diy solar

diy solar

Check out this compact buss bar

I am a fan of using the Class-T fuse as close as is practical to the Positive terminal of my LiFePO4 batteries. My 150A Class-T fuses are rated 125V DC & 20KA I.R..
My system is 24 volts composed of 4 12V 200Ah batteries.

Catastrophic being the key word, watch this video for about 30 seconds and find out why.
diysolarforum.com

Use a fuse - and wear safety glasses... This could have been very bad.

If she did not have that fuse, this would have been a lot worse... Definitely worth the cost of the Class T fuse.
diysolarforum.com diysolarforum.com
 
Last edited:
smoothJoey said:
The busbar in your picture is not common source which is not useful for typical system typologies.
Maybe you are doing something different and I've misunderstood.
Click to expand...

Sorry not clear what u mean (iNoob) - if you mean in laymans terms: the metal underneath the 5194 bolts is not thick enough to safely carry the currents you'd likely have, then add "replace existing metal busbar/under-bolts in 5194 with copper" to my prior queries.

smoothJoey said:
If your LFP battery is 24 volts or greater you want a class t fuse as close as possible to the positive terminal of the battery.
Class t fuses have the greatest breaking capacity.
That means they can quench an arc where lesser fuses will fail to extinguish the arc which is a nightmare scenario.
Click to expand...

This is as per my understanding - and as I have 2x200ah 12v, and not running high loads, was thinking Class-T would be overkill (and hence MRBF would suffice)? I guess that's the real question here - is MRBF suitable for my 2 x 200ah 12v (parallel - 12v) in lieu of MIDI & Class-T fuses as safe?

EDIT: This is handy: http://assets.bluesea.com/files/res...o_Blue_Sea_Systems_Fuses_and_Fuse_Holders.pdf
 
Last edited:
WYtreasure said:
I am a fan of using the Class-T fuse as close as is practical to the Positive terminal of my LiFePO4 batteries. My 150A Class-T fuses are rated 125V DC & 20KA I.R..

Catastrophic being the key word, watch this video for about 30 seconds and find out why.
diysolarforum.com

Use a fuse - and wear safety glasses... This could have been very bad.

If she did not have that fuse, this would have been a lot worse... Definitely worth the cost of the Class T fuse.
diysolarforum.com diysolarforum.com
Click to expand...
Holy crap, well that IS a reality check.

But 48v 800ah vs my 12v 400ah? Is that scenario and a 150a non-class-t fuse (a reasonable fuse size for me to have) on 12v the same risk?
 
Last edited:
pantechlife said:
Holy crap, well that IS a reality check.

But 48v vs my 12v? Is that scenario and a 150a non-class-t fuse (a reasonable fuse size for me to have) on 12v the same risk?
Click to expand...
I do not have an answer to your questions.
I think it all depends upon the discharge capacity of your batteries and "how long do you want to be welding".
 
pantechlife said:
Holy crap, well that IS a reality check.

But 48v vs my 12v? Is that scenario and a 150a non-class-t fuse (a reasonable fuse size for me to have) on 12v the same risk?
Click to expand...
I've done the math and I say an MRBF is fine for a single 12 volt battery.
The dead short ampacity of a battery is a function of its internal resistance and voltage.
diysolarforum.com

tool to explore dead shorts of LFP cells and batteries

The attached spreadsheet is in OpenDocument Spreadsheet format and is zip encapsulated. Its intent is to explore the dead short ampacity of LFP cells and batteries. The typical internal resistance for the big blue LFP cells is ~0.00015 ohms. The resistance of a typical shunt is ~0.0001 ohms...
diysolarforum.com diysolarforum.com
 
Last edited:
@pantechlife
Code: 
positive
|<->disconnect<->fuse<->battery<->shunt<->|
|->fuse->inverter------------------------>|
|<-fuse<-charger<-------------------------|
                                   negative
This is a simple and representative topology for the core of the systems we make.
It looks like a ladder where the risers are the busbars and the rungs are the circuits.

Another way to describe the topology is feeder and branch.

The battery(feeder) circuit should be fused as close as possible to the battery positive terminal.
This is done to minimize the chance of an upstream short.

The branch circuits(inverter and charger) are fused as close as possible to the positive busbar.
If the inverter circuit wire is smaller guage than the battery circuit it must be fused to prevent the wire from melting due to a fault.
If the wire is the same gauge as the battery circuit it is done to isolate the fault to the branch circuit so that the rest of the system can still function.

fuse criteria:
voltage in volts
breaking capacity in amps
trip rating in amps
trip curve in amps over time

protection strategy criteria:
amp rating:
The fuse must be sized to trip before the wire or wire like conductors melt or catch fire

breaking capacity:
The fuse breaking capacity must be greater than the dead short potential of the circuit.

fault isolation:
We want to design the system so that faults on branch circuits can be isolated to the circuit that experiences the fault condition.

With this explanation I think you will see the value of an fused positive busbar.
If you have any followup questions I will be glad to answer.
 
Last edited:
smoothJoey said:
@pantechlife
Code: 
positive
|<->disconnect<->fuse<->battery<->shunt<->|
|->fuse->inverter------------------------>|
|<-fuse<-charger<-------------------------|
                                   negative
This is a simple and representative topology for the core of the systems we make.
It looks like a ladder where the risers are the busbars and the rungs are the circuits.

Another way to describe the topology is feeder and branch.

The battery(feeder) circuit should be fused as close as possible to the battery positive terminal.
This is done to minimize the chance of an upstream short.

The branch circuits(inverter and charger) are fused as close as possible to the positive busbar.
If the inverter circuit wire is smaller guage than the battery circuit it must be fused to prevent the wire from melting due to a fault.
If the wire is the same gauge as the battery circuit it is done to isolate the fault to the branch circuit so that the rest of the system can still function.

fuse criteria:
voltage in volts
breaking capacity in amps
trip rating in amps
trip curve in amps over time

protection strategy criteria:
amp rating:
The fuse must be sized to trip before the wire or wire like conductors melt or catch fire

breaking capacity:
The fuse breaking capacity must be greater than the dead short potential of the circuit.

fault isolation:
We want to design the system so that faults on branch circuits can be isolated to the circuit that experiences the fault condition.

With this explanation I think you will see the value of an fused positive busbar.
If you have any followup questions I will be glad to answer.
Click to expand...
That's a great overview, thank you. I'll hark back here with my electrical diagram/anything I'm stuck on!
Thanks again :)
 
pantechlife said:
Ok, thanks, though I always understood what 5196 (4 mounts) is, maybe you missed that I was wondering if 5194 (6 mounts) can viably be *modified* (if you look closely at 5194, and at schematics it seems that the only reason it is 1 x bar, and not 2 seperate bars, is because both rows of bolts are joined by an angle of metal. If this angle was not joined (cut it or replace it) you would have 2 separate bus bars - whether this is a-very-bad-idea or not, I don't know). Note: the 5194/5196 both cost more than I thought coz *do not include* MRBF fuses.

I've edited posts above for clarity.

6 mounts seems like enough for many smaller setups, mine included (2 x 24v 370w panels to 12/24v MPPT to 2 x 12v 200AH batts, 3 kw inverter [that I inherited and likely doesn't hit 3kw, and batteries cant power 3kw anyway]).
And could be quite an elegant and tiny solution.

I'm totally open to being told this idea is not viable, or the MRBF not being suitable (short of being safer with a T-Fuse, my research says they are, but am a noob), hence me asking :) .
Click to expand...
Blue Sea 5194. It is a three circuit fuse holder. Three individual circuits. You could connect the three using a jumper, then you would have a three circuit fuse holder with a common power source, like the 5196. I have no idea what you mean by "6 mounts".
These are BusBars: https://www.bluesea.com/products/category/18/5/BusBars/PowerBar
In my home country I find Blue Sea products much lower than MSRP by searching online.
On a 12 volt LiFePo battery MRBF are fine as they have a 10,000 ampere interrupt capacity at 14 volts.
 
Zil said:
Blue Sea 5194. It is a three circuit fuse holder. Three individual circuits. You could connect the three using a jumper, then you would have a three circuit fuse holder with a common power source, like the 5196. I have no idea what you mean by "6 mounts".
Click to expand...

I've detailed a couple of times now it was a query about modifying/hacking the 5196, but it's neither actually worth it (I initially thought it included MRBF fuses, but it doesn't) and noone seems to understand my query, so let's move on.

EDIT: Meant hack/modify 5194, 5194!! Crikey. Anyway, bad idea, moving on.

Zil said:
These are BusBars: https://www.bluesea.com/products/category/18/5/BusBars/PowerBar
In my home country I find Blue Sea products much lower than MSRP by searching online.
On a 12 volt LiFePo battery MRBF are fine as they have a 10,000 ampere interrupt capacity at 14 volts.
Click to expand...

Yep there's a bunch of (generally overpriced) BlueSea in Australia, and yes searching helps, Littelfuse/Eaton/Bussman not so much.

I've resolved to use 2 x Blusea MRBF mounts + 300a fuses, and a smattering of ANL.
 
Last edited:
@toms do you have a recommendation for a fused busbar that is available in Australia?
 
You must log in or register to reply here.

Similar threads

D
Check this mess out
Replies
4
Views
512
DontUredRing
D
J
buss bar recommendations for 8 DC to DC converters?
Replies
14
Views
757
Reed Cole
R
R
Common Buss bar
Replies
5
Views
347
retroman
R
V
Buss bar question
Replies
2
Views
387
vtx1029
V
atelierminceur
Van build - setup design check?
2 3 4
Replies
67
Views
2K
12vDC
1
Back
Top