Good LVD + relay combination for 12V 100 ah 3C pack?

[createthis]

I just realized my Victron BMV-700 SOC meter has programmable relay contacts on the back. Looks like it'll drive 15mA @ 12v, which isn't a lot. However, it looks like I can use it in conjunction with either a 500A battery isolator relay, via a smaller relay, or else with this Victron BP-220: https://www.victronenergy.com/blog/2...says-and-more/

220A is a little lower than my 250A class-t fuse, but it'll probably be fine. They mention the VE Bus BMS in that article. I wonder why they don't mention using the relay outputs from the BMV-700?

[PNjunction]

The C rating for this pack is 3C, so, while I'll probably never draw anywhere close to 3C from the pack, I guess I should buy a 12V 300 amp relay?

That's right. That C rating of C3 is only for short bursts. C1 is the realistic maximum, and C/5 or less is better for max life.

High-current done safely doesn't come cheap, in both parts and the tools to make it safe as you've seen.

You may want to look into marine LVD's, like the Blue Sea Systems m-LVD product or similar.

[createthis]

Which inverters have the programmable low voltage shutoff, BTW? Outback and Magnasine? Those might be an option if I permanently mounted them in one location and maybe attached them to the rest of the generator with a 4/0 anderson connector when I want to use them. I doubt those 4/0 anderson connectors are NEC approved though, which I'm guessing they would have to be if they were permanently mounted. I just think those inverters are probably a little large for a portable solution, unless permanently mounted to an RV. These will be in pelican style cases for portability.

[createthis]

I'm going to be using a xantrex 2000w inverter. The low voltage cut off is set at 10.5v and not programmable. I'm betting that's too low at max load.

[Sunking]

I've got a GBS 100ah LifePO4 pack I've been sitting on for a couple of months. I finally have time to go through the bottom balancing procedure, so I've made my list of things to do in order, and now I'm starting to think about operating the pack on a regular basis. Which means I'll need to get my LVD operational sometime soon..

Hold the bus a minute. If you Bottom Balance, you eliminate the need for a LVD. Does not mean you cannot use one, it just means you do not need one. Top Balancing requires a LVD triggered on any cell that dips below 2.5 volts.

Having said that. if you intend to use an Inverter, even cheap ones have LVD built into the. Buy a good one and you can program what voltage you want to set the LVD voltage you want to disconnect at. The critical voltage on 4S Bottom Balance is 10 volts. However you want to disconnect at 12 volts or roughly 10 to 15%.

The beauty of Bottom Balance is it does not take any special equipment like a BMS or LVD to operate and protect the batteries.

[createthis]

I bought 25' of this in red and black: http://www.wireandcabletogo.com/Copp...09-Strand.html

It arrived today. Looks like it's tinned copper, which is nice.

I also bought some of these to go with it: http://www.amazon.com/TINNED-BATTERY.../dp/B008D54R0S
They also arrived today. They look a little short to me, but I reckon it'll do when crimped down.

Also bought some 1" dia adhesive backed heat shrink (hasn't arrived yet) and some 4/0 SB350 anderson connectors. Man those things are beasts.

[createthis]

That DLO RHH/RHW cable has a UL sun resistant listing although UV may still make the insulation a little brittle after a while in direct sunlight.

I saw that. Not sure what resistant means in this case. Is that like where they say it's water resistant, but if you splash water on it it breaks? ha.

[SunEagle]

I'll take a look at flexible water tight conduit. That might work if it's flexible enough.

Yup, it's going to be portable. As in, on wheels in small pelican style cases.

BTW, Machine Tool Wire (MTW) is a real pain to find. Nobody carries it locally, and all the online shops want you to contact them for a quote. I really hate products like that. It's so 1999.

That DLO RHH/RHW cable has a UL sun resistant listing although UV may still make the insulation a little brittle after a while in direct sunlight.

[createthis]

Either electrical conduit or the flexible water tight conduit, not garden hose. Only a couple wire types are rated for UV, wires are supposed to be protected.

This is going to be Portable ?

I'll take a look at flexible water tight conduit. That might work if it's flexible enough.

Yup, it's going to be portable. As in, on wheels in small pelican style cases.

BTW, Machine Tool Wire (MTW) is a real pain to find. Nobody carries it locally, and all the online shops want you to contact them for a quote. I really hate products like that. It's so 1999.

[Mike90250]

It's funny. I read the MTW spec and it looks inferior to welding cable. One thing both wires lack is UV resistance. This is a portable unit, so it will be outside most of the time. I guess I'll need to put the wire inside garden hose or something to keep it from rotting.

Either electrical conduit or the flexible water tight conduit, not garden hose. Only a couple wire types are rated for UV, wires are supposed to be protected.

This is going to be Portable ?

[createthis]

It's funny. I read the MTW spec and it looks inferior to welding cable. One thing both wires lack is UV resistance. This is a portable unit, so it will be outside most of the time. I guess I'll need to put the wire inside garden hose or something to keep it from rotting.

[Mike90250]

$400+ UL certified Crimpers put a code on the lug, so inspectors know it's a good crimp. When a crimp is done properly, it cold welds the strands to the lug and the metal internally stays corrosion free, in dry indoor conditions. Bare copper starts corroding the instant it comes out of the forming machine, tin plating stops most of that, and allows for a superior attachment.
When you are pushing 200A through a cable, even small amounts of resistance become dangerous and damage the cable insulation from the generated heat. That's one reason soldering is not a recommended method, the joint heats, solder melts, and wires fall off the lug.
Welding wire insulation is not rated for installs, you need machine tool wire (MTW)
http://www.quickcable.com/products.php?pageId=854 "can be used as battery cable, motor lead, and power hook-up cable"
I've also heard (maybe an electrician can back me up) that locomotive cable is also rated for battery use
DLO RHH/RHW Cable http://www.quickcable.com/products.php?pageId=855

Lugs
http://www.quickcable.com/products.php?pageId=78 "MagnaLugs feature a wider footprint and thicker walls than conventional lugs and are listed by UL/CUL when applied with Quick HexCrimp™ tools."

And these look interesting, compression lugs, like a flare pipe fitting http://www.quickcable.com/products.php?pageId=329 4/O is really big stuff !

A little more on codes and MTW / DLO cables ( look for RHH/RHW cert)
http://forums.mikeholt.com/showthread.php?t=98209 Scroll down to post #6 about the fine strands and required lugs for them.

What happens when it goes bad ?
see page 3 - https://www.altestore.com/store/medi...es_Article.pdf

[createthis]

1) the hydraulic crimper is the better, the Greenlee will be VERY difficult to use with 4/O cable
2) welding cable has extra fine strands and requires non-standard Lugs for crimping. Lugs need to be tin plated, not bare copper
3) will this ever be inspected or used in an insured structure ? If NO, then you have some room to play with.
4) the lugs may not stamp a cert # onto the barrel, = failed inspection

Which crimper would put a cert # on the barrel? I can't imagine this ever being inspected as it's a portable personal unit, but I like to know what will or won't pass an inspection anyway.

Welding wire lugs must be tin plated according to whom? Is that a personal experience statement or a code statement, and if code, which code? Some California code?
Also, are you saying the non-standard lugs are non-standard because they are tin plated, or are you saying they are non-standard AND they should be tin plated?

I've read tinned lugs slow corrosion, so that's fine. Apparently once the corrosion starts the cable must be cut to remove bad sections. Tinned welding wire is a thing too, so that might be something I look for. Will these work? http://www.amazon.com/TINNED-BATTERY.../dp/B008D54R0S

[Mike90250]

1) the hydraulic crimper is the better, the Greenlee will be VERY difficult to use with 4/O cable
2) welding cable has extra fine strands and requires non-standard Lugs for crimping. Lugs need to be tin plated, not bare copper
3) will this ever be inspected or used in an insured structure ? If NO, then you have some room to play with.
4) the lugs may not stamp a cert # onto the barrel, = failed inspection

[createthis]

When you purchase that 4/0 cable make sure you get a certified lug compression system or you could end up with less than desired krimps on the terminal lugs which will increase the resistance and heat generated.

I was planning to use this crimper: http://www.amazon.com/Hydraulic-Batt.../dp/B00GXQ2E5E
My second choice would probably be this: http://www.amazon.com/Greenlee-K09-2.../dp/B000LDGRV2

Which tool do you recommend?

I'll be keeping an eye on it either way, looking for heat, melting, etc. I won't trust it. But honestly, I probably won't use it at high amperages often. I mostly just plan to prove I can. But who knows. I might find a use case for high amps and use it that way all the time, in which case I'll be sure to watch it like a hawk. Sounds like a good excuse to buy a thermal camera.

I bought some 4/0 THHN today. It was fairly inexpensive, but after thinking about it for a minute, it's not going to work in this application. This is a portable system, so I need flexible cable. 4/0 THHN is super stiff. I can barely bend it with my bare hands.

I'm going to check the local welding supply tomorrow. Looks like 4/0 welding wire is what I want. Here's my benchmark for price. It ain't cheap: http://www.amazon.com/Crimp-Supply-U.../dp/B0161NYP1Y