How do I connect/solder bars to 18650 cells

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mckeand13
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How do I connect/solder bars to 18650 cells

I’ve got this 4×18650 battery pack for a bike light and the cells are pretty tired. I’d like to replace them, but I’m trying to figure out the best way to do so. They’ve got very thin bars connecting the cells on both the top and the bottom. It looks like those are spot welded, and I’m assuming won’t come off all that easily.

What options do I have as far as soldering something to join the cells. I’ve done plenty of soldering, just not directly to a battery. I assume heat is a major concern.

Thanks.

IMG-1813

Edited by: mckeand13 on 11/11/2021 - 23:18
wle
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use high heat and high power [minimize time on the cell contacts]

tin the bar and cell first

use lead solder [not lead free, melts lower]

use acid flux [i think]

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mckeand13
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Any suggestions on what to use for the strip? Maybe I could find some brass at the hardware store.

flydiver
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I use de-solder braid with a small bit of shrink for insulation in the middle. Easy to work with and has good throughput.

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d_t_a
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I often see pre-fabricated ‘nickel strips’ being sold by stores that cell batteries / battery pack / solar BMS (battery management system), I think they are used for joining batteries together to forma a a battery pack like the one on your bike.

However, I have no personal experience with those nickel strips nor with soldering directly to batteries.

I wonder if nickel strips are the best (budget?) choice or if there are some other better materials for joining a battery pack together though.

YuvalS
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mckeand13 wrote:
Any suggestions on what to use for the strip? Maybe I could find some brass at the hardware store.

I am using regular wires (according to the current rating).
make sure to have isolation on the positive side since the heat may damage the thin heatsrink and expose the negative side.

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