diy solar

diy solar

Do we still need T-Class Fuses?

12VoltInstalls said:
Right. But a breaker on the battery? Should, right?
Click to expand...
The way I did it was to have the T fuse at the battery which all connect to the busbar that runs up the side. 4/0 cable to the shunt trip ABB breaker which can be tripped by either the Batrium BMS due to over current (sensed by it's shunt) or the breaker itself. From there it goes to the Victron Lynx, from the Lynx it is split for each inverter and there is another pair of 200A Class T fuses, one for each inverter, inside the wiring trough.

I like fuses in many cases, if there is a problem I want shutdown. Size the wire and fuse appropriately. There should not be a blown fuse if done correctly unless there is a fault.
 
Zwy said:
Size the wire and fuse appropriately. There should not be a blown fuse if done correctly unless there is a fault.
Click to expand...
That’s like something I would say myself. However, when I ‘make’ battery cables myself they are always oversized by one or two gauges, BUT I fuse them for the maximum expected load or the drawing device’s (inverter) maximum output. Without Stupid Human Tricks by myself (rare if ever) or others (this has happened) I’ve never blown a 100A or 125A fuse on a 100A rated output battery.
In my own system the little tablesaw, a compressor, or 120V welder has freaked out the inverter at lesser states of charge, but no breakers have ever tripped or fuses have blown.

Anyways I’m interested in this for educational purposes. I installed 10kWh of the batteries I posted prior under a 6548 for someone.
They just ordered a second 6548 and two more batts for split/240 and the lack of fuses on the mfgr. supplied cabling bothers my head.
It also bothers my head to cut those cables. Nevertheless, I think I’m just going to use busbars and Class T’s, set it, and forget it.

image.jpg
 
Doesn’t something the Victron Lynx Power In (converted to take mega fuses) answer the mail for fusing parallel packs together? Hefty bus bar, fuses for each pack and protected with a cover to reduce other conductor contact.
 
ChrisG said:
Doesn’t something the Victron Lynx Power In (converted to take mega fuses) answer the mail for fusing parallel packs together? Hefty bus bar, fuses for each pack and protected with a cover to reduce other conductor contact.
Click to expand...
I believe best practice is to fuse as close to the positive battery terminal as possible (within 7 inches?). In your described case the fuse is at the far end of the battery cable.
 
Brucey said:
I believe best practice is to fuse as close to the positive battery terminal as possible (within 7 inches?). In your described case the fuse is at the far end of the battery cable.
Click to expand...
How is the 7” guideline being done in server racks with busbars?
 
I assume something like this could work on the positive terminal or as close as possible for each individual pack. 2000a interrupt IMG_4662.jpeg
 
ChrisG said:
Doesn’t something the Victron Lynx Power In (converted to take mega fuses) answer the mail for fusing parallel packs together? Hefty bus bar, fuses for each pack and protected with a cover to reduce other conductor contact.
Click to expand...
Not for a 48v system imo.
Victron is releasing a power in with class T fuse provisions this year though.
 
12VoltInstalls said:
That’s like something I would say myself. However, when I ‘make’ battery cables myself they are always oversized by one or two gauges, BUT I fuse them for the maximum expected load or the drawing device’s (inverter) maximum output. Without Stupid Human Tricks by myself (rare if ever) or others (this has happened) I’ve never blown a 100A or 125A fuse on a 100A rated output battery.
Click to expand...

I usually will bump the cable up one size. Limits voltage drop and for those times when there might be some heavy surge/load by the Official Loads Tester (saw 8Kw continuous drawn the other day, don't ask). Fuse size is according to load also but takes into consideration wire size.

I'm big on slight oversize, known to use 8AWG for PV wire when smaller than 10AWG would easily handle it.
12VoltInstalls said:
In my own system the little tablesaw, a compressor, or 120V welder has freaked out the inverter at lesser states of charge, but no breakers have ever tripped or fuses have blown.
Click to expand...

You need an Official Loads Tester, They will run the washing machine at the same time as the dishwasher and even turn the dryer on at the same time. Well pump kicks in for washing machine and dishwasher. This is with heat pump running and usually 800W of resistive heating load. Then out comes the vacuum cleaner and those things suck watts. :ROFLMAO:

Good thing I slightly oversize things.

If you go to the breaker panel and it is glowing red, you know the Official Loads Tester is performing official duties.

12VoltInstalls said:
Anyways I’m interested in this for educational purposes. I installed 10kWh of the batteries I posted prior under a 6548 for someone.
They just ordered a second 6548 and two more batts for split/240 and the lack of fuses on the mfgr. supplied cabling bothers my head.
It also bothers my head to cut those cables. Nevertheless, I think I’m just going to use busbars and Class T’s, set it, and forget it.
Click to expand...

It would depend on how long the cable is. One can undersize the fuse or breaker for the cable, this allows some leeway on over current but won't provide protection for the cable between fuse/breaker and battery. If the cable is protected such as inside an enclosure and is fastened down, it should never have a failure.
 
Zwy said:
You need an Official Loads Tester, They will run the washing machine at the same time as the dishwasher and even turn the dryer on at the same time. Well pump kicks in for washing machine and dishwasher. This is with heat pump running and usually 800W of resistive heating load. Then out comes the vacuum cleaner and those things suck watts. :ROFLMAO:
Click to expand...
While the oven is cooking a roast. Yep, have one of those. Should see the meter spinning up like a helicopter.
 
  • Haha
Reactions: Zwy
ChrisG said:
I assume something like this could work on the positive terminal or as close as possible for each individual pack. 2000a interrupt View attachment 198032
Click to expand...
Used these on pop's cabin solar build. They are very reasonably priced. Since it is 12v with a higher resistance lead acid battery bank, I'm ok with the 10k mrbf interrupt capacity, and they can be had in different blow characteristics. Not trusting them with LiFePo4 and especially with +48v.
 
G00SE said:
Not for a 48v system imo.
Victron is releasing a power in with class T fuse provisions this year though.
Click to expand...
Any idea when? I’m about to get a full Victron dual 10kva Quattro setup with accompanying Lynx setup.
 
NC_hydro said:
Any idea when? I’m about to get a full Victron dual 10kva Quattro setup with accompanying Lynx setup.
Click to expand...
Their price sheet was slated for March so I was figuring Q2 would be earliest theyd be seen in the wild.
As of 2 weeks ago I’ve spoken to 3 different Victron dealers and none had an update/eta so I just bought a regular one. Didn’t want to wait until fall if it doesn’t make it stateside until later
 
Made a sketch about my understanding of lug terminal connection contact resistance. Looks like 3 lugs stacked has less contact resistance. I am not sure about 4 or more stacked together.

LUG-BUSBAR.jpg
 
G00SE said:
Not for a 48v system imo.
Victron is releasing a power in with class T fuse provisions this year though.
Click to expand...
Without having to crimp multiple connections(more failure points) for a t-class fuse and holder on every battery, think the power in converted with mega fuses for each pack still makes the most sense, just keep the wire as short as physically possible between Lynx and battery.
 
Zwy said:
I usually will bump the cable up one size. Limits voltage drop and for those times when there might be some heavy surge/load by the Official Loads Tester (saw 8Kw continuous drawn the other day, don't ask). Fuse size is according to load also but takes into consideration wire size.

I'm big on slight oversize, known to use 8AWG for PV wire when smaller than 10AWG would easily handle it.


You need an Official Loads Tester, They will run the washing machine at the same time as the dishwasher and even turn the dryer on at the same time. Well pump kicks in for washing machine and dishwasher. This is with heat pump running and usually 800W of resistive heating load. Then out comes the vacuum cleaner and those things suck watts. :ROFLMAO:

Good thing I slightly oversize things.

If you go to the breaker panel and it is glowing red, you know the Official Loads Tester is performing official duties.



It would depend on how long the cable is. One can undersize the fuse or breaker for the cable, this allows some leeway on over current but won't provide protection for the cable between fuse/breaker and battery. If the cable is protected such as inside an enclosure and is fastened down, it should never have a failure.
Click to expand...
1000008197.jpg1000008196.jpg
Load testing? How about these 2 shots of my 2 systems feeding my house and shop.
 
So....going back to my main question...am I safe with my current setup of 7 eg4 batteries and an LG6548? no added fuses.
 
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