- Apr 17, 2016
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The danger of giving advice on the internet is that you don`t know what you don`t know.Great, thanks! Really good info.
I'm looking at getting either of these:
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May also get some 175A-rated Anderson plugs for the battery disconnect if I can't find a suitable size isolator switch - will go to the local hardware or electrical shop and have a look at the actual sizing of the isolator switches and the max diameter cable they can take. Ideally I want to create a sub-DB off the main DB with everything inverter-connected in one place, so looking at the DIN sizing/boxes.
The danger of giving advice on the internet is that you don`t know what you don`t know.
Your intentions are pure and you trying to assist other people but therein lies the danger if you are not a professional or have adequate experience.
So please don`t see my post as an attach, Im just trying to highlight the hidden or unknown danger. This is not wiring up a new amp to your 6x9 in the back of a City Golf, we are working with lethal voltages, and batteries that can easily burn your house down.
These fuses are an example of just this just. Lets look at a draft copy of the new SANS 10142-1-2
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An inexperienced person with only basic knowledge will only consider the voltage rating and current rating of the fuse when making a selection.
They don`t even know what Short-circuit current Isc is and why is so import to consider when selecting protective devices or equipment. And people don`t understand why equipment with high Isc rating are much more expensive and rather go for the cheaper option.
With parallel batteries the Isc can be potentially very high, and when a fault occurs and the protective device fails to operate then only does it become apparent.
Thanks for this good info - although I have a fair layman's knowledge of electricity/electrical circuits/AC vs DC/etc, I will not be doing the work myself - I always try to find out and understand what the requirements are beforehand so I don't get ripped off by someone claiming to be a qualified electrician; it's unfortunate, but I've been taken for a ride too many times before, so would rather find out what actually needs to be done so I can watch out for the chancers/errors made.
Although I've bought most of the main parts/equipment needed, I would still have a certified (and reliable/knowledgeable) sparky do the final install, connection, checking and CoC, as well as give advice on the breakers, fuses, circuits, etc - with the equipment cost outlay so far, I certainly don't want to take a chance on a sparky that says they know what they're doing and then takes shortcuts - way to costly in all manners.
I think I've posted pictures a fair while back showing my main DB spaghetti mess - essentially done by a reliable and qualified sparky (company), provided a CoC, but I also re-checked by another different sparky a few years later who also gave a clearance and CoC after some building work was done - the DB mess speaks for itself:
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Still not happy with it and would rather toss the whole lot and get it done properly - now is an ideal time while I'm introducing the backup/solar and also having the phases/balancing reviewed. Any info or advice from these threads is a bonus in understanding what and what not to avoid.
It is preferable to crimp lugs that carry high current. The problem with solder is that it is not a very good conductor. When a high current passes through the soldered joint (eg when charging the batteries), heat is generated due to the solder's resistance. This caused the solder to melt. Eventually the solder will set in such a way that there is little or no contact between the wire and the lug (ie, a dry joint).I got 100A ANL fuses from a car audio fitter. They were R150 each with the fuses. I can hook both leads for the battery to one terminal. I had to cut the arch out of the cover to get two cables in.
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I decided not to buy a dc isolator. I can just remove the cable from the battery or remove the fuse.
Cable I went with 25mm2 welding cable. It's about R75/m and can handle 400A. The ring terminals were easy to put on. Strip the cable back and remove a few strands if needed to get the cable into the lug. Heat the lug with a big solder iron. Behind the ring is a hole and you push your solder in there till it's full. Far better than crimping. remember to orientate the ring terminals. They have a raise and a flat side. Cables connecting batteries must have both flat sides on the bottom. The rest just dry fit first to see. Especially where two cables go onto one post.
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I used 10mm on the batteries, 8mm on the fuses and 6mm on the inverter. Get some red and black tape because the cable either blue, grey or green. Mark positive and negative ends with red and black respectively.
Cables must all be the same length. i.e the cables joining batteries in series must be the same length. Cables from the batteries to fuses must be the same length. Fuses to inverter the same length. Get your batteries as close to the inverter as possible. It is cheaper to raise the battery holder than to buy longer cable.
I'll take some close up pics today.
That is more common than you would expect.So a three-phase supply, with only one phase covered by E/L all using a common neutral bar?
i think you are spot on there. i have always soldered.It is preferable to crimp lugs that carry high current. The problem with solder is that it is not a very good conductor. When a high current passes through the soldered joint (eg when charging the batteries), heat is generated due to the solder's resistance. This caused the solder to melt. Eventually the solder will set in such a way that there is little or no contact between the wire and the lug (ie, a dry joint).
You will not find a soldered lug on a car battery lug, welding cables, etc for this reason.
It will never fail until it fails . These batteries charge at a fairly high current and the chances are that one or more joints will give intermittent problems some time in the future. It will be great fun, with long and interesting swear-words and bundles of expensive spare parts being replaced until the damned dry-joint is eventually discovered.Correct, but also a bit of a risk. The cabling, lugs, and terminal connections should all be rated at least 1.25 times the maximum short circuit current expected. If you monitor the voltages across the batteries and you start seeing issues of variations that should not be there, touch the terminals and connections. If any are hotter then the rest, it is starting to fail on you.
I personally prefer crimped connections only.