# Copper strips instead of nickel?

want to build said:
what does the lose of energy looks like with nickel.
to have an idea .
one cm cube for 1meter cube? if you havea visual comparison so i can decide how much it weights in my decision

tx

Cooper : Nickel = 1:4 (loss of energy)

could you retype it i feel there is missing caracters or at least i can not understand it

does that mean that with one same battery et motor setup i woud do 24 miles if nickel is used in welding but

100 miles with the same setup using copper welding?

like 4 times more distance achiveable?

No, it means that you will have less voltage sag during acceleration and four times less waste-heat in the bus material.

spinningmagnets said:
No, it means that you will have less voltage sag during acceleration and four times less waste-heat in the bus material.

How would less bus bar resistance decrease voltage sag during acceleration ? AFAIK the sag is due to cell chemistry. Wouldn't any additional resistance in the delivery circuitry act like a buffer and actually (slightly) decrease sag ?
There are only two ways to mitigate sag I know of: more cells and more power capacitors, the latter beeing by far the most efficient way to do it.

That beeing said a lower resistance in connectors is always welcome and will indeed slightly increase the effective battery capacity, since less energy is wasted on heat, though this is only noticeable in high power system. We are talking about mah gains here, not more.

Perhaps copper buses are not the reason that battery builders see less voltage sag when using the same number and configuration of cells, but with nickel. But lets look at that for a minute.

The voltage has to pass through the series buses. Lets imagine that it is 0.20 thick pure nickel (7mm wide), very common. In a 14S pack, the voltage must travel across 15 of these strips to get from the positive post of the pack to the negative post. If there is roughly one inch from the tip of one cell to the tip of the next cell, that's roughly 15 inches of nickel. There's no way of getting around having 15 inches of conductive material in that configuration, and it can be nickel, copper, or something else.

Try this...take your battery pack, measure how much actual length is in-between each cell on the bus material, then add it up. Lets be generous and say it's only 12-inches of nickel. Put the test battery under load with a \$20 watt-meter to see how much difference there is between resting voltage and max draw (voltage sag). Now add a 12-inch strip of nickel between the existing positive pack connector pin, and the watt meter. 0.20mm thick by 7mm wide.

You have now precisely doubled the amount of nickel that the battery pack is forced to operate under. Put that pack under the same identical load, and see if the voltage sag is the same, or if it is worse. Record the difference.

Now remove the 12-inches of nickel strip, and add 12-inches of 0.20mm thick copper (7mm wide) between the pack and the watt-meter. Put the pack under an identical load just as before, and record the voltage sag, plus...feel if the strip is getting as warm as the nickel strip was becoming.

I am certain that if you try this, you will get four times the voltage sag when adding 12 inches of nickel, compared to adding 12 inches of copper.

qwerkus said:
How would less bus bar resistance decrease voltage sag during acceleration ? AFAIK the sag is due to cell chemistry. Wouldn't any additional resistance in the delivery circuitry act like a buffer and actually (slightly) decrease sag ?
Any resistance in the circuit increases sag. Sag is a voltage drop across a resistance caused by current flow. V=IR.

Cell internal resistance. Cell connection resistance. Wiring resistance. Switch resistance. Fuse resistance. Connector resistance. Sag sag sag. It all adds up.

serious_sam said:
qwerkus said:
How would less bus bar resistance decrease voltage sag during acceleration ? AFAIK the sag is due to cell chemistry. Wouldn't any additional resistance in the delivery circuitry act like a buffer and actually (slightly) decrease sag ?
Any resistance in the circuit increases sag. Sag is a voltage drop across a resistance caused by current flow. V=IR.

Cell internal resistance. Cell connection resistance. Wiring resistance. Switch resistance. Fuse resistance. Connector resistance. Sag sag sag. It all adds up.

Got it -thanks!

hi
could someone give a general conclusion answer to the question plz
which is better and concretely what kind(amount of losses are we looking at?) or maybe it is negligable ?

tx

https://www.thoughtco.com/electrical-conductivity-in-metals-2340117

hi yes you share a picture of nice metal and mathematic. thanks for that .
concretly that doest not give me any conclusion ....

want to build said:
Hard to give solid concrete answer to your question because voltage sag resistive losses vary depending on the demand placed on the battery. Low demand (slow speeds, low load) = low voltage sag, high demand (high speed, steep hill) = higher voltage sag. Under high load, some of the stored energy in the cells is lost to heat before it make it to the motor to provide locomotion.

hi tx for your explanation, it allows me to clarify that im more interested in the how do nickel do compared to copper,
i mean is there a big difference big losses .

is it like if you go with nickel you lose one bite of a full apple or you lose like half the apple? like how big an impact does it make to choose nickel. is it even noticieable? how does it translate? 10% less time for a same battery that would use coppert? 1 % , 50%

want to build said:
hi tx for your explanation, it allows me to clarify that im more interested in the how do nickel do compared to copper,
i mean is there a big difference big losses .

is it like if you go with nickel you lose one bite of a full apple or you lose like half the apple? like how big an impact does it make to choose nickel. is it even noticieable? how does it translate? 10% less time for a same battery that would use coppert? 1 % , 50%
All depends on your application, but considering same cross-section copper conductor will be 1/4 of nickel conduction loses. On paper copper is the winner.
Here comes "but", nickel has many advantages if you can bare with conduction loses, it is easier to spot-weld, does not oxidize easily and adds some structural rigidity.
If you calculate your overall conduction loses of nickel and get some acceptable number, under 5% of packs energy on average for example, stay with nickel. If its to high, switching to copper will divide your loses by ~4 and you need to figure how to weld, protect from oxidation and minimize stress on weld spots of copper tabs.
My2C

A lot of the engineering considerations for deciding between nickel and copper buses are...how many amps will be drawn from each cell and from the entire pack?

No need to research exotic methods needed to use alternative materials if you are drawing low amps from a large pack. Nickel is easy, available, and affordable. Spot-welding nickel is widely understood, and can be accomplished with readily available machines.

However, if you are drawing high amps from a small pack, the resistance of nickel buses cannot be ignored. Using "low resistance" cells, and then choking the output with high resistance buses is a waste of time.

thx for the precisions it brings some light.

i know it might be considered rude or something like that but i feel i waited a bit and made due diligences and the reality is that i need helpadvice for my project; i ask if you could open my project topic to tell me what you think about my questions since im about to buy the materials for it.

title is:
is there a prob in this battery diy plan with prebuid case?

https://endless-sphere.com/forums/viewtopic.php?f=14&t=110667&p=1621412#p1621412

will be appreciated

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