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busbar decision
#1
Hai there,

I am finally ready with my first pack 14s100p
All the cells are 90%soh and 2500mah and up.
If i do my match correct i have 56v * 250a = 12kwh?

Next packs will be minimal 2750mah a cell

My pound needs 14.5 kwh a day on 230v.
Before i am going to put it in use i would like to have a minimum of 36-40kwh on storage.
So 3 of them(out of ten total 10*14p100s)

I am already making busbars of copper wire 6 * 2,5mm, they can handle up to 75 amp.
Do i really need this thickness? or can i go lower to 4*2,5mm

The first 3 packs (3*14p100s)will have 2 amp fuses, after that 1 amp fuses will be used per cell, i don't think those fuses are to light.

Any advice is very appreciated, thanks in advance
Still learning English. Learning Li ion and solar technology.

1400 cells in packs Exclamation above 2500mah and 90%soh.
~400 cells between 1800-2500 and above 90%soh(sell?)
600 cells between 2200 - 3000mah, 80-90%soh (sell?)
2600 waiting for testing.
approx: 500 cells not safe for use: dead, heaters, to high ir or sd

Time is our enemy, must work to, the sun is our friend, must relax to.
With best regards
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#2
(07-05-2019, 10:47 AM)100kwh-hunter Wrote: The first 3 packs (3*14p100s)will have 2 amp fuses, after that 1 amp fuses will be used per cell, i don't think those fuses are to light.

Any advice is very appreciated, thanks in advance

I really hope you mean 3* 14s100p, and not 14p100s. the latter would be a nightmare to wire up.
Proceed with caution. Knowledge is Power! Literally! Cool 
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#3
(07-05-2019, 10:47 AM)100kwh-hunter Wrote: my first pack 14s100p
All the cells are 90%soh and 2500mah and up.
If i do my math correct i have 56v * 250a = 12kwh?
Close....
56V = 14s x 4V per cell, but in realty the cells discharge & you'd pick a nominal voltage of 3.7V per cell so
14s x 3.7V = 51.8V.
If you're using 90% of the 100% DoD range of a 2500mAHr (2.5AHr) cell, then it's
2.5AHr x 0.9 = 2.25AHr per cell x 100 = 225AHrs
So stored power (ignoring charging losses, etc) = 51.8V x 225 AHrs = 11.6kWHrs
Sounding good!

(07-05-2019, 10:47 AM)100kwh-hunter Wrote: I am already making busbars of copper wire 6 * 2,5mm, they can handle up to 75 amp.
Do i really need this thickness? or can i go lower to 4*2,5mm
The busbar sizing depends on the full current from your load (ie how much DC current the inverter draws at full load).
You also want to minimize voltage drop losses on the DC side.
Running off solar, DIY & electronics fan :-)
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#4
@Korishan.
Yes i meant 14 packs that contains 100 cells each.
I was to quick and to confident with typing, sorry about that.
would be a nice challenge to solder that one up.

The first line was correct, the other two not.
Thanks for the wake up call.


@Redpacket,
The pond uses a steady draw(depends on water temperature and sun) 600 watts every hour (up to 950 watts an hour(rare)) at 230v.
How do i calculate the dc current draw?
Also taking in consideration that the packs are going to be expending, up to 10x 14s100p.
But the first use will be with 3x 14s100p and not with one 14s100p

Thank for the explanation on DoD, makes more sense now.

Thanks
Still learning English. Learning Li ion and solar technology.

1400 cells in packs Exclamation above 2500mah and 90%soh.
~400 cells between 1800-2500 and above 90%soh(sell?)
600 cells between 2200 - 3000mah, 80-90%soh (sell?)
2600 waiting for testing.
approx: 500 cells not safe for use: dead, heaters, to high ir or sd

Time is our enemy, must work to, the sun is our friend, must relax to.
With best regards
Reply
#5
(07-06-2019, 09:26 AM)100kwh-hunter Wrote: How do i calculate the dc current draw?

Same as you do with AC current draw. If you know the voltage and wattage, you can calculate amps

600W / 230VAC = 2.6A

We already know the wattage draw and that won't change (relatively. there will be losses incurred and inefficiencies)

So,

600W / 51.8VDC = 11.6A

Calculate about 20% for losses and inefficiencies:

12.5A * 20% = 2.32A + 11.6A = 13.92A total draw

With a 950W load

950W / 51.8VDC = 18.4A * 20% = 3.68A + 18.4A = 22.08A

So your busbars need to be able to handle about 24A comfortably. 100p configuration is nice as each cell will only dish out 139mA - 220mA.
100kwh-hunter likes this post
Proceed with caution. Knowledge is Power! Literally! Cool 
Knowledge is Power; Absolute Knowledge is Absolutely Shocking!
Certified 18650 Cell Reclamation Technician

Please come join in general chit-chat and randomness at Discord Chat (channels: general, 3d-printing, linux&coding, 18650, humor, ...)
(this chat is not directly affiliated with SecondLifeStorage; VALID email req'd)
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#6
I really thought there were some big formulas coming.

Awg 10 (5mm2) would be sufficient, i will go with Awg 7 (10mm2) is more than enough, i was planning on 5(15mm2)
I am very good to go, thanks for the confirmation and the lesson.

Tomorrow, solder solder solder x 2800!

Thanks
Still learning English. Learning Li ion and solar technology.

1400 cells in packs Exclamation above 2500mah and 90%soh.
~400 cells between 1800-2500 and above 90%soh(sell?)
600 cells between 2200 - 3000mah, 80-90%soh (sell?)
2600 waiting for testing.
approx: 500 cells not safe for use: dead, heaters, to high ir or sd

Time is our enemy, must work to, the sun is our friend, must relax to.
With best regards
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