is it plausible to re use "defective" E bike batteries? how would you do it?

[oldspice]

There's a short delay as the cell is inserted. As it's charging, it will alternate between displaying the charge current and the IR. When charging is complete, it will alternate between "Full" and "XXXmΩ"

I wait until they're fully charged before recording IR. It usually improves vs. the number reported when charging begins.

Thanks for some reason it wasnt showing before... i swear XD...

And thanks for the info on the battery side offgridinthecity

 

[oldspice]

so theres no such thing as desoldering those spot welded points? only force ? just wanting to double check

 

[sunshine_eggo]

so theres no such thing as desoldering those spot welded points? only force ? just wanting to double check

If they're soldered, yes, they can be desoldered, but the vast majority of them are spot welded, and there's likely no solder to desolder. Soldering also inputs a LOT of heat, which risks damaging the cell. Desoldering would present the same risk.

Pictures?

 

[OffGridInTheCity]

As @sunshine_eggo says they are spot-welded for the most part. In fact, over 5 years and 13,000 cells I've never seen any soldered. The spot-welds are weak enough to let you just pull/leverage off the original nickel strips 99.9% of the time.

When building batteries, spot-weld is preferred and quicker but takes a bit of time to learn. However, the risk of solder/heat is overblown in my experience - e.g. all 12,000 cells I've done are soldered with no issues.

Part of the solder trick is to use proper solder that doesn't corrode over the years such as this self-fluxing solder - https://www.amazon.com/gp/product/B00DE2QVIG/ref=ppx_yo_dt_b_search_asin_title. The other part is to minimize prolonged heat transfer. I use 100w soldering iron - https://www.amazon.com/gp/product/B002I7X7ZS/ref=ppx_yo_dt_b_search_asin_title - and do 2 passes.

1st pass is to apply small blobs (3-5sec) then on the second pass do wire -> buss (3sec to melt blob around wire). This keeps heat transfer minimal and I've never had an issue. Note: my oldest, soldered packs are >5years and 1,700 cycles now with no detectable degradation.

Here's an old but still relevant youtube on soldering/heat-transfer to illuminate the heat transfer in actuality. This guy was an early adopter when 18650 was 'hot' (ha ha) and this was a huge topic.....

He uses a monster 300w (level) iron but it was too heavy for me and the tip crumbled within a few hours whereas the 100w Weller does fine and lasts months / 1,000(s) of solders.

But again, spot welding is the preferred recommendation and quicker.

 

[oldspice]

As @sunshine_eggo says they are spot-welded for the most part. In fact, over 5 years and 13,000 cells I've never seen any soldered. The spot-welds are weak enough to let you just pull/leverage off the original nickel strips 99.9% of the time.

When building batteries, spot-weld is preferred and quicker but takes a bit of time to learn. However, the risk of solder/heat is overblown in my experience - e.g. all 12,000 cells I've done are soldered with no issues.

Part of the solder trick is to use proper solder that doesn't corrode over the years such as this self-fluxing solder - https://www.amazon.com/gp/product/B00DE2QVIG/ref=ppx_yo_dt_b_search_asin_title. The other part is to minimize prolonged heat transfer. I use 100w soldering iron - https://www.amazon.com/gp/product/B002I7X7ZS/ref=ppx_yo_dt_b_search_asin_title - and do 2 passes.

1st pass is to apply small blobs (3-5sec) then on the second pass do wire -> buss (3sec to melt blob around wire). This keeps heat transfer minimal and I've never had an issue. Note: my oldest, soldered packs are >5years and 1,700 cycles now with no detectable degradation.

Here's an old but still relevant youtube on soldering/heat-transfer to illuminate the heat transfer in actuality. This guy was an early adopter when 18650 was 'hot' (ha ha) and this was a huge topic.....

He uses a monster 300w (level) iron but it was too heavy for me and the tip crumbled within a few hours whereas the 100w Weller does fine and lasts months / 1,000(s) of solders.

But again, spot welding is the preferred recommendation and quicker.

thanks again for the reply. do you happen to have any recommendations or links to a good spot welder? - i have seen videos of people using DIY battery pack ones which look cool but i dont think im ready to make one myself. I have seen generic looking battery pack ones on ebay / amazon but some of the reviews have me turned off talking about them being too weak etc. trying to keep it low cost too

 

[OffGridInTheCity]

thanks again for the reply. do you happen to have any recommendations or links to a good spot welder?

I went solder and have stuck with it. There are youtubes but I don't have any experience. KWeld is a common name.

- i have seen videos of people using DIY battery pack ones which look cool but i dont think im ready to make one myself. I have seen generic looking battery pack ones on ebay / amazon but some of the reviews have me turned off talking about them being too weak etc.

The term 'weak' doesn't make sense - it's just a matter of number of cells, their specs, and load. 18650 NMC has significantly more power per weight/size than LifePo4 for example. High amp cells may be competitive with lead-acid for bursts. The term 'weak' doesn't mean anything without details.

trying to keep it low cost too

It sounded like you aquired 'free'? ebike packs in you're original post. Most of my 2nd hand cells cost ~$1/cell overall over the last 5years and this yielded ~$200/kwh overall. If you have cells for free + you have time, you could achieve ~$96/kwh in costs per my example.

It's all a matter of purchase price + labor + you're situation and these variables are changing all the time

As an example, @DavidPoz just put together a DIY powerwall type battery at ~$140/kwh - really great price if you're DIY inclined....