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incagarcilaso

Battery bank mid-point problems

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Thank you @Chris Hobson and @plonkster for these last points. I now have 4 HA02s but before connecting everything I wanted to run a quick connection scenario past you to see if you think it makes sense based on some readings I have taken. In the diagram you will see I propose wiring each HA02 between the top and bottom sections of the bank to improve the balancing effect more quickly because the biggest differences are between 6 or 7 low voltage cells in the top section (I have attached two readings so that you can see this). The coloured cells are the ones with the lower voltage readings (one in particular is very low, relative to the others). By wiring them in this way it strikes me that the current transfer will be more effective. The other decision I made is to work in pairs of cells, rather than 3s since one of the nominal voltages in the HA02 specs is 3.6V, which should be fine for pairs of 2.25V cells. This way I will use 3 HA02s.

My main question is: Is it OK to wire in this way, i.e. not following the sequence of the string but across/between the top and bottom sections? Hope the diagram is clear. With the first box (HA02 a) I am pairing cells 1 and 2, 3 and 4, 13 and 14 and 15 and 16 and having them equalizing with this box. HA02 b and HA02 c are similarly wired across the top and bottom sections. Does this look good to you and make sense?

Does the fact that there are 6 or 7 cells with a reading .05V  lower than the rest suggest anything to you about what is happening with these cells? Are they the healthy or the weak cells?

bancobatt.jpg

bancobattreadeg.pdf

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57 minutes ago, plonkster said:

I don't know the HA02 well enough. I think it's just two balancers in one box, and if that is the case, your diagram looks good to me.

0.05V is nothing to worry about.

OK. The 0.05 is when they have been discharged to 100 Ah or so and are charging or discharging. The problem is with the bulk charge towards the end of the charge cycle. At that point the difference between the cells with less voltage and those with more jumps out of control and becomes 0.2V and I have the bottom section at 28.8V (when it should be at 27.5V) and the top section at 26.6V (when it should be at 27.5). The BMV reads a mid-point variation of 4.2%, which is really high, too high. As soon as they go into discharge, this mid-point difference returns to just 0.7% again.

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Hi 

Two things

  1.  Sequentially I would call battery No 24 battery 13 and so on.
  2. The batteries being balanced by the HA02 although scattered for each HA02 unit they can described as discrete units with no overlap. Go with your configuration now but if the BMV show deviation of greater than 1% you will have to introduce some overlap.
4 hours ago, plonkster said:

I don't know the HA02 well enough. I think it's just two balancers in one box, and if that is the case, your diagram looks good to me.

0.05V is nothing to worry about.

The HA02 is equivalent of 3 HA01 balancers. From the video Youtube video shown recently it does not suffer from the "pass the parcel" drawback of individual balancers which can only pass excess energy to the battery next door. Battery 1 can transfer energy to battery 4.

I agree with Plonky  0.05V is nothing to worry about but the balancer will start to act at 10mV (0.01 V) so there will be an improvement. The correct time to look for imbalances is late absorb (roughly SOC 94-97%).

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38 minutes ago, Chris Hobson said:

From the video Youtube video shown recently it does not suffer from the "pass the parcel" drawback of individual balancers which can only pass excess energy to the battery next door. Battery 1 can transfer energy to battery 4.

That's rather neat. For a second there I was wondering if it could also pass it backwards (say from 4 back to 1), but then I realised there is no reason for that. If the last battery is high, you will end up bypassing the battery sending that charge back directly to the MPPT (where it would have gone anyway eventually), which will cycle it through the PV panels again (in a manner of speaking) where sunlight will give each electron another kick up the backside until they arrive back at battery 1.

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11 hours ago, Chris Hobson said:

Hi 

Two things

  1.  Sequentially I would call battery No 24 battery 13 and so on.
  2. The batteries being balanced by the HA02 although scattered for each HA02 unit they can described as discrete units with no overlap. Go with your configuration now but if the BMV show deviation of greater than 1% you will have to introduce some overlap.

Hi.

Sequence numbering. Of course, 24 is 13 - I will renumber them to avoid confusion later.

Overlap. I have one spare HA02, which I could add to this configuration, to avoid more work later. So:

  1. Where would you put this fourth HA02? My idea would be to link up 6-11 and 13-18 (based on new numbering in diagram below) purely because this links lower voltage cells with higher voltage ones and I thought this might have more effect; and, related to this,
  2. Do you envisage any problem with using this fourth HA02 on groups of 3 cells rather than on the pairs that I have in the diagram? That would mean I would have 3 HA02s working with pairs of cells (3.6V nominal) and the fourth working with 4 groupings of 3 cells (6V nominal).

If (2) is OK then that will mean that I can add in the fourth HA02 to balance between cells 6-12 and 18-24.

I have to say that I don't understand how overlapping can work. I just can't see how the balancers can be balancing pairs of cells and then other sets of 3 cells where the pairs are subsets of them.

Although there is only a 0.7% mid-point deviation during discharge (.05V difference between some cells), at late absorb this jumps out of control to over 4% and then stays like that until they have discharged 15Ah or so.

bancobatt.jpg

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1 hour ago, incagarcilaso said:

 

Overlap. I have one spare HA02, which I could add to this configuration, to avoid more work later. So:

  1. Where would you put this fourth HA02? My idea would be to link up 6-11 and 13-18 (based on new numbering in diagram below) purely because this links lower voltage cells with higher voltage ones and I thought this might have more effect; and, related to this,
  2. Do you envisage any problem with using this fourth HA02 on groups of 3 cells rather than on the pairs that I have in the diagram? That would mean I would have 3 HA02s working with pairs of cells (3.6V nominal) and the fourth working with 4 groupings of 3 cells (6V nominal).

HI I like the way you have arrange the HA02s so that you do not have very long cables. Clever idea. 

The problem is that if  Cell 2 is high and Cell 15 is low with your current arrangement Balancer A is going to evenly distribute that high charge over Cells 1-4 and 21-24.Balancer C is going to try and raise the low charge of Cell 15 by redistributing from the other 7 Cells connected to it. These Cells connected to C will be marginally lower than the average. The Cells connected to Balancer A will be marginally higher and Cells  connected to Balancer B will be just about average.

If you connect Balancer A as in your diagram and Balancer B to Cells 4-7 and 18-21 and Balancer C to 7-10 and 15-18 and your last balancer D 9-12 and 13 - 16.

Now if one cell goes high the balancers will "pass the parcel"  until all groups of cells are equal There is one and in some cases two reference cells that are common to adjacent balancer strings (string in this sense being a group of cells part of a much large 48V string). 

These reference cells ensure that Balancer A and Balancer B balance to the same voltage and so on, ending up with all balancers balancing to the same voltage. I have an advantage in that I have HA01s which are positioned between each 12V battery pair. This gives me an idea how the HA02s should be connected as they replace three HA01s.

 

Just remember to "hou kop" when connecting your wires.

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8 minutes ago, Chris Hobson said:

HI I like the way you have arrange the HA02s so that you do not have very long cables. Clever idea. 

The problem is that if  Cell 2 is high and Cell 15 is low with your current arrangement Balancer A is going to evenly distribute that high charge over Cells 1-4 and 21-24.Balancer C is going to try and raise the low charge of Cell 15 by redistributing from the other 7 Cells connected to it. These Cells connected to C will be marginally lower than the average. The Cells connected to Balancer A will be marginally higher and Cells  connected to Balancer B will be just about average.

If you connect Balancer A as in your diagram and Balancer B to Cells 4-7 and 18-21 and Balancer C to 7-10 and 15-18 and your last balancer D 9-12 and 13 - 16.

Now if one cell goes high the balancers will "pass the parcel"  until all groups of cells are equal There is one and in some cases two reference cells that are common to adjacent balancer strings (string in this sense being a group of cells part of a much large 48V string). 

Just remember to "hou kop" when connecting your wires.

Hi. OK,  I now understand why you suggest overlapping and the effect it has - reference cells and passing the parcel explains it well. Yes, the arrangement was partly so as not to have to lengthen the cables on the HA02s (the less I mess with them the better, I think). Your connection suggestion to include balancer D I think still works without having to lengthen cables and the overlapping has clear benefits by connecting the groupings together so that the groupings can also compensate eachother.

Sorry to be dense - what do you mean by "hou kop"?

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1 hour ago, incagarcilaso said:

Sorry to be dense - what do you mean by "hou kop"?

...... an Afrikaans expression "to keep one's head". You are going to have a myriad of wires and positive is on the one side on the first ½ of the bank and effectively on the other side on the second ½. 

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58 minutes ago, Chris Hobson said:

... myriad of wires and positive is on the one side on the first ½ of the bank and effectively on the other side on the second ½. 

Ooooo ... sounds like my kinda place ... NOT!

For that is exactly where I, in the most spectacularly fashion, can blow things up. 

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1 minute ago, The Terrible Triplett said:

Ooooo ... sounds like my kinda place ... NOT!

For that is exactly where I, in the most spectacularly fashion, can blow things up. 

I think you are too hard on yourself. You'll never connect a 24V SCC to a 12V inverter again. I won't either because my mate did it and said the results weren't favourable.

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1 hour ago, Chris Hobson said:

...... an Afrikaans expression "to keep one's head". You are going to have a myriad of wires and positive is on the one side on the first ½ of the bank and effectively on the other side on the second ½. 

I like the expression, and will certainly try. The reversing on the position of the positives and negatives of the batteries on the top and bottom sections has already driven me crazy while taking measurements with the multimeter!

The brief instruction in the HA02 recommends connecting all the positive wires first and then the negatives so I'll probably follow that advice.

I suppose it would be essential to shut everything down and cut all current to the bank of batteries while I connect the balancers?

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33 minutes ago, incagarcilaso said:

The brief instruction in the HA02 recommends connecting all the positive wires first and then the negatives so I'll probably follow that advice.

Sounds good.

33 minutes ago, incagarcilaso said:

I suppose it would be essential to shut everything down and cut all current to the bank of batteries while I connect the balancers?

Yes and remove your wedding band/ring if you wear one.

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3 hours ago, Chris Hobson said:

I think you are too hard on yourself.

Not at all ... it is one huge joke. All the stuff I let the smoke out of.

First I was "Grond dom". (Translated: You are as dumb as soil - poof, over your head as in soil blowing over your head in a dust storm.)

Now I have stepped up to "Klip dom" level. (Translated: You are as dumb as a rock - which is less dumber than ground/soil for you now get it, does not blow over your head, but you are still " 'n klipkop"  = blockhead.) 

One up from that is stupid - am still in training to reach this level.

After that you reach Expert level ... one day when I am grown up off course. The Wife said so.

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9 hours ago, Chris Hobson said:

Just remember to "hou kop" when connecting your wires.

Scene from the movie "The Three Muskteers (the 1993 one)", execution scene just before all hell breaks loose: D'artagnan! Don't lose your head! Bwahahaha!

Edit: Best version I could find. Audio is misaligned :-)

https://youtu.be/Ytkoye9b7_I?t=2785

 

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On 13/02/2017 at 2:25 PM, Chris Hobson said:

Sounds good.

Yes and remove your wedding band/ring if you wear one.

So, I have finally managed to fit the HA02s, following your last schema for overlapping the four boxes. I had calculated a couple of hours but it turned into 4 hours and I have serious back ache!

All seems to be fine and I have already noticed a slight improvement in the bulk charge stage - the mid-point variation takes longer to happen and you can almost see these boxes trying to pass more of the voltage to the lower voltage cells with the BMV readings. In the end, I still have a 3.4% mid-point variation in this last absorption stage but I know these may take several weeks to bring that to within a more acceptable range. Here's hoping so.

One thing I have noticed that is slightly worrying is that one of the boxes in particular gets very hot. The others are just warm but one is actually quite hot to touch. Has anybody had a similar experience with these? I don't suppose it is a fire hazard. Can't smell any burning plastic at the moment.

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Mine never get hot but I don't have a large bank with high amps flowing.  It could be an issue... I would swop it out.  Not worth the risk of a short or fire.

Edit:  If your wiring means that some balancers are balancing high loads (ie 10A - max) for long periods then heat may be an issue.  You have a 1500a bank so could be charging at 150A.  ie 10A max for each of the 4x balancer circuits in the one small box. 40A per HA02...    

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Aaagh! Help. I've had these wired up since Tuesday now and the situation is worse, yes worse! The higher-charged cells now have an even higher charge and the lower-charged cells have an even lower charge. My deviation is running at 4.5%. What could be wrong? I'm going to get a diagram of exactly how I have it all wired up and will post here. Any initial ideas how/why this could happen? It's as if the balancers were passing the compensating current the wrong way.

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45 minutes ago, incagarcilaso said:

Aaagh! Help. I've had these wired up since Tuesday now and the situation is worse, yes worse! The higher-charged cells now have an even higher charge and the lower-charged cells have an even lower charge. My deviation is running at 4.5%. What could be wrong? I'm going to get a diagram of exactly how I have it all wired up and will post here. Any initial ideas how/why this could happen? It's as if the balancers were passing the compensating current the wrong way.

That does not make sense. The HA02s are passive so there has to be a voltage difference for them to work.

Make sure each pair of wires goes to a battery pair. Positive to positve and negative to negative.

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20 minutes ago, Chris Hobson said:

That does not make sense. The HA02s are passive so there has to be a voltage difference for them to work.

Make sure each pair of wires goes to a battery pair. Positive to positve and negative to negative.

It makes no sense. I've checked and double checked the cell pairs. I'm attaching a diagram of exactly how the positives and negatives are connected in each case for each of the HA02s. Do you see any issue there? I have made the diagram exactly as the wires are connected. As you can see these cells have 4 connection points on each cell and I have made the diagram to represent exactly the way I connected them.

One of the odd things for me to grasp is how the overlapping can work with what is essentially half a cell. For example, I overlapped on cells 4 and 21 but both of those are only "half" of the groupings attached to the other HA02 (21-22 and 3-4).

I'm awaiting arrival of an ammeter because the one I have cannot measure DC current. This will help a lot as I will then be able to see what current is flowing to and from the HA02s and in which direction. I'm totally stumped as to what could be happening.

HA02sbancobatt.jpg

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