Derek Uzzell Posted May 1, 2020 Share Posted May 1, 2020 Dream in possibility. Live in simplicity. Link to comment Share on other sites More sharing options...
mikefitz Posted May 1, 2020 Share Posted May 1, 2020 Reducing the number of connections on a battery terminal will make the installation safer and reduce mechanical strain on the battery post. In similar situations I use a fuse distribution block that combines midi and mega fuses and bus bar in one unit. https://www.12voltplanet.co.uk/mega-midi-fuse-power-distribution-box.html For safety all positive connections to the battery require in line fuses as close as practical to the battery, rated to protect the cable. Using ring terminations on the cables and link fuses provides secure connections with minimal volt drop. One or two distribution blocks could be used depending on the wiring method chosen. The OP suggested using 40mm2 and larger cable. This seems an unnecessarily large cable CSA for a single battery leisure system. I would suggest 16mm2 as being practical for the high current paths, rated at just over 100 amps. The picture of the battery suggests the existing cables are 6mm2 or less. Ideally the solar controller should be near the batteries, a long run from panels to controller is preferred to a long run between battery and controller With a 100 watt solar panel, ( shown on the diagram) the maximum current is unlikely to exceed 8 amps even with a MPPT controller. Although volt drops will compromise charging slightly, with relatively low currents and a single battery it should not be a disaster. Assuming a 6 meter run between battery and controller, using 6mm2 cable, the drop at a typical 5 amp output will be 0.17 volts. On a practical note I doubt any 20 amp solar controller will accept large cable CSA, 6mm2 seems typical. There are a number of unknowns regarding power is the system, the power rating of the inverter, camper loads, actual solar panel power but it would seem that with a single battery these are not going to be excessive. Mike Link to comment Share on other sites More sharing options...
electric_nan Posted May 1, 2020 Author Share Posted May 1, 2020 mikefitz - 2020-05-01 2:39 PM Reducing the number of connections on a battery terminal will make the installation safer and reduce mechanical strain on the battery post. In similar situations I use a fuse distribution block that combines midi and mega fuses and bus bar in one unit. https://www.12voltplanet.co.uk/mega-midi-fuse-power-distribution-box.html For safety all positive connections to the battery require in line fuses as close as practical to the battery, rated to protect the cable. Using ring terminations on the cables and link fuses provides secure connections with minimal volt drop. One or two distribution blocks could be used depending on the wiring method chosen. The OP suggested using 40mm2 and larger cable. This seems an unnecessarily large cable CSA for a single battery leisure system. I would suggest 16mm2 as being practical for the high current paths, rated at just over 100 amps. The picture of the battery suggests the existing cables are 6mm2 or less. Ideally the solar controller should be near the batteries, a long run from panels to controller is preferred to a long run between battery and controller With a 100 watt solar panel, ( shown on the diagram) the maximum current is unlikely to exceed 8 amps even with a MPPT controller. Although volt drops will compromise charging slightly, with relatively low currents and a single battery it should not be a disaster. Assuming a 6 meter run between battery and controller, using 6mm2 cable, the drop at a typical 5 amp output will be 0.17 volts. On a practical note I doubt any 20 amp solar controller will accept large cable CSA, 6mm2 seems typical. There are a number of unknowns regarding power is the system, the power rating of the inverter, camper loads, actual solar panel power but it would seem that with a single battery these are not going to be excessive. Mike Hi Mike The solar panel I'm considering is 160W, not 100W, with a 6mm2 wire between them and the controller, this I'm guessing is roughly a 6 meter run. The distance between the controller and the battery is roughly 2.5 meters but will be hooked up to a fuse box, along with the other consumers listed, this has a max rating of 100A. The wire size is being determined by 100A over 2.5 meters and keeping the voltage drop below 2% as this includes the solar charge controller in the load, if it wasn't I would probably accept a greater voltage drop. According to https://www.12voltplanet.co.uk/cable-sizing-selection.html this would give me a 35mm2 cable, possible even less as my negative connection is a shorter run to the internal chassis and this is calculated assuming the negative length is identitcal. This connection will have a 125A midi fuse near the battery. Link to comment Share on other sites More sharing options...
mikefitz Posted May 2, 2020 Share Posted May 2, 2020 With a 160 watt panel and a MPPT controller the theoretical maximum current is about 13 amps. In practice around 10 amps will be the highest you will see. If you have a PWM controller the maximum current will be less, the rated current of the panel, around 8 amps. I think you are incorrectly using the voltage drop calculator. The wire size is determined by the maximum current you expect to flow through it and the maximum volt drop you can accept. You protect against overloading the cable with a suitable fuse. Your fuse box may be rated at 100 amps but in your camper its unlikely currents flowing will be anywhere near this. You state 'the wire size is determined by 100A over 2.5 meters', no that is incorrect. The volt drop is due to the actual current and is nothing to do with the fuse box rating. Examples, with a 2.5 meter run of 6mm2 cable between the controller and battery and 10 amps from the controller, the voltage drop using the calculator is 0.14v or 1.17%. If you connect as your first diagram the fuse for the controller cable at the battery needs to be 20 amps, the 6mm2 cable has a rating of 50 amps. Connecting as in the second diagram, use the same ratings with a 20 amp fuse in the fuse box. Without having a specification for the inverter I cannot suggest a cable size or fuse rating. The existing split charge cables and split charge control circuit are not specified but with a suitable control relay and a modest battery capacity ,16mm2 cable fused at 50 amps at each battery, will give good results. Mike Link to comment Share on other sites More sharing options...
Derek Uzzell Posted May 2, 2020 Share Posted May 2, 2020 Don't forget that there's a retro-fitted inverter in the mix - though I don't think its output has been stated... Link to comment Share on other sites More sharing options...
electric_nan Posted May 2, 2020 Author Share Posted May 2, 2020 mikefitz - 2020-05-02 10:29 AM With a 160 watt panel and a MPPT controller the theoretical maximum current is about 13 amps. In practice around 10 amps will be the highest you will see. If you have a PWM controller the maximum current will be less, the rated current of the panel, around 8 amps. I think you are incorrectly using the voltage drop calculator. The wire size is determined by the maximum current you expect to flow through it and the maximum volt drop you can accept. You protect against overloading the cable with a suitable fuse. Your fuse box may be rated at 100 amps but in your camper its unlikely currents flowing will be anywhere near this. You state 'the wire size is determined by 100A over 2.5 meters', no that is incorrect. The volt drop is due to the actual current and is nothing to do with the fuse box rating. Examples, with a 2.5 meter run of 6mm2 cable between the controller and battery and 10 amps from the controller, the voltage drop using the calculator is 0.14v or 1.17%. If you connect as your first diagram the fuse for the controller cable at the battery needs to be 20 amps, the 6mm2 cable has a rating of 50 amps. Connecting as in the second diagram, use the same ratings with a 20 amp fuse in the fuse box. Without having a specification for the inverter I cannot suggest a cable size or fuse rating. The existing split charge cables and split charge control circuit are not specified but with a suitable control relay and a modest battery capacity ,16mm2 cable fused at 50 amps at each battery, will give good results. Mike So the inverter is a french brand called TECH9 and can't find any info about it online. But, it's 300w and it has a 30amp fuse, which now looking at inverter - and not just the fuse - it doesn't sound large enough. At a rough calculation and while making assumptions on the inverter: 300w continuous power / 0.85 efficiency / 12v = 29.41 amps 29.41 x 1.25 = 36.76 = 40 amp fuse Dash socket has a 10amp fuse and the kitchen unit, which contains a 12v socket, voltage reader and 2 usb sockets at 5v 1amp and 5v 2.1amp, has a 20amp fuse. So realistically we're looking at around 70 amps or less with everything being used at the same time. Should I not then calculate the size of wire from this number, this giving me 25mm? Link to comment Share on other sites More sharing options...
Derek Uzzell Posted May 2, 2020 Share Posted May 2, 2020 “TECH9” ia a generic brand-name covering a multitude of inexpensive automotive-related items (sponges, shampoo, oil, car mats - you name it). A lot (all?) of these products are sold through the French “Leclerc” supermarket network and I note that a 300W Tech9-branded inverter (convertisseur de tension) is shown here. https://www.zounko.com/promo/detail/5ea66621852447440e6976b1 Link to comment Share on other sites More sharing options...
electric_nan Posted May 2, 2020 Author Share Posted May 2, 2020 That’s the one. To be honest, now knowing that it doesn't allow for me to use the standard 230v plugs placed around the motorhome and that I'm only intending to use 12v DC, I'm tempted to just get rid of it all together. Nothing will be running off of it and it's low power so it seems rather pointless. Link to comment Share on other sites More sharing options...
mikefitz Posted May 3, 2020 Share Posted May 3, 2020 In your motorhome not everything would be using/generating power at the same time. In reality the inverter would be used only for a short time. I see you are calculating for the absolute worst case, most of the time the solar controller will be the only device operating. I will offer my idea on a circuit to meet your requirements. I have used 16mm cable for the inverter to allow for a more powerful unit if required. The midi fuses need a 5.3 dia ring crimp connector and the mega fuse needs 8mm dia copper tube ring terminals. I have selected 16mm2 cable from the battery to the fuse block. If you have reservations about this increase to 25mm2. I cannot see the current exceeding 100 amps under normal conditions. Mike Link to comment Share on other sites More sharing options...
electric_nan Posted May 3, 2020 Author Share Posted May 3, 2020 Thanks for your suggestion Mike. Just so I understand this setup clearly, why would this setup beneficial over my original proposal using the one fuse box arrangement? Are there downsides to this that this overcomes, maybe by the solar, inverter and aux not sharing the same cable run helps when at normal operating times i.e. not all on at the same time, allowing for smaller sized cables, or is that this allows me to have one connection the battery? Also, would this need a large fuse between the midi fuse box and the battery? Thanks Link to comment Share on other sites More sharing options...
electric_nan Posted June 13, 2020 Author Share Posted June 13, 2020 Finally got round to finishing up the electronics today and happy with how it turned out in the end. Decided to go with a 3-way terminal and leave the original connections, as I wasn't 100% sure of what was going on there. One thing I hadn't noticed originally was that the split charge has a direct connection to the battery (don't know how I missed it tbh, the manual says it should share a fuse with the factory installed electronics), so left it and added a direct connection from the new fuse box/loads. Here's some pics: https://drive.google.com/file/d/12oGzF2ACb5uJB9mu-jZzmXSz9QI712D8/view?usp=sharing https://drive.google.com/file/d/1MxUM7Sr0iWPuMQehq_DaIsF7KQVXdR8x/view?usp=sharing Link to comment Share on other sites More sharing options...
mikefitz Posted June 13, 2020 Share Posted June 13, 2020 May I make the following suggestions for modifications to your system. For safety all connections to the battery positive post need fuses to protect the cables. . The blue cable to the split charge relay needs a fuse near the battery. It looks like 6mm2 so fuse at 30 amps, the charge rate is unlikely to exceed this. The fuse to the control panel at 50 amps seems to high a value, the brown cables after the fuse seem smaller than 6mm2, I would reduce this fuse to 30 amps. The 16mm2 cable is a bit overkill for a maximum current flow in the cable of 30 amps out and 13 amps in. I advise reducing the 70 amp fuse to 30 amps. However if this cable and fuse are in place for the addition of a inverter, then no problem as it stands. It would be useful to add some insulating material where the cables pass over the metalwork near the battery and to secure the cables and fuse holders against movement. Mike Link to comment Share on other sites More sharing options...
electric_nan Posted July 3, 2020 Author Share Posted July 3, 2020 Hi Mike I've already installed the wires so will leave them as be but I am going to reduce the 70 amp fuse while I'm not using the spare circuit, no harm in having oversized cables and I was mainly concerned about voltage drop between the charge controller and the battery, so minimising that was most important to me. The lack of fuse between the split charge relay and leisure battery does concern me, I was thinking this had been modified by an owner over the years as the manual seems to suggest that it once shared the 50 amp fuse with the control unit - bit confused by this admittedly. I believe it is fused going to the starter battery, should the fuse size be equal to this? Thanks Link to comment Share on other sites More sharing options...
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