I have been investigating LiPo batteries for a B-36 that I am building.
It didn't take much investigation before I was overwhelmed with information, making a choice very difficult.
I like comparison charts so I gathered information from the LiPo vendor websites and put it in a spreadsheet.
My chart contains a comparison of all 11.1 volt, 2000mah and larger battery packs that I came across.
When I was looking over the LiPo battery information I was trying to determine which battery pack gives me the best capacity to weight ratio. I consider this to be an energy density measurement.
I was surprised to see that one battery pack would provide over 22mah of capacity per gram of weight while another provided less than 11mah of capacity per gram of weight. Would a fuel powered flyer choose fuel that weighs twice as much with no apparent benefit? So why should I....
This chart could grow very large with all of the different battery specs. I whittled it down to these:
- Manufacturer Part Number
- Pack weight in grams
- Pack weight in ounces
- Pack capacity in mah
- mah per gram : how many mah are provided by each gram of weight
- grams per 1000 mah : how many grams would be needed to obtain 1000 mah
- Pack price in USD
- Price per 1000 mah : what is the price of this pack for each 1000 mah supplied
I should add that:
- All packs are 11.1V
- I used only information supplied on the vendor websites
- some packs do not have a connector on the power leads
- I didn't think to add the C rating until later in my efforts so only some packs have the C rating
That mistake kind-of messed me up. The leading choice in my battery selection was to use one Thunder Power Pro Lite 2100 pack per motor for a total of 6 LiPo packs and 12600mah on board.
Now my my best choices are limited to carrying three of the 8000 mah packs. The good part is that I will go from 12,600 mah on board to 24,000 mah on board. The Thunder Power Pro Lite packs are about 2.5 ounces lighter per pack, but the EFUEL packs are about $170 cheaper per pack..... maybe I need to double check those numbers too.
I think there is something magical in the Post Reply button. Prior to posting my information always looks good. After posting I seem to find errors.
Even after correcting the mistake I still see that you can get a range of 10.1 to 17.6 mah of capacity for each gram of battery weight. I suppose wire gauge, wire length, and connector would sway the numbers a bit, but there is no practical way for me to compensate for wire and connector.
If nothing else, the chart should help you pick a motor based on price per 1000 mah of capacity.
My motors (E-Flite Park 480 910kv) will not push the limit on the C rating so I can use anything on the chart. The 8000 mah packs will supply 80 amps each (to run 2 motors). That means that I COULD draw as much as 240 amps continuously for about 10 minutes. That would give new meaning to glow power. My ESCs are Phoenix 35's so I will burn up ESC's before I exceed battery current draw limits.
The chart will probably need a tweak or two more. At least my correction answered my question about how Thunder Power could get such a high capacity to weight ratio.... (they didn't).
My B-36 is 114" span and my target RTF fly weight is around 15 pounds. I believe that I am around 9.25 pounds now which includes the fuse, wing, retracts, wheels, motors, props, and ESCs. These batteries will add about 3.25 pounds so that should put me at 12.5 pounds. I still have covering, radio gear, and wiring to add.
It has six E-Flite Park 480 910kv motors, so that will provide 4000 mah per motor which should provide some long flights... well at least I think it will. This is my first scratch build, and experience with a multi motor plane, brushless motors, and LiPo packs. I am sure that the first flight will be impressive in one direction or another.
I have tried to confirm that in MotoCalc 8 but I am having difficulties specifying the battery packs. It is not straight forward when using multiple battery packs. I'm not sure that I am getting it right.
There are a few battery configuration choices for a six motor plane. I lost my favorite choice when I corrected the error in my table for the Thunder Power 2100 Pro Lite packs. Admittedly charging six battey packs per flight wasn't all that appealling so I'm not feeling tooooo bad about it. Charging 3 packs seems more appealling. I will likely need 3 chargers to get the charging down to a reasonable time.
By the way, my personal design goals would be quite different than yours seem to be.
Unless you need the weight of the packs for balance purposes, Id recomend you go with lighter packs. The plane will fly better if its not as heavy. Charge times will be much shorter and the cost will be less.
I like to set up for 10 minute flight times and then only fly for 7 to 8 minutes before landing. That leaves me a safe reserve and doesnt risk over discharging the packs. Thats about as long as I like to fly at one go anyway
I haven't purchased the LiPo packs yet, so I can always dial back the capacity and weight when I get to the puchase. It depends upon where my RTF weight ends up.
A flyer in Austrailia built his 112" B-36 at 12 pounds and he commented that it flies like a glider and is sometimes tossed around a bit by the wind like a glider. I had hoped to match his build weight but I will be very pleased at 15 pounds.
Ignore the links to the plans early in the build thread. Just like everything else in this project, sharing plans has been a learning experience. If you want to download the plans, use the link: http://b36.flugmodel.net/Updating_here/
The plans are out of date. I was naive enough to think that my plans were ready from the start. I have a few edits to make to them as well as put all of the parts on a single sheet for easy plotting.
Feel free to contribute your comments and opinions to the build thread. My B-36 has taken on a fair amount of change due to suggestions from other builders. I'm not too proud to learn from others.
I am installing linkages for flaps and ailerons now. Once that is complete I will skin the bottom of the wing, build the bottom half of the engine nacelles, and start getting ready to glass it. The final covering will be a combination of paint and FliteMetal. Ed from FliteMetal has been quite helpful in my build with his suggestions. He showed me how to make faux Fowler flaps and although I wasn't thrilled with reworking 6 flaps, they did come out rather nice. That's the problem with the B-36 is that it seems that the tedious work has to be done 6 times.
If anyone has wondered how to figure out exactly where the CG should be on a plane, Ed explained it and I posted photos showing how to located it on a B-36. The B-36 has swept tapered wings so I didn't really have a clue as to where the CG should be.
Well, I have gone on too long already. Enjoy the photos and read when interesting.
EFuel has recently changed the cells they are using. I did a review on the older Wanma cells. They preformed well for the price, but did not compare to the Korean cells that Thunder Power and Flight Power use.
Since that review, Efuel changed where they got their cells. I ran those, and I am going to write up a review as well. These cells held their voltage better than the original Wanma cells, but still they did not have the performance of a new TP or FP lipo.
I have been informed that the cells are changing again to a different supplier. Those batteries are on their way to me to do a review on. I have run these future cells before and was REALLY pleased with them. Once I get them, I will post my results for all to see.
I guess what I am getting at, is keep checking the Efuel site, as it mgiht change whenever they make the complete change over to the newer cells.
FWIW: The dimensions and weight of the Efuel lipos are spot on when it comes to dimensions and weight.
Thanks for the info. As I said, I am new to LiPo packs. I could compare weight, capacity, and price. I have no experience with the various aspects of quality so I could not add that to my chart.
I would be pleased to add comments to the chart so that it would help explain the reasons there are price differences. Just so long as it all stays as factual as practical it could be a valuable resource. Just so long as it doesn't turn in to vendor bashing I'm in.
My info has just been an information gathering effort. It seems that you have done the testing. I could add your info to my chart or perhaps it would actually be better to add my chart to your info.
My chart just covers the 2000 mah and up 11.1 volt packs that I came across because that is all that I am considering for my B-36. Perhaps there is merit in creating an information resource that goe further. Perhaps it already exists and I am unaware of it.
Well, let me know if you wish to combine information.
Thanks for adding the caveats to purchasing solely based on price.
Yes, I agree. The excerpt that you posted from the chart steers you toward the True RC 2500 pack. But if you think you will need higher current, then the FullyMax is a better choice.
It's true that my larger plane with smaller motors that need modest current capacity aren't affected much by the C rating. For example, if I use a 8000mah pack that has a 10C rating, I could draw 80 amps continuous to power a pair of E Flight Park 480 910kv brushless motors. The motors and ESCs will fry before I exceed 80 amps.
Initially I didn't include the C rating. Then it seemed to be a valuable parameter so I have added it to most of the batteries. If you look at the chart you will notice that the higher C rated packs provide fewer mah for each gram of pack weight.
The purpose of this chart was to direct me to the right battery choice. Too often I buy something and then a week later I realize I didn't make the best choice. LiPo packs are expensive so I want to make the right choice the first time around.
mah per gram is still the best parameter to monitor if your wallet is large. If your wallet is a bit thin and you can tolerate some extra weight, then you want to pick your pack based on price. So the price per 1000mah is the way to decide if a 3500 mah pack from vendor A is a better buy than 3300 mah pack from vendor B.
I am still hopeful that someone with in depth LiPo knowledge will add their comments. I noticed that MaxAmps don't do as well on these charts as I expected. But I have talked to a few who were quite pleased with their MaxAmps packs. So is that just a perception that the end user has, or is there something that the charts don't show.
It's true that some flyers will be pushing the current limits of a pack and will have fewer packs to consider. I suppose the charts could also be sorted by C rating. Actually the packs would better be sorted by maximum constant current rating (capacity divided by C).
Thanks for helping me to look at the data from a different point of view.
Thanks for the effort Jeff. I will check it out. I believe that your efforts will allow anyone to add or update the info on a LiPo pack.
Just a few minutes ago I added the C rating and max current for the MaxAmps packs on my charts. It appears that if you're looking for packs with a high current rating, MaxAmps is probably a good choice. I will try to get the MaxAmps info added to your website later tonight and if all looks good I think we should provide the link so everyone has access.
Interesting approach, but IMHO it would be easier to look in a single file for the various 11.1 volt LiPo packs. There MIGHT be a 25C 2000 mah or a 20C 2200 mah pack that could be had for a buck more. Sometimes the differences are minor which makes it difficult to compare when looking in multiple files. I could easily see an argument for allowing the chart to be sorted by C rating.
Again, this is just my opinion.
This chart covers ONLY 11.1volt LiPo packs because that is all I was looking for. In my case I will not be pushing the pack to it's Max Continuous Amps rating so I don't care if it is a 10C, 15C, or so on. I just want to find the pack that gives me the highest capacity to weight ratio or the most capacity per dollar. In my case the EFuel 8000 is the best capacity per dollar but the Thunder Power 8000 Pro Lite a has better capacity to weight ratio. In my B-36 this adds up to about a 1/3 pound flying weight difference. That leaves me with the question: How much am I willing to spend to knock a 1/3 pound off my plane?
If you don't mind another suggestion, I think it would be best to create a separate chart for each of the different voltage ratings. I KNOW that I want a 11.1 volt pack. I also know that I prefer to use 3 packs and the capacity can range from 4000 to 8000 mah per pack. I had hoped that this chart would identify 'a sweet spot'. I suspect that in many cases the desired pack voltage is a given, the desired current has a small range to consider, and it's the weight, capacity, and price that are the big variables. Well those are just my opinions.
I went to the link that you posted earlier: http://www.wattflyer.com/forums/showthread.php?t=26237 I believe that thread had a link to a webpage where they chose to have their information grouped by C rating like you suggest. So perhaps you are right, but then I would wonder why we should duplicate that information here.
I think charts like this could be a useful tool. My way is not necessarily the right way. Consider my suggestions and tell me which way you think they should go and I will agree.
FYI, maybe it hasn't been made clear in this thread but Jeff has created webspace to host LiPo pack comparison information (thanks Jeff!). The web page will allow anyone to add pack information for a pack that is not already there, and a link to where the pack information can be found. It's a great idea that should keep the information up to date as LiPo packs continue to improve.