hello all!

i recently watched dave-C of rekonfpv doing a video flying his rekon5 on a diy 4S lithium-ion pack using  a pair of battery holders bound and soldered in series together. anyone here who has attempted or done extensive flight testing on this before? i dare to ask bravely as dave’s flight demo video was done is quite benign surroundings. unlike the epic hostile mountain cruising he does to perform range tests.
https://youtu.be/d85_iGXrtWU?si=iSSRWMByZhCbZlEh
or does it subtly suggest it’s not a good idea using unsoldered battery connections for flight packs?

if this were a reliable option i was thinking of making one in the absence of having a spot welder. at least this guarantees the integrity and health of the 18650 cells. or at least use this for the goggles PSU duties.

Those trays are not light and will add dead weight to your quad. I believe there are many RC pilots (especially plane flyers) who solder their own li-ion packs. Of course there are risks, you do not want to over heat the li-ion cell to compromise its health or worse create a fire, but do your own research and make your own assessment. If you want to invest in a spot welder, that is an option, but you need to learn how to spot weld properly just as you would need to solder properly to prevent your connections from coming loose. If you are not comfortable soldering, you can always buy a premade li-ion pack, and simply charge it in your lipo charger with the appropriate settings.

For goggles use it is fine, I just ordered some cells and was going to prepare some packs to use on HDZ goggles. However you may want to go to 3S if your goggles minimum voltage is 7v. A lot of li-ion will run down to 2.6v, so if you are on 2S and your goggles cut-off at 3.5v, you will have quite a bit of unusable capacity left on the cells.

i highly respect dave for his designed race frames and micro frames but the use of this battery trays is complete fault, terrible its still a secret.
dave tried to get a new simplicity but it realy ignores the main rules for a good connection. so strange it got somehow popular for "lr builds" which does need high reliability and not powersupply connection as potentional issu

there is not enough conductivity and even worse its variable overtime.

its experience based to use decent connectors for many kind of electronics and specialy in rc sports: no battery trays seems nimh battery days are over xD
we need well soldered cables and connectors :-)
i would highly suggest to use the well proven common connectors: xt60, xt30...

If you are getting into using Li-ion and making your own packs, then you need a spot welder. Something like this would do.

https://sequremall.com/products/sq-sw2-m...ng-machine

Soldering is ok for say a 2S (but do it on a well discharged cell, so get the voltage low so it isn't packing so much power, be really quick when you do it and have a fire extinguisher on hand and wear some protective gloves), but Li-ion is a dangerous chemistry and they do explode from time to time, so be careful.

i appreciate the wealth of (entirely) safety concerns feedback on handling lithium-ion cells. it just piqued my interest and ultimately reality sets in…

i know someone who does diy his lithium-ion packs. he has both spot weld and soldering methods. oddly though he expresses some concern over the integrity of spot weld hence he upped his soldering skills to make it work. but not without its fair share of toasted cells in the process. i always thought spot weld even during those nimh and nicd days were still the gold standard in making battery packs. gotta get deeper into his doubts about spot weld…

I've soldered up a couple of 6S packs made up of Molicel P42a cells. It was a huge pain in the butt, but it was worth it. They're way cheaper if done that way, and you can configure them in whatever shape you like. If you go end to end, do a little curl to bring that wire in close.

Big thing to watch out for is accidental short circuits. Almost welded my battery wires to my helping hands once.

(25-Jan-2024, 02:47 AM)hawk01 Wrote: i appreciate the wealth of (entirely) safety concerns feedback on handling lithium-ion cells. it just piqued my interest and ultimately reality sets in…

i know someone who does diy his lithium-ion packs. he has both spot weld and soldering methods. oddly though he expresses some concern over the integrity of spot weld hence he upped his soldering skills to make it work. but not without its fair share of toasted cells in the process. i always thought spot weld even during those nimh and nicd days were still the gold standard in making battery packs. gotta get deeper into his doubts about spot weld…

I've used them on bigger stuff.  But in alt energy stuff we use them to create massive battery arrays from used 18650's and 21700's.  Like 48V 100Ah+ level where you could be spot welding 100x 18650's in parallel, four times for a 12V battery, eight for a 24V, etc.  You can't easily do the same by soldering.  Spot welding is really the only correct way to do such things on such small batteries.

If you do it right, it works and the strips are a massive pain to remove afterwards.  If you do it incorrectly, then they don't hold and make a good enough connection.  In the past I used a friends DIY spot welder made from a microwave power supply.  Sketchiest thing i ever saw and used, but it worked ok.  Unfortunately the batteries didn't and his shed went up in smoke.

I don't have a lot of experience making liion packs, but have soldered a handful of them. I found it a lot easier to solder than say an AIO, you have a flat unobstructed surface to solder to. You can rough up the surface with a little sandpaper, add flux, use a fat tip, and then tin quickly with just 2-3 seconds contact. If solder did not stick, let it cool, reapply flux and retry. Of course you should take the necessary safety precautions too.
It is important to remember that basically the whole cell case is the negative terminal covered in a layer of shrink wrap, so when you assemble the battery you want to use spacers/isolation between cells to insure there is no chance of them rubbing together in case the shrink wrap ruptures. My packs started out for long range flights, but I don't really fly far and those 20-30 minute flights are just way too tiring, so they are mostly on my goggles and gets cycled weekly. Using just some foam and electrical tape, the assembly was pretty fugly, but the packs have held up well over several seasons. I haven't built a 6S packs though, with that many more balance wires I could see it getting messy.

I've been flying Li-Ion only for many years now and they are magic compared to the old Li-Po. I would never use a battery case for fpv flying and i would not invest in a spot welder as this is a common mistake. of course it matters how much amps are you going to draw. I've used the Samsung 40T in the past but switched now over to the magical Molicel P45B. they can for a few seconds output 200A! enough for me to take-off with a 90mm EDF jet. they don't get so hot anymore as the Samsung and have 500mAh more capacity. I solder mine with some high quality 1mm copper strip. copper is the 2nd best conductor out there as with spot welding you use nickel max 0.15mm thick ranking #11 in the conductivity list. this is key for a reliable powerful battery. you want that high power to flow! and never ever shrink tube any Li-Ion cells in order to allow cooling. on custom orders i produce and sell those batteries 3s, 4s or 6s config. if you don't want to do it youself, just let me know. but it's not as hard as it seems. all you need is a 200W soldering iron for 20$ and high quality copper.

(25-Jan-2024, 05:19 PM)StuweFPV Wrote: I solder mine with some high quality 1mm copper strip. copper is the 2nd best conductor out there as with spot welding you use nickel max 0.15mm thick ranking #11 in the conductivity list. this is key for a reliable powerful battery. you want that high power to flow!

If you are soldering, what is the advantage of using the copper strip versus an appropriate gauge silicone wire?

Also were you selling packs on RCgroups several years back with Tesla? cells. I wanted to buy some, but the seller sold out and that started me on building my own pack, so thanks if you were the one

(25-Jan-2024, 07:28 PM)mstc Wrote: If you are soldering, what is the advantage of using the copper strip versus an appropriate gauge silicone wire?

Also were you selling packs on RCgroups several years back with Tesla? cells. I wanted to buy some, but the seller sold out and that started me on building my own pack, so thanks if you were the one

I guess you could use a wire with the propper gauge. the strips are clean and solid. once they're on, the cells don't move a inch. It gives the whole battery the strength it needs and it's surely easier to solder than the wire. it needs lots of heat to get solder stick to the cells and if you stay on too long, the battery will fry. I'm seeing your wire's insulation melting away.. but i've never tried it. 1mm stripes work the best for me.
and no - i was not advertising on RCG nor do i deal with Tesla - but i've heard that they used the Samsung 40T in the past. sorry

(25-Jan-2024, 05:19 PM)StuweFPV Wrote: I've been flying Li-Ion only for many years now and they are magic compared to the old Li-Po. I would never use a battery case for fpv flying and i would not invest in a spot welder as this is a common mistake. of course it matters how much amps are you going to draw. I've used the Samsung 40T in the past but switched now over to the magical Molicel P45B. they can for a few seconds output 200A! enough for me to take-off with a 90mm EDF jet. they don't get so hot anymore as the Samsung and have 500mAh more capacity. I solder mine with some high quality 1mm copper strip. copper is the 2nd best conductor out there as with spot welding you use nickel max 0.15mm thick ranking #11 in the conductivity list. this is key for a reliable powerful battery. you want that high power to flow! and never ever shrink tube any Li-Ion cells in order to allow cooling. on custom orders i produce and sell those batteries 3s, 4s or 6s config. if you don't want to do it youself, just let me know. but it's not as hard as it seems. all you need is a 200W soldering iron for 20$ and high quality copper.

highly informative on the virtues of soldering against the usually recommended spot welding. it would be very convenient for me to purchase a custom built pack from you sir if you lived next door. sadly i believe we are oceans away which makes shipping lithium batteries almost impossible.

I solder them because I dont have a spot welder. Also for high current those strips can get toasty
Tools needed:
- Dremel Tool
- Hot Soldering iron
- flux

Soldering water as alternative to sanding down the poles is also possible but highly corrosive. You need to wash everything well or you'll get a lot of rust quick

Everything you need has been here for a long time, you just need to look for it...
https://intofpv.com/t-elrs-long-range-an...ybe?page=4

(26-Jan-2024, 04:37 PM)MomoBrut Wrote: Everything you need has been here for a long time, you just need to look for it...
https://intofpv.com/t-elrs-long-range-an...ybe?page=4

very nice job! respect! did you never have temperature/delivery problems with the shrink on? how many amps do you require of your pack when you take-off?