18650b-pack-kit.htm
Single Cells: http://store.mygeekshow.com/product-p/ncr18650b-single-cell.htm
Raptor 100 Kits
Kit: http://store.mygeekshow.com/product-p/raptor-100-kit.htm
ARF: http://store.mygeekshow.com/product-p/raptor-140-arf.htm
Learn More:
Raptor Details: http://www.mygeekshow.com/theairplanes/Raptor100.html
USA Trip Details: http://www.mygeekshow.com/usatrip/
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Comments
My bad, sometimes what comes out my mouth doesn't match what is in my head : )
Very interesting on the LVC, that could get interesting if you weren't expecting it! : )
Sorry Trent, I misunderstood, thinking you had been using 4S LiPo originally on your Raptor.
As for LVC, most can't be turned off but some can be set to 2.8V or otherwise one can just set it to NiMh/NiCd setting which will cut much lower than the LiPo setting but I don't recall the exact cutoff voltages. Will see if I can find out.
Graham is correct. You use the 4.2V charge rate (LiPo) setting to properly charge these. If you use the Li-Ion setting, it won't fully charge the cell.
Graham: Sorry if I was misunderstood, the voltage load of a 4S1P Li-Ion is higher than the voltage load of the 3S1P pack I was using. As for the LVC, can't you just turn off the LVC on the ESC?
Trent, you say that the voltage under load was higher than a 4S LiPo? I found the the opposite actually and the official discharge graphs also show lower voltages under load.
According to those official graphs in the PDF I linked above: at 2C load only 650mAh is used before the cell hits 3.5V (which is my cut-off for LiPo's as this usually equates to ~80% consumed).
To consume 3000mAh of the cell at 2C the voltage has to go to 2.75V per cell or to ~2.95V at 1C.
Just a note of caution to users of these cells: most ESC's have a LVC cutoff at 3.0V per cell or higher if set to LiPo (they autocount the cells based on the connect voltage) so a normal ESC would hit LVC well before the entire capacity has been used and cut power to the motor.
I used to have this problem with the (now old) A123 cells I used a few years ago where I was using 4S packs to equal a 3S LiPo, the ESC's would go into LVC just after takeoff as the voltage would drop below what the ESC was programmed to cut off for a 4S pack. The trick was to run the plane at full throttle for 15 secs, stop and unplug, then reconnect quickly, before the voltage recovered thus registering an equivalent 3S pack voltage to the ESC.
Charging the 18650b's is stated (from the Panasonic website) as constant current/constant voltage (like LiPo's).
Charge voltage 4.2V (same as LiPo), charge current 1625mA (0.5C), charge time 4hrs. +10～+45°C.
(ref: http://industrial.panasonic.com/www-data/pdf2/ACI4000/ACI4000CE54.pdf)
While I agree, I'd like to see more info about how to properly charge Li-Ion. A LiPo charger won't have the exact correct voltages for Li-Ion, since the voltage range for LiPo cells and Li-Ion cells is somewhat different, so I'm wondering how to charge them properly. I haven't seen any tutorials out there besides "charge them as you would a LiPo", which just doesn't seem right to me.
Sorry, but using anything other than a good quality dedicated charger for Li-XX batteries and not following exactly the recommendations of both the charger and battery manufacturers has been demonstrated time and time again to be a really, really bad idea. Just don't do it! The "safety features" in proper chargers, casually dismissed by an earlier poster, are NOT mere concessions to the nanny state or lawyers. They are essential to the health of the batteries, never mind to your health and to your house remaining standing.
Gray and Trent, there seems to be a version with soldering tabs:
Random link: http://www.akkula.fi/Panasonic-NCR18650B-3400-mAh-with-soldering-tags
This should make things easier and saver.
Hi Trent,
Definitely sounds like good practice, soldering these things is definitely not for the faint hearted.
A Stained glass soldering iron is perfect.
It might be good to cycle the packs once after you've made them to ensure they are up to snuff.
If you do eventually get a welder I would recommend that you get one with at least 250 watt seconds and dual pulse (makes a better joint).
Unfortunately the Chinese ones on EBay and Amazon don't actually publish their watt seconds, but I suspect 100 to 140 somewhere.
Most of them will work for tiny little button cells and things, but not bigger batteries like the 18650's.
There are some DIY ones, but farad size capacitors can be seriously dangerous if dealt with improperly.
This one is a relatively solid design: http://zeva.com.au/Projects/SpotWelderV2/
And this $100.00 one is a bit half baked but probably battery weld capable: http://www.ledhacks.com/power/battery_tab_welder.htm
If you decide to do that last one I would truly like to hear about the outcome, probably good to keep notes so your next of kin could let us know in case something unforeseen happens.
Here is his version 2 $200.00 battery welder and I may give it a try myself: http://www.ledhacks.com/power/tab_welder%20ii.htm
All the Best,
Gary
Gary: Totally agreed. The battery kits are intended for those with higher skill levels and better equipment. I am carefully soldering these on with a high wattage iron, in a safe room with cool air being blown over the cells, and have fire suppression immediately available in case the "fire works" start up. If I sell enough packs, I'll invest in a battery welder to avoid all that. Thank you for your concern and support! It really helps!
Rob: 260W! I thought my 80W was big... I agree, you have to be dang quick and cool those packs off fast. I'm only touching them just long enough to get a good solder job then I cool it off with a fan on a very high speed. Cools it down in seconds. I pushed one pack to 12.6A, which is 3.7C, and it held it's voltage, but I'm sure that is NOT good for it for very long or very often. I love the 2x Ah per same weight, it really changes the game.
titeuf007: I'm not a quad master, but these cells like to operate at around 1C to 2C to keep them cool and maintain their long use life. So, if your quad drew 8A at 14.4v, you'd want 2 of these packs (operate at 1.2C), which would offer you roughly 40 minutes of flight with 480g of battery weight. Not bad!
Mike: Interesting, I've only used the hobby battery chargers. Sounds like those constant Volt and Amp benchtop power supplies could work as well!
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