Battery cable length - from Lynx distributor

[FilterGuy]

See 6.9

What is that?

 

[sunshine_eggo]

What is that?

Doh! 6.7

 

[FilterGuy]

I've only been referring to one resource...

There is no 6.9 in the copy of wiring unlimited that I got from your signature link.

 

[sunshine_eggo]

There is no 6.9 in the copy of wiring unlimited that I got from your signature link.

You caught me before the edit! :D

 

[FilterGuy]

You caught me before the edit! :D

We all make mistakes. Just like the OP did with the calculator. It is a good thing people are forgiven for their mistakes.


6.7 is talking about the pass-through mode. This is a known problem for all inverters that have a pass-through mode. In pass-through mode, the current through each path is determined by ohms law and there is very little the inverter can do about it due to the variations in the contact resistance of the relays. (I do find their solution interesting. They are saying to make the total AC resistance high enough to make the variations in the relay meaningless)

I am referring to when the inverter is driving the load from battery power. In this case the inverter can adjust it's output current and if it is properly coordinating with the other parallel inverter it can balance it.

BTW, I am pretty sure Lux and EG4 18Kpv inverters coordinate the outputs on parallel systems. As I said before, I would bet that Victron does as well and I would not be at all surprised if Solark does.

 

[G00SE]

@FilterGuy if it was your install, would you have used those cables/kept them?

 

[FilterGuy]

@FilterGuy if it was your install, would you have used those cables/kept them?

I would have left it unless I saw a problem. (Unless I am missing something I don't think there is a problem)
What I would do is not what the OP asked. He asked if it is an issue with the install as pictured. In post #2 I answered that I did not think so. I have seen nothing in this thread that changes my answer.

My problem with the install is not the cable lengths. My problem is the dangling spaghetti. I would much prefer to see all of the wiring enclosed in conduit and or conduit boxes.

 

[SenileOldGit]

My electrician is coming round later this week to finish the rest of the installation, I imagine he will put the cables into trunking. I will report back as soon as the inverters are up and running, so we can see if there is a problem or not. I can't imagine there will be, going by the length of the cables in the Voltacon video. They would be encouraging their customers to set up their inverters the same way, and then have problems, which the customers would then complain to Voltacon about.

As for the poster (sorry, I've forgotten who it was) who suggested I mount the Lynx Distributor and the Lynx Power In one above the other, and use cables to join them together - I think that's an even worse layout - I presumably would have to use larger than 25mm2 cables to link the two together, and I would have the upper unit's four cables (presuming the upper unit is the Lynx Distributor) having to go down and past the lower unit, AND get past the two cables that I would be using to link the two units together.

If there IS a problem with these cable lengths, then and only then I will buy some more 70mm2 cable (it's £20 a metre) and I'll fit exactly the same length to the left hand inverter, as is already going to the right, it's not difficult to do. I will have the definitive answer in a few days' time, and that will help other people who are setting up similar systems. (i.e. if the cable length doesn't matter - as set up in my photo - then other people needn't worry about making the cables exactly the same length, if it would make it more difficult for them to set up, fit in trunking, etc.)

Since I started a year and a half ago, I have learnt so much that I am confident I could connect up the entire system, but I know I'm not qualified and not allowed to do it, and I don't have the proper testing gear, so I am very happy to let my new electrician do it all - the difference between now and a year and a half ago is that if my new electrician does something wrong, I will probably notice it, because I now (finally) understand what every component does, and why it's there - that's a nice feeling. (Yes, I know, I made some errors in this thread and therefore I'm incompetent and shouldn't be let loose near an inverter...)

 

[SenileOldGit]

View attachment 189165

That’s odd

So not only does it talk about bus bars, but also says you’re using the wrong wire size (ya know, since we’re being “technical” now)

So you're suggesting that I should have used a thinner cable than 70mm2, because the manual only says two times 22m2? (in my case, 'X' is 2 inverters). And thus the voltage drop would be even greater?

 

[G00SE]

So you're suggesting that I should have used a thinner cable than 70mm2, because the manual only says two times 22m2? (in my case, 'X' is 2 inverters). And thus the voltage drop would be even greater?

I’m not suggesting anything. I’m refuting your statement of something not being in the manual and utilizing your own verbiage about deviation

 

[sunshine_eggo]

We all make mistakes. Just like the OP did with the calculator. It is a good thing people are forgiven for their mistakes.

I see what you did there.

6.7 is talking about the pass-through mode. This is a known problem for all inverters that have a pass-through mode. In pass-through mode, the current through each path is determined by ohms law and there is very little the inverter can do about it due to the variations in the contact resistance of the relays. (I do find their solution interesting. They are saying to make the total AC resistance high enough to make the variations in the relay meaningless)

I am referring to when the inverter is driving the load from battery power. In this case the inverter can adjust it's output current and if it is properly coordinating with the other parallel inverter it can balance it.

BTW, I am pretty sure Lux and EG4 18Kpv inverters coordinate the outputs on parallel systems. As I said before, I would bet that Victron does as well and I would not be at all surprised if Solark does.

That section refers you to:

Parallel, split- and three-phase VE.Bus systems [Victron Energy]

www.victronenergy.com

For units in parallel: Both the DC and AC wiring needs to be symmetrical per phase: use the same length, type and cross-section to every unit in the phase. To make this easy, use a bus-bar or power-post before and after the inverter/chargers. Also, apply the same torque on all connections.

 

[Chris72]

My electrician is installing my Voltacon 5kW inverters in a new shed I built for them - does it matter that the 70mm cables shown are different lengths? Or are they so thick that the resistance difference won't affect the voltage that each inverter sees from the three Pylontech US5000 batteries I have? (Which will be fitted to the Lynx Power In on the right, next week.)

View attachment 188897

Why don't you lower the lynx equipment down cut the longer cable in half and move the inverters closer together?

 

[Dave (Boog)]

Does it really take 93 and counting, replies to this post? I read through this and I’d say that 90% of the responses are either incorrect or superfluous. Some of the responses are just plain rude. If I asked a question and got these sort of responses it would make me want to quit this forum!

 

[SenileOldGit]

So, I have had the two inverters working for three weeks now. Everything is perfect. The right hand inverter sometimes shows the voltage 0.1V higher than the left hand inverter, but then, they only display increments of 0.1V, so I imagine they are often, say, 46.16V on one, rounded up to 46.2V, and 46.14V on the other, rounded down to 46.1V. Absolutely no problems with either inverter 'working harder' than the other, just as I predicted. I got 9.23kW at one point yesterday, not bad for a 12kW array at the end of February in the U.K.!
The whole system is working like a dream, I control everything from Solar Assistant. My new Motorola e13 phone, which cost £70, runs Solar Assistant really well, much better than the Victron Gerbo, or whatever it's called.
I also have Solar Assistant running on both my PCs, via a browser, so wherever I am in the house, I can see what the inverters are doing, and how much charge the batteries have.
My three Pylontech US5000 batteries are wrapped in a hot water cylinder jacket, and I have two heated pet pads between them, so I can raise the temperature. These worked well too, when the inverters were first turned on, the batteries were under 10C, so I used the pads and raised the temperature to 30C after several hours (I can't remember how many, no more than 12, and solar output was bad for days after first turning everything on, so charging the batteries at such a low rate wouldn't have warmed them anywhere near as quickly.)
Any comments from the purveyors of doom and gloom?

 

[SenileOldGit]

I will try to post up some screenshots of the Solar Assistant Inverter and Battery screens tomorrow.

 

[Zwy]

Load it down heavy when taking the screenshots. As these are 5Kw 240V Euro units, that will take some load.

Like I said in my first reply, slight differences in supply voltage may or may not cause a shutdown. It would be interesting under heavy loads.

 

[SenileOldGit]

Well, every day I use a 4.5kW shower and a 1.5kW fan heater for ten minutes or so, I also turn on as much as I can when the kW are high on a sunny day (currently getting 8kW in the U.K. at 12:30), and no problems at all.

 

[Zwy]

Well, every day I use a 4.5kW shower and a 1.5kW fan heater for ten minutes or so, I also turn on as much as I can when the kW are high on a sunny day (currently getting 8kW in the U.K. at 12:30), and no problems at all.

I forgot to add it should be done under battery power only, no PV.

When PV is available, the battery cable length can have minimal effect on the results. I am curious about the results and see if it matches up with voltage drop calculators and the effects on the inverters.

 

[SenileOldGit]

 

[SenileOldGit]

I've just turned on the heated pads in between the batteries, as I believe the ideal temperature is 25C. I'm going to buy a couple of 'smart sockets' which you control with a mobile phone app, so that I can turn the heated pads on and off from inside my house, rather than having to go outside when it's freezing cold, and opening the door on the inverter shed to turn them on (which will allow more cold air in.)

Toolstation have a special offer of three for the price of two on D-Link Smart Sockets (I think they were D-Link), £21 for 3, including free delivery.