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Breakers, Fuses and Shunt Trips
#1
Hey Guys,

So I am at a point where all my 18650 cells are ready and I'm about to start building them out and installing.

My question is breakers, fuses and shunt trips.

So I'll be building 2 x 7s80p banks connected to 24v 3000kvs ( 2400w ) ( 100A ) inverter, and here is my design

Each 7s80P bank will have its own 100A Fuse on the Positive which I'll use as an isolator when I want to disconnected it from the load.
Each bank will be connected to the main shunt trip which then connects to the Inverter.

Do I still need breaks for each bank or can the fuse do the same function ?
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#2
Either a fuse or a breaker per bank is fine.
Nice things about breakers are:
- you can also use them easily as an on/off switch +
- if you get a trip, you can reset at no cost
Running off solar, DIY & electronics fan :-)
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#3
As for the shunt trip switch, these are only used where you can monitor the pack voltage, so for example your BMS is configured to activate the shunt trip in the event of under or over voltage ?

I see a few people using these very large ABB 200A shunt trips, for their main bank breaker and shunt trip. Are there any other option available ?
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#4
ABB s3 are quite small. You can find even smaller Schneider breakers att 63a
The Ultimate DIY Solar and build place
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Current: 10kW Mpp Hybrid | 4kW PIP4048 | 2x PCM60x | 100kWh LiFePo4 | 20kWh 14s 18650 |  66*260W Poly | ABB S3 and S5 Trip breakers
Upcoming: 14S 18650~30kWh
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#5
Thanks you, the ABB S3 are shunt trips ?, and by small are you referring to din rail mount ?
I have done some google searching and I can't find a supplier of new units. Do you have a link ?
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#6
ABB is to expensive new to be honest. 2nd hand is around 50-90USD.
Not standard din rail im afraid. Then you have to go for example schneider 63A or equal.

I dont have link to the schneider right now. Batrium sold some back in the days and i think you can find them on ebay.
The Ultimate DIY Solar and build place
YouTube / Forum system setup / My webpage  Diy Tech & Repairs

Current: 10kW Mpp Hybrid | 4kW PIP4048 | 2x PCM60x | 100kWh LiFePo4 | 20kWh 14s 18650 |  66*260W Poly | ABB S3 and S5 Trip breakers
Upcoming: 14S 18650~30kWh
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#7
Here is a product by schnieder which is just the trip, you pair it with a protection breaker which is available in 100A. Cost though from what I gather is more than the ABB 2nd hand, but a nice small option
https://www.se.com/au/en/product/A9N2694...-24vac-dc/
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#8
(05-05-2020, 03:29 PM)rolfbartels Wrote: Here is a product by schnieder which is just the trip, you pair it with a protection breaker which is available in 100A. Cost though from what I gather is more than the ABB 2nd hand, but a nice small option
https://www.se.com/au/en/product/A9N2694...-24vac-dc/

Looking at some of the related products to the shunt trip you posted, one is a 100A breaker (https://www.se.com/au/en/product/A9N1835...--c-curve/) Looking at the product description it lists voltages and breaking currents for AC and DC but it looks to be an AC breaker. Would that breaker work in a DC system?
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#9
If it listed DC ratings (it does) that meet your system specs (your voltages should be max 144VDC, pref 125VDC or less), then yes you can use it.
Running off solar, DIY & electronics fan :-)
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#10
Ok so I have been speaking to various different electrical companies and some say don't use DC Breakers rather use fuses and some say its fine.

So here is what I was going to do

I am building a 3 x 7s80p banks, my inverter is currently 24V 2400W so 125A ( max inverter rating + 25% temperature degradation ) and unless is dies will remain, I do aim to eventually have even numbered banks.

I was planning on installing 40A fast blow fuses on each of the positive lines of the 7s80p banks, this give me 0.5a draw per cell average max
Then between the inverter and the banks i was going to install 125A DC MCB with a 24v-48v shunt trip.
Now i am being told I should rather use 125A fuses ? instead of the 125A MCB.

My other option is to install the 125A fast blow fuses and an 125A DC Isolator with shunt trip, but this gets expensive, and I do need the shunt trip for the BMS to be able to protect the packs

How are you guys protecting your systems ?
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