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Battery bank mid-point problems


incagarcilaso

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1 minute ago, incagarcilaso said:

...they still struggle to reach the same levels as the rest of the cells in the bank?

If it was me ...

1 minute ago, The Terrible Triplett said:

... take them back to supplier for assessment?

 

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4 minutes ago, Chris Hobson said:

A 48 V system composed of 2V cells and one made up of 12V batteries are essentially the same. 2V cells have a huge advantage in that one knows what is going on with each cell.  A 12 V battery is composed if six 2V cells conveniently packaged and permanently wired together. So where Incagarcilaso (de la Vega?) can identify exactly what is going wrong - it is a bit of a guessing game with 12V batteries. Once things really go wrong it is no longer a guessing game for 12V owners but it is also too late to do anything about it.

Yes, it comes from El Inca Garcilaso de la Vega - not many people have heard of him.

I'm beginning to understand this now - that it is an advantage to have the individual 2V cells. I am now taking daily voltage readings and will post a sample here to see what story it may suggest to anyone. At the moment they are all over the place with about 6 in total with very obvious extremely high and extremely low voltages. I will be patient and see what magic the HA02s can work over the next few weeks. If the challenge is too much for them I may need to look at changing the weak cells as @The Terrible Triplett suggests (although I'm not sure if the "weak" ones are the high or low voltage ones). Having said that, I'm not sure how easy it is to slot in new idividual cells in a bank like this because of the voltage differences and the age differences - it could lead to the same problems occurring again.

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Having chatted to Incagarcilaso the cells are 115kg each installed in his cellar (little over 2.5 tons for the set). It not just whip one out to give it individual TLC. The are ex communication tower batteries and so were secondhand but has spent the bulk of their time on float. (Bit like TTT's UPS batteries - just a bit more ooomf). 

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7 minutes ago, Don said:

I would measure the voltage on all the cells and take out the 6 x cells with the lowest voltage to make up a 12 volt battery, put them on a charger for 24 hours.

Certainly sounds like it should work - good idea. I think for curiousity's sake I would do that right now if it weren't for the weight of each cell (90kg) and the solid couplings tieing them all in together. If the balancers aren't able to do much over the next few weeks I'll look at doing this. I'm feeling optimistic about the HA02s - I think they just need some time.

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4 minutes ago, incagarcilaso said:

I would do that right now if it weren't for the weight of each cell (90kg) and the solid couplings tieing them all in together.

Just to charge those low voltage cells, seeing that you need a crane to move them around, I would disconnect them from the other batteries and leave them in their current position and connect them up with some heavy duty jumper leads. Those you drive around with in the back of your car to jump start a car.  

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2 minutes ago, Mark said:

A thought:  You could double up a balancer on the affected cells if you have a spare...?

I have four balancers on the whole bank. Luck would have it that two balancers on these two very low voltage cells - just a fluke. I was measuring amps in the HA02 connection wires yesterday and I was surprised to see the values fairly low - around 1 or 1.5 amps in most cases. I was expecting higher readings. However, on the wiring conneceted to these very low voltage cells the readings were at 2.5A. This probably means that the HA02s are doing more with these particular cells, right? At any rate, I was expecting to see amps closer to the max values of 10A for the HA02s.

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2 minutes ago, Chris Hobson said:

I think TTT would deny his affection of Trojans to lay his hands on a bank like that:lol:.

You are preaching to the choir. :D 

I will get a crane.

Would do as Don say, leave them in place and charge them there. 

As it is a older bank, like I did with my old bank, I would add the best of the lot together and split the worst ones out, then drive them into the ground and then use the better ones.

But jinne, 115kg per batt, that sure complicated things a LOT.

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5 minutes ago, Mark said:

Dream: SOC of 90% is 150ah :wub:

At around 220ah they are at 90% SOC - yes I'm lucky. I bought these second hand. They were 12 months old and came from a telecoms installation where they were in float for most of the time (emergency back up, which rarely kicked in). They have to change them every 12 months. They came with history, provenance and a 2-year guarantee but cost just 30% of the new price - otherwise I would never have been able to justify the cost.

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1 minute ago, incagarcilaso said:

I have four balancers on the whole bank. Luck would have it that two balancers on these two very low voltage cells - just a fluke

That's nice and convenient.

Low voltage cells can be due to plates starting to short circuit OR they may in fact be in better health than the others and just take longer to reach voltage as there is still electrolyte available and the cell therefore has a lower resistance. 

Batteries that go high are definitely weaker than your other cells . Electrolyte is used up in the charging process resistance increases and the voltage goes up faster than the other cells.

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3 minutes ago, incagarcilaso said:

I'm not sure how easy it is to slot in new idividual cells in a bank like this because of the voltage differences and the age differences

Yes, to replace them with new cells is a problem. I think a person should take the "Cricket" approach, lol. Granted, this will be very difficult to do as second hand batteries with a history is not something that is readily available. Are you familiar with cricket or have ever watched a cricket game? If someone hits a six and the ball goes over the pavilion and is lost, they bring out a box with balls that have done more or less the same amount of overs, that looks and feels the same as the ball that just got lost. They don't replace it with a new ball.  

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Just now, Chris Hobson said:

If only one cell is troublesome one could have a 23 cell bank and just adjust bulk and float.

Sounds to me this is staging up for a mother of an issue if the balancers cannot sort it, no matter how many balls you have at play with. :D

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5 minutes ago, Chris Hobson said:

Incagarcilaso is an Englishman so the cricket analogy will resonate with him.

If only one cell is troublesome one could have a 23 cell bank and just adjust bulk and float.

Yes, I get the cricket analogy. Noted @Don, so if it becomes absolutely necessary I may be able to get some used cells to replace faulty ones from the same source as these, since they have to replace theirs every 12 months for brand new ones.

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13 minutes ago, The Terrible Triplett said:

Sounds to me this is staging up for a mother of an issue if the balancers cannot sort it, no matter how many balls you have at play with. :D

Yes, I'll try in this order:

  1. Balancers
  2. Conventional charge on discrete sets of problem cells as @Don suggests but without moving anything
  3. Replace the very high voltage cells because it seems that these are faulty as @Chris explains.
  4. If 1-3 don't work give up, throw the towel in, pay a slightly larger electric bill and have more free time to watch some cricket!
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3 minutes ago, Chris Hobson said:

TTT when are we going on holiday in Spain with your 10 ton truck? :lol:

O my ... did you want to come along! I just passed Cairo in my Isuzu with the trailer. :P

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