Pardon the dumb question… but what is currently the best source for buying a kWeld complete kit for someone in the USA?
There’s a distributor in the US, but I bought mine from Germany and it got here faster than ground shipping within the us would’ve arrived. Then I got my lipos from hobbyking.
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Same - took about a week from Germany to US, $220 or so shipped.
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Hi folks,
I’m looking to build a lifepo4 pack for LED strips, and I kind of want to use these 32650 cells from battery hookup. NEW BATTERY HOOKUP LIFEP04 32650 3.2V 6000MAH CELLS – Battery Hookup
At $2.60 for 6000mah, is there any other deal that comes close?
Alas, I have no spot welder, but I do have a 3d printer, so I’m hoping for some kind of NESE-like thing. Has anyone designed something for 32650 / 32700 cells yet? I didn’t want to post on an old thread, but @winfly @shaman maybe one of you has made some progress on this? Another Printable Modular 18650 Battery System - #11 by shaman
One more thing, since it’s meant to drive LEDs, and the 12v strips can’t really handle the 14.4v of a fully-charged 4s lifepo4, I think I’ll need some kind of voltage regulator?
Does anyone use voltage regulators in their packs or know what I should do to bring 14.4 down to a steady 12v? A bit lower voltage would be okay, but the diodes can’t really be driven higher than 12v.
Thanks!
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12V DC Buck converters cost basically nothing and should work
The amperage will be so low and lifepo4 is so much safer that a compression system will be fine. You could even use bog standard battery springs in your rig if the amperage is low enough (what wattage LED strip? its probably under 5A in which case these are good to go), i.e
also you can use a $30 spot welder for this. Because you can use .1 nickel plated steel strips the welder can be garbage and it’ll still weld it.
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100% just buy direct from www.keenlab.de
Too many horror stories buying from the US ‘distributor’
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Yep, that’s what I did. Thanks man!
Oh he’s not THAT bad…
Btw, ya like spreadsheets!?
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Can anyone recommend a 21700 cell smart charger (4 bays or thereabouts)?
Or what is the preferred method of measuring IR and charge prior to assembly?
idk about measuring IR but I run all my 21700s through my Nitecore D4 charger (it’s a 4-bay)
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Lol, he seems completely unreliable and untrustworthy.
#fuckthespreadsheets
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I’m using one of these for checking cells prior to assembly:
The IR measurements are nowhere near what is listed on the cell’s datasheet, but the readings are consistent, which is what matters. I’m pretty much just checking for outliers.
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Round cell chargers are almost all useless for IR measurements unless you want to just compare cells against each other and not know the actual resistance. Whichever one you buy you MUST press up against the bottom contact when making the measurements and insert/remove each cell a couple of times to ensure that the readings are consistent.
Inaccurate readings are okay for comparing cells against at each other as long as they are consistent. Inconsistency makes any measurements useless.
@BenjaminF’s YR1035+ meter is a fantastic AC IR meter, very accurate. All round cell chargers measure DC IR. Both types of IR can be used to sort cells but DC IR is what’s needed to calculate potential (no pun intended) voltage sag.
The cell-to-cell differences are larger with DC IR so that makes sorting easier for me but I also use YR1030 and YR1035 meters all the time (in addition to a BK Precision battery analyzer) for AC IR measurements so don’t think that just because DC IR is what’s needed for voltage sag calculations that AC IR should be avoided.
Those YR meters make getting accurate IR measurements verrrrry easy to do and they are inexpensive too. A decent DC IR meter is much more expensive, starting at around $150 IIRC. I recommend the progressiverc.com ESR Meter.
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Gasp
How dare you.
The au (and I can’t stress this enough) DACITY!
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I honestly had no idea. I thought this was a very inaccurate DC IR meter 
I have been eyeing the progressiverc meter for a while, but the fact that it’s designed for a 6s LiPo pack has always turned me off to it. I dont know how it would work to measure one cell at a time (though I’m sure its possible)
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LOL…it’s actually a decent AC IR meter.
It was within about 7% of the readings from my calibrated BK Precision BA6010 battery analyzer. I thought that was incredibly good for the price.
The datasheet AC IR numbers are maximums that I have never seen in a cell I’ve tested. They can be a lot higher than what you might measure so they can be tough to judge cells against.
What is nice about AC IR meters is that they use very low current levels so the readings are not affected much by cell interconnect, wiring, and connector resistance. DC IR meters measure the resistance of everything they’re connected to. This can be great for things like actual total pack resistance and estimating voltage sag but can be a real problem if the wiring, connector, etc., resistance is not taken into account.
The Mark II versions sold are 1S-6S capable so single cell measurements are possible. Here’s the all-things-ESR Meter thread with some great info: The official new ESR/IR Mark II meter thread NB: READ THE FIRST 10 POSTS - RC Groups
I’ve been reading single cells with them for years now. All of my posts and tables use those numbers.
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Could you post a pic of your test stand for single-cell testing? I’m having trouble picturing what the actual usage of this device would look like, though I’m certain that’s just a lack of imagination on my part.
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Here is the jig. This unit needed a external PSU mod to do high-res testing of single cells as 1S didn’t supply a high enough voltage to operate. I also removed the balance connector and wires as this is a single-cell-only setup for me.
Check with Progressive RC or the manual to see if the external PSU mod is still needed for 1S. IIRC the manual had a graphic showing the connections for single cell testing.
The two loose leads are for any cells/packs that won’t fit in the holder.
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Okay, welcome to the reality show called: Will Jan put his office on fire?
I’m starting to rebuild my 12S3P NESE battery to a 12S5P. Now, the problem is that I don’t have space for 12S5P with NESE modules. Spot welding seems inevitable. I haven’t done it before but I have read about on the Internet. 
To start with, here’s my idea of the parallel groups. Since I’m generally clumsy and I don’t like glueing things together and I don’t have enough fishpaper on hand and I like to 3D print stuff, I came up with this to both make the cells hold together and to insulate the P-groups:
Here’s a mock up of how I imagine the end result will look like:
The walls are only 0.8mm thin so this actually isn’t a lot bigger than if I wrapped the cells in fishpaper. It takes quite long to print but after that assembling the P-groups is super easy.
One potential issue I have considered is that when soldering wires on the nickel to connect the series, the printed part under the nickel gets hot and may deform. I have actually tested it and it doesn’t seem too bad. It’s printed from PETG so the heat resistance is decent.
Any other thoughts why this could be a bad idea before I go down?
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