Opinion on stacking lug terminals on inverter post?

[WYtreasure]

Thank you, this was a useful read. I certainly had no intention of putting the washer on the terminal side. DOH! With the new incoming 1/4" lugs, the service area laying on the terminal will increase and the washer that came with the inverter should put plenty of pressure on the lugs against the terminal. The manual did not provide a torque spec, so I guess I'll go "pretty darn tight".

Maybe a "quarter-grunt"?

 

[DurkaDurka]

10 volts actually.
10 volts is the low voltage disconnect for your inverter and BMS.
BTW your BMS will very likely disconnect on cell under voltage before the inverter disconnects.
Doing that at significant current is absolutely brutal on the FET based BMSs in your batteries.
Typical scenario is one BMS disconnects on cell under voltage and the second BMS disconnects nearly immediately on over current.
Not a good day for either one.
FETs have a habit of failing closed which means your BMS may fail to protect your batteries and you won't know until the damage is done.

I wish the cutoff was adjustable for the inverter - the manual states 9.5V +-.5V DC. I'm not sure what the cutoff for the Ampere Time battery's BMS is...probably 10V. The shunt monitor does have an alarm function based on % of capacity, so I can set it conservatively at 15% or so.

Edit - I could use Victron's battery protect, but I believe Will doesn't recommend it anymore. ?

 

[DurkaDurka]

Maybe a "quarter-grunt"?

"full grunt", or go home! Well, I'll already be home...go to office, I guess.

 

[John Frum]

I wish the cutoff was adjustable for the inverter - the manual states 9.5V +-.5V DC. I'm not sure what the cutoff for the Ampere Time battery's BMS is...probably 10V. The shunt monitor does have an alarm function based on % of capacity, so I can set it conservatively at 15% or so.

Edit - I could use Victron's battery protect, but I believe Will doesn't recommend it anymore. ?

Victron battery protects can't be used in front of an inverter, the fets will melt when the inverter's capicators are primed.
Also the Giandel inverters don't have a simple switch that could be controlled by the battery protect.
I guess you will have to rely on the shunt alarm.

 

[DurkaDurka]

Victron battery protects can't be used in front of an inverter, the fets will melt when the inverter's capicators are primed.
Also the Giandel inverters don't have a simple switch that could be controlled by the battery protect.
I guess you will have to rely on the shunt alarm.

Can you explain this a little further?

 

[John Frum]

Can you explain this a little further?

Which part?

 

[DurkaDurka]

Which part?

"Victron battery protects can't be used in front of an inverter, the fets will melt when the inverter's capicators are primed."

Do you mean when the battery is reconnected to the inverter? Interestingly enough, I'm assembling a monitary switch connected to a 25W 30 ohm resistor inside a plastic box. I'm going to put this across my battery shutoff so I can pre-charge the inverter for a few seconds, release the switch, then apply power.

 

[chrisski]

As odd as it seems, the Victron Battery Protect will only operate a switch for a high wattage appliance. If you put it in line with a high wattage appliance, could be destroyed. It's designed for a remote off switch on the inverter itself. This fact is also not explained in the documentation for all Victron protects, just one of them. Victron has good documentation, but has holes.

I was getting ready to purchase a battery protect but opted out when I found out here it had to be remoted and not in line.

 

[John Frum]

"Victron battery protects can't be used in front of an inverter, the fets will melt when the inverter's capicators are primed."

Do you mean when the battery is reconnected to the inverter?

Yes.
From the manual... "4. The short circuit protection of the SBP will be activated if you try to directly connect loads with capacitors on their input (eg inverters). For that use case, please use the SBP to control the remote on/off switch on the inverter, instead of disconnecting the higher power DC line" -- https://www.victronenergy.com/uploa...A-100-A--220-A-EN-NL-FR-SV-DE-PT-ES-IT-TR.pdf
On a positive note it doesn't say anything about the FETs melting.
On a negative note you can't use a battery protect because your solar charge controller would melt the BP's FETs with reverse current.
Another thing is by the time you buy a high capacity battery protect you would be better served to buy either an inverter charger or an inverter that supports remote switching.
Either way you should consider making a system using busbars.
I like fused busbars for the positive side.

This one is rated for 300 amps and supports one feeder circuit and 3 branch circuits.

MRBF Surface Mount Fuse Block - Common Source - Blue Sea Systems

Easily and economically satisfies ABYC 7 circuit protection rule by mounting on a 3/8 battery post, battery switch or bus bar.

www.bluesea.com

 

[DurkaDurka]

Oh, bluesea.com has class T fuses as well. $45 for a 250A and $60 for the fuse block. Man, that's over $105 + shipping. Whew!

Found a local dealer that has this exact equipment for $33 and $45. I see they are out of stock though :

"CLASS T FUSES HAVE BEEN OUT OF STOCK FOR AN EXTENDED PERIOD AND WE ARE NOT EXPECTING MORE ANY TIME SOON."

I guess ANL it is.

 

[Ampster]

The bolt is only there to keep the lugs pressed tightly to the underlying terminal and any other lugs.

I agree about the function of the bolt. I can not see the surface area of the inverter terminal and that was the point of my comment that is was the surface area of the contact surface that is important.
NOTE: This thread has obviously moved on from concerns about the size of the lug. Size does matter.

 

[12VoltInstalls]

manual did not provide a torque spec, so I guess I'll go "pretty darn tight"

If it is a 1/4” stud use Grade 5 specs:

Size	Tightening Torque (Wet) / lb-ft	Tightening Torque (Dry) / lb-ft
1/4-20	6.3	8
1/4-28	7.2	10
5/16-18	13	17
5/16-24	14

putting a GFCI that will not allow more than 120VAC / 15A draw.

Th as t is its rating- I does not limit power until it is on fire. Fuses and breakers ‘limit power.’

 

[DurkaDurka]

If it is a 1/4” stud use Grade 5 specs:

Size	Tightening Torque (Wet) / lb-ft	Tightening Torque (Dry) / lb-ft
1/4-20	6.3	8
1/4-28	7.2	10
5/16-18	13	17
5/16-24	14

Th as t is its rating- I does not limit power until it is on fire. Fuses and breakers ‘limit power.’

Apologies, I'd have to put a breaker before the GFCI outlet. Looking for suggestions on maybe a 15A MCB and GFCI that fits on a DIN rail? I assume this has to be enclosed in a plastic box as well.

 

[Zil]

You will need at least 2/0 cable from the battery to the inverter. Why not wire the CC to the battery?

 

[DurkaDurka]

You will need at least 2/0 cable from the battery to the inverter. Why not wire the CC to the battery?

The surface area on the 12V inverter is probably bigger and will keep the wires shorter based on my layout. As for the 2/0, I do not intend to draw more than 1000 watts. Probably will shift to 24V as well later on. I could also double up the 1/0 wires for more ampacity?

 

[chrisski]

Not a fan of doubling up wires, but here is a calculator

Voltage Drop Calculator

This free voltage drop calculator estimates the voltage drop of an electrical circuit based on the wire size, distance, and anticipated load current.

www.calculator.net

just choose “2 conductors in parallel” instead of a “single set of conductors.”

 

[12VoltInstalls]

Not a fan of doubling up wires, but here is a calculator

Me either.
Plus: When I started living off solar I was just about broke but I still bought 2/0 for my 1200W inverter. I did several ‘upgrades’ and didn’t need to re-buy cables.
EDIT: if I’d had a bunch of 1/0 I probably would have used it and doubled up I guess. But if you’re gonna spend money think longterm and you actually save money.

 

[chrisski]

I avoid doubling up on wires because I was taught that even though the wires should have the same resistance, there’s instances they may not. This wold cause the amps to unevenly flow through the wire, perhaps melting one. This could get worst the more conductors that are put in Parallel.

This uneven resistance could be caused by uneven wire length or a bad crimp on one end in the lug where the wires are joined, or a couple other instances.

There’s also how to fuse that wire now. Whether the wire is fused after they are joined with 200 amps, or if each individual wire needs to be fused at 100 amps. Adding a fuse to each individual wire could cause these connections to have different internal resistance. I don’t have the equipment to measure resistances so small over the wires, fuses and connections,

My google searches never turned up industry standards on this. Just turned up YouTube videos, forum posts, Quora, and some articles, but no NEC standards.

I’ve had to double up a couple of times. My Overkill BMS was delivered with 2 AWG wires in each of the positive and negative sides, so I crimped those to a single 6 AWG lug to go on the busbar. My DC to DC converter would not fit the 12 volt ground and 24 volt ground with two lugs into the stud, so that got crimped in the same lug. On a short run once, I did double up with the wire with two gauges below what I wanted to use, but ran it through the voltage drop calculator in post #36.

 

[LithiumSolar]

I will be putting a GFCI that will not allow more than 120VAC / 15A draw

That's not how GFCI outlets work. They are not circuit breakers and do not have over-current protection built in. Unless you're talking about GFCI circuit breakers, but I do not see any indication that you'll be wiring a breaker panel to it.

Edit: It looks like someone already said this. I didn't realize there was a 2nd page to the thread (it's too early in the morning).

 

[DurkaDurka]

That's not how GFCI outlets work. They are not circuit breakers and do not have over-current protection built in. Unless you're talking about GFCI circuit breakers, but I do not see any indication that you'll be wiring a breaker panel to it.

Edit: It looks like someone already said this. I didn't realize there was a 2nd page to the thread (it's too early in the morning).

Thanks. When I wrote it, I had a breaker in mind before the GFCI, I just didn't write it properly. LOL!