DIY Li Ion Battery Packs - Better than Li Po for RC Planes and FPV?

[@stedenvideos3825]

Great video! I've recently discovered that Li-ion packs don't have to be low current anymore. I use 4S2P soldered packs of Molicel 21700 P45B cells to power a Arrows Hobby Edge 1300mm plane. Pulls up to 75A, 1000W at max throttle. Each cell has a capacity of 4500mAH and can supply up to 45A continuous - so double those numbers for 2P. I manually solder my packs and include balance leads so I can balance charge them in the same way as a Lipo pack. I did look at using commercially available connection frames but found them too bulky for 21700 cells. I use tin/lead solder rather than spot welding - works fine so far - I've made two packs so far and flown dozens of times already without mishap. The drawbacks with 21700 cells are that they are bigger and heavier than the typical Lipo packs that they are replacing in my planes. But the extra flight time is amazing. I'm getting around three times longer in the air. Video of one of my first Li-ion test flights in a Dynam Waco 1270mm biplane: kzbin.info/www/bejne/qGOyf4ejoZmtiLs

[@usefulaircraft]

I love the li-ion cells. Don’t get me wrong - Li-Po still has its place in my sub250 stuff - but for my FPV or bigger builds - Li-Ion is my pack of choice. I started off with commercial packs, then tried soldering - and eventually built a spot welder, but then I saw the battery racks, and thought to try them after a particularly bad crash that punctured a cell. Sure, the battery racks weigh more - but the added capacity make it a non issue. For balance considerations - I just charge each cell independently, and monitor their internal resistance and temperatures at charging. If any individual cell draws my concern, it’s trivial to swap it out with a cell more similar to the profiles of the remaining batteries in that pack. I much prefer being able to isolate my cells completely for travel, as it (in my mind) reduces the risk of connected packs (albeit this may only be in my use case in a cramped carry on bag). I do have a few planes that fly off the 21700’s - and some that really benefit from their added capacity, but just be wary that unlike fuel tanks on full size planes, the weight of an empty cell is the same as the weight of a full cell, and it takes fuel to tanker fuel. So in some use cases - you may find that 18650’s could give you a better specific range due to lower cruise power requirements (because of lower overalll weight). But this all depends on if you’re solving for endurance or distance, and would require very exacting power control and testing. Most times - it just depends on the airframe I’ve built, or CG purposes. Either way - we’re really lucky to be flying with these amazing batteries. Cool video, and thanks for the comment!

[@douglasdarby7123]

In awe of your skills and presentation. Superb information and fabulous in all the videos and pertinent. Some clever comedy happening is always great.

[@usefulaircraft]

Thank you for your note, I'm glad you enjoy it. I'm working on an interesting new project and should have something out shortly. Thank you!

[@11coso]

A great solution! You are right, nothing wrong with soldering a pack but the flexibility this give is really appealing. Thanks for the video.

[@usefulaircraft]

I appreciate your feedback. I'm willing to admit I'm not the smartest guy, but I love the flexibility of swapping individual cells vs assembling packs of questionable history. Thanks for your time and consideration.

[@SwoopsRP]

The autofocus on whatever camera you are using is super fast. Pretty wild.

[@usefulaircraft]

Osmo Pocket 3. I’m very impressed with it. Thanks for the comment!

[@chiparooo]

Very interesting battery philosophy! Never thought about using the 18650s. Lipos do make me nervous. Thanks for sharing!

[@usefulaircraft]

I agree. A lipo fire is hard to fight- it's a risk I'd rather avoid. Let me know what works for you, as I'm always open to a better path forward. Thanks for your comment

[@speedmasteriv1]

Great video. Thanks for sharing. Is a BMS not required for these type of battery pacs?

[@MrZeek101]

Another Great video always a pleasure to watch . I have most of my long range on solderd 18650s and 21700 but I have always wanted to try this thanks for the how too . Again just keep up the great videos . Take Care

[@usefulaircraft]

Thanks for the comment. I was willing to take the weight penalty for the ability to swap cells, and better isolate my packs for travel. This system has worked great for me for several years, and I wouldn't go back to lipos. You've gotta be careful when loading your packs, but for me it's well worth it.

[@Elsagitario]

Interesting video! Thanks for sharing. If I understand correctly from the connections you place them all in serie? i am looking for a solution like this, placing two series in parallel. (3.7 + 3.7V = 7.4V)

[@solarguy6043]

All other things being equal......the lithium ion cells like 18650s (and all the sisters and cousins) typically will give you more useful cycles than lipo. That's assuming good quality 18650s vs good quality lipo cells and proper/decent care. Charging each cell individually counts for a lot. That also means you need to keep the sets of batteries reasonably well matched. This is both a feature (since you *can* do it with this style pack) and a minor hassle.

[@copiercer]

Brett.. you are awesome.. !! Thanks for all the great info !!

[@usefulaircraft]

I’m happy to help. Share what you can - it helps all of us. Thanks for your comment.

[@ilan8465]

Nice idea and well explained. Thanks.

[@usefulaircraft]

Thanks!

[@chiparooo]

Is there a reason you are using the Samsung 20R vs say the 30Q or 35E that have 3000mah & 3500mha respectively? I just started looking to see what is available on Amazon and saw these higher rated choices. I don’t know much about these type of batteries and was wondering your thoughts. Thanks!

[@usefulaircraft]

I bought these batteries nearly two years ago. It may have just been availability. I've not bought off Amazon, but I'm sure there are good sellers there. IMR has been my vendor, but I've got no particular loyalty to them, I'd just say shop around. I've had really great longevity from my packs, as right now I've probably got around 20 individual cells in my active circulating pool. They have lasted remarkably well, despite me oftentimes putting them in half baked planes that don't always fly great. I'll be curious to hear your experiences going forward. I'm very satisfied with my batteries. No regrets. Thanks for your comment

[@aklmini-makers4304]

Hi. Could you please provide link to the 18650 battery holders, that match your 3d prinable spacer. Am looking forward to giving it a go

[@usefulaircraft]

I got mine off AliExpress - search for: 1x2x3x4x 18650 SMT Battery Holder 18650 SMD Battery Box Storage Case Container Power Bank With Bronze Pins Rechargeable SMT I’ve ordered them from amazon, aliexpress, and other random places - they’re pretty generic. I hope they work out for you. I really enjoy my packs. Thanks for your comment.

[@hubba002123]

Very nice!

[@usefulaircraft]

Thank you. I’m glad to share.

[@gasisthepastendoil]

i welded 5000 mah li -ion

[@usefulaircraft]

Nothing wrong with welded packs. I arrived at my solution after having bought welded packs and having built my own welding setup to weld my own packs. My packs suit my needs better for when I travel and I want to ensure the packs are isolated, and I do enjoy the ability to swap out cells, but a welded pack will be lighter if it's built right. At the end of the day, they both get you flying. Thanks for your comment.