So, I just gotta know...

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Dr. Dickie

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Sep 23, 2020
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286
When making a "48V" battery out of 18650 cells, why do we use a 14S configuration rather than a 13S configuration?
I never thought about it when I was making my pack, I just excepted what folks did and did it. But, I can never just except something, I am cursed with always wanting to know why. And in doing a video a few weeks back I started to think, why 14when 13 fits the bill?
The 13S configuration would be 52 V top (with a cell voltage of 4.0 V) and 45.5 V bottom (with a 3.5 cell voltage). That is right in the sweet spot for my (and I think most) inverter.
Is it just the result for folks preferring even numbers to odd--which I find odd, or the old superstition of unlucky number 13???
 

Oberfail

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Jun 22, 2021
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I just like the number 14 more than 13.
14 is an even number, which i like more. It can also be devided with the number 2, which results in 7 which is a commonly used config aswell.
Makes my monkey brain happy.

Most 48 volt inverters, also allow for voltages up to 60v, And i can run a little bit more power, trough the same cables.
13s - 3.6v per cell - 2.5mm² 16A cable -> 749 watts
14s - 3.6v per cell - 2.5mm² 16A cable -> 806 watts
Thats about 7% more power i could push trough the same cable.
 

DiggsUt

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Oct 30, 2019
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I usually build 52V packs and they are always 14s. I always associate 13s with 48V packs. I guess I've never heard of a 14s pack referred to as 48V.
 

Dr. Dickie

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Sep 23, 2020
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I usually build 52V packs and they are always 14s. I always associate 13s with 48V packs. I guess I've never heard of a 14s pack referred to as 48V.
Well, I have never seen a 52 V inverter, so the battery it "sees" is a 48V battery. So, I thought most folks (or maybe it is just me) referred to them as a 48 V battery.
Just like we call a car battery 12V, but really is is more like 13 V.
 
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Dr. Dickie

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Sep 23, 2020
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286
I just like the number 14 more than 13.
14 is an even number, which i like more. It can also be devided with the number 2, which results in 7 which is a commonly used config aswell.
Makes my monkey brain happy.

Most 48 volt inverters, also allow for voltages up to 60v, And i can run a little bit more power, trough the same cables.
13s - 3.6v per cell - 2.5mm² 16A cable -> 749 watts
14s - 3.6v per cell - 2.5mm² 16A cable -> 806 watts
Thats about 7% more power i could push trough the same cable.
They did a study I saw years ago, where folks like even numbers better than odd numbers. Something in the human brain that wires us that way.:):)
Of course me being odd in many, many ways, I prefer prime numbers (13 is one of them) and they are all odd, except for two; which in an of itself is rather odd.
 

Oberfail

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Jun 22, 2021
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Nothing stops you from using 13s for your battery, if you prefer it more, just use it ^^
 

OffGridInTheCity

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Dec 15, 2018
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Its a matter of voltage range vs available equipment. I find that there are more options for 14s than 13s - e.g. more to choose from which leads to less $, especially if you're original choice dies and you need to look for new/alternate equipment.
 

Redpacket

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Most 48 volt inverters, also allow for voltages up to 60v, And i can run a little bit more power, trough the same cables.
13s - 3.6v per cell - 2.5mm² 16A cable -> 749 watts
14s - 3.6v per cell - 2.5mm² 16A cable -> 806 watts
Thats about 7% more power i could push trough the same cable.

+1 to above.
Higher voltages would help efficiency too as higher currents (ie w lower voltage systems) mean more IxR losses.
But if your inverter & other gear doesn't like the higher end, you've got to do what suits....
 

Dr. Dickie

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Sep 23, 2020
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286
+1 to above.
Higher voltages would help efficiency too as higher currents (ie w lower voltage systems) mean more IxR losses.
But if your inverter & other gear doesn't like the higher end, you've got to do what suits....
No, no, the inverter has no issues,
I have a 14s 240P battery already done and running for over half a year. I was just curious as to why when you look at 18650 cell configuration to make a "48 V" battery, they give a 14s configuration.
Just curious, not looking to change anything,. I an cursed (and it is a curse, trust me) with having to know the "why" of everything I do, if even after the fact:ROFLMAO:
Not sure about less loss, we are talking about a small voltage difference over a short run.
I got the sneaking suspicion that not being 13 was probably the origin of it. :ninja:
 
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italianuser

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Feb 25, 2020
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I suppose the lower voltage makes the difference, because under a certain voltage the inverter goes off:

13S @ 3.2V = 41.6V
13S @ 4.2V = 54.6V

That's a 13V range for a 13S.

14S @ 3.2V = 44.8V
14S @ 4.2V = 58.8V

And this is a 14V range for a 14S. So you have a wider range for 14S... well, at least that's what I always thought... :)
 

cak

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Mar 14, 2021
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For me I like 14s because I also do a lot of 24vdc with 7s so I can easily combine multiple of my 7s AmmoBatts together to get the higher 48vdc or 72vdc system standards. I have a lot of GreenWorks 82v(20s) tools that I am wanting to be able to run on my AmmoBats, I also have a lot of DeWalt 60v tools so those don't fit so well. But overall when I have looked at motors for electrifying things 72vdc is pretty common for higher efficiency.

I have noticed that that my 48vdc electric bike is 13s but there is an upgraded "extra power" battery that is 14s that I could have gotten. I wish I had gotten it since currently with the voltage drop I am only able to get go juice for about half the battery capacity. It still works after that but less power from the motor to go really fast :D

Well there is my rambling.
 
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