Did Victron BlueSolar Kill My Batteries?

[zboss]

Originally Posted by john61ct

Yes FFR there are other good reasons to go with even numbers...

Which are?

[admiralslater]

Originally Posted by john61ct

For future reference, as in next time the bank needs replacing.

Devices that let you series two halves of a bank for 24V usage as needed, otherwise paralleled as a 12V bank for charging.

"Split bank" voltage monitoring, can give you advance warning of a single batt failing, without having to use individual cell monitors.

That makes sense thanks a lot. Next 4 solar panels and three controllers

[john61ct]

I hope you don't think the second sentence you just wrote relates to the post you're quoting.

[foggysail]

Wire size matters when considering how to wire parallel banks along with the controller's output current. I wired my banks using #2 stranded copper which has a resistance of .16 ohms/1000 feet. For reference purposes #6 copper is spec'ed at .4 ohms/1000 feet and I mention this because somewhere in this thread #6 wire was mentioned. There is a slight error with the resistance (DC) for stranded and one should drop one wire size for stranded resistance which I am not bothering with.

So in my situation, my banks are about 3' deep so the voltage drop in such a length is minute at (.0001) X (current)/foot. If the current supplied by the controller was as high as 100 amperes, the voltage drop/foot would only be .01 volt in the first foot (to the second battery) or 10 millivolts and that voltage will diminish as each battery bank absorbs current.

Run the numbers with the wire sizes you use along with the expected current from the controller. My take is for reasonable sized wire such as #6 it is a waste of effort to have one polarity wired to battery 1 and the other to battery 3. At first glance wiring to 1 and 3 seem important and without running the numbers, maybe it is if your using lamp cord but then you have other problems.

Make it easy on yourselves, wire both polarities to battery 2 as John mentioned and even that IMHO is not necessary.

The other issue pertaining to wiring voltage drops which is ignored are the banks' acceptance of current. You may not be able to charge at this rate even if you wanted to

[john61ct]

Originally Posted by foggysail

Make it easy on yourselves, wire both polarities to battery 2 as John mentioned

If you mean me I said no such thing.

#2 if Gibbo's diagrams I linked to, each polarity from opposite ends of the bank.

[admiralslater]

Originally Posted by john61ct

I hope you don't think the second sentence you just wrote relates to the post you're quoting.

Sorry John I was referring to the next big project I am under taking this November

[foggysail]

Originally Posted by john61ct

If you mean me I said no such thing.

#2 if Gibbo's diagrams I linked to, each polarity from opposite ends of the bank.

This has gotten too confusing for me, wire the things anyway you wish. Mine work just fine. If the connecting bus wires are large enough it makes no difference how charger/load connections are made.

[zstine]

OP here. I did some more checks to determine why the Solar Controller and actual voltage at the batteries was different by over 2V. Before disconnecting the old batteries, I turned the solar charger back on (it was off/disconn for 2 weeks) and I could not recreate the problem. The batteries were at 11.2V and the charge controller was reading only 0.2V higher, fine. I allowed it to charge for 30 minutes and the voltage difference was never more than 0.2V. So I removed the old batteries and checked resistance from the controller through the breaker to the battery terminal and found 0.51ohms. Half an ohm sounds fine. All connections were tight and free of any visible corrosion. I put 3 new house batteries in....
My current connection is both the load and negative is connected to the center battery (as is the charger). I believe John is saying that the optimum set up is to have the load and negative on far opposite ends of the bank. (See attached drawing). I can/will rewire it that way if optimum, but having it wired with load connected on the middle of the 3 batteries should not cause a 2+V difference in what the charge controller sees. At this point, I could not recreate the problem with the controller, but I do not trust it while not on board and have emptied the refrigerator and turned everything off... not ideal. Sorry I can't post to the forum on my boat via my android phone b/c of redirect issues at login and couldn't get real-time advice from you guys.

[fallingeggs]

Guess that is an improvement. Try and watch the solar do a full charge cycle one sunny day.

[foggysail]

There are various connections methods that can be made to battery bus wiring, each claiming a benefit over another. But be real! If the bus wiring is made with heavy wires such as #6 or heavier and the batteries are mounted closely together, it will not make any difference at all how the load/charger connection is done as long as the wiring is short, proper connections made and the electrical topology is correct.

If in doubt, try measuring the voltage drop across a properly sized bus wire under charge/loaded conditions and prove it to yourself. My earlier post listed the wire resistances of both #6 and #2 copper, you dealing in microhms for short distances.

[john61ct]

Originally Posted by foggysail

This has gotten too confusing for me, wire the things anyway you wish. Mine work just fine. If the connecting bus wires are large enough it makes no difference how charger/load connections are made.

Not true, but your bank, your call.

I think most can go to the page , look at diagram #2 and clearly see what to do without even reading the text.

There are plenty of YouTubes showing people proving the way you're wired makes a huge difference, an unbalanced bank very quickly becomes just like mixing old and new.

[john61ct]

Here's a closeup

[john61ct]

Originally Posted by zstine

I believe John is saying that the optimum set up is to have the load and negative on far opposite ends of the bank. (See attached drawing). I can/will rewire it that way if optimum

Yes. Not me but ​Chris Gibson, a very clever fellow indeed wrt batteries and DC electrics, as in military supplier contract consulting.

And not optimal, but simple, easy to do, and very very good, as opposed to "will lead to bank's early death".

All wires same gauge and length, right sized terminations, all top quality and well-crimped of course.

If the original issue does not return, fuggedabout it.

Do a full manual equalization on the bank, stress test it a few cycles, ideally a full 20-hour load test comparing the individual batts.

[foggysail]

Originally Posted by john61ct

Not true, but your bank, your call.

I think most can go to the page , look at diagram #2 and clearly see what to do without even reading the text.

There are plenty of YouTubes showing people proving the way you're wired makes a huge difference, an unbalanced bank very quickly becomes just like mixing old and new.

I do agree that the schematic shown does equalize the voltage drops but I contend that the voltage drops are insignificant when heavier wire sizes are used regardless of how the banks are wired. I was aware of your referenced schematic when I wired my bank a couple of months ago. Because I used #2 wire I saw no need to add mechanical complexity to my installation for the trivial gain the circuit offered. The end feeding circuit shown will have advantages when smaller bus wires are used which I always avoid in battery wiring.


My circuit's DC resistance with #2 copper = 0.16 ohms/1000 feet or 160 microhms/foot. So a current of 10 amperes will have only 1.6 millivolts (0.0016)/ foot. There is another factor that is overlooked in parallel charging and that has to do with the battery internal resistance. That resistance also helps balance parallel charging.

[john61ct]

The issue is not voltage drops. It is that in #1, very common but doing it wrong, the electron flow is "exercising" some units more so than others, so they get imbalanced, wear out very unevenly and the whole bank dies prematurely, at the rate of the weakest link.