Easterdown Equalisation Question

[Tinbum]

So it's all about the bubbles?

No, the bubbles mix the electrolyte up which is great but the equalise is to balance the cells and remove the sulfation.

[V]

Thanks for this reply. I have cells in parallel too and you've reminded me that this is what SMA were most worried about. But I'm still inclined to think I should reduce the time and not overcharge for 12 hours. And isn't sulfation supposed to be caused by leaving the batteries in a deeply discharged state? ie. undercharging?

The SI does a Full charge (either with sunlight or asks for the Generator) every 14 days. That's 6 hours of overcharging. SI does a Boost charge approximately every week, this is two hours of overcharging. What I don't know is whether anything special/different happens during the SI Equalization charge, anything other than x hour(s) of overcharging.

Am I right to think that everyone so far is saying that an Equalization charge is x hour(s) of overcharging?

Thanks,

V

[Tinbum]

I'm in the process of changing over to 24no 2v cells which will give me the same capacity as I already had, but with nothing in parallel. I think possibly one mistake I made was to do the equalise with the cells paralleled up. I should have done one string at a time. This would ensure the equalise was at the maximum set voltage not just at the maximum voltage that could be applied for the current available. The Morningstar can be set for say 64v (temp compensated) equalise but it actually counts equalise time as any time when the voltage is above what would be the absorption set voltage.

For the equalise time I think its a case of educated trial and error. In the winter its likely to be longer than in the summer due to the heavier discharges.

I would try a set time depending on battery type and size and measure SG for each cell. Personally I would think a longer equalise will do no harm as long as you keep the water topped up and make sure the batteries don't overheat.     

[biff]

Yes V,
        An equalizing charge is nothing more than a forced overcharge,
                                               Biff

[going green]

this has given me a prompt to do mine tomorrow desulfator charge when they are full  

[V]

Thank you all so much for the replies.
 

I'm in the process of changing over to 24no 2v cells which will give me the same capacity as I already had, but with nothing in parallel. I think possibly one mistake I made was to do the equalise with the cells paralleled up. I should have done one string at a time.

According to SMA, the SI is trying to educate itself about our batteries,(like me!) and it bases the frequency of Boost charges on its logs so I probably shouldn't try to alternate the configuration of the battery, not that it is even remotely within my skill to do so! Also I think that Paul Byrne would have alerted me if the parallel configuration of forklifts was considered bad/unusual or required special charging treatment. But I won't forget to ask Eternity about this tomorrow. Maybe parallel'ness' has an impact on the length of the Equalisation charge? Just curious, how long did you have those batteries for? 

Thanks Biff. I probably now need to find out if the SI does some fancy voltage checking while it does the EQ charge, but I can't really see how it could. Only thing I reckon it can do is keep track of temperature and act accordingly.

And Going Green, how long will you overcharge for?

Thanks

V.

[heatherhopper]

V

Although my batteries are Rolls and you do need to check with the manufacturers with regard to the charge settings for your specific battery make here is my operating method with the SI off-grid. Experience gained with progressive combinations of - generator only, generator/PV and generator/PV/wind. This is a 24v system but the principles should be the same.

Float setting - 2.26
Boost setting - 2.55
Full charge and Equalisation setting - 2.55

The SI will usually Boost charge around every 24 hours for 1.5 hours. The SI trigger for this is either nominal throughput or SOC below 70%. SOC at the end of Boost is entirely dependent on starting SOC. When PV and/or Wind is in excess of demand the periods between Boost increase correspondingly. I imagine every system will behave a bit differently according to the attached generation and usage - we effectively use ours as a buffer most of the time.

I have used the SI Full and Equalisation defaults of 5 and 10 hours every 14 and 180 days (and some variations on those defaults) but now operate both of these charges manually as required. Although the defaults worked fine I find that it is more convenient (and efficient) to activate these charges for periods of excess renewable generation manually - something auto cycles can not be guaranteed to achieve. Currently I rarely use Full charge and usually activate an Equalisation every 4-6 weeks. I did find that it is beneficial to have summer and winter settings if using auto activation with shorter cycle periods during the winter mainly to compensate for the reduced capacity of the battteries with temperature change.

When the SI is not in Boost, Full or Equalisation mode it is obviously in Float. The voltage setting I use is as high as I can get it to operate before gassing starts.

I think that the various terminologies used for battery charging can be a little misleading. Essentially SMA Boost, Full and Equalisation are all combined, sequential  Bulk and Absorption phases just with different triggers and durations. I have heard Boost charge referred to as "passive equalisation".

The SI SOC number is a complex mixture of voltage and throughput calculation and at least the SOE also needs to be referenced if using it as a benchmark when assessing the charging performance.

My batteries are now well into their fourth year and showing no obvious signs of reduced performance although there must be some. I trust the general SI charging regime but it does need to be set up for each specific system.

[V]

V

Although my batteries are Rolls and you do need to check with the manufacturers with regard to the charge settings for your specific battery make here is my operating method with the SI off-grid. Experience gained with progressive combinations of - generator only, generator/PV and generator/PV/wind. This is a 24v system but the principles should be the same.

Float setting - 2.26
Boost setting - 2.55
Full charge and Equalisation setting - 2.55

The SI will usually Boost charge around every 24 hours for 1.5 hours. The SI trigger for this is either nominal throughput or SOC below 70%. SOC at the end of Boost is entirely dependent on starting SOC. When PV and/or Wind is in excess of demand the periods between Boost increase correspondingly. I imagine every system will behave a bit differently according to the attached generation and usage - we effectively use ours as a buffer most of the time.

Yes, this is how the Boost seems to work for me too. Only the frequency is different but consistent with the SOC you are talking about.

I have used the SI Full and Equalisation defaults of 5 and 10 hours every 14 and 180 days (and some variations on those defaults) but now operate both of these charges manually as required. Although the defaults worked fine I find that it is more convenient (and efficient) to activate these charges for periods of excess renewable generation manually - something auto cycles can not be guaranteed to achieve. Currently I rarely use Full charge and usually activate an Equalisation every 4-6 weeks. I did find that it is beneficial to have summer and winter settings if using auto activation with shorter cycle periods during the winter mainly to compensate for the reduced capacity of the battteries with temperature change.

My version of the SI doesn't give me an option to manually do the full or boost charges, only the EQ. But the SI asked for the Boost two days ago and I knew it would be sunny today so I waited and it worked well. I could do the same with the full charge and give it some generator time in the evening to get the starting SOC higher.

When the SI is not in Boost, Full or Equalisation mode it is obviously in Float. The voltage setting I use is as high as I can get it to operate before gassing starts.

Once my PV was in I did similar - I increased the float to 2.33 per cell and found that the batteries were gassing every day. I decreased it back to 2.25 which was recommended by Paul Byrne who supplied my batteries and by SMA. Just for info, Paul is not the installer, nor is he anything to do with the problems I had of incorrect settings. He has been fantastic and hugely helpful. A knowledgable person who has no problem saying 'I don't know' if he doesn't know the answer.

I think that the various terminologies used for battery charging can be a little misleading. Essentially SMA Boost, Full and Equalisation are all combined, sequential  Bulk and Absorption phases just with different triggers and durations. I have heard Boost charge referred to as "passive equalisation".

Understood. Thanks. Except for the phrase Passive Equalisation !

The SI SOC number is a complex mixture of voltage and throughput calculation and at least the SOE also needs to be referenced if using it as a benchmark when assessing the charging performance.

Sorry to be so naive, but SOE? I know about SOC and SOH, but E? Is that equalisation?

My batteries are now well into their fourth year and showing no obvious signs of reduced performance although there must be some. I trust the general SI charging regime but it does need to be set up for each specific system.

Do you do the SG measurements on them or Multimeter, or both?

Thank you so much for all of this detail.

V.

[Tinbum]

Maybe parallel'ness' has an impact on the length of the Equalisation charge? Just curious, how long did you have those batteries for? 

I wouldn't have thought so and would expect it to be dependant on the max the output of the chargers, capacity of the battery bank, the charge state of the batteries and how sulphated the batteries are. I think the biggest problem with parallel strings is making sure each string is supplying exactly the same power and receiving the same charge. I have done interconnections before in mid string between the strings.

The batteries are only about 2 years old now. It was purely initial expense and I found the bank too small that resulted in me expanding to 3 strings in parallel. There was only a few months between purchasing string 1 and  3 and with hindsight I should have just taken the plunge initially with one large string but its a learning thing!!  

[heatherhopper]

V

Boost frequency will depend on a few things but I expect your larger battery bank means you will see a less frequent trigger - ours is a bit on the modest side. Because all our generation is AC coupled and we use the battery bank as a "buffer" or "float" against quite large demand/generation swings (our dump system is a bit crude) the SI sees quite considerable throughput activity, this will also increase Boost frequency.

I don't manually activate Boost. You should be able to manually "defer" or "activate" the Full and Equalisation charges by simply changing the frequency cycle number as required. If it is cloudy today but forecast sunny tomorrow set the cycle to complete tomorrow. You can deactivate auto cycling of both Full and equalisation and just activate Equalisation manually as required (serves the same purpose as Full charge - just do it a bit more frequently and for a shorter period, I found 5 hours more than enough).

2.25 for float sounds fine.

I think "passive equalisation" means just that - equalisation characteristics but not intended to complete that function.

SOE - State Of Error. This is the SI's own assessment of it's own error margin when calculating the SOC. The SI recalculates the voltage element of the SOC periodically and in between the error margin of the SOC can be quite high - so 90% may not actually be 90%. I think this is how it works anyway. Compact meter view gives the best representation of this number.

I used to check the batteries state religously including SG and voltage measurement. I do this rather less frequently now. After much research it became quite apparent that unless done under very comprehensive controlled conditions it is a little pointless and potentially misleading. All methods are less than reliable although still worth doing periodically to flag up any cell anomalies in particular. In an off-grid situation like ours the opportunity to contrive a controlled position is rare.

[V]

I wouldn't have thought so and would expect it to be dependant on the max the output of the chargers, capacity of the battery bank, the charge state of the batteries and how sulphated the batteries are.
...
The batteries are only about 2 years old now.
... its a learning thing!!  

Thanks for this. Output of chargers - that's another discussion. It IS a learning thing! Sorry to hear you've had some bad luck with your batteries but unlike me, you have the skill to solve your problems!

I don't manually activate Boost. You should be able to manually "defer" or "activate" the Full and Equalisation charges by simply changing the frequency cycle number as required. If it is cloudy today but forecast sunny tomorrow set the cycle to complete tomorrow. You can deactivate auto cycling of both Full and equalisation and just activate Equalisation manually as required (serves the same purpose as Full charge - just do it a bit more frequently and for a shorter period, I found 5 hours more than enough).

Thanks Heatherhopper, I didn't know about deactivating auto cycling, only the manual Equalisation which I intend to do at the end of this week. Sods law that SI has scheduled it for the first day since we moved in where nobody will be at Easterdown! Still trying to work out the frequency of this overcharge, and 5 hours was my thinking for duration, based on recent experience.

SOE - State Of Error. This is the SI's own assessment of it's own error margin when calculating the SOC. The SI recalculates the voltage element of the SOC periodically and in between the error margin of the SOC can be quite high - so 90% may not actually be 90%. I think this is how it works anyway. Compact meter view gives the best representation of this number.

Oh yes! I'd forgotton about SOE, which was the parameter that first got my alarm bells going about my installer. In May it was 22% for Estimated error of voltage calibrated state and 7% for Estimated error of full charge calibrated SOC. The two values are now 7% and 4% respectively. When I told SMA that I tended to stay at 97%SOC and struggled to get to 100%, they told me that I could regard 97% as 100% because the calibration works just as you say.

I used to check the batteries state religously including SG and voltage measurement. I do this rather less frequently now. After much research it became quite apparent that unless done under very comprehensive controlled conditions it is a little pointless and potentially misleading. All methods are less than reliable although still worth doing periodically to flag up any cell anomalies in particular. In an off-grid situation like ours the opportunity to contrive a controlled position is rare.

Thanks so much for talking about this, I read that you need to measure the SG just as the equalisation charge has finished. The prospect of extracting hot, bubbling acid from the batteries doesn't have great appeal for me, nor the idea of taking them off load in order to test and retest and compare. I wasn't sure how or if I could do this anyway. But I'm now thinking I should get the volt meter out.