how many amps should i plan for a Diy battery and which nickel strips?

Batteries, Chargers, and Battery Management Systems.
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want to build   100 W

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how many amps should i plan for a Diy battery and which nickel strips?

Post by want to build » May 24 2020 7:17am

How many amps minimum should i plan when construction a battery that opens for possibilities for future project needs?

I am planning my welding sheets… and i have a need for knowledge so here are some questions if you can help me i would greatly appreciate .


My firts motor will be xiongda so it takes 7 amps max i believe . But i build my pack for future setups that will probably require more continuous amps.

I have seen people make 120 amps continuous battery (i wonder what uses that but anyway)
i have vtc4 18650 cells and they can do 30amps so i could do in theory 120 amps battery if 4p.

Ill build 4p13s 48v.
Now i want to avoid building a battery of 20 amps and discover in 3 years that i need 50 amps and have to say « i wish ».

Correct me if im wrong but 60 amps continuous should be fine right for most ambitious motors projects? Would a 60 amps batter be sufficient for most projects?If the setup asks temporarily more amps that 60 i would heat just a bit before coming back to 60 amps . I m trying to find the number of amp minimum so that i have a lot of possibilities for the future.


Ok if i just use 7mm 0.15 stripes of 5amp each it just makes 20 amps for 4 links.
If i use 70 centimetre large full nickel sheet it makes 50 amps which is 10 less than 60

now how to allow more amps? In see three ways, which is the easiest and which should choose(cause there might be other considerations that i dont see since i am noob.

Providing i use a kweld and lipo battery.
A) simply use a 0.20 mm thick nickel sheel 70cm wich allows 64 amps
(note i will be my first spotwelding, i read 0.15 is easy buy 0.3 is difficult. how about 0.2 ? is it easily doable?. Is it findable 30mm wide 0.2mm thick sheet of pure nickel?)

B) add a second layer of 0.15mm(4 between each parallel groupe on top of a prior 0.15mm nickel complete sheet welded on the cells so that would allow 50 amps plus 20 =70 amps
c) overlap 2 complete sheet of 0.15 mm which gives 100 amps which might be overkill?


anything i should consider keep in mind?
tx
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spinningmagnets   100 GW

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Re: how many amps should i plan for a Diy battery and wich nickel strips?

Post by spinningmagnets » May 24 2020 7:56am

Be aware that the series strips carry the current, and the parallel strips only keep the cells in that P-group equalized. This means the parallel strips carry very little current, less than 1A, even on an ebike that is using 60A peaks.

Resistance in the P-strips is a good thing, it limits the cells to equalizing slowly. Resistance in the series strips is bad and should be kept to the minimum. Do you know what welder you will be using?

want to build   100 W

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Re: how many amps should i plan for a Diy battery and which nickel strips?

Post by want to build » May 28 2020 7:24pm

hi yes
it was witten over a set of questions kweld and lipo battery.

I know it is a long introduction to my questions ... better be more spécific than less.

999zip999   100 GW

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Re: how many amps should i plan for a Diy battery and which nickel strips?

Post by 999zip999 » May 28 2020 10:22pm

Use new cells all with same voltage as that helps but is not capacity. Is good to put all cells in parallel if ex and let sit. But same voltage is good. As was said all in parallel act as one cell . But only as strong as weakest cell. More or less. Power Wise.

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Re: how many amps should i plan for a Diy battery and which nickel strips?

Post by Smoke » May 28 2020 11:07pm

Nickel is almost free so use as much as you can. Go for the thickest your welder can handle and as wide as you can fit.

Instead of amps, I like to think about discharge rates measured in C.

I'm building a 20Ah 48V pack for a 1,800 watt motor but I intend to cruise at around 500 watt output. That's a 0.5C cruise discharge and 1.8C maximum peak discharge. In amps, with my 13s4p layout each cell is drawing 2.5A at cruise and about 8.25A maximum peak (they are 5,000mAh 21700s). I think the calculators say 15mm wide by 0.2mm thick pure nickel should be ok for that current range but I'm going to try to double it up because why not?

A high discharge rating is great but it's better to size your pack so your discharge rates are reasonable.

At the same time, why try to save $10 on nickel strip if you are using high discharge cells? That would hamstring the pack if you ever needed to use it for high discharge.
Don't let me out.

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Re: how many amps should i plan for a Diy battery and wich nickel strips?

Post by want to build » May 31 2020 2:54am

spinningmagnets wrote:
May 24 2020 7:56am
Be aware that the series strips carry the current, and the parallel strips only keep the cells in that P-group equalized. This means the parallel strips carry very little current, less than 1A, even on an ebike that is using 60A peaks.

Resistance in the P-strips is a good thing, it limits the cells to equalizing slowly. Resistance in the series strips is bad and should be kept to the minimum. Do you know what welder you will be using?
do you suggest to use material other than nickel between cells in parrallel ? or maybe 4 mm wide instead of 7 wide 0.15 nickel stips?

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Re: how many amps should i plan for a Diy battery and which nickel strips?

Post by want to build » May 31 2020 3:01am

Smoke wrote:
May 28 2020 11:07pm
Nickel is almost free so use as much as you can. Go for the thickest your welder can handle and as wide as you can fit.

Instead of amps, I like to think about discharge rates measured in C.

I'm building a 20Ah 48V pack for a 1,800 watt motor but I intend to cruise at around 500 watt output. That's a 0.5C cruise discharge and 1.8C maximum peak discharge. In amps, with my 13s4p layout each cell is drawing 2.5A at cruise and about 8.25A maximum peak (they are 5,000mAh 21700s). I think the calculators say 15mm wide by 0.2mm thick pure nickel should be ok for that current range but I'm going to try to double it up because why not?

A high discharge rating is great but it's better to size your pack so your discharge rates are reasonable.

At the same time, why try to save $10 on nickel strip if you are using high discharge cells? That would hamstring the pack if you ever needed to use it for high discharge.
HI yes my concern is not about the cost of nickel.
ill use kweld spot welder for my first time so probably 0.15 (not 0.3 is seems to complicated)

What do you mean by :A high discharge rating is great but it's better to size your pack so your discharge rates are reasonable[/i]. can you use other words, i dont understand the idea your trying to convey.
Last edited by want to build on May 31 2020 3:53am, edited 1 time in total.

want to build   100 W

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Re: how many amps should i plan for a Diy battery and which nickel strips?

Post by want to build » May 31 2020 3:52am

Ill use kweld probably buy i dont wish to try the 0.3 cause i look for a simple method .HI here is a pic of my cells. i took them from lightly used drill pack i left a bit of original nickel sheet on them since i was thinking about soldering them with lead tin but now i understand spot welding is better and cleaner.
Im concerned that even if i put a green ring on top of the cells, the extra original nickel material could do a short cut so i beleive i will either pull all the original nickel pieces remaining with a pair of plyer or use a dremel to remove all original nickel apart from a circle where the 4 points are. What do you think?

Full nickel sheet would be nice but i dont know how i could find the precise sites to do the solder since i would be able to see the cells ends precisely (they would be covered by the sheet of nickel..) . Also if i use reentions battery case and their (pic with the hand)holder below it seems the plastic round black thing would put the sheet too high from the cell ends.Height problems.
I could use the alternate loose 18650 holder below which has no height problem for a sheet but i still could not know precisely where to spot weld to be right on the positive ends.... What do you think?

On the picture with the red cells, i could put 3 layers between the parallel groups . the red and green represent the 0.15 ,7mmstrips that i would add. this would make15 amp (3 layers of 5 amp) per bridge x4 bridge so 60 amps continuous . is this overkill?
more importantly how strong would that be to have 3 layers (4 layers if i include the parallel strip of nickel one on top of the other ( adding one layer at the time of course) how safe would that be? anybody did that kind of setup how solid is it?
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spinningmagnets   100 GW

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Re: how many amps should i plan for a Diy battery and which nickel strips?

Post by spinningmagnets » May 31 2020 6:54am

maybe 4mm wide instead of 7mm wide 0.15 nickel strips?
That's fine for the parallel strips. When it comes to the parallel connections, just about any material will work, and any common thickness (0.15mm/0.20mm). I would select the material that is easiest to weld, with whatever welder you are using. If you are trying to save money on nickel, you could slice them into 3.5mm wide, and it would not change the parallel performance.

It seems that most new builders want to create parallel groups first, and I imagine that it's probably because this is the easiest way to assemble the pack

However, if you plan to assemble a high-amp pack, I'd recommend using the copper/nickel sandwich method (experiment on old dead cells first), so that the series strips are touching the cell-ends, and the parallel strips are overlaid on top of that.

john61ct   100 GW

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Re: how many amps should i plan for a Diy battery and which nickel strips?

Post by john61ct » May 31 2020 8:27am


want to build wrote:
A high discharge rating is great but it's better to size your pack so your discharge rates are reasonable.
i dont understand the idea your trying to convey.
Since the C-rate is what is relevant, you can keep that more reasonable by increasing the pack Ah capacity

Higher cost and larger size/weight of course


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Re: how many amps should i plan for a Diy battery and which nickel strips?

Post by want to build » Jun 01 2020 5:45am

Hi John,
You are saying that viewing the situation in terms of Current C is makes more sense if i understand you. Unfortunately i do not have this knowledge, i, m not used to it and the motor world... if it is a neccessity where can i learn it? if it is not absolutely necessary can we do wihtout it like maybe the way i approched it?

Are my questions relevant from your stand point? and if so can you share you thoughts? tx
ps, im not sure if you refer to the qte of energy buy i have already my cells 13s4p i wish not to make it bigger number of cells)

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Re: how many amps should i plan for a Diy battery and which nickel strips?

Post by john61ct » Jun 01 2020 8:38am

C-rate means the current as a proportion of Ah capacity.

Round number examples:

5000mh pack, 5A is 1C, 100A is 20C, 1A is 0.2C

Double Ah capacity to 10Ah, now 5A is half the C-rate at 0.5C, 100A is only 10C, 1A is 0.1C

Doubles the range of course, very likely extending lifespan by a very large number as well.

Disadvantages are the pack is bigger, weighs more, and costs more up front.

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Re: how many amps should i plan for a Diy battery and which nickel strips?

Post by want to build » Jun 01 2020 8:45am

ok i think i understand you mean have larger parallel groups. but that is not my intention, i do not want to add more cells than 52 i have. tx for the proposition.

So come back to my questions ...lol they are on top of my nice pictures, can anyone try to answer it ? i would apreciate.

a plus

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Re: how many amps should i plan for a Diy battery and which nickel strips?

Post by john61ct » Jun 01 2020 9:17am

Yes I was simply answering this
want to build wrote:
A high discharge rating is great but it's better to size your pack so your discharge rates are reasonable.
can you use other words, i dont understand the idea your trying to convey.

Last edited by john61ct on Jun 01 2020 9:17am, edited 1 time in total.

want to build   100 W

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Re: how many amps should i plan for a Diy battery and which nickel strips?

Post by want to build » Jun 01 2020 12:25pm

yes thank you for that.

I hope people have/will read my text containing questions.

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