First Battery Build 21700 Molicel P42A

Batteries, Chargers, and Battery Management Systems.
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Re: First Battery Build 21700 Molicel P42A

Post by 999zip999 » Feb 22 2021 9:58pm

I was thinking of that sell but in the 18650 version

Has anyone already tilt a pack out of either one of these cells and how do you like it I'm battery Texas


MOLICEL P26A 18650 2600MAH 35A BATTERY
(412)
Regular price $4.99 or $3.99 over one hundred.
I did want Samsung 30q but hearing bad things about it. Then Samsung 25r but if some Samsung with self discharge ???

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Re: First Battery Build 21700 Molicel P42A

Post by kudos » Mar 03 2021 11:40am

Image

I have a question, I accidentally bought some nickel strip which is specified as nickel plated steel, when I actually wanted pure nickel.

Out of interest, I've tried the scratch and submerge in salt water technique to check for rust, but no matter what I do I can't seem to get any rust to appear. I've re-scratched on both sides and re-submerged in saltwater for two days and nothing.

I'm not sure what I'm doing wrong?
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flippy   10 MW

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Re: First Battery Build 21700 Molicel P42A

Post by flippy » Mar 03 2021 1:18pm

then you have real nickel.
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Re: First Battery Build 21700 Molicel P42A

Post by kudos » Mar 03 2021 1:25pm

Maybe the seller mixed up the pure with the plated...?
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Re: First Battery Build 21700 Molicel P42A

Post by kudos » Mar 04 2021 4:37am

Image

So I tried again with some other nickel I received when I bought my cheap spot welder and hey presto - rust.

I'm glad I have a way of testing nickel and even more glad I received pure nickel from the seller when he was advertising nickel plate... :D
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Re: First Battery Build 21700 Molicel P42A

Post by kudos » Mar 06 2021 11:24am

Image

My cheapy spot welder can’t weld 0.15 nickel to the 21700 but can weld 0.10

According to the nickel current charts this is still very capable of handling the 6.6A peak that i need.(40A / 6)

I would prefer to use 0.15 but even after watching every video on YT I can find I’m still not sure what welder can do this?

Most videos show a single nickel step being welded to cells but they don’t then add the second strip required for paralleling.

Most welders require a separate power source such as 3S Lipo which I don’t have and is a pain to get in my area, can’t send lithium in the post unless it’s contained within a device already. I can get it, but it requires expensive special delivery now, which isn’t ideal for such a small battery.
Edit: just checked hobbyking and they are basically sold out of lipo by the looks of it.

Can anyone recommend a welder, that’s readily available online, that will reliably weld 0.15 to 21700’s ??
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Re: First Battery Build 21700 Molicel P42A

Post by flippy » Mar 06 2021 1:05pm

kudos wrote:
Mar 06 2021 11:24am
Can anyone recommend a welder, that’s readily available online, that will reliably weld 0.15 to 21700’s ??
kweld.
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Re: First Battery Build 21700 Molicel P42A

Post by kudos » Mar 06 2021 2:57pm

https://flipsky.net/products/mini-intel ... ine-sq-sw1

This also looks good but no suitable 3S lipo available on HK.
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Re: First Battery Build 21700 Molicel P42A

Post by Inwo » Mar 06 2021 9:35pm

What makes this welder suitable for aluminum?
Over, say this one.
Screenshot_20210306-204444.jpg
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Re: First Battery Build 21700 Molicel P42A

Post by Inwo » Mar 07 2021 2:11am

Can't find a place to order k weld in USA.
Anyone have one for sale?
Although, I haven't found an aluminum success story yet.

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Re: First Battery Build 21700 Molicel P42A

Post by kudos » Mar 07 2021 4:19am

https://youtu.be/KUBtBJR1PVU

This video shows the Flipsky welding 0.3 nickel.

https://www.sunkko.net/content/JFHSW/709AD-MANUAL.pdf

The tech specs of the 709ad state 0.15 max
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Re: First Battery Build 21700 Molicel P42A

Post by kudos » Mar 07 2021 6:36am

Image

First side done.

I thought 3 metres of nickel strip would be enough but it only lasted one side.
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Re: First Battery Build 21700 Molicel P42A

Post by kudos » Mar 21 2021 5:49am

:wink: Image

I’m not sure why nearly everyone leaves off discharge lead attachment in their tutorial videos, it would be really useful to have a detailed vid on this.

In the end I went with flippy’s suggestion of adding serial tabs but then folding them over the discharge lead and welding them in place. Also soldering the lead along its length using a flux pen.

I find soldering quite difficult but I was just getting the hang of it by the time I’d finished, so the next one should be cleaner.

What I find interesting is that many videos I’ve seen by people who have been building battery’s for years, they simply solder discharge leads to opposite corners of the battery, sometimes by extending tabs off the corners. So I don’t know how important it is for the discharge lead to directly contact every cell in the P group?
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Re: First Battery Build 21700 Molicel P42A

Post by kudos » Mar 22 2021 3:36am

Can anyone suggest a variable voltage charger that can work around 50V ?

I don’t want to charge to 4.2V cell, I want a bit lower for lifespan.

I know the cycle satiator can do this but is there anything else?
Last edited by kudos on Mar 22 2021 4:53pm, edited 1 time in total.
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Re: First Battery Build 21700 Molicel P42A

Post by flippy » Mar 22 2021 12:35pm

kudos wrote:
Mar 22 2021 3:36am
Can’t anyone suggest a variable voltage charger that can work around 50V ?

I don’t want to charge to 4.2V cell, I want a bit lower for lifespan.

I know the cycle satiator can do this but is there anything else?
what current level are you seeking?
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Re: First Battery Build 21700 Molicel P42A

Post by kudos » Mar 22 2021 4:49pm

Hi flippy,

It's a really good question.

Since asking this I've found two options:

Meanwell HLG-100-48A - Cheap, only a piddly 2A but voltage and current adjustable, not that you would adjust 2A downwards but the voltage can be adjusted to the region I'm looking for. Also I see from other posts on here that you can add these chargers in parallel to up the amps.

Chargery C10325 - Expensive but can do 25A. The cells I'm using are amazing according to the data sheet. I could charge the pack I've built at full power with this and still wouldn't reach the max they can take by some way.

I'm currently using a 6A charger, so to be honest I think around 10-15A would be fine.
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Re: First Battery Build 21700 Molicel P42A

Post by flippy » Mar 23 2021 5:57am

HRP-600-48

has a range of 40.8 ~ 55.2V wich should put it nicely in your 12S battery wich tops out at 50.4V.

current is not ajustable so it will always top out at 13A. but that is sort of your sweet spot if you want semi-fast charging at 2A per cell. wich should be fine for these cells.
for slower charging you can still grab your 6A charger you are already using. soemthing i recommend whenever possible.
advantage is that the meanwell is vastly smaller and lighter and higher quality then the chargery so semi-fast charging on the road is possible. 80+% charge would be less then an hour in normal use. its also cheaper and has 5 year warranty versus 2 on the chargery. but i doubt you will ever break it. i never seen a dead one and i have sold hundreds of them.

personal note: your cells are not as great as you think. be gentle with them. dont charger faster then you have to. if you can manage with a 6A charger: use that. this is a pricy investment, take care of your investment and dont abuse it if you dont have to. fast charging is the main killer in most batteries.

Ps: next time weld the series tabs first, then the parralel tabs. The series tabs need to carry the current so they go on first. Also: 1 parralel strip was enough. Its only there to keep the cells equal, it does not carry any current.
Its a very common mistake but one that need to be pointed out every time so others that see this dont make the same mistake.

If you create the tabs for the leads: make the tabs longer so you can fold it down the side and keep the top of the pack flat to put a sheet of polycarbonate or acetal on it and glue/tape it down flush on the pack for structural support. The cell holders are not -that- strong. a sheet of hard plastic also protects the cell terminals from "ingress" if something hits it and pierces the kapton. use at least some of that "good" ducktape with textile fabric stuff to protect the pack a bit more. that kapton does nothing for physical protection.
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Re: First Battery Build 21700 Molicel P42A

Post by kudos » Mar 23 2021 8:23am

Thanks for your detailed response.

Regarding the welding, having read the relevant posts on here before I started, I was well aware it’s best practice to weld the series tabs first, which I did. I then added a single parallel strip, then doubled up the series tabs. I’m not sure if it would have been better to double up the series tabs first then add the parallel, thinking about now that probably would have been better.

If my 6A charger wasn’t fixed at 50.4V I probably could live with this, but I need to adjust it down, I’d like to charge to 4.08V cell.

Regarding physical protection, the battery is being housed inside a plastic box which I had handy, just happens to fit really well in the bike. I’ll be adding some foam protection to cushion the battery inside the box too.

Image

I get your point about charging at the lowest current that’s acceptable for longevity too.
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Re: First Battery Build 21700 Molicel P42A

Post by izy » Mar 23 2021 8:38am

kudos wrote:
Mar 23 2021 8:23am
Thanks for your detailed response.

Regarding the welding, having read the relevant posts on here before I started, I was well aware it’s best practice to weld the series tabs first, which I did. I then added a single parallel strip, then doubled up the series tabs. I’m not sure if it would have been better to double up the series tabs first then add the parallel, thinking about now that probably would have been better.

If my 6A charger wasn’t fixed at 50.4V I probably could live with this, but I need to adjust it down, I’d like to charge to 4.08V cell.

Regarding physical protection, the battery is being housed inside a plastic box which I had handy, just happens to fit really well in the bike. I’ll be adding some foam protection to cushion the battery inside the box too.

Image

I get your point about charging at the lowest current that’s acceptable for longevity too.
haha you instil some confidence in me.

im building a triangle bag pack for my own personal build using 21700's

im doing 14x6 noticed you got the same welder i did and worked out fine.
any tips for what settings you used?
mine is yet to arrive and it there is 6 power settings what worked best for you.
did it spot weld better head on with pressure or at a slant?

im using samsung 50G for my build and a smart bms give me some monitoring.

thanks again

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Re: First Battery Build 21700 Molicel P42A

Post by flippy » Mar 23 2021 9:41am

kudos wrote:
Mar 23 2021 8:23am
Thanks for your detailed response.

Regarding the welding, having read the relevant posts on here before I started, I was well aware it’s best practice to weld the series tabs first, which I did. I then added a single parallel strip, then doubled up the series tabs. I’m not sure if it would have been better to double up the series tabs first then add the parallel, thinking about now that probably would have been better.

If my 6A charger wasn’t fixed at 50.4V I probably could live with this, but I need to adjust it down, I’d like to charge to 4.08V cell.

Regarding physical protection, the battery is being housed inside a plastic box which I had handy, just happens to fit really well in the bike. I’ll be adding some foam protection to cushion the battery inside the box too.

Image

I get your point about charging at the lowest current that’s acceptable for longevity too.
yes, doing the series first would have been better.

from the looks of it you can fit that charger inside the box. probably does need some ventilation to keep it cool tho.

i do notice a distinct lack of a bms.... :roll:
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Re: First Battery Build 21700 Molicel P42A

Post by kudos » Mar 23 2021 1:21pm

Izy, I used the most powerful setting level 6 on the welder for all welds. I found this was able to weld 0.1 to 0.1 no problem but 0.15 or larger was a no go. I was however able to weld 0.1 to 0.1 to 0.1 ie three layers deep.

I didn’t find a lot of pressure was required, but definitely some.
I also noticed after a fair few welds the tips would blacken up a bit so twisting them would help sometimes.
I gave them a few cleans but I’m not sure it made much difference.

Good luck with your build.
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Re: First Battery Build 21700 Molicel P42A

Post by kudos » Mar 23 2021 1:32pm

Flippy , this is my test battery to learn.

I’ve managed 10 years without a BMS using lipo zero issues, so I’m seeing if I really need one with these cells.

I just measured my four 16AH multistars that I haven’t balanced charged in 4 years, all within 0.1V

If I find I do need a BMS, it’s straightforward to wire one up to the balance leads I’ve attached.

I do have another question on low voltage cut off.

I set LVC on my Cycle Analyst, what do people suggest as LVC per cell ? 3.6V or lower maybe ?
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Re: First Battery Build 21700 Molicel P42A

Post by flippy » Mar 23 2021 1:55pm

if you plan to run these cells hard you set the LVC to 2.5V. otherwise it will cut out well before its empty.

3.6V is dumb, that is litteraly 50% of capacity.

if you dont run this pack hard and you want some lifespan you can hold 3V als your LVC.

ps: 0.1V is a LOT. inbalance should never exeed 0.01V.
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Re: First Battery Build 21700 Molicel P42A

Post by kudos » Mar 23 2021 2:26pm

I’ve had my lipo set at 3.67V LVC for years, with 32AH available and only taking half, I still get 20 miles which has been enough for me and cells stay balanced.

Probably why they have lasted so long.

You’re right 0.1V is a lot, typo, I meant 0.01V

I’ve just had my first ride WOT for half an hour including very steep hill, battery barely warm to the touch.

PS Just ordered an ANT BMS.
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Re: First Battery Build 21700 Molicel P42A

Post by kudos » Mar 23 2021 3:07pm

Izy, I see those Samsung 50G are rated at 9.8A max continuous so 6P gives 58.8A, what size amp controller are you using?
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