Would 30 Headway 38120 cells be enough?

[AltCtrlNik]

Hey guys! New here to Endless sphere and this is my first post/ question
So after browsing the topics, I can't seem to find what I'm looking for.
I was wanting to know... (first of many questions)

1. How many Headway 3.2v 8ah 38120hp cells would I need, to build a 48v 40ah battery pack?

2. What kind of battery pack, can I build with 24 to 30 of these cells?

I'm looking to make a purchase, with the guys over at Battery hook-up.

 

[eee291]

One cell has 8Ah so you will need at least 5 in parallel to get 40Ah.

Then for the voltage.
4 in series for 12V
8 for 24V
12 for 36V and
24 for 48V, 120 cells in total.

Since they are used you may want to go with 6 in parallel for a total of 144 cells for about 1600$.

I feel that I have to mention that this not the best price to Wh battery you can buy. It's only good if you actually need to pull more than 1000 amps.

 

[john61ct]

I feel that I have to mention that this not the best price to Wh battery you can buy.

Cheaper US-based LFP sources would be greatly appreciated, especially for new.

Not asking for discussion about other chemistries.

 

[john61ct]

24 for 48V, 120 cells in total

Actually, 48V nominal is 16S,

times 5P to get 40Ah, so total is 90 cells.

> only good if you actually need to pull more than 1000 amps

of course range may require that 40Ah / 2kWh, regardless of the C-rate needed.

______
And to the OP, that 48V or 3.0Vpc should be the minimum voltage to allow.

51.2V is actual, mid-range SoC under load.

Charge up to around 55V.

 

[999zip999]

200 amp cell I don't believe it

 

[DjSpaceGhost]

200 amp cell I don't believe it

Have you ever seen one of these cells up close? It's believeable just due to the size of those things.

 

[DjSpaceGhost]

I feel that I have to mention that this not the best price to Wh battery you can buy.

Cheaper US-based LFP sources would be greatly appreciated, especially for new.

Not asking for discussion about other chemistries.

That's the only reason I don't use LiFe . I haven't found a US vendor that's trustworthy , decent priced, and has the range of size/power/capacity I need. They're either $10 per cell for 3ah at 10amps max or $50+ per cell for 20ah. Plus shipping of course.

 

[999zip999]

There's lots of threads of Headway packs having trouble with keeping balance at 200 amps I wonder how there balance would be ?

 

[999zip999]

What's this for go-kart motor bike pedal cab what motor and what controller and what type of Hills should you be climbing ?

 

[eee291]

24 for 48V, 120 cells in total

Actually, 48V nominal is 16S,

times 5P to get 40Ah, so total is 90 cells.

Oops

I was on the road when writing this.

My point was that these are still too expensive for a 2kwh pack especially if you don't draw high currents.

 

[john61ct]

Depends how they're used. Lifetime can be 5000+ cycles so can end up the cheapest chemistry per Ah **per year**.

 

[eee291]

That figure is way too high for high power lifepo4.
From my experience with Headway Cells I'd say these can give you about 1000 maybe 1500 good cycles if used moderately, about half or less if you discharge them at 200A.

 

[john61ct]

As I said, the usage factor rules, more than tweaking variations in the LFP chemistry.

What kind of C-rate would you mean by that 200A?

Some "vehicles" do not need to go higher than 2-5C, was what I had in mind.

In any case, comparing LFP to nearly all other LI chemistries, the lifecycle ratio will be pretty constant if (ab)used equally.

 

[amberwolf]

1. How many Headway 3.2v 8ah 38120hp cells would I need, to build a 48v 40ah battery pack?

48v / 3.2v = z
40ah / 8ah = y
z * y = total number of cells.

2. What kind of battery pack, can I build with 24 to 30 of these cells?

It doesn't matter.

What matters is what kind of battery pack you *need*.

If you build a pack that doesn't do what you need it to, it doesn't matter what kind of pack it is.

So, what you need to do is determine at least these system requirements:

--max continuous current
--max peak current
--max range
--wh/mile estimate

Once you know how far you have to go, and how many wh it takes to go that far, then you can size your pack to give you enough wh to get that range, plus some extra for detours, unexpected headwinds, etc.

Once you know how much current your system will need then you can size the pack so it can deliver that current without heating or sagging significantly in voltage.


The voltage of the pack also matters for the speed you want to go, based on the motor you use and the wheel size and any gearing between them.

I'm looking to make a purchase, with the guys over at Battery hook-up.
20190603_211206.jpg

You should ask for a test chart that shows the voltage sag at various currents and temperatures and states of charge. You'll probably find those cells get pretty hot at high discharge rates, and sag in voltage quite a bit. (which means you don't get as much power (watts) out of them as cells that don't sag that much.)