LiitoKala 21700 12s5p 20Ah Build

iirc cells typically improve after a few cycles as well correct? When you put your board specs into the calculator what kind of mileage did it give?

good news! the metr pro came today and I installed in the unity… will try and squeeze a ride in tomorrow around central park or something if i can… bad news…no big local rides around my area until after the weekend =/

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This will burn the pack sooner than later. Although it is a short piece of nickel. The heat generated cannot dissipated enough to the copper and cell. I highly recommend to improve your design. That piece of nickel can only handle max 8-10A. Please take the advice seriously.

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Are there actually some real world test to confirm this?

Doesn’t the current run through the entire length of the nickel strip?

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I don’t think it will fuse as the fusing current is still higher than what the OP will ever draw from that pack.
But higher resistance in the nickel only can lead to the fact that the pack gets out of balance more „fast“.
In fact it will work, but the design idea with the copper doesn’t make much sense if you don’t do the copper from cell to cell :tipping_hand_man:

Yes, but :face_with_monocle: let me pull out my Picasso skills :sweat_smile:
Like in a water pipe which is slimmer on one part, the speed of the flow gets higher

Or let’s make it more electrical.
You charge with 10A.
Once you use 12Awg for the charge wires, the other time you use 22Awg.
Which wire gets warmer?

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I checked this table against my own bench testing with a primary injection tool (up to 70A).
The table is spot on.

Of course we are talking about continuous current. While the loads during riding vary a lot.
However your battery pack should be designed for certain base load.

In the battery above you are playing with fire…

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But do you think there is a difference in heat if you were to series the connection directly to the next p group as opposed to what is done here?

And I mean one connection then not two.

If it’s one it would be probably the same.
Hard to say from the picture, but the length from cell terminal to the copper x2 is probably the same length if you would go from one terminal directly to the other.

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Of course he wouldn’t have the same flexibility but good to know it wouldn’t matter.

Basically it’d be fine if there is at least another nickel strip on each side connecting it all together.

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it was kind of a hybrid idea off of the pcb’s people use and copper braid… in the past ive use silicone wire to make series connections but since these were 20700s and my particular case there is zero room for anything to be inbetween the pack or on the sides…if you watch the video you can see the tight fit… but with that said I could add an extra nickle strip up top on each pack to connect to the braid once Im done testing… this isnt a forever pack although its been running great so far… more to come on that later… but I already have a a bunch of 30qs coming for another build so eventually Ill probably pass this pack off once done testing and maybe add a lil wire upgrade for it.

like wise… i guess i could have made one long strip up top and used silicone or copper just like a pcb

What is the length of material used for each category? Current capabilities are relative to length. Longer strips= higher resistance= higher heat= lower current.

Longer strips= higher resistance= higher heat= even higher resistance = even more heat :wink:

these test are done witch short pieces of nickel (5-10cm). Depending on the application. Length is more an issue for voltage drop rather than current issues.

I don’t think that pressure gets higher in slimmer water pipes.

In slimmer pipe the speed increase in cost of pressure.

But electrons can’t flow faster since they always go at speed of light.

I’m not scientist I don’t understand this properly, correct me if I’m wrong.

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Part of it depends on the fluid. Water is essentially in-compressible so theoretically the pressure should not increase, but the speed would for sure. The velocity increases to zero out the equation.

Ok… Just got back from another biz trip but was able to squeeze a quick ride in today and first time recording with the metr so this is a new tool/toy for me. Not sure if this data helps or shows anything BUT one interesting thing today was at the end of the ride my batt meter was reading about 30% but I had almost zero off the line amp acceleration…! It felt like it was at zero… Then I came around the corner for a semi steep climb and the board was dead…dead as in no power to carry my weight …interesting

I also find ot interesting my max current is 79 when my battery max is set at 70… Maybe it’s a newbie observation of using metr.

well what is 30%. It could be that the voltage droped below cutoff or soft cuttoff. combined with the incline…

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That´s some interesting stuff…
so you have a solid 6V sag at 60A draw from the battery.
what esc you have on this build?
the metr add up the values if it´s set to dual. so as long as it´s not a unity than its esc1 current + esc2 current.
about the cut out at the end :tipping_hand_man:
you at 88 degree on your esc. power down starts at 80 degree.
looks like your esc settings defintely a bit high for what you use or you need better cooling.
the total cut off should happen only at 100degree, so maybe you hit your battery cut off as well. we don´t know to which you set this value when yous set up your esc.

So running unity… 60/60 and 70/-24 on.battery… 6" tires at 20/60 …gearing could suck someof that up as its not the most efficent ratio but I’m only 140lbs but might drop back.down to.18/60 to.see if that has any effect once I get a few more test rides and data in.

Batt soft cutoff was left at unity specs which I think is 40.8 which at the very end I see it dip to 40.7 for a hot second… But this would be the first time in the weeks ive ridden this pack its acted this way =\ hmmmm

88 degree is definitely too hot.
I mean for this settings the unity should run way cooler? :thinking:

Well… It is in a case…and it was hot yesterday…and humid… But there have been days recently way worse weather wise where it still ran well… More testing needed lol

Will have time for another long ride tomorrow if it doesnt rain

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