Rotating batteries in a battery bank!

Farmerboyz1721

I would like to get everyone's opinion on rotating batteries. I have tried to google this and can't find anything.

I have a 12 volt battery bank @ 1248 Amphr. Built with 12 6 volt batteries in parallel and series. 
I have a DC amp clamp and i can monitor and see that the bulk of the amps get pulled from the front of the battery bank.(60 amps) Where the load is connected too. The batteries on the back end of the bank pull a much smaller (8 amps) .

This got me to wonder if the batteries should be rotated in different spots of the battery bank every so often. Any thoughts on this???

vtmaps

Welcome to the forum,

The basic problem is that you have too many parallel batteries... it's doomed to failure.  I just explained this to someone with 4 strings in parallel:   http://forum.solar-electric.com/discussion/comment/356663/#Comment_356663

If you want to make the best of a bad (parallel) situation, it helps to wire them with bus bars.  

Another factor that can cause batteries (series or parallel) to diverge is temperature variation.  All the batteries must be at the same temperature. 

If you decide to do an equalization, disconnect 5 of your battery strings and equalize just one string at a time.

--vtMaps

Farmerboyz1721

vtmaps,

Thank you for the information. Did not know that there should be limits to parallel connections. Could you elaborate on wiring them with bus bars? I would love to do what i can to keep this battery bank alive. It has no more then 150 cycles on it. Also i will ask again is there any logic to battery rotation? What about wiring the main line into the middle of the battery bank?

Farmerboyz1721

I did find this site. It defiantly helped me see some of my errors. It also explained balancing the batteries better. 

It sounds like to me that the answer is not to rotate batteries but to get them balanced. 

http://www.smartgauge.co.uk/batt_con.html

Brock

On that diagram basically #3 is how you would wire up a bus bar, with each battery sting + leading to the + bus bar and each - to the - bus bar.  If you have more than 2 stings you really need to wire them that way.  If you do this you will get as even of a draw from each string as you can and then there is no need to rotate.  Rotating them helps, but they will get further and further out of balance from each other to a point where they start a cascading failure.

BB.

Getting the battery bank "rewired" to balance current (load and charging) will help a lot.

There has been discussion here by a few people that even with one string of batteries (no current balancing issues) that find they have better battery life/performance if they rotate the batteries once a year. For some folks, the battery near the + bus may not charge to the same level as the battery at the other end of the string.

I cannot give you a reason why this is true for some folks (other than if battery ventilation is uneven--temperature variations)--But it has been seen.

-Bill

Dave Angelini

I can give you 87 examples of why not rotating batteries in a single string bank has done no harm.

BB.

Just to be clear--It was a "few people" here (handful or less?) that found rotating battery positions was helpful for them.

I certainly do not recommend it as a matter of standard operating procedure.

-Bill

Dave Angelini

It makes my back hurt just thinking about it.

Johann

Looks like the way you measure makes it look like that you get the wrong results or even make it look like that you have a major  problem.


The way you got it wired the way I understand is like in this link http://www.smartgauge.co.uk/batt_con.html
  figure #1.
You have the incoming wire to the battery and then you measure the amps right in front of the battery bank at the incoming wire to the batteries.......this will give you the total amps that all your batteries will take since the battery-supply-wire in front of the bank will supply power to all of the batteries and strings.
Then if you take a measurement between string # 1 and string # 2 you will measure only the last 5 strings while you leave the 1st string out of your measurement and this will lower the amp reading since you only measure the amps of 5 strings and not 6 strings now.
If you go between the 5th and 6th string (last string of the batteries) then you read only the amps of the last or 6th string ....right at that location of your measurement, you are reading the amps of one string only and that is why you get the lowest reading there.


I hope that I understood it right the way you got it wired and the way you measure it..

Farmerboyz1721

First off i want to thank everyone for there inputs. I have decided to show my battery bank. I have also noted where and what the readings were. There is a correction to my original post. It is 30 amps at the load of the bank and 8 amps at the end. It appears that i need to rewire this to accommodate method #3 of the http://www.smartgauge.co.uk/batt_con.html . 

vtmaps

Farmerboyz1721 said:

 It appears that i need to rewire this to accommodate method #3 of the http://www.smartgauge.co.uk/batt_con.html . 

Smartgauge does a good job of explaining how to put batteries in parallel.  The fault I find is that they do not emphasize the extent to which parallel batteries are a compromise of optimal design.  Even with perfect wiring and bus bars, 6 parallel strings is unstable. 

By the way, it appears that you are doubling up cables on your battery interconnects.  That will increase the potential points of failure and the instability of the system.

--vtMaps

Johann

Farmerboyz1721 said:

First off i want to thank everyone for there inputs. I have decided to show my battery bank. I have also noted where and what the readings were. There is a correction to my original post. It is 30 amps at the load of the bank and 8 amps at the end. It appears that i need to rewire this to accommodate method #3 of the http://www.smartgauge.co.uk/batt_con.html . 

That is exactly what I thought you have and the way you are measuring it.
30 Amps is what your total battery bank is taking, while your 8 amp point is only part of one battery string out of 6 battery strings.
To measure the 8 amp point more precise, you need to put both of your red wire (parallel wire) into your amp meter. If you clamp only 1 wire at the 8 amp point you are going to read only part of the amp reading for the last string.  You may have used both wire to measure already....

If you want to measure the amps for each battery string (2 batteries in series), clamp your amp meter on the red and black wire together between the 2 batteries. Do this for each string,  Now compare your readings.

Like this image below where the blue circle represents your amp clamp. Then go to the next battery string and so on. This way, you will read each battery string.

mike95490

I find it much easier to rotate the flywheel on my generator, and leave the batteries alone.

vtmaps

mike95490 said:

I find it much easier to rotate the flywheel on my generator, and leave the batteries alone.

Well, if you made some improvements to your battery box it would be easier to rotate them... you need to put your batteries on a turntable and connect them to the bus bars with some big brushes and commutator.

The ability to rotate the batteries makes it easier to water them...  the cells in the back of the box can be rotated to the front.

There is no reason you can't rig a motor, powered directly by solar panels, to the turntable.  The batteries would rotate continuously while charging.   Don't let them turn fast enough to develop lateral stratification.

Good luck with the project!

--vtMaps

Brock

 But seriously about every year or so I disconnect everything, take the batteries out, clean everything, charge each battery individually, check each battery resting, write on the battery the resting voltage on the battery, check gravity and write that on the battery as well and make sure they are topped off and then put them all back in but move them around.  I do rock them around as move them, that might be the part that is pointless, but I do it anyway, maybe a motorized turntable  

Dave Angelini

Are you folks using a moving coil cartridge on the turntable?

WaterWheel

I use a turn table with a slip ring to maintain the connection.     Works great and much easier on the back.

I've been considering adding an automatic waterer, saw one on ebay. 

Farmerboyz1721

   

Bunch of jokers on here today

Here is the total amp draw on each connection when the charger is on bulk charging mode.

Dave Angelini

How do you check the water?

Brock

If you don't plan to go with the bus bar idea you might actually consider rotating where you main leads attach to the bank.  So leaving the bank wired as is, but move the left side or negative lead to the second battery up and move the positive lead or right side to the second from the top.  With the way yours is setup I am guessing that would be the most balanced loading per battery, but you could move it take those same center readings again.

The good thing is with the double wire on everything is you should have lower resistance, but the bad part of that is more connection points that could fail.

As Dave noted, that has got to be difficult to check water they way it is now.

Farmerboyz1721

It might not appear so. But, i can remove the tops and check/fill the water. It is not the greatest access but does work. 

Farmerboyz1721

Would there be a problem doubling up on the studs of the bus-bar?
I have a 6 stud bus-bar and 6 parallel batteries to tie in. But, then i still need to wire in the inverter/charger and 12 volt load.
 

vtmaps

Farmerboyz1721 said:

Would there be a problem doubling up on the studs of the bus-bar?
I have a 6 stud bus-bar and 6 parallel batteries to tie in. But, then i still need to wire in the inverter/charger and 12 volt load.

I am not aware of any bus bars that permit doubling of the conductors.  What is the amp rating of your 6 stud bus bar? 

To combine 6 batteries properly you should have a battery combiner box with circuit breakers or fuses for each of the combined batteries.  Of course, combining 6 batteries in a cycling application is foolish, but with a combiner box you could be properly foolish.

--vtMaps

Farmerboyz1721

The bus bar is rated for 250 amps. 

Farmerboyz1721

I quickly rewired to method # 2 because that was easy. http://www.smartgauge.co.uk/batt_con.html

 I don't think it balanced it out any better. 

Next step to work on rewiring a bus bar. 

Where is the best place to find a bus bar? The one i have is https://www.bluesea.com/products/2126/MaxiBus_250A_BusBar_-_Six_5_16in-18_Studs I need more terminals then 6 and i can't find one. 

vtmaps

Farmerboyz1721 said:

Where is the best place to find a bus bar?

I don't know if this is the best place, but it is a place:
 http://www.electrical-insulators-and-copper-ground-bars.com/ground-bar.html

-vtMaps

Mountain Don

The company vtmaps linked to also sells copper bar stock in many sizes if you are interested in making your own buss bars from scratch.  That is what I did.

mike95490

I find it much easier to rotate the flywheel on my generator, and leave the batteries alone.

BB.

Some folks here have found physically moving their batteries helps distribute wear (their high/low SG seem to follow string position and not physical battery--At least at times).

Why--I have no clue if all is otherwise OK (good ventilation, one battery not hotter than the rest, etc.).

-Bill

dennis461

The setup you have looks OK to me, I wouldn't change anything.