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The finish-ish of a pcb based 14S 80P powerwall
#21
Too late ... calls have been made ...  Tongue
grumble likes this post
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18x 300Wp solar off grid and 10x 180Wp solar tracker grid-tie
10KW 3phase hybrid inverter. 40Kwh 18650 storage (for now)
My setup: https://secondlifestorage.com/t-Instant-powerwall
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#22
i would add blown fuse indicator to the board as well, it will speed up diagnostics if needed, and will also alert faster to blown fuses as there wouldn't be immediate effects visible if one or even 2 are blown and it can't be any simpler, it's just one resistor and led needed.

Blown Fuse indicator

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#23
(08-13-2018, 03:51 PM)HandyAndy Wrote: i would add blown fuse indicator to the board as well, it will speed up diagnostics if needed, and will also alert faster to blown fuses as there wouldn't be immediate effects visible if one or even 2 are blown and it can't be any simpler, it's just one resistor and led needed.

Blown Fuse indicator


That makes perfect sense... how dare you.
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#24
(08-13-2018, 06:15 PM)grumble Wrote:
(08-13-2018, 03:51 PM)HandyAndy Wrote: i would add blown fuse indicator to the board as well, it will speed up diagnostics if needed, and will also alert faster to blown fuses as there wouldn't be immediate effects visible if one or even 2 are blown and it can't be any simpler, it's just one resistor and led needed.

Blown Fuse indicator


That makes perfect sense... how dare you.

That fuse detection method shall be unreliable for battery situations.

Consider what happens if the pack is subject to a brief over current event on the pack main output terminals. Ie a large motor start up in rush.

Fuses take anywhere from a few 10s of milliseconds to several hours to blow depending on the level of over load. It is likely that some weak fuses shall open first and that those cells shall have little in the way of total charge removed. Other fuses survive intact until the over current event is finished. If the over current event was sufficiently short duration the cell terminal voltages will remain close to each other. Thus the voltage across the open fuse shall be close to zero. Your LED will not light up. 

The only way that LED shall light up is if the protected cell voltage collapses to such a low level that the difference between the pack +ve and the individual cell exceeds the forward voltage drop of the LED. So the method posted is only really capable of detecting a cell with internal short that discharges it deeply or fully.

Tim
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#25
Thanks Tim.
 I wouldn't do it as in the schematic, but I get what you're saying.
wim likes this post
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#26
There is a little bit of confusing going on here i think... 
In the drawing of HandyAndy the big rectangle is the fuse not the cell ... ( the cell is the "power supply" as a V in a circle ) 
So it will work, and is already in use in fuseboxes of ie cars.

The led and resistor are bypassed by the fuse as long its intact, once blown the cell voltage (and the voltage of all cells with still intact fuses) is over the led and resistor....
It is just the drawing thats not very clear ... HandyAndy has to redo it ...  Smile

---------------------------------------------------
EDIT: forget this post... just me be a bit stupid
___________________________________
18x 300Wp solar off grid and 10x 180Wp solar tracker grid-tie
10KW 3phase hybrid inverter. 40Kwh 18650 storage (for now)
My setup: https://secondlifestorage.com/t-Instant-powerwall
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#27
Wim,
If you put a fuse across a cell... it's going to blow, but you knew that. There are ways to do it, but that schematic isn't it.
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#28
V in the diagram is more akin to the "Load" circuit and the power source together. That portion was just not added.

So if we instead put a Battery symbol and a Load symbol where the circled V is, this will be more true to the actual meaning of what was meant.

(08-13-2018, 08:12 PM)w0067814 Wrote: The only way that LED shall light up is if the protected cell voltage collapses to such a low level that the difference between the pack +ve and the individual cell exceeds the forward voltage drop of the LED. So the method posted is only really capable of detecting a cell with internal short that discharges it deeply or fully.

I'm guessing you are stating this because the LED in the diagram is backwards(?) and therefore wouldn't work unless the flow of power was in reverse. However, the diagram does not show Pos or Neg, so it doesn't matter. The resistor can be on either the cathode or the anode side of the diode and work just the same.


If you wanted true detection regardless of flow of current, two diodes could be connected in parallel but in opposite directions. This would allow the LED to be visible under discharge and charge.
As wim stated, this application is already in place in car fuse boxes (that is, if you buy those particular fuses. they are a bit pricey, imho). So it does work
Proceed with caution. Knowledge is Power! Literally! Cool 
Knowledge is Power; Absolute Knowledge is Absolutely Shocking!
Certified 18650 Cell Reclamation Technician

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#29
Grumble and Tim are right ... i am wrong ... ( sleepy eyes, chould be in bed    Wink )
___________________________________
18x 300Wp solar off grid and 10x 180Wp solar tracker grid-tie
10KW 3phase hybrid inverter. 40Kwh 18650 storage (for now)
My setup: https://secondlifestorage.com/t-Instant-powerwall
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#30
I don't want no stinkin leds. It's all Andy's fault.
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