Good way to measure high (100A+) amperage amps DC - Page 1
Forum section: electronics / beginners

author: Red Squirrel
author_rank: Super Contributor
timestamp: December 11, 2014, 02:54:47 am
content: I have a panel meter I bought from ebay which is used to display volts and amps of a DC battery bank. Problem is, the amps portion is garbage, the numbers just jump all over the place and never actually display anything of significant value. My guess is some kind of interference between the shunt and the meter.This is the meter in question:There is a shunt on the back where telecom wires go to for the data.Is there a better way to measure DC current? Perhaps an arduino compatible way? If I want a panel meter I can then use regular LED number displays and bit shift registers and have the arduino output it back, and I'd have the advantage of having the data going to my monitoring server as well instead of using something proprietary.

author: IanB
author_rank: Super Contributor
timestamp: December 11, 2014, 04:23:08 am
content: Quote from: Red Squirrel on December 11, 2014, 02:54:47 amThis does not compute. A current shunt for 100 A is by definition a low resistance, which means if you measure the voltage across it is a low impedance voltage source, which means it should be very immune to interference. So maybe something else is wrong, like maybe the meter is faulty, or there is a loose connection somewhere?

author: mij59
author_rank: Frequent Contributor
timestamp: December 11, 2014, 05:09:10 am
content: You could use a current transducer like this one[url=http://www.lem.com/docs/products/hais_e_rev11.pdf]http://www.lem.com/docs/products/hais_e_rev11.pdf

author: LabSpokane
author_rank: Super Contributor
timestamp: December 11, 2014, 05:31:13 am
content: I'm happy you admit the wiring isn't the best. First off. Telco wire is for punch down blocks. Get some proper stranded wire that's the correct gauge for those screw terminals. Second, draw a schematic and follow it. Third, rip that out and start over- preferably using a licensed electrician. That's just no way to mess around with that kind of amperage.Sorry to be harsh, but you're in over your head with this.

author: mtdoc
author_rank: Super Contributor
timestamp: December 11, 2014, 06:22:39 am
content: Lab Spokane is right. That's a fire or burned limb waiting to happen. I hope you have it properly fused.....If you want to measure current from your battery bank, get a proper 500 amp shunt likethis oneand a proper battery monitor likeTHIS. Xantrex (Schnieder electric) and Victron also make nice monitors.

author: coppice
author_rank: Super Contributor
timestamp: December 11, 2014, 07:34:55 am
content: A shunt gives you a rather small differential signal, ideal for conveying over a reasonable distance to a meter,ifyou respect its differential nature. That means you take one of your twisted pairs and connect one end across the terminals of the shunt. You make sure the pair stays together over its length, and only spreads out at the far end to connect to the sense terminals of the meter. You take another wire, and connect one end to a point nearby, put not actually on, the shunt. You connect the other end of this wire to the third terminal on the meter, which could be labelled in one of a variety of ways. This third wire acts as a general voltage reference, to avoid a large common mode voltage between the meter and the shunt. The voltage across the pair is actually used to measure the current. Wired properly, the pair should have reasonable immunity to noise pickup along its length, and your readings should be steady and accurate.As others have said, do beware of the potential for fires in a setup like this. If you don't know what you are doing, ask for help from someone who does.

author: rs20
author_rank: Super Contributor
timestamp: December 11, 2014, 10:21:25 am
content: Quote from: coppice on December 11, 2014, 07:34:55 amI assume it's important to mention that there should be zero other galvanic connections to anything else on the same circuit as the shunt, right?

author: richard.cs
author_rank: Super Contributor
timestamp: December 11, 2014, 12:09:31 pm
content: I have to say the existing wiring is rather dissapointing, in particular the shunt and various bolted joints hanging in mid-air. Is that aluminium cable or just tinned copper? Does a dangerous situation occur if you ever switch both off at once (as instructed not to do)? If so they should be mechanically interlocked.You're likely picking up noise and switching hash from the inverter, if you are careful with your routing of the twisted pair you should be able to get a meaningful output from the meter. You need to keep then balanced and symetrical, and it would be nice to use shielded twisted pair as it matters far less when you run them past other conductors, the shield ensuring that both halves of the pair see the same capacitance to whatever it is. It's possible that the meter just has terrible common mode rejection, or possibly even terrible power supply rejection, is it being supplied from the same battery bank? It looks like it's supplied by its own voltage sense lines which is always a bit dubious but can be made to work. Does it work properly if you apply a resistive load instead of the inverter? Fence wire in a bucket of water is good for this.When you take a thin twisted pair from the current shunt you should fuse down both sides, and the same for your voltage sense lines. If the mess of wiring by the meter came astray and shorted the thin wires (which are connected to a shunt in the negative) to those big bolted terminals on battery positive the whole length will flash white-hot and dissapear in a cloud of nasty fumes if you're lucky, but if it's long enough it'll sit there glowing red, dripping flaming PCB onto your woodwork and you'll have a very bad day. And while we're on the subject of fire hazzards get rid of that sheet of plastic running up the back of the wood.

author: max_torque
author_rank: Super Contributor
timestamp: December 11, 2014, 12:33:24 pm
content: Unfortunately my crystal ball broke last week and is currently sent away for repairs........So in the meantime, rather than just guess, how about actually measuring some stuff? Like for example, across the shunt when the system is running? Ideally with an scope, so you can see what's going on, but otherwise, even a normal multimeter you should be able to at least get an idea what is going on (measure at shunt, and at meter etc)I assume your system is less than 60Vdc btw, if it isn't. get some insulation on all those bare terminals..........

author: Red Squirrel
author_rank: Super Contributor
timestamp: December 11, 2014, 02:53:20 pm
content: Yes it's fused, it's split between two battery banks for redundancy (allows me to take one offline to do maintenance). They are also fused separately, so if there is a thermal runaway condition or hard short it will blow one fuse but one bank will continue to operate. If I switch both off I risk dropping all the equipment if the power happens to go out so that's what the warning is there for, as a reminder to myself. The DC power part works 100% fine, there is zero reason to get an electrician to do 12v wiring. Or even 48v for that matter, which is what I will upgrade this to eventually, and I might take that opportunity to redo the wiring as all my systems will have to be taken offline for that switchover anyway. This wiring is practically as stiff as rebar, it aint going anywhere.I don't have a scope but when I put a volt meter on it I just get 0v. I'm guessing the voltage difference between two contacts on a shunt is rather low so a standard volt meter wont be able to see anything.Those voltage transducers mentioned by mij59 look interesting, how do those work? Do they output a decently higher voltage (like 0-5 or something) based on current draw?

author: Seekonk
author_rank: Super Contributor
timestamp: December 11, 2014, 02:56:49 pm
content: I use several of those meters in my solar system except it is the 20A with internal shunt and they seem to work quire nice. It is possible that you are getting induced interference. You should use twisted pairs up to the meter. I have mine connected near inverters and PWM water hearer so my environment is not quiet at all.

author: jahonen
author_rank: Super Contributor
timestamp: December 11, 2014, 03:02:59 pm
content: I'd like to point out that besides the wiring, it is also a possibility that the current drawn through the shunt is not pure DC but is in worst case, pulsed. That is a possibility as you have an inverter as a load. In that case, no matter how clean the wiring is, the reading won't be stable, but of course, the battery won't care.Can you test this by replacing the inverter with some kind of resistive load and see if the reading is stable?Regards,Janne

author: Red Squirrel
author_rank: Super Contributor
timestamp: December 11, 2014, 03:08:45 pm
content: I'll see if I can figure something out without bringing the system off line. I might be able to simply add a couple light bulbs or something as the inverter does not draw when hydro is on so I should be able to leave it as part of the circuit.Part of the issue might be that the meter is sampling often and not doing any averaging, is there anything I can do to smooth out the reading? I experimented with capacitors but was probably not doing it right.

author: Richard Crowley
author_rank: Super Contributor
timestamp: December 11, 2014, 03:24:04 pm
content: What exactly is the nature of the load? It seems likely that some sort of intermittent/pulsing load would be incompatible with the sample-rate of the meter.It also seems quite possible that the meter itself is bad. Those things are so cheap, it wouldn't be unreasonable to buy 2 or 3 of them.A 100A shunt has extraordinarily low "impedance" so picking up noise or interference in the sampling wiring seems almost impossible unless there is actually a fault in the sampling wiring itself. As others have mentioned, twisting the pair would be appropriate.

author: jahonen
author_rank: Super Contributor
timestamp: December 11, 2014, 03:27:52 pm
content: You could add series resistors to the meter end and then a parallel cap across the meter current shunt input. Don't know how low the meter input impedance is but you could try 100 ohm-10k series resistors on both shunt wires and then something like 1 µF polyester capacitor across the meter. That should reduce the differential noise considerably, both wiring induced and current AC components. Resistors are important ingredient, otherwise that won't work due to low impedance.Regards,Janne

author: Richard Crowley
author_rank: Super Contributor
timestamp: December 11, 2014, 03:35:05 pm
content: With something as extraordinarily low impedance as a 100A shunt, you would need capacitance the size of your car to "smooth" that. Of course, you could throw a resistor in series with the sample signal to artifically raise the impedance, and then you could create an R/C filter. But if you are going to re-design the circuit, you really need a better knowledge of what you are dealing with. i.e. you need to look at the signal with a scope.A Hall-effect sensor would be subject to the same problems if the measured current is not smooth. Unlike the old-school shunt, they are active devices that require power and calibration and introduce an additional level of complexity that seems unwarranted in your application.

author: Seekonk
author_rank: Super Contributor
timestamp: December 11, 2014, 04:04:09 pm
content: Your wiring just looks bad. Even with a low impedence, running a single wire parallel to a high current wire will induce a voltage. Twisting the two current sense wires will prevent that. I would imagine that meters input is well below 20 ohms since it draws power from that connection. An inductor capacitor combination may be a better choice because of the low resistance. Trying a couple resistors will quickly point out an issue. One lead may be different than the other as it draws operating power from the shunt. REALLY, try a twisted pair first. You inverter may be old and its input capacitors may not be up to the job by now. An external set may be needed.

author: Red Squirrel
author_rank: Super Contributor
timestamp: December 11, 2014, 04:12:56 pm
content: I'll give twisted pair a try then. Failing that the resistor/capacitor. (diode too maybe?) How would I wire those in?This is what my circuit looks like now:I omited other wires going to the meter such as voltage reading/supply. The meter's instruction specifically states to put the shunt on negative side. Inverter is not that old, this is it here:http://www.tripplite.com/sku/APS750.It is not pure sine wave though so that might affect the draw on the DC side.

author: richard.cs
author_rank: Super Contributor
timestamp: December 11, 2014, 05:31:21 pm
content: My point on fusing is that the green wires (in your diagram) want fuses, or series resistance, where they leave the shunt because their other end may be shorted to battery positive in a number of places.With a modified sine inveter the input current may well (actually very likely) be square wave rounded off just a little by the capacitors in the inverter. Any digital meter will misread on that but it's probably solveable with filtering. You need to look at the current waveform on a scope. Any information you can deduce about the sampling rate of the meter would be useful too.

author: Red Squirrel
author_rank: Super Contributor
timestamp: December 11, 2014, 05:55:49 pm
content: Actually yeah I've thought of adding a small fuse on the small comm wire too, just need to find a way of doing it. Some kind of inline holder I guess. I don't have a scope or anything fancy to test with though. I'd like to buy a scope eventually as I've been wanting to get more into electronics.

author: mtdoc
author_rank: Super Contributor
timestamp: December 11, 2014, 06:11:07 pm
content: You can fuse right at the battery terminal with one ofTHESE. They're rated to 58V I believe. With the fuse that close to the terminal it would prevent any possibility of an unfused short (except directly across the battery terminals!).

author: LabSpokane
author_rank: Super Contributor
timestamp: December 11, 2014, 06:15:48 pm
content: I have to ask if this is in a residential structure. If so, please reconsider disconnecting this instead of "fixing" it. At this point you have a battery system that is almost purposely designed to start a fire.

author: Red Squirrel
author_rank: Super Contributor
timestamp: December 11, 2014, 06:36:02 pm
content: Quote from: mtdoc on December 11, 2014, 06:11:07 pmInteresting, I never found those when I was searching for fuses. I wanted to fuse closer to the battery but could not find anything that would make it easy to do so.As for fire... LOL. You should see the kind of stuff that goes into a telecom CO... much thicker wires carrying much more current, lots of exposed wiring and bus bars etc. It's just common sense to not start probing in there with large metal objects. Such low voltage is also not going to arc or do weird things like thousands of volts would. TBH I'm not even sure if the main battery plant is fused in telecom, they have fuses and breakers for individual loads but from batteries to bus bars there are no fuses. You drop something metal between the terminals and you can kiss your ass good bye. That's why you don't do that.

author: richard.cs
author_rank: Super Contributor
timestamp: December 11, 2014, 07:15:46 pm
content: Telco installs have a rather different standard of mechanical construction, you're unlikely to find bolted joints suspended in mid air by plastic clips and cable ties, or wooden frames with polythene sheeting over them. Nor are telco installs covered by your typical home insurance policy. You have several potential problems with your setup, one of which is the unfused thin cable as I poined out previously, another is the plastic fixings, you only need a high resistance joint somewhere get the few inches of cable back from it hot and the clips will fail, potentially dropping your -ve shunt onto one of your many exposed +ve terminals.If your install matched the schematic it would be a little safer than currently. Contrary to what you've drawn there are great long cables going down to the switches and back up before they get to a fuse. Putting the fuses just where they leave the battery box, or even inside it would improve things a lot. The cables might be stiff but don't rely on them for mechanical support. Your shunt should be bolted down in the same way as your fuse holders, similarly with the other joins, I like to use Henley blocks for this kind of thing (giant insulated screw terminals).Have you accounted for the 500A or so that will flow when you switch a fully charged battery in parallel with a fairly discharged one that's on load? That kind of thing can catch people out.

author: Richard Crowley
author_rank: Super Contributor
timestamp: December 11, 2014, 07:23:02 pm
content: After watching my next-door neighbor's garage go up in flames last week, I have a much more focused sense of wiring safety.The use of wood structure in general, and particularly the use of what appears to be scrap cardboard would be condemned by any safety inspection.

author: Red Squirrel
author_rank: Super Contributor
timestamp: December 11, 2014, 07:37:05 pm
content: Typically if I introduce new batteries into the system I ensure their charge rate is fairly equal to avoid sudden current shifts. I also try to avoid connecting at the terminals, that's why I added switches so I can connect stuff first then turn the switches on. Spark near battery = bad.On slightly different note, whatever I end up doing I will need to calibrate it and make sure it's actually the right current. Will a meter like this work for DC amps using the clamp?http://www.amazon.ca/Sinometer-UT204-True-RMS-Auto-ranging-Clamp/dp/B005G4VKFY/ref=sr_1_1?ie=UTF8&qid=1418324929&sr=8-1&keywords=dc+clamp+meterIt's not clear whether or not the clamp part actually measures DC current. Is it the case? I know you can measure DC with the leads by inserting as part of the circuit but not what I want, and already have meters that can do that up to 10 amps.I might even just forget about fixing this for now and buy that meter so I can check manually when needed. Eventually I want to fully redo this as a -48v rectifier -> batteries -> inverter setup and I can revisit current measurement at that point and redo wiring. This was done quickly with scrap wire and I was limited by sizes and did not want to cut too short so ended up leaving lot of slack in places that I should not have which made it hard to bend where I needed to. I don't have tools to work with metal or even know where I'd start as far as what metal based materials to get so wood is the only option for structure. This is not any different than the fact that 120v wiring is stapled on wood or passes through holes in studs. When using proper wire size the wire should not even be warm let alone hot enough to melt plastic or catch wood on fire.

author: IanB
author_rank: Super Contributor
timestamp: December 11, 2014, 07:42:23 pm
content: Quote from: Red Squirrel on December 11, 2014, 02:53:20 pmThis statement seems to be a major WTF.The most significant danger from electrical faults is fire, and fire is a risk in all high energy circuits no matter what the voltage.You hire an electrician to mitigate risk and achieve a safe installation, so your house doesn't burn down.Brushing off that concern is foolish.

author: Red Squirrel
author_rank: Super Contributor
timestamp: December 11, 2014, 08:02:03 pm
content: Quote from: IanB on December 11, 2014, 07:42:23 pmDo you get an electrician to change your smoke detector battery? A 9 volt battery can cause a fire in the right conditions.

author: LabSpokane
author_rank: Super Contributor
timestamp: December 11, 2014, 09:04:40 pm
content: Mr Squirrel,The responsible thing for you to do at this point is to disconnect and STOP. IF you want to incinerate yourself like a Vietnamese monk, I guess that's one thing. But crap like this will likely endanger others.I'd respectfully request others to stop "helping" Mr. Squirrel. You're only validating him at this point.And for your information, Mr Squirrel, I've spent plenty of time in wiring closets and network centers and we shitcanned installations such as yours, on sight, with extreme prejudice.<\ToughLove>

author: Red Squirrel
author_rank: Super Contributor
timestamp: December 11, 2014, 09:30:19 pm
content: What part of it is dangerous exactly? Making blanket statements just because the cable management may not be the best does not help at all. This setup has been in operation for over a year and has been fine. I just decided that I wanted to see if I can get help fixing the meter, but guess I will have to seek help elsewhere or figure something out myself.

author: AG6QR
author_rank: Frequent Contributor
timestamp: December 11, 2014, 09:31:24 pm
content: Quote from: Red Squirrel on December 11, 2014, 08:02:03 pmA transistor radio battery has a lot less energy than a large high current battery bank, so its range of "right conditions" is very much narrower.You have created a substantial portion of the right conditions for a fire, and we can see those conditions in the picture. If that narrow gauge Telco wire completes a circuit from positive to negative, it will heat up very quickly and very hot. Your fuses are apparently sized for the heavy cable, not the narrow gauge wire. Those fuses will pass more than enough current to heat the narrow wire enough to melt or burn its insulation. The narrow wires are wrapped around the heavy cables and pass very close to uninsulated portions.The fact that you think this job is comparable to changing a smoke detector battery speaks for itself.

author: Red Squirrel
author_rank: Super Contributor
timestamp: December 11, 2014, 09:44:30 pm
content: Quote from: AG6QR on December 11, 2014, 09:31:24 pmIf I can find a small value fuse/holder and add it to that wire, it will solve that problem... not really a big deal. I already acknowledged that I probably should have added one. The diagram I posted also is accurate.

author: LabSpokane
author_rank: Super Contributor
timestamp: December 11, 2014, 09:56:33 pm
content: Mr SquirrelWhat you have shown is so far from what would meet any type of code it isn't even worth discussing the details. The fact that you neither see, nor comprehend the failure modes or hazard they pose speaks volumes. I also come away with the distinct impression that you have "liberated" your electrical components from your local telco. Or is it your employer?

author: Red Squirrel
author_rank: Super Contributor
timestamp: December 11, 2014, 10:06:43 pm
content: Most of the stuff I got from ebay such as the fuses and meter. The wiring I got for free with permission. Was end of spool, too short for actual use in a work setting. They had a bunch of 000000 gauge too, but complete overkill.

author: jlmoon
author_rank: Unknown
timestamp: December 11, 2014, 10:11:16 pm
content: Quote from: LabSpokane on December 11, 2014, 06:15:48 pmI hope his insurance company isn't seeing these photos. If they are, they are sure to cancel a policy!

author: richard.cs
author_rank: Super Contributor
timestamp: December 11, 2014, 11:13:49 pm
content: The clamp meter looks like is should work, but a detailed read of the manual would be good. You likely have a very pulse-ey waveform and unless it's entirely square the mean and RMS values will not be equal. To determine battery life you need the mean current not the RMS, this is probably what it will show in "DC" mode but it may have several options. It is also possible it will be confused by the waveform if it's got lots of content at higher frequencies than it can handle, but it'll undoubtably be better than your ebay meter.Coming back to the safety side, it needs work but not an insurmountable amount. Re-doing the thin stuff, moving the big fuses to earlier in the circuit*, buying a reel of large heatshrink and using it liberally, sorting out the routing and clamping will make a lot of difference without throwing too much of the difficult/expensive bits away or taking more than a few hours work. It's clear that you didn't expect the kind of reaction your photos got, we can't force you to change it but when someone posts something that's clearly dangerous and doesn't appear able to see that it is then that's the natural reaction. It's the kind of setup I might lash-up for charging some batteries or getting the lights back on in a powercut, but it's far from anything I'd leave unattended in the basement while I slept.*I see you've deleted the photos now, I assure you they do not match up with the schematic, the positive cables go down from the box to the switches, then up to the fuses, then join to go to the inverter.

author: Seekonk
author_rank: Super Contributor
timestamp: December 12, 2014, 03:49:59 pm
content: Invariably a poster asks for help and supplies incomplete or inaccurate information. Often details are not included because in their infinite wisdom seems unimportant to them. This failure to pay attention to detail is often the reason their stuff doesn't work in the first place. We ask for a schematic of how the meter is hooked up and your schematic is crap, leaving out all detail of how it is hooked up. I know for sure it is not hooked up the way the manufacturer told you to do it. I've been on BB's a long time. Posts probably number more than ten thousand. In that time I have probably helped less that a dozen people. It could be that I don't know anything or my piss poor attitude. OR it just might be that even given the right answer, the OP never listens or has the ability to comprehend what is being said. I've seen worse wiring. I still believe it is not hooked up as is should be.

author: Red Squirrel
author_rank: Super Contributor
timestamp: December 18, 2014, 04:06:18 am
content: Well since I've been wanting to get into electronics I ended up buying a scope. It's definitely ugly output off the shunt:Guessing the inverter or some outside factor is causing that. Though, The last one (testing the voltage between + and - on the bank) is kinda odd, for a big battery plant is it normal to see that on the voltage side? I would expect a smooth line that very slowly goes down as batteries discharge. The voltage test was done in discharge mode, so were most of the others, but TBH I kinda lost track, I should have wrote down the tests in order as I took them. The data looked fairly similar either way though. If anyone wants to see a specific reading I can always go back and take it. To test I had the probe on the far end of the shunt and the ground on the battery side (shunt is on negative side as per meter's instructions, so I could do that without causing a short through the scope).Also, I'm wondering if this shunt meter is not unidirectional, could it be an issue or would it just go to 0 when power is going "backwards". Since it's an inverter charger the source changes direction. On AC fail the inverter-charger is the load, when AC power is on, the inverter-charger is the supply and the batteries are the load till fully charged.It seems to me this meter is just garbage though, instead of doing some kind of averaging it just does nn readings per second and displays the literal value of that particular reading so that's why the numbers are all over the place.I was looking at current transducers on Digikey and found a few interesting ones, this one has the most useful data sheet where I get to know the output voltage range:http://www.digikey.ca/product-detail/en/L01Z200S05/MT7176-ND/529408These seem nice, as I don't need a shunt and it is non invasive. Removes a potential point of failure in the system as well.Though I'm a little concerned about the actual working range. According to the graph I basically have .5v of play between 0 and 200a, and my expected load is well under 50a and currently it's a 100a system. Connecting that to the arduino not sure what the accuracy is going to be like. I want to be able to read up to 200a though, I may potentially upgrade the system in the future, and it's a good idea to be able to read past the fuse rating so I can set a proper alarm point for a unlikely situation that the fuse does not blow when it should.There's a lot of others too but the data sheet is not clear on range, not sure how to interpret them. Open to ideas with better explanation. More can be found here:http://www.digikey.ca/product-search/en?FV=fff4001e%2Cfff801ed%2C564006f%2C5640070%2C56400c0%2C56400c3%2C10d0001a%2C10d0001b%2C12040010%2C12040013%2C1204005b%2C12040091%2C12040096%2C120400b3&k=current+transducer&mnonly=0&newproducts=0&ColumnSort=1000011&page=1&stock=1&pbfree=0&rohs=0&quantity=&ptm=0&fid=0&pageSize=250They also have stand alone ones that are invasive but much cheaper, just not sure how you'd go about introducing that physically to #2 wiring and I don't even see how those two prongs are rated for 200A. I'm thinking these may be meant to be used with a shunt and not actually directly. Not closed to the idea of a shunt though, I think my issue is that the meter is crappy. I can either passively smooth the output or read it with an arduino or similar device and smooth it out with averaging.I also read about op amps, could I use one in a case like this with the existing shunt? Perhaps with a potentiometer so I can tweak the range with a known load then introduce it to an arduino.As for the safety issues, perhaps a few clarifications I need to make:- Those plastic clips are designed for PEX pipe, it was the most appropriate thing I could find. In a proper battery bank bus bars would be used to interconnect supply/load/devices but not sure where to find those and don't have equipment to make them. PEX pipe can handle much more heat than they will ever see there. (think: hot water line)- The system is rated for 100A but the actual load is about 30 so everything is actually quite oversized. I want to upgrade to -48v eventually which will quadruple my capacity without increasing amperage.- RE. Fuses being closer to the battery: You do not want anything that could potentially create sparks inside the battery cabinet. I wanted to ensure that each run from the batteries are a single cable with absolutely no junctions. The purpose of the switches is to turn cut one bank out so they can be disconnected for semi annually maintenance. Checking connections for any corrosion, checking electrolyte etc... Though I imagine I could figure out a better way of routing the cabling so that the fuses are near the exit of the hole. I think I may get rid of that 2x6 and put plywood, it will give me a nice flat surface to mount wires and things on. I could even put drywall over the plywood for fire rating, but really not needed but guess it would not hurt. If I keep the shunt method, I need to keep the shunt from touching anything though, or it could alter the reading. That's why it's in mid air like that, but I guess there could be a better way of doing it.- For those who really think this gets hot enough to cause a fire, while I don't have a thermal imaging camera to prove it I can use a rather non scientific method to prove that it's not: Coconut oil. It melts at about 25C. I can almost guarantee if I put a chunk on those cables it will not melt while the system is under load. (when AC power fails, I can throw the breaker for test for a couple hours)I do eventually want to redo the wiring though, just so that it looks nicer. Telco flex is just really tough to work with and I should have taken more time and effort to make nicer routing. In a telco application the turn radius needed tends to be much larger than a small system like mine where everything is closer together. It typically travels on cable ladders and held in place with string or tie wraps. In my case I don't really have anything to tie wrap to so went with the pex clips as the cable fits nicely in there.