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

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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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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?
 
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.
 
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.
 
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.
 
spinningmagnets said:
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?
 
Smoke said:
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.
 
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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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.
 
want to build said:
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

 
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)
 
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.
 
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
 
Yes I was simply answering this

want to build said:
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.


 
Smoke said:
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 for 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
do you mean that i should use paper sheets of nickel instead of strips?
 
spinningmagnets said:
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.
hi spinning magnet and every one ,
i hope you are well .
thanks for having answered my post.
i do not wish to use the sandwich method because kweld will be my first experience (sandwich seems like yet another thing to learn and master i dont feel like doing) and also i want to be able to see throug the nickel cut to verify with my eyes if i am welding directly on the positive end of the cell or the envelop(to avoid)

so i though about getting a battery case 65 or 70 cell(i build 4p13s (52) makita dr bass recycled cell see pict) plus i need to preview space for my bms inside of the case that is why i take 65 or 70 case) that would fit with a sheet with precut tiny lines for me to see where i weld and to facilitate the welding). i beleive usually they are 0.15 thick, buy since i want to take benifit of those high decharge sony vtc4 cells for future demanding motor i would solder 2 sheets or maybe 3 sheet on top of each other . is this realistic an easy ? would 1 or 2 sheet allow enough energy fluidity not to heat to much high discharge?

reention case would be my preference DP-6C 65 http://www.reention.com/en/xzdch/yingwuxilie/115.html
, do you know any pure nicel sheet WITH LINES PRECUT that fit inside these case . or wider question : since i want the holed sheet to fit perfectly on top of end what combination of case and sheet with holes would you suggest my that would do the job? here are example of what i call hole or line precut see pict.

other questions should i solder on cells like the one on top right like that , square (original plate still on)or with the square excess taken out into a kinda circle like pict with red white?
 

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