March 24, 20197 yr Hi All, How would one work out cabling requirements? like what pv cable to use, what solar controller to batteries and on batteries and batteries to inverter? setup: 2 x ~350W panels (series or parellel i can't seem to find definitive answers) 1 x 30/100 victron mppt 2 x 100AH lead acid 2 x 105Ah lead acid (batteries are in a 24V config) 2000VA inverter
March 24, 20197 yr 11 minutes ago, Dex_ said: 2 x ~350W panels (series or parellel i can't seem to find definitive answers) Depends where you live. Below -4°C these 350W modules make more than 50V each and will exceed 100V in series, the max input on the MPPT. If it gets that cold where you live, put them in parallel. Series would be preferred though. 11 minutes ago, Dex_ said: 1 x 30/100 victron mppt 30A at +- 25V (to make the math easy) is 750W, and you have 700W worth of PV modules. Looks good. 11 minutes ago, Dex_ said: 2 x 100AH lead acid 2 x 105Ah lead acid (batteries are in a 24V config) Do you intend paralleling dissimilar batteries? If you do, remember that you will shorten the life of all the batteries, and to always make sure the entire bank gets a good charge (ie... you will overcharge some batteries slightly). It is not advisable in the long term. 2000VA, let's say 2400VA to make the math easy. Then you have to size the cables for 100A. I'd advise no smaller than 35mm^2 for that (between inverter and batteries). Remember a good fuse as well. Between solar charger and battery, no less than 10mm^2, and fuses/breakers. For PV, you can use 4mm^2 PV cable (it's UV resistant). You also get 6mm^2 but 4 is good enough and costs less. Edited March 24, 20197 yr by plonkster
March 24, 20197 yr Author 1 minute ago, plonkster said: Depends where you live. Below -4°C these 350W modules make more than 50V each and will exceed 100V in series, the max input on the MPPT. If it gets that cold where you live, put them in parallel. Series would be preferred though. 30A at +- 25V (to make the math easy) is 750W, and you have 700W worth of PV modules. Looks good. Do you intend paralleling dissimilar batteries? If you do, remember that you will shorten the life of all the batteries, and to always make sure the entire bank gets a good charge (ie... you will overcharge some batteries slightly). It is not advisable in the long term. 2000VA, let's say 2400VA to make the math easy. Then you have to size the cables for 100A. I'd advise no smaller than 35mm^2 for that (between inverter and batteries). Remember a good fuse as well. Between solar charger and battery, no less than 10mm^2, and fuses/breakers. For PV, you can use 4mm^2 PV cable (it's UV resistant). You also get 6mm^2 but 4 is good enough and costs less. sadly the batteries are existing so i intend to series the similar and parallel the 2 banks - in future when i replace i will probably go gel and of course the same. i have a good fuse on the batteries to inverter - 125A. What do you suggest between the solar charge controller and batteries?
March 24, 20197 yr 1 minute ago, Dex_ said: i have a good fuse on the batteries to inverter - 125A. That's good. 1 minute ago, Dex_ said: What do you suggest between the solar charge controller and batteries? Fuse is there to protect the cable. In other words, this is in case something goes wrong inside the charger controller and hundreds of amps from the battery decides to take this route 🙂 A fuse larger than 30A and less than the current capabilities of the wire is what you need. 40A would be a good one.
March 24, 20197 yr Author plonkster do you think on that controller i could add an additional paenl or two later if parallel?
March 24, 20197 yr Just now, Dex_ said: plonkster do you think on that controller i could add an additional paenl or two later if parallel? Nope. It's close to maxed-out already. Get a 100/50 if you want some room for later.
March 24, 20197 yr Author 2 minutes ago, plonkster said: That's good. Fuse is there to protect the cable. In other words, this is in case something goes wrong inside the charger controller and hundreds of amps from the battery decides to take this route 🙂 A fuse larger than 30A and less than the current capabilities of the wire is what you need. 40A would be a good one. cool i was advised 80Amp, so i should go lower? and cabling?
March 24, 20197 yr Just now, Dex_ said: advised 80Amp I believe 80A is a tad high for 10mm^2 cable. On 16mm^2 maybe. As long as it is smaller or equal to the capability of the cable. Just google for an ampacity table. Usually takes a while to find one in metric 🙂
March 24, 20197 yr Author 37 minutes ago, plonkster said: Nope. It's close to maxed-out already. Get a 100/50 if you want some room for later. HMM i still have a lot to understand, i thought in parallel i would be under the amp rating.
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