diy solar

diy solar

Battery cable

Skypower said:
You can NOT use undersized cable on the DC side. Do not use a residential wiring ampacity chart/Calculator for this. What the cables are rated at is irrelevant because of the DC voltage drop in this application is more important to the inverter’s performance than you can imagine. A one volt drop under load is a lot and could make the inverter shut down early and you could even see that with the right stuff. Remember your working range is normally only between 55 and 50 volts. Look at the plaque on the side of the inverter. It says 2/0 and that’s per inverter. If you run two inverters, than up to the distribution buss from the server buss/batteries, you’d be running 4/0 and so on. Yes you can run small cable but why buy the big inverter if you struggle with a 2000 watt load. Use quality breakers AND T class fast blow fuses and not something cheap that gets hot and drops voltage. Going cheap now just means you’ll be replacing it later. Use quality Ancor or Selterm lugs and get at least an impact crimper. Hydraulic crimpers are either expensive or and the cheap ones need the dies modded to crimp correctly.
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You guys are all pro and knowledgeable. Please help me with this: I have EG4 6500 EX. (eg4 3x 100 amp 48v. this is fine But) But the question part is: It expensive and I trying to save money so I bought 16s lifepo4 302 Ah CATL batteries. BMS: overkill solar 100 amp (I think i understand now that if I run 2x EG4 6500 inverter then this 100 amp BMS is under size) sorry... but the question is on the Wire length. I using 1/0 cable from battery to bus bar. 2/0 dc battery cable from busbar to each Inverter. What is the Length is correct? The positive Red from battery to busbar is 30 inches. The Blue line of the BMS from battery to BMS is 10 -12 inches. the bms is like 6 inches width. The black out of BMS is 10 inches, Then I use the breaker that like 5 inches include the copper on it. Then black connection from the breaker to the busbar. So how do U guys calculate cable length. Please help me out with this. Thanks a lot
 
Steve_S said:
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You guys are all pro and knowledgeable. Please help me with this: I have EG4 6500 EX. (eg4 3x 100 amp 48v. this is fine But) But the question part is: It expensive and I trying to save money so I bought 16s lifepo4 302 Ah CATL batteries. BMS: overkill solar 100 amp (I think i understand now that if I run 2x EG4 6500 inverter then this 100 amp BMS is under size) sorry... but the question is on the Wire length. I using 1/0 cable from battery to bus bar. 2/0 dc battery cable from busbar to each Inverter. What is the Length is correct? The positive Red from battery to busbar is 30 inches. The Blue line of the BMS from battery to BMS is 10 -12 inches. the bms is like 6 inches width. The black out of BMS is 10 inches, Then I use the breaker that like 5 inches include the copper on it. Then black connection from the breaker to the busbar. So how do U guys calculate cable length. Please help me out with this. Thanks a lot
 
timselectric said:
When batteries are placed in parallel. Each battery should have its own OCP. If one battery has a short, the other/s will dump all of their power into the shorted one.
Also, if one batteries BMS shuts off. The other battery will try to feed the inverter on its own. Then you will have a 200a breaker protecting a #6 wire. The wire now becomes the weak point.
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I'm working to get as fully educated as I can here.
I have two JBD 200A BMS's for a 16S2P plan using LF280Ks. They unexpectedly included these two 400A fuses. Does that sound right, a 400A fuse to protect a 200A BMS?
 

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16s2p is 32 cells in one battery with one BMS.
With two BMS's, I think that you mean two 16s batteries in parallel. Each battery should have OCP (Over Current Protection) for its primary conductors.
Protection can be sized up to 125%. Which would be 250a for 200a max expected load.
 
timselectric said:
16s2p is 32 cells in one battery with one BMS.
With two BMS's, I think that you mean two 16s batteries in parallel. Each battery should have OCP (Over Current Protection) for its primary conductors.
Protection can be sized up to 125%. Which would be 250a for 200a max expected load.
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Thank you.
I learned something and was already on the right track with 250A fuses before I discovered what else was in the bottom of the JBD box.
 
I have 40 feet of 2/0 that I need to get rid of. With crimp on ends.
 

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