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Solar Battery Issue


djacobs
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Hi Guys

Please have a look at the attached picture of my setup. The issue I have is that only the front 4 batteries are charging and bubbling during the day. The water was empty and got refilled but the other were still fine. Is there a problem with my setup that not all batteries are being charged. The Blue from Negative is longer than the positive cable, there are no buzz bars, fuses, and is directly connected to the Inverter. Your input will be highly appreciated.

Thanks

Daniel

 

Battery Setup.JPG

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10 hours ago, djacobs said:

Hi Guys

Please have a look at the attached picture of my setup. The issue I have is that only the front 4 batteries are charging and bubbling during the day. The water was empty and got refilled but the other were still fine. Is there a problem with my setup that not all batteries are being charged. The Blue from Negative is longer than the positive cable, there are no buzz bars, fuses, and is directly connected to the Inverter. Your input will be highly appreciated.

Thanks

Daniel

Hi Daniel

With more than two strings I would suggest you go for busbars.

The battery strings need to have the same resistance from the positive node (where the cabling gets combined) to the negative node (where the negative tails of the battery strings combine)..

 

 

To this end

  1. cables A B C and D need to be the same length. The cabling from the node to the inverter need not be the same length as that cable is common to all the strings.
  2. The interconnects (cables between the batteries) need to be the same length.
  3. The batteries need to be the same size and model (from the same manufacturer) and of a similar age.

More than 2 strings without busbars are always problematic. It can be done but somehow there are always niggling issues.Without a busbar fusing is problematic as cables A B C and D are common to more than one string of the battery bank. You could go for those post mounted fuses Energy sells.

 

DJacobs.jpg

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6 hours ago, djacobs said:

The issue I have is that only the front 4 batteries are charging and bubbling during the day. The water was empty and got refilled but the other were still fine.

Yes, you are probably overcharging the front batteries and under charging the ones at the back. 

6 hours ago, djacobs said:

Is there a problem with my setup that not all batteries are being charged.

Yes, you have a few problems that you need to sort out:

1. Get your cable lengths correct as Chris advised above. (Search "batteries" or "cable" on the forum). There are many threads where this was discussed in detail. We cannot repeat everything every 2 weeks. 

2. You need a 125 amp fuse on each string and one after combining all the strings together. The way things are going now, there is a good chance something will go wrong with your batteries and nothing to protect your inverter. You will probably blow the inverter at the same time.

This is the bare minimum you need to do before you do anything else.

 

No energy monitoring software can give you accurate battery values or statistics. You are not even aware of half your problems, because you are not measuring anything. If you want to monitor the state of your batteries and look after them, then I suggest the following:

1. Get a Victron BMV 702. The battery monitor will give you accurate battery State of Charge, Battery Voltage, Discharge and Charge Rates, etc. Everything you need.

2. To distribute the charge evenly throughout your 3 x strings, you will need at least 3 x Battery Balancers. I have the Victron, but I see a lot of guys are making use of  the HA02 with success. Once again, you can search it on the forum, many threads and info available on them. 

Unless you are comfortable guessing State of Charge on your batteries, Discharge and Charge rates, last Depth of Discharge, average Discharge Rate and don't care if you abuse the batteries or not, then it is fine, you don't need the above.

Currently you have batteries being over charged and others that are under charged and no measurement or any device to intervene and correct it. As long as you are aware that you will not get 5 to 8 years use out of your batteries. You will probably be replacing them every 12 - 18 months. Keep in mind you can't replace batteries as they fail, you replace the whole bank of batteries (all of them) at the same time.

 

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14 minutes ago, djacobs said:

Hi, installed the buzz bars today and have been monitoring batteries. Front four are still  the only batteries bubling and getting very hot. Have checked cables and all are the same length.

Can I suggest you first disconnect the 3 strings and charge each string separately with their own balancers checking the batteries regularly.  Once all strings are deemed healthy then you can reconnect them as a full bank. 

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Sounds like the one string is floating and the others have lagged behind.  the hassle is you now sit with the inverter thinking the bank is floating but the other 2 strings are behind.  Split them up as above and monitor closely.

You may need to charge each battery separately using a good 12V charger which can help revive them properly.  Still to just eskom while you do this.  Been there, done it, and its a pain ;(  (I also have 12V 102ah batts)

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45 minutes ago, Mark said:

Sounds like the one string is floating and the others have lagged behind.

I agree Mark.

If you don't have a 12 V charger, do the following:

1. As Mark suggested, disconnect 2 strings and only leave 1 string connected to the buzz bars at a time.

2. Set the charging rate to 10 amps in setting 11 and fully charge each string in turn with AC/Grid power. 

Once that is done, you might even need to consider swapping batteries around to get a mix of batteries between the strings and then reconnect all the strings together again at the buzz bars. 

3. With all 3 strings connected together, change setting 11 to 30 amps and charge them 12 hours at a time for a few days. 

This will be an endless struggle to get the batteries balanced without battery balancers. 

 

 

 

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1 hour ago, djacobs said:

Hi, installed the buzz bars today and have been monitoring batteries. Front four are still  the only batteries bubling and getting very hot. Have checked cables and all are the same length.

Something troubles me with this setup.With busbars and even cable lengths I would expect to see some normality.

Either the battery bank is way off kilter or the is something else going on which we are overlooking.

Hot batteries are cause for alarm!

My batteries are usually a degree or two above ambient temperature at the end of the day.

 

 

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37 minutes ago, Chris Hobson said:

Something troubles me with this setup.With busbars and even cable lengths I would expect to see some normality.

Yes, it does not make sense to me either that the same string still gets hot and is the only string that seems to be taking charge. 

I don't have any temperature monitoring on my batteries, but when I go past them I would just put my hand on them to try and establish if there is a change in temperature. Charging or not charging, I have never felt any difference. To me they seem to be at the same temperature all the time. 

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4 hours ago, Chris Hobson said:

Something troubles me with this setup.With busbars and even cable lengths I would expect to see some normality.

I tend to agree. You have a bad cell in that string. Take that string out and run just on the other two, if normality returns, you can go about finding the bad battery in that string.

4 hours ago, Chris Hobson said:

Hot batteries are cause for alarm!

 

4 hours ago, Don said:

Yes, it does not make sense to me either that the same string still gets hot and is the only string that seems to be taking charge. 

It does make sense if there is a bad cell or two. The resistance of that string is lower. And you likely have your maximum charge current set to 10-15% (or thereabouts) of the combined capacity of the three strings, which means that in extreme cases you could be pushing three-quarters of that current through just one string. If that is the case, then of course they are getting hot!

If you start disconnecting strings, you could try this:

1. Connect just one string to the inverter/charger (one of the seemingly good ones).

2. Using car jumper leads, connect up a second string (the other presumably good one), with an amp-meter in series. Might want to turn the max charge current to 10A or so if using a DMM, most can't handle more than that.

3. Do the same with the presumably bad string.

If I'm right, that string will measure a much higher current than the other(s).

Ideally -- no such device exists but it is something I've been contemplating -- you want a shunt in series with each string. It won't help you with balancing, but you can use it to detect an imbalance in charging.

I should really explore that idea a bit more...

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Hi,  I disconnected the front row, and it seems that the back 4 strings where fully charged. Somewhere the Axpert got confused and only focused on the front 4. It was late afternoon so I could not see what the charge reaction was and will monitor it today and feedback.

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10 minutes ago, djacobs said:

 Somewhere the Axpert got confused and only focused on the front 4. 

The Axpert cannot focus on the front 4. It "sees" the battery bank as a whole. Either there is a dead cell(s) or a wiring mismatch (which you have eliminated).. Blaming the inverter is like blaming the kid eating an orange for a worm in one of the segments.

 

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If it was me, I would test each battery separately.

Buying balancers and adding a BMV's after the event, does not solve original cause that led to the concerned question.

Find the cause, solve it, then continue forward with the balancers and BMV.

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3 hours ago, The Terrible Triplett said:

Buying balancers and adding a BMV's after the event, does not solve original cause that led to the concerned question.

I disagree. Without a BMV how do you know how many times the batteries were abused due to deep discharge cycles or overcharging due to incorrect Bulk Charging Voltage, etc. Yes, a BMV cannot repair damage that happened in the past, but probably would have prevented a lot of unwanted events. You cannot manage what you do not measure. If you look at the initial post, no buzz bars present and therefore batteries were incorrectly connected to inverter. The fact that no battery balancers were installed also contributed to the current situation. Therefore, the non existence of a BMV and battery balancers are part of the original cause of the problem. To add a BMV and battery balancers after the event is essential if you want prevent any further damage to the batteries going forward and to try and recover the batteries over time. 

 

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3 hours ago, The Terrible Triplett said:

If it was me, I would test each battery separately.

Yes, I agree, especially the string of batteries getting hot. I would take them to a battery center to have them checked out. Probably a dead cell or two among those batteries.   

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