Thread Rating:
  • 0 Vote(s) - 0 Average
  • 1
  • 2
  • 3
  • 4
  • 5
newbie question about amps/loads
#11
Those are decent bus bars!
Are the cables from the busbar to the batteries equal length?
Assuming the batteries are connected toward the "back" of the image and the load at the "front" there might be a small imbalance in voltage drops.
You seem to have "diagram #1" layout from Korishan's post above.
Maybe test with your multi-meter on mV, put one probe on the 1st batteries neg connection point on busbar & the other probe on the neg point for the 2nd battery.
Turn on a bigger load (or charge) & measure. If there's much drop it might be worth correcting.
If you swapped positions of eg the battery neg cables (keeping pos the same, carefully!) you would get "diagram #2"
You could also swap one of the "load leads" from the front to the back, this way future additions would be correct too.
Running off solar, DIY & electronics fan :-)
Reply
#12
I love the busbars!   but I cringe picturing slipping with a wrench in my hand and shorting across them.    Maybe some kind or cover or barrier in the future?   That's why I use a large metal box (with a cover) and bus bars inside - its the left most metal box in my ID picture to the left Smile
Reply
#13
Redpacket, below is the link to a wider shot of the bus bars and leads. Are you saying move the red lead to the other end of the bus bar?

Bus bars 2 https://imgur.com/a/CS0n5HB
Reply
#14
I also had a similar question to the OP's Post, So to add to the OP's question: A 7S80P pack using 3000 mAh cells, Assuming a 0.5C (1.5 amp) discharge rate

That would be 120 amps at 29.4(ish) volts = 3528 Max Watts
240Ah * 29.4 = 7.056 Kwh (not taking into account any losses.

Are these safe numbers, 1.5 amps seems like a lot from each cell, i have read where some are not expecting over 200-500ma draw per cell, but I assume this is why you build larger sized "P" packs.
Reply
#15
(08-15-2020, 01:31 AM)Eddieb Wrote: Redpacket, below is the link to a wider shot of the bus bars and leads. Are you saying move the red lead to the other end of the bus bar?

Bus bars 2 https://imgur.com/a/CS0n5HB

Yes. You could move either the black or the red to the other end.
To OffGrid's comments about insulating it, you could fit this duct or similar over it:
https://www.cabac.com.au/products/condui...c/19201505

(08-26-2020, 05:20 AM)enzo86 Wrote: I also had a similar question to the OP's Post, So to add to the OP's question: A 7S80P pack using 3000 mAh cells, Assuming a 0.5C (1.5 amp) discharge rate

That would be 120 amps at 29.4(ish) volts = 3528 Max Watts
240Ah * 29.4 = 7.056 Kwh (not taking into account any losses.

Are these safe numbers, 1.5 amps seems like a lot from each cell, i have read where some are not expecting over 200-500ma draw per cell, but I assume this is why you build larger sized "P" packs.

You don't use Ahr (current over a period of time) to calculate instantaneous current per cell, you use Amps
So if you are drawing say approx 3.5kW at 29V, total current is kW/V so 3500/29 = ~120A.
To get the amps per cell, it's # of cells / amps, eg 120p cell pack would be 120/120A = 1A per cell (still high)

For load power levels over about 2kW, you should move to 48V (nominal) systems to keep the currents manageable.
Running off solar, DIY & electronics fan :-)
Reply
#16
"You don't use Ahr (current over a period of time) to calculate instantaneous current " Correct, i was just doing a rough calculation on capacity. Thanks for your response and information, looks like ill need to start looking at 48v designs. What is the typical amp draw per cell that everyone shoots for ?
Reply


Forum Jump:


Users browsing this thread: 1 Guest(s)