DIY Battery Pack with copper cable, need help

A

andurilmik

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Apr 8, 2017
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Good evening,

I would like to make a pack of 18650.

But I would like it to be connected between it with 1.5mm copper wire intended for 16A in 220V.

Could that be okay?

The battery will power a 12V - 220V converter.

Which produce maximum 150watts therefore 12.50A in 12V.

Will that be enough?

Knowing that I intend to use 3 rows of 18650 connected in parallel and the rows itself connected in series.

This will give more or less 12V.

Thank you

A +
 
As far as I am aware 1.5mm will be able to cope with 12.5A of current, but it might get warm. I would personally go with 2mm.
 
That's what I thought.

What if I twist several copper cables together?

Like a braid.

I wanted to use nickel strip this week end but soldering with tin and not spot welding.

I saw a part of the nickel band catch fire and one of the piles had the + and the - link because of the tin.

It chilled me, I'm a little scared now.

But everything is back in order, I manage is nothing caught fire and nothing explode.

More fear than harm.
 
Twisted is better than just plain straight because its guarantees 100% contact between 2 strands and that they are evenly carrying the load.

Did you get the sparky's on video? :p

It's good that nothing really happened except you possibly needing to change pants. You were only dealing with 12v or so and things were probably relatively safe. That's something we all have to watch out for when connecting side 2 together since the danger level jumps drastically of shorting out. Pete (HBPowerwall) did that a few days ago. He accidently connected the two ends together and create lots of sparks, shocking experience (both to the equipment and him), and possibly a new pair of pants afterwards (he never did say if he had to change or not). BUT, he caught it on tape :p A lesson learned for all of us.
 
thank you,

It is true that it happens but it is quite shocking.

Especially when you see flames, it's really scary.

So I should tweak the cables, but 2 of 1.5mm will suffice or not?

I did not need to change pants.

And now I hate the nickel bands.

Thank you
 
Elmo could better give you advise on the cabling. *nudge, nudge*

But you should be able to look up wire sizes and losses based off those numbers. Remember, you don't loose voltage in just one cable, you loose it in both. So if you have your battery pack 10 feet from you inverter, then that's 20 feet of loss. To quote Elmo from another thread if you're using 10awg cable (not sure what 1.5mm2 equates to):

------------------------------
At 17A you are losing 17mV for every foot of 10 AWG (1mOhm per foot) in both leads. If your panels are only 5 feet from your controller you'll be losing 170mV (5 feet * 2 cables * 0.017), 50 feet and you'll be losing 1700mV.

At 50 feet and 30A you would be losing 3V in the 10 AWG cables
------------------------------

He's referring to solar panels, but the info still is valid.
 
The resistance of 1.5mm^2 CU wire is about 11 mOhms/meter, the math is fairly simple, multiply Amps times resistance expressed as a decimal so .011 * 12 = .132V/meter loss or .013V/cm.

Twist two together and you halve that number.
 
andurilmik said:
Good evening,

I would like to make a pack of 18650.

But I would like it to be connected between it with 1.5mm copper wire intended for 16A in 220V.

Could that be okay?

The battery will power a 12V - 220V converter.

Which produce maximum 150watts therefore 12.50A in 12V.

Will that be enough?

Knowing that I intend to use 3 rows of 18650 connected in parallel and the rows itself connected in series.

This will give more or less 12V.

Thank you

A +
Click to expand...
It will absolutely be OK ... you are using less current than the max. recommended 16 Amps ... and 16 A is extremely cautious , in reality 30A would still be OK ... they always calculate the maxcurrent for worst possible conditions( where the wire is put in a loft with insulation on top so the heat can't escape).
As has been pointed out if the length of cable islong(over about5 meters)it will be worth doubling up to keep power losses down.
 
OK thanks for the answers.

In fact I plan to manufacture a portable battery.

That will hold in a case, so the cable will not be very long.

May be 1 meter or 2.

Thank you

A +

Edit :

This is what I intend to do:




I just put a picture because I translate with google, I'm French.

And I wanted to be sure that everyone is understanding what I want to do.
 
That's a little sloppy, but it will do. I've seen some methods where you take two ends and place in an electric drill and tighten the chuck down. Then take the other two ends and do a quick wrap around a nail or something, then slowly turn the drill and twist the wires together. That will give you an even twist all the way down.
 
Oh yeah!!! MUCH better :D

that looks great
 
On a different note - correct me if I am wrong but I think electricity follows the path of least resistance. In this case (twisted copper pair of solid wires) would it flow on both wires, or just one, and switch if it encounters resistance (like impurities in the wire, etc.)?
 
Regarding twisting its just to twist it. It will be nice in the end if you just stretch it while doing it. I have done 40meter so far atleast and no problem at all :)
 
Thank you for the answers, so according to you I can go there?

I put tension in the wires, so they are twisted well and tightened uniformly.

Thank you

A +
 
Hello,

I finished my battery a few days ago.



I started assembling my project.

But I have some questions?

Regarding the recharging of the battery, I recharge the battery entirely or by 3 level.

I explain, there are 30 x 18650 so I will solder a + wire and - at each end of a series of 10 x 18650 in parallel.

Then I intend to connect this to connectors for female banana plugs.

This is panel mount connectors.



But I do not know if I have to put a + and - or 3 + and 3 -?

Basically is that I can recharge the battery but 10 by 10?

And what sections of wire would you advise you, from 1.5 mm to 16A for 220V or 24 AWG?

Thank you

A +
 
it might have been easier to switch the middle row to minus top, but hey, its your battery^^

you want to charge 3 stacks of 3,7v 10parallel individual? you could do that, you could also just charge them im series, it wouldnt matter that much, timewise
 
I would like to load each set of 10 separately.

Basically 3 pairs of connectors so 3 + and 3 -

I ask you because either I make 6 holes or I make 2 holes.

And since it's plastic I do not have the right to make mistakes.
 
question remains why you would want to charge it that way? you would need to make sure you charge them evenly, btw any bms planned on it?
 
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