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Fuse Sizing

I assume these are 48V server rack batteries with breakers built in.
I didn't draw them but yes, you assumed correctly.

However, I've also read some discussion that breakers are not sufficient for a dead short in 48V batteries. A Class T seems to be the best protection against a fire.

I don't mean to hijack this thread. I'm in process of designing my system. My eraser is getting too much use. :LOL:
 
I didn't draw them but yes, you assumed correctly.

However, I've also read some discussion that breakers are not sufficient for a dead short in 48V batteries. A Class T seems to be the best protection against a fire.

I don't mean to hijack this thread. I'm in process of designing my system. My eraser is getting too much use. :LOL:
Depends on the breaker.
@signaturesolarrichard is looking into it for us.
 
Either if the breaker is sufficient or Class T fuses are installed at each battery, a Class T fuse at the "trunk" cable close to the battery bus bar would be good practice?
Yes ideally fused at the battery side of the trunk.
 
These are 3 busbars that enforce best practice for branch circuits.
 
These are 3 busbars that enforce best practice for branch circuits.
I wanted to use Victron's Lynx DC Distributor and in fact have it on a shelf. With all the recent class T fuse discussion I've been questioning if it would be better to send it back before the return period expires in about 10 days.

I like the clean look when installed but don't want to sacrifice safety for aesthetics.
 
I wanted to use Victron's Lynx DC distributor and in fact have it on a shelf. With all the recent class T fuse discussion I've been questioning if it would be better to send it back before the return period expires in about 10 days.

I like the clean look when installed but don't want to sacrifice safety for aesthetics.
The lynx distributor is used to fuse up to 4 branch circuits and its a great tool for that use.
The class t fuses are to protect the batteries which is where all hell breaks loose.
To aggregate the batteries use a lynx power in

To re-iterate the lynx distributor gives the possibility to isolate a fault to a branch circuit which can allow the rest of the system to continue functioning.
The class t fuses protect the batteries.
We want to isolate the faults on the branches if possible but if things turn ugly the last line of defense is the class t fuses as close to the battery terminals as possible.
I feel like I'm repeating myself.
I guess I'm not making myself clear.
 
No, you've been clear. I'm just taking in other sources of information and questioning my original plan.

I've read some from the Victron community that recommend a class T fuse between the inverter and branch bus. Much the same as Will displayed in his recent Current Sharing videos.

I'd prefer to use a Mega Fuse with the Victron Distributor. And hoping the signature solar information on their breakers is reassuring.
 
Here is a drawing that illustrates what I am describing.
So. I have a LVX6048 coming.
6000 Watt inverter. 4-12v, 400 watt, 100 Ah AGM's in series. 1*2 AWG wire is required to supply inverter.
A 20% discharge rate is 43.6 (can be user defined min/max) at 54v max charge.
Using your formula I come up with 202.375 or uped to a 225 amp fuse at battery at 43.6 min volts.
Am I correct that you are suggesting a T fuse between each battery series connection? Or one at the positive conductor going to an isolation switch?
Newbie here just trying to learn and safely construct this system.
Thank you so much for your replies!
 
So. I have a LVX6048 coming.
6000 Watt inverter. 4-12v, 400 watt, 100 Ah AGM's in series. 1*2 AWG wire is required to supply inverter.
6000 ac watts / .85 conversion factor / 43.6 volts low cutoff = 161.899622234 service amps
161.899622234 service amps / .8 fuse headroom = 202.374527793 fault amps.

You want to bump that wire size up to minimum 1/0awg and use a 250 amp fuse.
The wire should be pure copper with insulation rated for 105C.

4x 100ah AGM batteries in series is not enough to feed that LVX.
They would be able to feed that all_in_one flat out for ~30 minutes and the peukert effect will be brutal.
I'm not sure what 400 watt means in the context of an agm battery, please explain.
A 20% discharge rate is 43.6 (can be user defined min/max) at 54v max charge.
I'm not experienced with AGM batteries so I will have to take your word for it that 43.6 volts is an appropriate disconnect.
My gut says its too low.
Using your formula I come up with 202.375 or uped to a 225 amp fuse at battery at 43.6 min volts.
As above I suggest 1/0 awg with a 250amp fuse.
Am I correct that you are suggesting a T fuse between each battery series connection?
Nope, class -t is not required for AGM batteries.
Also since they are in series they are treated as 1 battery.
I suggest a 1 of these https://www.waytekwire.com/products/1646/Bolt-Down-Fuses/&Series=MRBF-Series&Current-Rating=250A
On 1 of these https://www.waytekwire.com/item/45567/EATON-s-Bussmann-Series-MRBF-Mounting-Bar-3-8-/
Or one at the positive conductor going to an isolation switch?
Newbie here just trying to learn and safely construct this system.
Thank you so much for your replies!
 
6000 ac watts / .85 conversion factor / 43.6 volts low cutoff = 161.899622234 service amps
161.899622234 service amps / .8 fuse headroom = 202.374527793 fault amps.

You want to bump that wire size up to minimum 1/0awg and use a 250 amp fuse.
The wire should be pure copper with insulation rated for 105C.

4x 100ah AGM batteries in series is not enough to feed that LVX.
They would be able to feed that all_in_one flat out for ~30 minutes and the peukert effect will be brutal.
I'm not sure what 400 watt means in the context of an agm battery, please explain.

I'm not experienced with AGM batteries so I will have to take your word for it that 43.6 volts is an appropriate disconnect.
My gut says its too low.

As above I suggest 1/0 awg with a 250amp fuse.

Nope, class -t is not required for AGM batteries.
Also since they are in series they are treated as 1 battery.
I suggest a 1 of these https://www.waytekwire.com/products/1646/Bolt-Down-Fuses/&Series=MRBF-Series&Current-Rating=250A
On 1 of these https://www.waytekwire.com/item/45567/EATON-s-Bussmann-Series-MRBF-Mounting-Bar-3-8-/
"4x 100ah AGM batteries in series is not enough to feed that LVX.
They would be able to feed that all_in_one flat out for ~30 minutes and the peukert effect will be brutal.
I'm not sure what 400 watt means in the context of an agm battery, please explain."
I was planning to get 4 more of them
 

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"4x 100ah AGM batteries in series is not enough to feed that LVX.
They would be able to feed that all_in_one flat out for ~30 minutes and the peukert effect will be brutal.
I'm not sure what 400 watt means in the context of an agm battery, please explain."
I was planning to get 4 more of them
I'll defer to someone who knows lead acid batteries better than I do.
 
What loads are you serving that depict your need that sized inverter? What does the load audit say for your daily KWHr consumption?

What solar array are serving the inverter as well? No point in having a massive battery if it’ll never get charged via the PV array.
 
What loads are you serving that depict your need that sized inverter? What does the load audit say for your daily KWHr consumption?

What solar array are serving the inverter as well? No point in having a massive battery if it’ll never get charged via the PV array.
Thanks for the reply. I found a calculator on-line to determine the watt hours I need.
That told me that I need 8 of the AGM batteries to meet the 10400 Wh daily load.
 
8 100ah 12v batteries and you expect to serve 10kwh of load?

And what sized solar array does that equate to?
 
@John Frum or others.
I wanted yours or others feedback based on the T-fuse calculation you mentioned on this post.

"Example:
2000 ac watts / .85 conversion factor / 10 volts low cutoff = 235.294117647 service amps.
235.294117647 service amps / .8 fuse headroom = 294.117647059 fault amps."

Based on this example, would my 2 Rich Solar LV6548 setup as split phase (13kW) All in One inverters T-fuse selection be as follows?
13000 watts / 0.91 (assuming conversion factor = efficiency) / 44 volts low cutoff (Does this get doubled if I am putting 2 units together?) = 324.6753 servicing amps

324.6753 servicing amps / 0.8 fuse headroom = 405.8442 fault amps.

If the calculation above is correct, I should buy something the next step up from the 400A but I can't seem to find it on a google search. Would using a 400A T-fuse be good enough even though the calculation above shows it is 5.8442 amp short of what it should be? If my calculations are wrong, please let me know where I miscalculated.

Thanks.
 
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