It's like a jigsaw puzzle that could kill me (setting up my bus bar) - my thoughts make sense?

[AlaskanNoob]

I was taking the Teaser Headline literally. Setting up the puzzle will not kill you, especially if there is no power during set up. Your thread did result in a number of good suggestions

From your mouth to God's ears, sir! I'm not going to lie, the day of connecting sparkys is coming and I'm a bit nervous. I feel like I should have studied harder in school...

 

[AlaskanNoob]

Yeah, that one is kind of an outlier. Current flows in both directions so should there be a fuse at both ends, right? But the normal placement is on the battery/bus end of the cable, not the inverter end.

Well I seem to end up with a lot of extra things in this project as I do some research, buy something, then find out I should have bought something else. Maybe I'll have extra fuses for that after all.

If the previous poster is correct that I should have sized my t-fuses for the max continuous inverter draw (250A) rather than what I did, which was sizing for max surge (520A) then I'm going to have to get smaller t-fuses anyway for the cables to the inverter. Maybe I'll put fuses on both ends of the cables.

 

[HRTKD]

One thing I'm not seeing in your diagram in post #35 is a battery cutoff switch. An appropriate cutoff switch makes the final connections a lot less stressful. Connect all the wires, then throw the switch. No sparks. At least none that you'll see.

 

[HRTKD]

If the previous poster is correct that I should have sized my t-fuses for the max continuous inverter draw (250A) rather than what I did, which was sizing for max surge (520A) then I'm going to have get smaller t-fuses anyway for the cables to the inverter.

Continuous is the correct sizing. I won't ever pull as much as the Victron manual specified for the fusing, which was 400 amps. But I went with their requirement anyhow.

 

[AlaskanNoob]

One thing I'm not seeing in your diagram in post #35 is a battery cutoff switch. An appropriate cutoff switch makes the final connections a lot less stressful. Connect all the wires, then throw the switch. No sparks. At least none that you'll see.

Yeah, no cut off switch. Just a t-fuse between each battery and the bus bar. But they're Pylontech US5000 so I should be able to just shut them off at the battery itself.

I'm planning on setting up the Quatro and connecting it to our generator, having each Pylontech connected individually to the bus, but we'll use a different 48V battery to charge the caps of the Quatro before we turn on the batteries. Then we'll crank up the generator, and charge the Pylontech to 100 as slowly as possible to get them all full up. I don't know if "balancing" them is really an issue for me since they're all going to be wired independently to the bus, but just in case.

 

[HRTKD]

Yeah, no cut off switch. Just a t-fuse between each battery and the bus bar. But they're Pylontech US5000 so I should be able to just shut them off at the battery itself.

That'll work.

 

[Shimmy]

Quickly though, our solar consultant seemed to think the t-fuses should be by the bus bar. But you think they should be closer to the devices instead?

The fuse/breaker protects the wire.

It can safely be done at either end. The charge controller is a current limited device so it can't source sufficient energy to blow the fuse. The only way the fuse blows is if the energy comes from the battery bus.

From an overall safety standpoint, logically segregating your + and - busbars and shielding them from touch is going to go further than anything else.

 

[Shimmy]

Maybe I'll put fuses on both ends of the cables.

In this case, the fuses are not protecting the cables they are protecting the inverter from a short. The sizing of the wires is what protects them from an overload.

The only time you see (properly designed) systems with fuses at both ends of a cable is when you have parallel sets that each need to be fused to be properly protected. This is a very rare condition (and a maintenance nightmare).

For your system, it would be perfectly fine to have a single 300A fuse and terminate two sets of cables on it (preferrably with an extra bus rather than double-lugging).

 

[Ampster]

In this case, the fuses are not protecting the cables they are protecting the inverter from a short. The sizing of the wires is what protects them from an overload.

I take a different approach based on my risk aversion and always use a fuse at the pack to protect the wire. My inverter also has a breaker. I have never understood the logic of protecting an inverter? What could go wrong if the DC inputs to an inverter are shorted? A fuse at the pack would protect the wire. If the short was internal to the inverter the inverter is probably fried anyway and further damage to the cables is prevented by the breaker or the fuse..

 

[FilterGuy]

Actually I just wanted to see how close in cost it comes to my Lynx Power Ins. You are doing it right and there are 50 ways to skin the cat.

The disappointing thing about Lynx is that it uses Mega Fuses with a very low AIC. If you need Tclass, it has to be external to the Lynx and that takes the nice clean design of the Lynx system and adds ugly warts to it.

Victron is usually pretty good about addressing the needs of people but this is one area they have failed to address. This surprises me because even the Victron Ambassadors tell me LiFePO4 needs more than Meag Fuse

 

[AlaskanNoob]

Does anybody know how these covers for the fuse blocks and bus bars work with the Blue Sea products? Do I bend these plastic tabs so cables can attach or should I just cut them off?

 

[FilterGuy]

It certainly looks like the protective tabs are designed to be removed. I have never played with one but I suspect if you bend it, it will snap at the line.



If you try to bend it and it doesn't snap. cut it at the line.

 

[629658]

The disappointing thing about Lynx is that it uses Mega Fuses with a very low AIC. If you need Tclass, it has to be external to the Lynx and that takes the nice clean design of the Lynx system and adds ugly warts to it.

Victron is usually pretty good about addressing the needs of people but this is one area they have failed to address. This surprises me because even the Victron Ambassadors tell me LiFePO4 needs more than Meag Fuse

Perhaps but I’m confident about my setup. If 4 sets of redundancy isn’t enough then a 5th isn’t going to make any difference.

 

[HRTKD]

On one of my covers, I tried to break it where the plastic was scored and it didn't work out so well. After that, I used a Dremel with a cutoff wheel.

 

[SamG340]

A) I measure my positive cable length as 18" for the two Quattro positive cables, and 19" for the two MPPT positive cables. Should I go with those numbers to keep it as short as possible, or round it up to 24" to give me some wiggle room? I could also move the bus bars closer to the devices and shorten the lengths if needed a bit.

I just put the cable in place and cut it where looks about right ,

 

[rhino]

For your system, it would be perfectly fine to have a single 300A fuse and terminate two sets of cables on it (preferrably with an extra bus rather than double-lugging).

Doing this will make for cleaner easier to maintain system. How would you even know if only one of the fuses blew since the inverter would still have power.

 

[HRTKD]

How would you even know if only one of the fuses blew since the inverter would still have power.

That's question that I had. But only after I had installed the twin fuses.

 

[AlaskanNoob]

Doing this will make for cleaner easier to maintain system. How would you even know if only one of the fuses blew since the inverter would still have power.

I guess I'll know once the second fuse blows because it demands too much power through the only remaining cable.

 

[AlaskanNoob]

Continuous is the correct sizing. I won't ever pull as much as the Victron manual specified for the fusing, which was 400 amps. But I went with their requirement anyhow.

The consultant we hired said:

There is a lot of confusion about overcurrent protection on forums etc
Overcurrent protection (fuse or breaker) is to protect wires only, not equipment.
Thus, overcurrent protection is sized based on wire size. In this case, 300A is perfectly suitable for 4/0 cables.
You could certainly downsize the fuses, but there's no advantage that I can see in doing that and you risk nuisance tripping of the fuse.

 

[Ampster]

The consultant we hired said:

There is a lot of confusion about overcurrent protection on forums etc​

Overcurrent protection (fuse or breaker) is to protect wires only, not equipment.​

That was the point I made earlier to the comment from @Shimmy