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[General] How many cells in parallel without fuses ?
#1
In the Project folder i describe my planned Virtual Battery.

I use Pedelec Blocks, as 10s6p, and want to use several in parallel.  If i would use 5 Blocks, it would result in a 10s30p configuration.
Different to nearly all projects here this would have NO fuses.

I am aware about the advantage of fuses, question is - how much safety, or cell fail tolerance, is gained by fusing ?
All bikes are running around in a xs6p configuration, obviously without severe problems.

But how far can parallelizing been done without fuses, 12p ? 18 p? 24p?

Specialists, what is your opinion ?

Thanks in advance.
1 kWp in Test
4 kWh battery target - plus Mobile Home battery
Ultra low cost
Electronics ? No clue. Am machinery engineer.
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#2
The CID's in the end of the cells provide some protection right but only at very cell stress/overheating?
If you had an short circuit incident & the CID's pop, then the cell is damaged & not reuseable - with the typical cell fuses, the cells are usually fine, just the fuses blow.
Running off solar, DIY & electronics fan :-)
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#3
(05-24-2019, 02:44 PM)Redpacket Wrote: The CID's in the end of the cells provide some protection right but only at very cell stress/overheating?
If you had an short circuit incident & the CID's pop, then the cell is damaged & not reuseable - with the typical cell fuses, the cells are usually fine, just the fuses blow.

Interesting aspect, my fear was more in the fire event/possibility range.
1 kWp in Test
4 kWh battery target - plus Mobile Home battery
Ultra low cost
Electronics ? No clue. Am machinery engineer.
Reply
#4
Quote:The CID's in the end of the cells provide some protection right but only at very cell stress/overheating?

If you had an short circuit incident & the CID's pop, then the cell is damaged & not reuseable - with the typical cell fuses, the cells are usually fine, just the fuses blow.
I would not trust a cell that popped it's fuse.  The whole point of cell level fusing is that it won't blow unless, A) the cell is providing more current then the fuse is rated for, in which case your pack level fusing is to high, or B) the cell has a short and the fuse has stopped the other cells in the pack from igniting the shorted cell.  In a properly fused pack a blown fuse level cell is cause for binning.
Quote:I am aware about the advantage of fuses, question is - how much safety, or cell fail tolerance, is gained by fusing ?

All bikes are running around in a xs6p configuration, obviously without severe problems.
Fusing protects against uncertainties, and newly manufactured packs, made from cells with the same source, chemistry, capacity and age, have fewer uncertainties so fusing is less of an issue, but for powerwall size packs where a failure could burn your house down, fuse it regardless IMO.
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#5
It looks like you have little headaches about parallelizing 20p without fuses.
Thanks to all.
1 kWp in Test
4 kWh battery target - plus Mobile Home battery
Ultra low cost
Electronics ? No clue. Am machinery engineer.
Reply
#6
Our 90kWh systems run 16S36P, and no per cell fusing - using very closely matched cells.

Not per cell fusing packs built using a random assortment of vaguely matched cells, of differing age and origin will be fraught with risk.

When building systems of this nature we all adopt the role of personal and public risk assessor.
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#7
(06-06-2019, 09:12 AM)Sean Wrote: Our 90kWh systems run 16S36P, and no per cell fusing - using very closely matched cells.

Not per cell fusing packs built using a random assortment of vaguely matched cells, of differing age and origin will be fraught with risk.

When building systems of this nature we all adopt the role of personal and public risk assessor.

Sean, thanks.
Very clear picture you paint.

Then blocks i use are checked in several cycles, are in sync (cell to cell) VERY close, and have a similar degradation.

I think i have the case of very closely matched cells, without excessive wear, so mostly your said condition is fulfilled for leaving out fuses.

So i will start with a 2 Block marriage as a test, later ill try a 3 Block Marriage.
1 kWp in Test
4 kWh battery target - plus Mobile Home battery
Ultra low cost
Electronics ? No clue. Am machinery engineer.
Reply


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