LiPo batteries are difficult to deal and maintain, Can I use Li-ion batteries?
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LiPo batteries are difficult to deal and maintain, Can I use Li-ion batteries?
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I have a xcopter and I want to use general power tool battery in it instead of Custom LiPo. such as Milwakee M12.
All batteries age. They will puff up near the end of their life cycle (or a flight that abuses them). You can tell age by how much shorter your flight times are.
LiIon can only be used on highly efficient ships that draw less than about 2 amps per series (so 4S < 8 amps to hover). They seem to age better, but suffer the same problems as LiPo.
I'm guessing that LiIon will not work for you unless you are into ultra-light and lower speed. LiPo is probably best for you. Welcome to the variable (expendable) costs of flying quads.
With current li-ion technology most uavs work well, we find with our packs that we get roughly double the mAh for the same weight of lipo, with no issues with current draw. A good li-ion pack should last 500 cycles minimum, roughly compared to 100 for a lipo (this is dependent on quality and use). We can manufacture many different sizes and shapes to fit most aircraft. As an example, our standard 4s pack gives 9000 mah with 60 amps continous current and weighs 540 gms.
At what voltage ?
9Ah x 3.7V = 33.3 Wh only
can be replaced by 4 2200 mah Li-Ion cells at $2/piece
So money makes the difference - $8
If i did the math right, 9000 mah at 60 amps means a battery capable of 6.7 C. The Panasonic NCR18650B is rated to 2C. Are you using a different battery or are you saying that the Panasonic is under rated and can actually handle 6.7C?
The Panasonic ncr is not a suitable cell for high drain use. There are four main li- ion cell manufacturers, two of which produce high drain cells for power tools and e-bikes etc. These cells are rated at 20 amps cont. discharge, which we have proved in our testing.
Be very wary of higher discharge claims from other companies, there is a massive market in re-wrapping b grade cells from the four main manufacturers with false claims of performance. Avoid Chinese resellers like the plague!
Martin - Do you sell batteries made from the 20A Li-Ion? I make my own, but i know people that would be interested. And, yours might be better made than mine.
We are in the process of setting up an online store for batteries but we want to make sure everything is in place first. Getting the right packs for our use requires comprehensive selection and testing to give 100 percent reliable figures. As Alasdair has said, we derate specifications to real world tested figures with a margin for safety. As we build aircraft too, we know the time and effort required for the construction of these machines, not something to be risked with over specified components. There are so many fake and re-wrapped cells with poor provenance and some outrageous and dangerous claims of their capability, that only buying direct from the manufacturer is viable. We aim to provide A grade packs, fully tested and certified, customised to suit and that will last vastly longer than lipo and have greater capacity for the same weight. We will let you know when we are ready to go but please feel free to PM me anytime if I can help.
Love your work on the endurance quad by the way, great stuff!
Would love to hear about how you end up making the battery pack.
In case some of this helps, i chose the following based on the trade between heat loss due to resistance (converted to watts) versus watt loss due to lifting the wire. The basic trade being that a fat wire has very little heat loss but takes watts to lift it off the ground. Let me know if you would like the worksheet that makes the trade calculation.
I consistently add 2% more weight to a 20 cell (4S5P) battery (19 grams to a 911g battery pack; but you will have to add more to make the pack more commercially durable):
- .25" x inch x .005" flat nickel connectors (Stone SN250N54)
- 18 AWG wire main leads (for low C apps; i'm guessing that the trade for your higher C packs will be 16 AWG); Allied Wire and Cable, Inc, Part# 1429-18-19T-9 is the lightest multistrand wire i can find. it's amazing how much wire coating weighs.
- 2mm bullet connectors (you will probably have to use heavier connectors to be somewhat standard)
- (4) 0.124" OD x 4.5" long carbon tubes that are bonded in the fillet between the round battery cells to stiffen the battery pack during a crash
- Scotch-weld 2216 adhesive to bond the battery pack together
- Electrical tape at the ends
- Shrink tubing to protect the bullet leads
- Access to the ends of each cell in case one cell needs to be balanced charged (using a thin paddle that fits between the cell ends)
Please keep me in touch with your findings.
Another consideration is traveling with LiIon. According to the FAA:
- check-in luggage 100 Wh max (don't know how many)
- two carry-on 200 Wh max
Then there is you to your customer shipping. To avoid the dangerous shipping category with Li-Ion:
- Large batteries cannot be shipped on passenger aircraft (UPS can fly them only on cargo ships)
- two or fewer batteries of 8 cell each (this means that your limit is two 4S2P that plug into each other for a 4S4P but are shipped without being connected). larger sizes than that would need to be shipped separately.
- then again, maybe the dangerous category isn't that cumbersome.
http://www.ups.com/media/news/en/intl_lithium_battery_regulations.pdf
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