LIFEPO4 Battery discussion thread

DTBA said:
was reading this
Click to expand...
I guess it makes sense.

But still, they are trying to say that when a short happens, the other batteries will supply the current to the shorted battery so quickly that you will pass 2500A in an instant before the mega fuse trips?

Keeping in mind you still have a healthy BMS in the other 2 batteries that will cut out at 150A?

I don't know. I think it's overkill. Would need to see an actual real-world situation where the fuse failed because of that.
 
denmendez65 said:
I guess it makes sense.

But still, they are trying to say that when a short happens, the other batteries will supply the current to the shorted battery so quickly that you will pass 2500A in an instant before the mega fuse trips?

Keeping in mind you still have a healthy BMS in the other 2 batteries that will cut out at 150A?

I don't know. I think it's overkill. Would need to see an actual real-world situation where the fuse failed because of that.
Click to expand...
Like i said it was not much more expensive for me to do it this way, I also get a battery disconnect per battery that I wanted.

I just did it this way cause the price difference did not make much sense. Also just posted it here cause I wanted to use megafuses.
 
denmendez65 said:
I guess it makes sense.

But still, they are trying to say that when a short happens, the other batteries will supply the current to the shorted battery so quickly that you will pass 2500A in an instant before the mega fuse trips?

Keeping in mind you still have a healthy BMS in the other 2 batteries that will cut out at 150A?

I don't know. I think it's overkill. Would need to see an actual real-world situation where the fuse failed because of that.
Click to expand...
Imagine the cell is venting into the room before the fuse explodes, I guess thats where the spark comes from that blows the side of the house off.
1779272850322.png1779272940885.png
 
wingnut771 said:
Imagine the cell is venting into the room before the fuse explodes, I guess thats where the spark comes from that blows the side of the house off.
View attachment 1909402View attachment 1909404
Click to expand...
Applies for LA batteries. If enclosed you cant install protective devices inside the enclosure. But LA vents Hydrogen. What does Lithium Vent? Does it go kaput from a spark like LA?
 
You guys are confusing me. So how do you fuse 3 x 5.12kW batteries in parallel?

I have a 160A battery disconnect before the inverter but now that is not good enough because I have 2 x batteries and want a 3rd.

This means I need to fuse each battery. Do I install another battery disconnect fuse holder and just get 3 x 125A Chint fuses?
 
denmendez65 said:
Applies for LA batteries. If enclosed you cant install protective devices inside the enclosure. But LA vents Hydrogen. What does Lithium Vent? Does it go kaput from a spark like LA?
Click to expand...
Have you not watched any of the videos posted?

Yes LA vents H2, but all the time when charging and only a small amount.
LFP also vents H2, 50% of the gas is H2, but only when there is a problem, and if it vents it vents like the thunder, 10000x more than LA.

1779273457702.png1779273471998.png
 
cavedog said:
You guys are confusing me. So how do you fuse 3 x 5.12kW batteries in parallel?

I have a 160A battery disconnect before the inverter but now that is not good enough because I have 2 x batteries and want a 3rd.

This means I need to fuse each battery. Do I install another battery disconnect fuse holder and just get 3 x 125A Chint fuses?
Click to expand...
Go with @DTBA method. Allows for individual battery disconnecting, even under load.

MEGA and your current disconnect switch only allows the whole bank to be disconnected but not the individual batteries.

I like his method better.
 
denmendez65 said:
Go with @DTBA method. Allows for individual battery disconnecting, even under load.

MEGA and your current disconnect switch only allows the whole bank to be disconnected but not the individual batteries.

I like his method better.
Click to expand...
How do you connect the 3 disconnects to the inverter?
 
denmendez65 said:
Go with @DTBA method. Allows for individual battery disconnecting, even under load.

MEGA and your current disconnect switch only allows the whole bank to be disconnected but not the individual batteries.

I like his method better.
Click to expand...

Watching this video.

 
cavedog said:
Watching this video.

Click to expand...
All positive and negative cables have equal length from the battery terminals to the busbars. Positive side cables of a similar length to the negative, including the fuse disconnect. If you want to be fancy, measure the ohms of the positive (including fuse holder) and cut it till you match the negative.

Equal length on the outgoing cable from the busbar to the inverter. Can throw in the main disconnector if you want, between the busbar and inverter (I have to check if it is a requirement for both positive and negative cables to be disconnected from the inverter in the event of isolation, I can't remember, mine is like that, it isolates both legs).

Thats how I would do it.


WhatsApp Image 2026-05-20 at 13.00.35.jpeg
 
denmendez65 said:
All positive and negative cables have equal length from the battery terminals to the busbars. Positive side cables of a similar length to the negative, including the fuse disconnect. If you want to be fancy, measure the ohms of the positive (including fuse holder) and cut it till you match the negative.

Equal length on the outgoing cable from the busbar to the inverter. Can throw in the main disconnector if you want, between the busbar and inverter (I have to check if it is a requirement for both positive and negative cables to be disconnected from the inverter in the event of isolation, I can't remember, mine is like that, it isolates both legs).

Thats how I would do it.


View attachment 1909424
Click to expand...

That is also what I'm thinking then I repurpose my exisitng 3 pole fuse holder for this setup and maybe just add a breaker for a battery disconnect between the inverter and the positive busbar.
 
cavedog said:
That is also what I'm thinking then I repurpose my exisitng 3 pole fuse holder for this setup and maybe just add a breaker for a battery disconnect between the inverter and the positive busbar.
Click to expand...
and one of these:
1779275587269.png1779275617558.png1779275648591.png
 
denmendez65 said:
All positive and negative cables have equal length from the battery terminals to the busbars. Positive side cables of a similar length to the negative, including the fuse disconnect. If you want to be fancy, measure the ohms of the positive (including fuse holder) and cut it till you match the negative.

Equal length on the outgoing cable from the busbar to the inverter. Can throw in the main disconnector if you want, between the busbar and inverter (I have to check if it is a requirement for both positive and negative cables to be disconnected from the inverter in the event of isolation, I can't remember, mine is like that, it isolates both legs).

Thats how I would do it.


View attachment 1909424
Click to expand...
You need the main disconnector switch.

Screenshot 2026-05-20 131910.jpg
 
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