value of the cell fuse

S

Stefaan De Ridder

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dear forummembers.

what is the general value of cell level fuses to use?

for typical 14S60P or more, I see glassfuses of about 2 amp, 3 amp.

This would be about 3 to 6 times the expected currentdraw, if I'm not too far off. (calculated at 500mA or 1000mA draw per cell)

if I have cells that have a capacity of10Ah and a 1C continuous discharge rating and 3C max discharge, should I be looking for something like a 20Amp fuse?

if i put those cells in parallel (like 14S5P), i could normally safely draw about 50a from the pack.

any suggestions?

Best regards

Stefaan
 
You should have the fuse below a cells max continues rating and above ur max draw. IF you plan 1a a 5a fuse Wire works great. Dont overcomplicate it.... Cell level fuses are NOT for overall current protection... That you got the Main fuse for. Main fuse should be max 1/3rd of ur cell level fuses IF you ask me
 
daromer said:
You should have the fuse below a cells max continues rating and above ur max draw. IF you plan 1a a 5a fuse Wire works great. Dont overcomplicate it.... Cell level fuses are NOT for overall current protection... That you got the Main fuse for. Main fuse should be max 1/3rd of ur cell level fuses IF you ask me
Click to expand...

thanks for the reply:

for my setup: 1C = 10A, which would be the max continuous estimated current draw per cell.

so I may need a fuse of something like 20A per cell, maybe a bit higher.

you suggest main fuse to be 1/3 of cell fuse. so maybe cell fuse at 30A- 40A and string at 15A?

I think this will be complcated to find glass fuses of this rating

best regards

Stefaan
 
Why 10A per cell? Do you use laptop cells? If you do that you should stay below 2A and preferable not above 1A...

Cells with 10Ah? What type of cells do you have then since it cannot be 18650 cells.
 
daromer said:
Why 10A per cell? Do you use laptop cells? If you do that you should stay below 2A and preferable not above 1A...

Cells with 10Ah? What type of cells do you have then since it cannot be 18650 cells.
Click to expand...

it's not a 18650, it a GP4105054T1000L, prismatic, but difficult to find spec. there is a post somewhere on the forum.

I'm still collecting 18650, slowly getting there.

my collection of 18650 is mainly from e-bike batterypacks. sometimes difficult to collect them, but mostly the bms is dead and the cells still test at +95% capacity.

I recently received 14 packs of 8 or10 cells of the prismatic type (some are 10Ah, some 13.6Ah)

that's why I think I can go to about 10A-20A dischargerate for fuse

best regards

Stefaan

https://secondlifestorage.com/t-Testing-GP4105054T1000L-battery-block?highlight=gp4105054
 
would not even fuse those cells. But thats me... If you want to fuse them put the fuse at max 1/2 the cells max current so you have some head-room.
 
daromer said:
would not even fuse those cells. But thats me... If you want to fuse them put the fuse at max 1/2 the cells max current so you have some head-room.
Click to expand...

not fuse?: living on the edge? :)

I think I'm going to fuse, just to be on the save side, until I gain a bit more experience.

Ok, I will start googling for 15A fuses or something in that rating.

best regards

Stefaan
 
Living on safe side or not...The fusing was introduced on the smaller 18650 cylindrical LiIon cells. I would say those come from the same system basically and dont behave in same way and therefore I would skip it but thats me. If you are going to have 100s of them in parallel i would do different

Not hard to find datasheet for those cells? First hit on Google: http://www.farnell.com/datasheets/1708366.pdf
 
StefaanDeRidder said:
wim said:
Those carfuses chouldwork ... but testing oncell voltage is advised.

https://www.benl.ebay.be/itm/Car-Fu...717861?hash=item214605fb25:g:VtsAAOSwgd1bdwKG
Click to expand...

more difficult to solder, but a good option if I can't find glass fuses

best regards

Stefaan
Click to expand...

In a holder like this ...https://www.benl.ebay.be/itm/2-x-In-line-Standard-Blade-Fuse-Holder-Splash-Proof-for-12V-20A-Fuses-Car-Bike/251994755449?hash=item3aac0ed179:g:tIcAAOSwlPRTb-vP
 
daromer said:
Living on safe side or not...The fusing was introduced on the smaller 18650 cylindrical LiIon cells. I would say those come from the same system basically and dont behave in same way and therefore I would skip it but thats me. If you are going to have 100s of them in parallel i would do different

Not hard to find datasheet for those cells? First hit on Google: http://www.farnell.com/datasheets/1708366.pdf
Click to expand...

thatdatasheet is more the safety sheet, not the actual technical datasheet, with currents and chargerates. I found that, but not much more.

some references found (russian) say it's manufacured by Sony.

same site stated the 1C and 3C rating.

max charging at 2a

thanks anyway

best regards

Stefaan
 
Cell level fusing as Daromer mentioned needs to be considered with regard to overall pack fusing,


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The main element is that you want the overall pack fuse to go before any of the cell level fuses in a fault condition.

The overrall fuse level then also needs to take into account the surge capability of any large load you have attached, which is usually the inverter. If the inverter is capable of sustaining say 2x the rated output for more than a second then that surge would run the risk of blowing a fuse at that level,

Example of a 48V system would be say an inverter rated for 2.5KWand a surge capability of 6kW. The fusing would need to consider the 6kW load level (depending on how long this can be sustained for).

In this instance you then have a nominal 2.5kW (52 Amps at 48V) and would also be higher at minimum a charge state of the battery of say 46V so around 54 Amps.

The surge of 6kW would also drop the battery pack voltage (depending on size of the pack) and could be say 2V for example. In this situation you may at a low pack charge level then end up with 44V (close to your minimum inverter voltage) going in at maximum surge of 6kW which would then mean a 136A peak.

For a parallel cell setup at 1A per cell this then means your looking at a 136p system minimum (adjust for whatever cell level fuse value your using).

Thougth this might be usefull a bit for this post and a bit more generic explanation for others.
 
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