This could be interesting

Haugen

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@Bob B @ghostwriter66 I won't have time this weekend as I planned, but I made a quick concept version - see pictures below. This is done with the wrong vice and at the end of the braid which I usually discard since it tends to be all 'fluffy' - it's also not fully inserted. I also didn't drill the hole. The annealed copper tube was 18mm outer, 16mm inner diameter and the braid is ~25mm wide. One can tin the end part with a torch if needed/desired without solder wicking all the way on the braid (it's a pretty controlled process, you can also feed solder through the drilled hole, etc.).

One nice thing about using tube like this is that you can create single strands with multiple contacts, so if you for example want to have one with three holes (two ends and middle), this is easy as well.

View attachment 15209

View attachment 15210

If needed, you can also grind the ends a little should they not be fully flat. However in the pictures above that's just because of the wrong vice.
So, you are soldering the braid together to make it possible to secure it on the terminal?
Adding lead, tin, and copper to aluminum battery terminals is inviting galvanic corrosion.
The hidden nooks and crannies of the braid could trap moisture and prevent discovery of degradation at the early stages.
 

Bob B

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Sep 21, 2019
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@Bob B @ghostwriter66 I won't have time this weekend as I planned, but I made a quick concept version - see pictures below. This is done with the wrong vise and at the end of the braid which I usually discard since it tends to be all 'fluffy' - it's also not fully inserted. I also didn't drill the hole. The annealed copper tube was 18mm outer, 16mm inner diameter and the braid is ~25mm wide. One can tin the end part with a torch if needed/desired without solder wicking all the way on the braid (it's a pretty controlled process, you can also feed solder through the drilled hole, etc.).

One nice thing about using tube like this is that you can create single strands with multiple contacts, so if you for example want to have one with three holes (two ends and middle), this is easy as well.

View attachment 15209

View attachment 15210

If needed, you can also grind the ends a little should they not be fully flat. However in the pictures above that's just because of the wrong vise.
Thanks for the pictures.
What do you use to cut the braid?
 

Haugen

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No, I'm not soldering anything together. I said one could solder (the inside) if needed/wanted, but the basic principle is just like a crimp: a cold weld between the tube and the braid by compressing them.
Got it!
I misread and didn't catch the annealed copper part. It looked silver in the pics and the mention of solder got me concerned.
Sorry about that.
 

JoeHam

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Available pre made also:

 

Sojourner

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Nov 28, 2019
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What BMS is this? Can you post or re-post the link?

The BMS is compact and feels very robust, encased in metal all the way. Proper copper leads, two external temperature sensors. It supports low and high temp cut-off. Of course, 'manual' is lacking, so just for reference: it won't turn on until you put a charger on it (voltage applied needs to be higher than the battery voltage), the Bluetooth pairing code is '1234' and the pin code to make changes to the BMS values is '123456'.
DSC_1348-preview3.jpg


Screenshot of the app. I just put a quick 16 cell pack together, so ignore things like wire resistances and remaining capacity etc. The voltages are looking good, and the integrated balancing seems to work very well. This is the 100A discharge current with 0.6A balancing current version I got to test and play with. If this thing works properly, I'll get the one with 300A discharge current with 2A balancing current version.
Screenshot_2020-06-10-14-48-36.png
 

Sojourner

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Is cold salt water colder than ice water?
hah, I dunno, but Will uses salt water for low temp cutoff tests in his more recent videos after others suggested it to him. What the significance is, I'm not sure.
 

Sparky

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hah, I dunno, but Will uses salt water for low temp cutoff tests in his more recent videos after others suggested it to him. What the significance is, I'm not sure.

Idk off-hand what temp he's using, but it's true that saltwater has a lower freezing temp than fresh water.


NOAA said:
Fresh water freezes at 32 degrees Fahrenheit but seawater freezes at about 28.4 degrees Fahrenheit , because of the salt in it.
 

Sojourner

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For instance...


I suppose it makes sense if you're testing cutoff at freezing temp of 32F, you'd want a liquid at less than that, otherwise you'd be trying to stick the sensors into solid (ice).
 
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Haugen

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Idk off-hand what temp he's using, but it's true that saltwater has a lower freezing temp than fresh water.
That's all true, but unless he freezes the ice water and uses it to create the ice bath, it will be no colder than 32. You can't lower the temperature of the water by adding salt.
The fresh water ice will not accept more heat just because it is in a saltwater environment.
 
D

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That's all true, but unless he freezes the ice water and uses it to create the ice bath, it will be no colder than 32. You can't lower the temperature of the water by adding salt.
The fresh water ice will not accept more heat just because it is in a saltwater environment.

Not quite. It needs to get to 32, which will not freeze salt water, but will trigger the sensor.
 

Sparky

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No, adding salt to water that doesn't contain ice doesn't magically decrease the water's temperature, however, adding salt to iced water will do so, by chemically stimulating the ice into melting "early", causing it to absorb the heat necessary to melt.

"At 0C equilibrium is reached and the temperature cannot go any lower. This is not cold enough for making ice cream. When salt is added, the equilibrium will be reached, and kept at the lower temperatures required. "
https://www.mcgill.ca/oss/article/you-asked/salt-used-melt-ice-it-also-used-make-ice-cream-why
 
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