Guest Posted October 25, 2016 Share Posted October 25, 2016 I think with 50mm2 cable on the batteries, their was no problem. Quote Link to comment Share on other sites More sharing options...
superdiy Posted October 25, 2016 Share Posted October 25, 2016 23 minutes ago, Marie1 said: I'm on my way to Somerset to fetch the BMV and VE direct cable. Also want to get the battery bank cables. The question: the cables(links) on batteries are 50mm, the 2 cables going to inverter are 35mm. I need 8x same lenght cables and 2 bushbars. Those 8 x1meter cables: should they be 55mm or 35mm? Yes, since the battery interconnect cables are 50mm2 already, get 50mm2 cables to connect the batteries to the buss-bars as well; you can always replace the cables between the buss-bars and inverter with 50mm2 cables at a later stage. Chris Hobson 1 Quote Link to comment Share on other sites More sharing options...
Chris Hobson Posted October 25, 2016 Share Posted October 25, 2016 36 minutes ago, Marie1 said: I'm on my way to Somerset to fetch the BMV and VE direct cable. Also want to get the battery bank cables. The question: the cables(links) on batteries are 50mm, the 2 cables going to inverter are 35mm. I need 8x same lenght cables and 2 bushbars. Those 8 x1meter cables: should they be 55mm or 35mm? Just to clarify you could have various lengths of cable so long as the length of cable connecting the entire string is the same length. For a individual string you could have two longer cables to connect to the busbars and three shorter cables connecting the batteries batteries in series (which you have already). So long as you replicate that for each string you are fine. Obviously the shorter each individual cable length the better but within reason. Do the 8 cables have to be 1m?. Addition : Thinking about it with 4 strings you going to battle with a cable much shorter than 1m. Ignore my comment. Quote Link to comment Share on other sites More sharing options...
___ Posted October 25, 2016 Share Posted October 25, 2016 48 minutes ago, Marie1 said: I'm on my way to Somerset I'm not far from that place where you are probably headed (either OnTrack of ExSolar, both at The Interchange)... I'm just not home at the moment :-) Quote Link to comment Share on other sites More sharing options...
DeepBass9 Posted October 25, 2016 Share Posted October 25, 2016 14 hours ago, TinkerBoy said: I agree with Chris. You will need around 18 x 300 panels on a 400ah bank. If you have 2 Axperts that will give you 8kw and you can put 9 panels per inverter. You sure? I have 1800W of panels on a 300Ah bank with no problem. Although I never draw down to anywhere near 46V PaulF007 1 Quote Link to comment Share on other sites More sharing options...
Chris Hobson Posted October 25, 2016 Share Posted October 25, 2016 7 minutes ago, DeepBass9 said: You sure? I have 1800W of panels on a 300Ah bank with no problem. Although I never draw down to anywhere near 46V I also never draw down much beyond 49V and so in effect our battery banks function like a smaller battery bank. From the limited info available Marie has large loads during the day with a draw of just below 2000W for several hours. 2700W of panels are just not going to cut it. viper_za 1 Quote Link to comment Share on other sites More sharing options...
Marie1 Posted October 25, 2016 Author Share Posted October 25, 2016 Hi guys, got the BMV702, jayyy! I need help now, monitor set on factory value 200 Ah, should I set it to 400ah, which is the total size of our bank? See b): Quote Link to comment Share on other sites More sharing options...
superdiy Posted October 25, 2016 Share Posted October 25, 2016 3 minutes ago, Marie1 said: should I set it to 400ah, which is the total size of our bank? Yes, are you also going to install the shunt, buss-bars and the new cables yourself? Quote Link to comment Share on other sites More sharing options...
Marie1 Posted October 25, 2016 Author Share Posted October 25, 2016 Didn't get the 8x50mm cables, they didn't stock it. I have an electrician friend that can help me on Saterday. Quote Link to comment Share on other sites More sharing options...
superdiy Posted October 25, 2016 Share Posted October 25, 2016 7 minutes ago, Marie1 said: Didn't get the 8x50mm cables, they didn't stock it. I have an electrician friend that can help me on Saterday. OK, he can use 50mm2 welding cable and just crimp on the appropriate lugs - you should be able to get the cable and lugs from a welding supplier or car parts shop, even Brights or Builders Warehouse might be able to help (at a price). Are you going to install the battery monitor's shunt yourself, because you'll have to cut the negative battery cable between the battery bank and inverter as close as possible to the battery bank and you'll have to also crimp on some lugs to connect to the battery monitor. Maybe you should ask the electrician to do that as well. And check the rotation of the shunt, if you connect it the wrong way around, some readings will be incorrect and some will be reversed. Quote Link to comment Share on other sites More sharing options...
Marie1 Posted October 25, 2016 Author Share Posted October 25, 2016 The batteries are currently like this, the guy at the place where I bought the BMV said I should move the cables.(see green crosses in next pic) in the meanwhile untill Saturday when the new cables get installed. Want to confirm if it is correct. Quote Link to comment Share on other sites More sharing options...
Marie1 Posted October 25, 2016 Author Share Posted October 25, 2016 Quote Link to comment Share on other sites More sharing options...
superdiy Posted October 25, 2016 Share Posted October 25, 2016 2 minutes ago, Marie1 said: The batteries are currently like this, the guy at the place where I bought the BMV said I should move the cables.(see green crosses in next pic) in the meanwhile untill Saturday when the new cables get installed. Want to confirm if it is correct. Yes, that is already a better option, but I won't worry about it for now if it is in any case going to be connected correctly on Saturday. A few more days won't make that much of a difference. Quote Link to comment Share on other sites More sharing options...
superdiy Posted October 25, 2016 Share Posted October 25, 2016 I'm not sure how good you are with tools, nuts and bolts, but when working with batteries and battery cables you should be very careful not to cause any accidental shorts with tools etc. and to double-check all your connections before you even attempt to make them. If you do something wrong, you can easily create havoc, cause a fire and even an explosion. So not trying to scare you, but if you are not 110% comfortable and not 110% certain about what you have to do, rather leave it for the electrician. Ask @The Terrible Triplett about smoke, he has a few tales to tell. Sorry TTT, just had to. PaulF007, Chris Hobson and ibiza 3 Quote Link to comment Share on other sites More sharing options...
PaulF007 Posted October 25, 2016 Share Posted October 25, 2016 3 minutes ago, superdiy said: So not trying to scare you, but if you are not 110% comfortable and not 110% certain about what you have to do, rather leave it for the electrician. I concur the thing with dc is where ac gives a byte and trips dc melts and burns BADLY . This has been shown many a times on this forum and gives you a good idea not to get windgat with dc... Quote Link to comment Share on other sites More sharing options...
Marie1 Posted October 25, 2016 Author Share Posted October 25, 2016 Ha ha, I will do a lot of things, but the batteries and cables, I will leave for Saturday! How close should the monitor shunt be? The inverter are inside the house an the shed with batteries outside, with other words back to back with a wall inbetween. With the shunt inside under the inverter, it will be about 1meter from bank. Will that be to far? Quote Link to comment Share on other sites More sharing options...
superdiy Posted October 25, 2016 Share Posted October 25, 2016 It does not matter where in the circuit you measure the current, but the voltage measurement needs to be taken as close as possible to the battery bank to ensure that it is as accurate as possible and since the voltage measurements are used to calculate many other values, all of them depend on the accuracy of the voltage measurements. If the shunt is installed closer to the battery bank, the voltage drop over the cable between the battery bank and shunt will be lower (especially under high load and charging conditions) and thus the voltage (and other values) measured by the BMV will be more accurate. Also keep in mind that the supplied +Vbattery and +Vmidpoint cables are quite short although they can be extended if required. Since the length of the supplied cable between the shunt and the display is 10m and the inverter and battery bank is back-to-back, I will install the shunt as close as possible to the battery bank or the neutral buss-bar (once installed) instead of on the other side of the wall at the inverter. Chris Hobson 1 Quote Link to comment Share on other sites More sharing options...
Guest Posted October 25, 2016 Share Posted October 25, 2016 Guys, just a question. If the current battery cables are 50mm2 already, why is Marie replacing them? I ask for before she goes and spends the money, anyone cared to work out the actual losses on the 50mm2 existing cables? Quote Link to comment Share on other sites More sharing options...
superdiy Posted October 25, 2016 Share Posted October 25, 2016 5 minutes ago, The Terrible Triplett said: Guys, just a question. If the current battery cables are 50mm2 already, why is Marie replacing them? I ask for before she goes and spends the money, anyone cared to work out the actual losses on the 50mm2 existing cables? She will install buss-bars and then needs to replace the cables between the positives and negatives of the different strings and the new buss-bars. Currently the parallel strings are not connected correctly. Quote Link to comment Share on other sites More sharing options...
Guest Posted October 25, 2016 Share Posted October 25, 2016 6 minutes ago, superdiy said: She will install buss-bars and then needs to replace the cables between the positives and negatives of the different strings and the new buss-bars. Currently the parallel strings are not connected correctly. Cool, THAT makes sense. Quote Link to comment Share on other sites More sharing options...
Guest Posted October 25, 2016 Share Posted October 25, 2016 2 hours ago, superdiy said: Ask @The Terrible Triplett about smoke, he has a few tales to tell. Sorry TTT, just had to. Let me tell you, @superdiy, I wear that badge with honour. It was earned! With tears at the costs ... Yet a LOT of laughs in sharing it ... FWIW: The only part of an entire solar setup that I have not yet let the smoke out of, are BMV's. Quote Link to comment Share on other sites More sharing options...
Marie1 Posted October 25, 2016 Author Share Posted October 25, 2016 Hi all, the monitor is now installed, now the midpoint cables... (I have someone helping me) When done, what do I have to change on the BMV settings exept the battery details (400ah), and I've read somewhere about setting the midpoint. I want to get everything ready for the night, so that I can take readings asap. I've fully charged the batteries from Eskom during the night,(according to Chris settings) changed the settings back at 9am, (when changing the settings back at 9am I've notice the batteries volts were 54, and not 56.4(so not totally full) Axpert showed system was on bypass till 1 this afternoon. Only start working then. I thought with the batteries full(or suppose to be full), system (available solar) will start at 9, when I changed the settings back. Anyways doesn't make sense to me, want to get the BMV and software running asap to sort out this problem. Got the cable to link BMV to software. Almost there! Quote Link to comment Share on other sites More sharing options...
Mark Posted October 25, 2016 Share Posted October 25, 2016 The only 3 things I would do is: Set Battery Ah - already done Zero the BMV with zero load on the batteries (ie Inverter/etc off) - Batteries must be full and settled. The mid point will need to be enabled as you have 3 choices (Temp/MPoint/?) - It calculates itself. Sound like you are almost there!! All the best. Mark Jaco De Jongh 1 Quote Link to comment Share on other sites More sharing options...
Marie1 Posted October 25, 2016 Author Share Posted October 25, 2016 Batteries must be full? Is that now when the inverter tells me they are full? And from here I just let the software run? Quote Link to comment Share on other sites More sharing options...
___ Posted October 25, 2016 Share Posted October 25, 2016 3 minutes ago, Marie1 said: Batteries must be full? Is that now when the inverter tells me they are full? The BMV has tail-current detection. Without getting into it, it means it will automatically detect when the batteries is full. It can only do this if there are no loads on the batteries (ie inverter must be in bypass and charging the batteries). When the charge current tapers off (as the battery stops accepting more charge) the BMV detects and auto-syncs. So you should be able to install it and just run a charge cycle over night... Right guys? Mark 1 Quote Link to comment Share on other sites More sharing options...
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