Battery sulphated?

[monte]

Hi, I've had an issue with our batteries and wondering what the experts say. We have wet cell exide duel batteries. 6/140Ah.
They are charged by 1200W solar using a victron MPPT controller set at 14.8 abs for 12 hrs, 13.8 float 16.2 eq. These settings are in line with the manufacturers brochure.
We use around 10ah at anchor and 20Ah underway, so they cycle between 80-100% usually.
The last time in shore power was 2 months ago.
The manufacture also states SOC should be 12.44@50% 12.52@60% 12.6@70% 12.77@90%
Last overnight sail after leaving with what should have been fully charged batteries, we had a low voltage warning come on at 12V at about 2am. The batteries shouldn't be draining that fast and we should have had enough sun to be at least 90% charged when we departed, so I have checked the batteries and the voltage readings all seem ok and I had an electrician do a test with a pulse tester that showed they're ok, but the hydrometer test shows all cells sg around 1.2 +/- .015 which seems too low.
So I'm wondering the best course of action and if these tests might show that the batteries are sulphated. The batteries wee new in May 2014. Obviously the BM might be showing 100% when it's actually a bit less as we haven't been plugged in to confirm a full charge, but usually the amps in are less than the amps produced so I'm guessing the batteries aren't accepting them because they are 90% plus.
So all appears fine except the two clues of rapid voltage drop underway and low specific gravity.
Options may be to head to the marina and fully charge and then run more tests, or buy a 220v battery charger and disconnect one battery at a time and charge it and equalise it from the remaining 5 batteries via the inverter and then test.
Any thoughts much appreciated.
Cheers
Monte

[svlamorocha]

Originally Posted by monte

Hi, I've had an issue with our batteries and wondering what the experts say. We have wet cell exide duel batteries. 6/140Ah.

I suspect (based on SG) that your batteries are sulfated because of poor charging. I presume that the SG reading was taken at full charge of course.

I bet that the root cause can be corrected without spending any money. In order to confirm and correct the root cause in the best possible way that can you please provide the following info (or at least whatever you can provide now) ?

I know these are lots of questions, but the fact of the matter is that this systems are typically sold as very smart but in fact they are only as smart as the dumber of its many settings!

1. - Exact battery model (eg 4DMDC, but that is a 160 Ah model)
2. - Do you have 6 of those in parallel?
3. - What was the SG of the batteries at full charge when you bought them?
4. - Do you know what is the manufacturing date of those batteries or what is the date code marked in the case?
5. - How many controllers you have (one connected to the 6 batteries?)
6. - What is the exact model name of the solar controller (something like "BlueSolar MPPT 100/30")?
7. - Please send a photo of the controller because there is at least one model name that corresponds to to different pieces of kit.
8. - What are the dip-switch settings of the controller?
9. - How you used the Victron software to program the controller? What settings did you enter?
10. - What is the cross section and length of the cables between the solar controller and whatever they are connected going towards the battery (shunt or whatever)? What is the cross section and length of the cables between that point and the batteries?
11. - How you actually measured the voltage across battery terminals at the beginning of the absorption stage? What was it?
12. - What is the current going into one of those batteries (measured with a clamp around all the cables that go into one of the terminals) after a typical day of solar charging at 14.8V and before voltage starts to drop because the sun went down or because the controller moved to float?
13. - Are you saying that your solar controller only moves to "float" after 10 continuous hours at 14.8V? Does it actually move to float every day then?
14. - How does your battery monitory "synchronize" ie realize that batteries are 100% full? Do you do it manually (based on what criteria) or does it do it automatically (based on what settings?).
15. - What battery monitor do you have?
16. - Can you please confirm that the 1.20 SG reading was taken at full charge (or as full as you can charge them).
17. - What do you mean "We use around 10ah at anchor and 20Ah underway". What is the time period over which you add up those amp-hours? Are you referring to net amp-hours (ie consumption by loads minus charging)?
18. - If you disconnect one battery after fully charging it an dlet it rest 24 hours. What is the voltage across its terminals?
19. - Where do you get the voltage warning from? What was the voltage across the battery terminals when you got that warning?
20. - Is the main panel with the house loads (fridge, etc) connected to the LOAD terminal of the solar controller or to some point in between the BATTERY terminal of the controller and the batteries?

That was about the underlying root cause. Now let´s worry about your current batteries. If the 1.20 SG reading was taken at full charge then IMHO the best you can do is to equalize and hope you can get some of that sulphur back into solution to do its job. In my not so humble opinion it is a waste of time to try to equalize with solar directly, but if you have a good charger that can do equalization the way Exide wants it and your inverter (and 5 of the batteries) can handle it then go for it! Otherwise you may have to go to a marina. Note that equalization may not help much if the sulfation has been there for a long time.

I look forward to hearing form you.

Charlie

[monte]

Thanks Charlie, Ill answer your questions below and look forward to any feedback..

I suspect (based on SG) that your batteries are sulfated because of poor charging. I presume that the SG reading was taken at full charge of course.

I bet that the root cause can be corrected without spending any money. In order to confirm and correct the root cause in the best possible way that can you please provide the following info (or at least whatever you can provide now) ?

I know these are lots of questions, but the fact of the matter is that this systems are typically sold as very smart but in fact they are only as smart as the dumber of its many settings!
- Exact battery model (eg 4DMDC, but that is a 160 Ah model)
Exide marine multifit DUAL ER660 660Wh 140Ah 750A(EN) 12V
These batteries are dificult to find online details for. I think they may have been branded for Benetau or Lagoon but the one information sheet I have found online shows the charging parameters as set out in my original post

Absorption Charge with 14.8V - 15.0V limit for 12 to 24 hrs or when current drops below 1% of the C20 rating (example; C20=100Ahr, the low current shut off is 1%x 100 or 1A).

Float 13.5v - 13.8

- Do you have 6 of those in parallel?
YES

- What was the SG of the batteries at full charge when you bought them?
I think it was close to or above 1.25. I didnt record my initial SG readings

- Do you know what is the manufacturing date of those batteries or what is the date code marked in the case?
The code stamp says in large font - 14A and below in smaller font - 981AB406 - The boat was delivered new in May 2014

- How many controllers you have (one connected to the 6 batteries?)
One solar controller connected to all solar and batteries

- What is the exact model name of the solar controller (something like "BlueSolar MPPT 100/30")?
BlueSolar charge controller MPPT 150/85

- Please send a photo of the controller because there is at least one model name that corresponds to to different pieces of kit.
Let me know if you need this as internet is very slow here for sending photos. It should be found online fairly easily.
- What are the dip-switch settings of the controller?
It doesnt have dip switches. Set points are programed into the LED screen. My settings 14.8 abs for 12 hrs, 13.8 float 16.2 eq. Eq is set to manual rather than automatically on a set date. I have been attempting to equilize for one hour the last day or two but the highest voltage I am seeing is 15.5. I may need to try for a longer period.

- How you used the Victron software to program the controller? What settings did you enter?

As above

- What is the cross section and length of the cables between the solar controller and whatever they are connected going towards the battery (shunt or whatever)? What is the cross section and length of the cables between that point and the batteries?
I think its 7mm and approximately 6m from panels to controller. I did check at the installation and it was adequate. The controller shows amps going in on the LED display and it usually seems correct. I am currently seeing 34A going in. The battery monitor is showing me 24A going in and the difference is appliances and fridges drawing 10A. I have seen as much as 60A going in at the controller LED

- How you actually measured the voltage across battery terminals at the beginning of the absorption stage? What was it?

I have measured with a multimeter across the terminals. Its currently in Abs mode. At the battery measures 14.36
At the panel reads 14.4 on the basic panel readout, and 14.24 on the Mastervolt Easy BM which has the more detailed information and runs directly from the batteries via the Mastervolt Mastershunt

- What is the current going into one of those batteries (measured with a clamp around all the cables that go into one of the terminals) after a typical day of solar charging at 14.8V and before voltage starts to drop because the sun went down or because the controller moved to float?

I dont have a clamp on ammeter but when they are full or close to full I usually see around 10A going in at around 14.4V

- Are you saying that your solar controller only moves to "float" after 10 continuous hours at 14.8V? Does it actually move to float every day then?

Im not sure but I think it rarely moves to float at all. Its set for 14.8V for 12 hrs but thinking about it now, it usually seems to be closer to 14.4V for most of the day

- How does your battery monitory "synchronize" ie realize that batteries are 100% full? Do you do it manually (based on what criteria) or does it do it automatically (based on what settings?).

Im not sure but I believe it syncs when the amps going in reach 99% and are below a set point of around 1-2% of total bank. ie, It is currently showing 98% with 20A going in. Its showing capacity consumed as 18Ah. When the Amps drop to around 10 for an hour it might go to 100%. It has never mysteriously jumped to 100% after being tricked by the controller under certain conditions. I usually see a maximum amps in of 10-12A for at least 2 hrs before it will show 100%

- What battery monitor do you have?

Its a Mastervolt Easy montor connected to the Mastervolt mastershunt. It seems reliable and fairly accurate. I have it displaying SOC, voltage, Amps in/out, Capacity consumed and battery temp which ive only ever seen 22-24 degrees C

- Can you please confirm that the 1.20 SG reading was taken at full charge (or as full as you can charge them).

YES

- What do you mean "We use around 10ah at anchor and 20Ah underway". What is the time period over which you add up those amp-hours? Are you referring to net amp-hours (ie consumption by loads minus charging)?

Sorry for the terminology, We draw 10 Amperes constantly at anchor and 20 Amperes underay, so a total of 240Ah at anchor and 480Ah underway per day. It may be a little less than this but close enough.

- If you disconnect one battery after fully charging it an dlet it rest 24 hours. What is the voltage across its terminals?

I havent done this but I can if it helps.

- Where do you get the voltage warning from? What was the voltage across the battery terminals when you got that warning?

I get the warning on the Masterview BM. I havent checked the voltage at the terminals at that time.

- Is the main panel with the house loads (fridge, etc) connected to the LOAD terminal of the solar controller or to some point in between the BATTERY terminal of the controller and the batteries?

No I believe the solar panels go directly to the controller and then the controller goes directly to the batteries.

That was about the underlying root cause. Now let´s worry about your current batteries. If the 1.20 SG reading was taken at full charge then IMHO the best you can do is to equalize and hope you can get some of that sulphur back into solution to do its job. In my not so humble opinion it is a waste of time to try to equalize with solar directly, but if you have a good charger that can do equalization the way Exide wants it and your inverter (and 5 of the batteries) can handle it then go for it! Otherwise you may have to go to a marina. Note that equalization may not help much if the sulfation has been there for a long time.

Thanks again Charlie. I am wondering about a couple of things now. The Abs stage is set to 14.8V, but as I said it rarely seems to reach or stay at 14.8V
And also the Eq stage hasnt gone over 15.5V when it should be reaching 16.2. Its 1pm and the BM is showing 99%, 14.48V 20A going in, 13Ah consumed. The solar controller is showing 25A in, which seems a bit low considering its full sun now and theres no shading.
I just checked on the controller and its showing Pv current 8A, Pv Voltage 33V, Pv Power 270W. Thats in full sun, so it would appear the input it much lower than it should be. The panels are 4x 280W. Im assuming the readings shown on the controller are actual readings and not the readings after the controller has reduced the amounts for the battery to accept...
OK that was strange/confusing. I just boiled the kettle to draw some amps and noticed the Amps in on the panels rose to 55A and now dropped back down to 12 again on the solar controller so I guess the reading is actually the controller output and not the solar panel output...

[svlamorocha]

Your batteries are shot. There are a few things to correct in your charging but before we get to that we need to know if your present arrangement adds to the damage or the damage comes from the past.

You need to measure the "rested open circuit voltage" of the batteries starting at the "most charged" time in your daily cycle (probably afternoon if you are on 100% solar). Disconnect one or a few batteries completely from each other and from the boat and let them sit for 24 hours. Then measure voltage across terminals with a good multimeter (Fluke brand or another brand of digital multimeter that has been checked against a Fluke multimeter) and report back. When you measure voltage also measure SG for each cell.


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[ullar]

Thanks you guys for a detailed case study. Very interesting reading.

1200W of solar sounds like a dream come true for many of us. World all in flowers Where lies the problem then? I would suspect the solar controller is either faulty or just plain bad design. You have all that power available and it's still not even able to put out required equalizing voltage.

Another thought, if you are going to buy new set of batteries why not to go for real deep cycle ones instead of dual purpose you are using now? Never understood how those cranking batteries find their way into house banks.

Keep us posted

[svlamorocha]

" Its 1pm and the BM is showing 99%, 14.48V 20A going in, 13Ah consumed. The solar controller is showing 25A in, which seems a bit low considering its full sun now and theres no shading.
I just checked on the controller and its showing Pv current 8A, Pv Voltage 33V, Pv Power 270W. Thats in full sun, so it would appear the input it much lower than it should be. The panels are 4x 280W. Im assuming the readings shown on the controller are actual readings and not the readings after the controller has reduced the amounts for the battery to accept...
OK that was strange/confusing. I just boiled the kettle to draw some amps and noticed the Amps in on the panels rose to 55A and now dropped back down to 12 again on the solar controller so I guess the reading is actually the controller output and not the solar panel output..."

I get the impression that it is possible that you don't completeley understand how an MPPT controller works (vs a cheap "load dump" setup). One more reason to get a good DC clamp and get "guaranteed real" readings that do not depend on voltage drop or the undestanding or wiring being correct.



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[Screefer]

Some random thoughts on this string:


- most or all battery monitors require frequent recalibration to maintain accuracy WRT whether a battery is low or full. Voltage & current readings are usually fine. Possible exception MIGHT be the Balmar BM. I haven't tested it myself;


- check with the battery manufacturer to see if that exact type of battery can withstand an EQ;


- 15.5vdc is an average EQ voltage setting;


- rule of thumb is a full battery (flooded) at rest is 12.6vdc and a fully discharged battery at rest is 10.5vdc;


- 10a of load will induce a voltage drop causing the solar controller to "think" a bank is lower than it is. Try reducing the bulk charge voltage to 14.4 (an average bulk charge level) and see if the controller drops into absorb sooner than previously experienced;


- if after a proper dockside EQ (or two but no more) the SG does not come back up then the batts need replacing. Go with proper deep cycle batts flooded, AGM or Gel. BUT make very sure that there's no EQ set if cealed batts installed; and


- ANY shadow at all, a line, a corner, a vague darker spot etc WILL remove nearly all that panel from electrical production.


Hope some of this helps.

Cheers

[CharlieJ]

Monte-
A few big picture thoughts:
1.

Exide marine multifit DUAL ER660 660Wh 140Ah 750A(EN) 12V

These are not deep cycle batteries, no matter what the label says and you have them in a purely deep cycle application. They will not provide a service life even close to the published life.
2. With 6 x 140Ahr batteries in parallel, you have 840Ahr available.
3. Using the 50% rule, of the 840Ahr available, you have 420Ahr that are useable.
4. Understanding that most cruisers do not fully charge the batteries on a regular basis because of the extended time that it takes to replace the last 15% of capacity (adsorbtion stage), your operating envelope is between 50% SOC and 85% SOC.
5. These system design constraints mean that you have a true 294Ahr available between charging cycles.
6. With the daily load of 240Ahr at anchor and 480Ahr, and based on the above, your bank is undersized.
7. At 34A and 6m from the panel to the MPPT, your 7mm conductors are undersized. To achieve <3% voltage drop (recommended) the conductors should be 19mm (AWG 4).
8. If by "pulse tester", you mean a Midtronics battery capacitance tester, or similar, understand that that type of tester tests for cranking amps, not amp-hour capacity. Generally, if the batteries are still showing >90% cranking amp capacity, then the amp-hr capacity is not too degraded.

The bottom line:
1. The batteries are not the correct type. They should be deep cycle; e.g., golf cart batteries.
2. The bank is sulfated from chronic undercharging. Equalizing may recover some of the capacity. Note that proper equalizing is not a set and forget operation. You terminate after all the cells' SG have stabilized and have not changed for ½ hr. With a your bank, equalization could take as much as 8 to 10 hours.
3. The conductors from the panels to the controller are undersized.

Hope this helps.

[Screefer]

Charlie,

Excellent summation. I think you have perfectly identified the complete issue.

JD

[darylat8750]

sorry, double post

[darylat8750]

If you are still in the Southern part of the U.S. Sam's club has very good 6 volt golf cart batteries. Six of the Duracel GC2 at about $84 each should fit in the space you have and give you about 630 amps. I'm of the 30% usable school of thought. (The top 20% goes in very slowly and I don't want to go below 50%) so this would give you 645 amps at 12 volt. If you have the hight available for the Group size 230 you would have more capacity for more $$$. When mine need replacing I will go with the Duracell GC2. These are not available in all states but most of the southern states have them.

Duracell® Golf Car Battery - Group Size GC2 - Sam's Club

Golf Cart Batteries - Sam's Club

[monte]

Thanks guys. Slow internet here so I haven't had a chance to respond but will as soon as possible. Thanks a lot for the details and I will double check the solar able size as well

[svlamorocha]

Originally Posted by monte

- What is the cross section and length of the cables between the solar controller and whatever they are connected going towards the battery (shunt or whatever)? What is the cross section and length of the cables between that point and the batteries?
I think its 7mm and approximately 6m from panels to controller. I did check at the installation and it was adequate. The controller shows amps going in on the LED display and it usually seems correct.

ISn´t this boat equippeCross-section of European (metric) wiring is measured in square milimeters, not milimeters. There is no "7 square milimeter" size anyway; it jumps from 6 to 10. We are looking for a number that follows the characters "AWG" or a number that preceeds the characters "mm2". We need the cross-section of those wires to estimate voltage drop because you lead us to believe that there are no dedicated voltage sensing wires.

Most importantly, at this time we don´t care that much about the wires between panels and controller (which only affect efficiency); we care the most about the wires from controller to batteries (where each 0.1V of drop is 0.1V of undercharging).

[monte]

I see the controller to batteries is 25mm2 and approximately 9mm diameter. The run is approximately 1.5m
The controller to panels, I can't see a size on the wire but it is approximately 7mm diameter. The run is approximately 6m

[ullar]

Originally Posted by monte

I see the controller to batteries is 25mm2 and approximately 9mm diameter. The run is approximately 1.5m

Looks like a decent installation. I assume 9 mm is the diameter with insulation. Otherwise it would be more like a starter cable already (more than 50mm2).