Can someone help me decide between HE4, HE2 and 25Rs?
They basically cost the same, have the same capacity and similar discharge rates. I heard from @chaka that some batteries have a higher capacity than others at the discharge we typically use. So which is the “best” one? I want to build a 10S3P pack für my jacob hub motors plus a 6S4P pack to improve my first build (which has pneumatics now 
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25r>he4>he2
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I think @chaka mentioned HE4’s are his favorite right now, but I forgot what the reasoning was. I use 25R’s myself for 2 10s4p packs and they’ve been great so far
I’ve got a 10s4p with 25Rs. Definitely very solid. If the HG2’s were slightly cheaper I would have probably gone for them.
I’ve looked at what the vaping community has done in researching cells. They look at voltage sag, temperature changes, and a slew of other things, all at varying discharge currents. Here’s links to the list of a lot of the cells they’ve tested, and the HE2, HE4, and HG2 specifically.
TLDR (from the links): HE2 = a very good 20A battery HE4 = a good 20A battery but 25R5 is better HG2 = a great 20A battery!
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i´m just thinking about the same thing 
How about Sony VTC4 and VTC5? Anyone use them before?
@elkick and a few others use them, due to their small internal resistance and great life cycle. But they are not cheap
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We used VTC5 and VTC5a only, but Sony stopped production a while ago and it’s difficult to find genuine ones.
They were initially produced for OEMs only and not intended for end users, even though it was possible to get them anyway. But there were s lot of fakes sold.
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Sorry if this is off topic but, is it necessary to spot weld the connections? What are the drawbacks of just soldering them ?
High heat will deform the surface of the cathode/anode which will decrease the capacitance of the cell. It’s certainly possible to solder, but you need a high power iron in order to get the job done as quick as possible. A less powerful iron will need to stay on the cell for too long which will cause damage to the internals of the cell.
yeah, better get someone to weld it for you… soldering (even with tabs on)… is a pain in the A##…
I also used tinned braid wire (flat)… it got so hot quickly that I started to worry about the cells… I think someone suggested using towel or some other methods to cool everything down, though Im not so sure, perhaps it was an idea to use towel if you were using heat gun or something…
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It will be quite hard… almost impossible in some cases… to make decent / strong solder points directly onto the cell… at least I tried it a few times… but the job did not look very nice… I did not test the connections though but it just looked ugly
There’s a second method discussed - use little ‘‘fuse wires’’, then connect these to the ‘‘bus’’ rail. Check some other threads ‘‘cell level fuse’’ to see how it might work. Did not try it though but it is a lot more wise / easier to do than solder fat 12awg cables to each cell I think…
My high heat iron did a pretty good job soldering the cells to my wire. Much easier to solder wire to the cell vs tabs IMO. See below.
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So is spot welding what makes building a Li-ion packs pretty expensive, as far as I could tell the batteries, BMS and other parts needed for the build seem relatively cheap.
Well cells will still be the bulk of the cost. You can get a decent spot welder for $100-200 so it’s a bit of an investment, but you can build a ton of packs with it!
I’m very interested in building my own pack, but I don’t think buying a spot welder to use just one time is worth it for me.
Might be a dumb question but do you think hot glue would do the job? 
Glue the contacts and heat shrink the whole thing so it stays in place.
Definitely not. The glue would probably melt and lose contact after a while due to the vibrations. It may work with a sled, but you’ll have to solder support tabs because the sleds won’t handle much current. The plastic of the sled may melt too depending on the pack and conditions.
If anyone needs new samsung 25Rs i now sell them for 4.25 each. straight from Liion wholesale.
Ill also spotweld them for you for a small fee
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Ive made only one pack so far but yeah soldering with 60w iron was not that easy. It did melt the solder quite quick, i think the problem was that i did not think hard enough how to hold the tabs in place where i want to solder them.
U can try to find cells with tabs welded onto them already. One option is to buy power tool batteries which have tabs soldered. Though you will pay extra for the brand, casing and perhaps bms which you dont need
Thanks for the input! I’ve got a 100w soldering iron, I’m gonna try it out on a few cells. If its too hot i’ll find someone to spot weld it.
I think i’m going to go for the Samsung 25r cells (to make a 8s3p or 8s4p) as they’ve got great reviews here. The only thing I am unsure of is the Samsung 25R shows that it only has a 20A continuous discharge current. My motor has a max of 82A , 3000W. From what I have read so far an “#s4p” pack would multiply the 20A max output of the cell to 80A, is this correct ?
Also if the motor demands more current, that could be limited by a VESC right, I could just limit it to draw 80a?
What is your oppinion about the sony vtc5? Anyone used some? 30A discharge and 2.6a capacity