Is my system safe?

[robbob2112]

Will definitely have to try that! What is the mrbf?

MRBF = marine rated battery fuse. They have 10k amps interupt rating

ANN fuse only has 2500a interupt rating.

 

[Sennen]

ANN fuse only has 2500a interupt rating.

For a 12v system, this may be plenty.

 

[robbob2112]

For a 12v system, this may be plenty.

Yes for a single battery, no for 4 batteries in parallel. The instantaneous current from a short will exceed even this until something interrupts it.

 

[robbob2112]

Forgot the bus bars... if they were listed as pure copper and aren't a good brand take them loose from the mounting and file off a corner and see what it is really made of. Make sure to go deep enough to get into the actual metal. There are a lot of brass bars plated first with copper then with nickle out there. This is fine if they are the right size and labeled correctly.

Measure them in mm. Get the area of the end by multiplying length times height. Then
by 4.96amps for copper and 1.89 for brass. That gives you the current carry capacity.

On amazon there are MANY two bar sets sold for $40 or less rated 300amps that are to small to carry half that. The make them from brass and rate them as if they were copper.

I looked at the breakers and they look like good quality so no fire from them

 

[Austin92]

Sorry for the novel

Let me count the ways you could have issues:

1. Mounting it all in wood - appears to be partical board shelf. Bad idea - buy a metal/wire shelf that is strong enough for you to stand on. More than one post in the "Up in smoke... learn from my mistake!" forum started with partical board shelves. Put the batteries on a lower shelf, cut a piece of Durock cement board like they lay tile with to mount everything else on. Nothing flamable touching any part of it.

2. Using an ANL fuse inline with 4 parallel batteries - should be a class T - lookup AIC

3. With 4 in parallel you should use a pair of bus bars, 600amp rated - 400 plus 20% is 480. Nearest size is 600amp. Make sure they aren't cheap no-name. If you insist on running wires instead of bus bars, put a 125a MRBF fuse and holder on the positive post of all batteries.

4. Those breakers - if they aren't blue sea or eaton or quality they will likely have a firey fail.

5. This is opinion - that sort of hammer crimper is really only intended as an emergency. To do a proper crimp you need a 2lb sledge and anvil or solid surface. It takes a pretty hard hit. If the lug bends in the process the lug is to thin a metal. The right lug is thick walled to use in these.
Get a quality hydraulic crimper (temco or good brand, not the $40 version on amazon or from harbor freight) or order cables to length fron windy nation. This isn't opinion - if you crimp cables and it leaves wings the die size is incorrect or the lugs aren't the right specs. A lot of the cheap ones are marked in AWG and are actually metric. To pass an inspection the wire size must be imprinted in the metal of the crimp.

6. What brand and type of lugs did you use? Many of the cheap ones on amazon are thin crap. Do they have UL and size listings on them? Selterm, temco, Ancor, or marine rated lugs. If you use the cheap crappy ones most of the time they leave wings from not fitting the crimper and wire correctly.

7. I would buy enough rubber boots to cover the ends of every cable. Exposed metal is asking for a short.

8. Did you use any anti-oxide compound on all your connections? If not order a can of No-Ox-ID and put a thin coat on all connections. It keeps corrosion at bay and will cut through any lite oxide coating present on the battery terminals. No-ox-id is conductive dark colored grease. It is not the white stuff in the tube manufactured by Ideal.

https://www.amazon.com/NO-OX-ID-Special-Electrical-Contact-Corrosion/dp/B00HDF9EXE

9. Every wire in your system should be fused. Either inline or preferably at the point closest to the power source.

10. Try not to stack lugs and terminals. If you must biggest goes closest to the bus bar. And don't stack more than 2 high. Make sure to ONLY use washers. Not saying you are as I can't tell from the pictures.

11. If any part of your system is to warm to touch and hold your hand on, you are doing something wrong.

12. If this is in a living space get a battery powered smoke detector that is the ionizing variety. That will alarm based on smoke if something gets hot. Even if you can't see the smoke. And if there is actually a fire it will alarm as well. The standard type smoke alarm only alarms on smoke breaking an infrared beam inside it, so the smoke has to be pretty thick. The ionizing ones cost about $30 verse $10 but are well worth it.

ideally put this in the garage and run an AC cord into the house through a hole in the wall. Seal around it. Garage walls are generally required to have a 4 hour burn time before the fire can get into the living area.

What kind of cable are you using? There are many kinds and temperature ratings. Pretty much all of your cable should be welding wire 105c rated.

You may think the fuses and nothing flamable is overkill but the math shows - if you short a wrench across one of the batteries - all 400amps will cross through it. A MRBF on the post takes 0.01 to 0.1 seconds to blow. In that time the wrench will hit around 145F in 0.1 seconds and if not corrected the wire insulation melts in around 2 seconds. In around 5 minutes the wrench is red hot and melts. This assume 2/0 welding wire between the batteries. And it assume the BMS limits current to 100a per verse just shutting down. BMS control current by manipulating MOSFETs to turn them off and on, and there is a chance for them to fail shorted until they burn open.

So if you have fuses the most likely outcome is you pop all 4 of them because of how they are wired. If you switch to bus bars you put a MRBF/class T at the bar end and depend on the BMS to shut down current on one battery. Drop that wrench or otherwise cut the wire and you pop 1 fuse.

Lots of good info, thank you.

Shelf is made of 1x12 pine that I stained.

Cement board is not a bad idea, I will
consider redesigning my shelf but I really hope to keep things safe with proper sized wire and fusing.

The buss bars are 600a rated. Skar audio, pic below, have not filed to confirm copper through and through.

Breakers were t tocas, upgraded to busman recently.

Crimper is threaded, not hammer style and I am bottoming out my dewalt 1/4 impact.

Thank you for the no ox id recommendation, will order some on payday.

Copper lugs are from Amazon, seem to be good quality but not ul listed. Some are from harbor freight and some are from work also.

Cable is 1/0 between batteries from local audio shop, from bank to switch/buss bars is 2/0 from windy nation.

Looking into mrbf fuses for each battery vs the single anl at the end I’m currently running, thought I was safe, thank you again for the ideas.

 

[Austin92]

Also upgraded to blue sea anl fuse and holder recently that another member suggested.

 

[ScrotpusGobbleBottom]

cheap crappy ones most of the time they leave wings from not fitting the crimper and wire correctly

Yup, I learned this by buying cheap ones.......

 

[Bluedog225]

I’m ok with small wings on my crimps. It’s some evidence I crimped hard enough. I file them off.

Did not know about ionizing smoke alarms. Thanks!

I use simple and non-toxic super lube as a dielectric grease to prevent oxidation. Keeps the oxygen out. Do you think no-ox is better?

 

[seneysolar]

ANN satisfies code. ANL isn't a limiter per se. ANN is.

https://up.codes/viewer/texas/nfpa-70-2023/chapter/7/special-conditions#706.31_(D)

Where does it say that?

 

[Sennen]

Where does it say that?

It's the subtlety of the phrasing current limiter. ANN 35a fuse will blow in about 0.3 seconds at 70 amps, ANL will blow in 10 seconds.

 

[wpns]

Nice build! Yeah, some potential improvements, but your first search for weak points (what gets hot under load) is right on.

 

[robbob2112]

I’m ok with small wings on my crimps. It’s some evidence I crimped hard enough. I file them off.

Did not know about ionizing smoke alarms. Thanks!

I use simple and non-toxic super lube as a dielectric grease to prevent oxidation. Keeps the oxygen out. Do you think no-ox is better?

I do.

It needs to be conductive verse dielectric. And the no-ox-id will cut through any aluminum oxide that has already formed.

This is how it works

https://www.sciencedirect.com/science/article/abs/pii/S0266353813000699

 

[robbob2112]

It's the subtlety of the phrasing current limiter. ANN 35a fuse will blow in about 0.3 seconds at 70 amps, ANL will blow in 10 seconds.

To slow IMO at the current all 100amp each of the 4 batteries puts out. The ann takes .2 seconds at 400amps. Longer at lower currents.

The 1/0 would be at 145f but sheath intact when it blew.


ANN Data Sheet 11-16-11
Eaton
https://www.eaton.com › bus-ele-ds-2023-ann

If you missed it, put the MRBF at the bus bar end of each battery cable.

 

[Sennen]

Also upgraded to blue sea anl fuse and holder recently that another member suggested.

Is the fuse still 175 degrees?

 

[Austin92]

Nice build! Yeah, some potential improvements, but your first search for weak points (what gets hot under load) is right on.

Thank you, what would you improve?

 

[Austin92]

Is the fuse still 175 degrees?

I ran the 2000w inverter on the edge of its ability and as much 12v stuff I could find, shunt was showing the system touching 2.2kw at times and after an hour the hottest temp I could get my cheap temp gun to read was 156F directly on the fuse.

 

[wpns]

Thank you, what would you improve?

Well, I wouldn't take every suggestion above, but I'd start with the hot-spots (*) identified above. Swap the fuse for something better, cover the exposed terminals, think about the structure of the shelf and maybe beef it up and/or put the batteries lower, load-test it for a few cycles and see if it works like you think it should, run off it for a weekend to test it 'real-world' and see if it meets your expectations. I'm still impressed, you've put a lot of work into it, and it's a solid beginners build. [There's a wealth of knowledge here, but Perfect Is The Enemy Of Good, so don't try to meet everyone's goals here, just yours.]

Is there any side-to-side sway of the shelving unit? Maybe it needs a board or two across one of the open sides?

(*) If you see what I did there

 

[mad.styles]

Hi @Austin92, I was thinking about buying these busbars for my system. Do you have any issues with it in regards to heat?