Surrette Batteries power British Isles

waynefromnscanada · February 2013

Since 2008, the Isle of Eigg and the Isle of Rum, small islands with fewer than 100 residents, have been using Surrette Battery Co. Ltd.’s Rolls line of deep-cycle lead-acid batteries for off-grid power generation.
A similar project on the nearby Isle of Muck is scheduled to be completed in April.
http://www.thechronicleherald.ca/business/718574-ns-batteries-help-power-scottish-isles

victoradjei · February 2013

Re: Surrette Batteries power British Isles

Would be nice to see some details/shots. Would this be based on a central "mains" or smaller power stations?

PS. My signature will come up this evening:cool:

stephendv · February 2013

Re: Surrette Batteries power British Isles

There are more technical details about the projects here: http://www.windandsun.co.uk/case-studies/islands/isle-of-eigg.aspx
and here: http://www.windandsun.co.uk/case-studies/islands/isle-of-rum.aspx

waynefromnscanada · February 2013

Re: Surrette Batteries power British Isles

Very interesting links Stephendv.
One of the very interesting things I noticed was the graph of battery state of charge, indicating the max day to day high SOC was limited to 80% max!
If this comparatively huge system normally cycles it's batteries between 60% low and 80% high - - - - is there a need to charge our own batteries past 80% SOC if we normally don't take them below 60% and bring them back to 80% daily or almost every day? Is there some advantage to not taking them to 100% other than in preparation for EQ when it's needed?
What do these folks know that we don't? My thought train is years of battery life, not the efficiency loss in getting them up those final few % points.

stephendv · February 2013

Re: Surrette Batteries power British Isles

waynefromnscanada wrote: »

One of the very interesting things I noticed was the graph of battery state of charge, indicating the max day to day high SOC was limited to 80% max!

This may be because of the Sunny Islands charge management system, in a nutshell:
- If SoC is more than 70%, then skip bulk and absorb and go straight to float for the whole day
- If it's been floating for 3-4 days straight, or the SoC is below 70% then do a "Boost" charge, usually bulk + a shortish absorb, the idea being to bring the battery up to 90% ish SoC.
- Every X days do a "Full" charge which has it's own set of parameters to bring the battery to 100% SoC.

They say that they've chosen this method to reduce corrosion of the positive grid due to overcharging. Since Boost and Full can have their own independent voltages and times you could for example, set to Boost at 2.5V for 2 hours to encourage some gassing, then do a Full charge at 2.4V for 6 hours, every 20 days or so.

The other reference to this type of charging strategy is from the guys at Victron: http://www.victronenergy.com/upload/documents/ElectricityonBoard_rev8_july2004.pdf where they mention that it's not necessary to reach 100% SoC every day, but instead once a month is enough.
However, there's no mention of what is a good minimum SoC to reach at teh end of every day to prevent sulfation... 80%? 90%?

waynefromnscanada · February 2013

Re: Surrette Batteries power British Isles

Very interesting. Thanks for that Stephendv. I'll have to study that more, as it could well apply to my situation.

westbranch · February 2013

Re: Surrette Batteries power British Isles

Stephendv, I think the answer to your final question lies on lines 2 & 3 of your post,

If SoC is more than 70%, then skip bulk and absorb and go straight to float for the whole day

If it's been floating for 3-4 days straight, or the SoC is below 70% then do a "Boost" charge,

from what I read here 70% is the point below which Sulphation is imminent, above it you are OK except if you have been floating a long time then it needs a quick kick to remove any light sulphation..

I'll be digging into that Victron doc, looks very complete, thanks for the link.

NorthGuy · February 2013

Re: Surrette Batteries power British Isles

westbranch wrote: »

If SoC is more than 70%, then skip bulk and absorb and go straight to float for the whole day
If it's been floating for 3-4 days straight, or the SoC is below 70% then do a "Boost" charge,

from what I read here 70% is the point below which Sulphation is imminent, above it you are OK except if you have been floating a long time then it needs a quick kick to remove any light sulphation.

I see it a little bit differently:

stephendv wrote: »

If SoC is more than 70%, then skip bulk and absorb and go straight to float for the whole day.

If your discharge was low (above 70% SOC) then the electrolyte is not seriously stratified, so keep voltages low to avoid bubbling

stephendv wrote: »

If it's been floating for 3-4 days straight, or the SoC is below 70% then do a "Boost" charge, usually bulk + a shortish absorb, the idea being to bring the battery up to 90% ish SoC.

If you discharged below 70% or have been cycling fo a while without mixing the electrolyte, then electrolyte stratification may be bad enough. Go to higher voltages and induce some bubbling to mix things up.

stephendv wrote: »

Every X days do a "Full" charge which has it's own set of parameters to bring the battery to 100% SoC.

Do periodic full charges to eliminate sulphation.

niel · February 2013

Re: Surrette Batteries power British Isles

to give this a name, this is deficit charging. the float charge will only keep the 70% soc from going lower due to self discharge. rushing through an absorb charge does also stop the batteries from being completely recharged when giving the periodic boost charge. sulfation is the result of this and just because many british isles are doing this does not mean that it has rolls/surrettes' blessing on it. imo they are causing more harm than they are possibly preventing.

waynefromnscanada · February 2013

Re: Surrette Batteries power British Isles

Thanks Niel, your post makes sense and agrees with all I've learned, or thought I'd learned over the years.

stephendv · February 2013

Re: Surrette Batteries power British Isles

niel wrote: »

to give this a name, this is deficit charging. the float charge will only keep the 70% soc from going lower due to self discharge.

Applying a float charge when the battery is at 70% SoC will charge it ok, just not as fast as a higher voltage charge. I've seen mine pull 20A on a float charge (900Ah battery).

niel wrote: »

rushing through an absorb charge does also stop the batteries from being completely recharged when giving the periodic boost charge. sulfation is the result of this

Yeah, agree that sulfation would be the result eventually and only if you didn't also do a periodic full charge.

niel wrote: »

and just because many british isles are doing this does not mean that it has rolls/surrettes' blessing on it. imo they are causing more harm than they are possibly preventing.

It's not the isles that are doing this, this is how the sunny island charges. Although it's up to you which voltages and times you use for Boost and how often and at what voltages you use for Full charge. But one parameter you can't change is when it decides to do the float charge, it chooses to go straight to float some days and there's no parameter to disable that. Personally, I trust that SMA did their homework on this feature.

NorthGuy · February 2013

Re: Surrette Batteries power British Isles

stephendv wrote: »

It's not the isles that are doing this, this is how the sunny island charges.

Ah. That's what it is. I was going through Web pages for the Isles trying to find descriptions of these charge methods ...

Do you have a link to a document that would discuss these?

westbranch · February 2013

Re: Surrette Batteries power British Isles

those batteries are a bit bigger than we usually see

"48V 2242 Ah (C10) battery bank consisting of 24 Rolls Solar RB 4KS25PS batteries" from the Eigg site

but Rolls says CAPACITY AT THE 20 HOUR RATE (1.265 SP. GR.) 1350Ah 67.5a
CAPACITY AT THE 10 HOUR RATE (1.265 SP. GR.) 1121Ah 112.1a

looks like the Eiggers has a bit of 'egg on their face'... looks like they doubled the rating

NorthGuy · February 2013

Re: Surrette Batteries power British Isles

westbranch wrote: »

those batteries are a bit bigger than we usually se

"48V 2242 Ah (C10) battery bank consisting of 24 Rolls Solar RB 4KS25PS batteries" from the Eigg site

but Rolls says CAPACITY AT THE 20 HOUR RATE (1.265 SP. GR.) 1350Ah 67.5a
CAPACITY AT THE 10 HOUR RATE (1.265 SP. GR.) 1121Ah 112.1a

looks like Eiggers has a bit of 'egg on their face'... looks like they doubled the rating

I think it's just two parallel strings

inetdog · February 2013

Re: Surrette Batteries power British Isles

NorthGuy wrote: »

I think it's just two parallel strings

Since these are four volt batteries and they are using 24 of them to make a 48 volt system, that does seem to fit. :-)

Vic · February 2013

Re: Surrette Batteries power British Isles

AND, the ACTUAL 20 Hr Capacity at the ACTUAL SG of the electrolyte that is almost always shipped in these Surrette batteries (1.265) is 5% less than the 1350 AH speced if it had 1.280 SG. So about 1280 AH (1282.5 AH nom.) Surrette and most other manufacturers are always in a Specmanship game -- "mine IS larger than yours"! FWIW.

Yea, NG assumed that it was two strings. Vic

westbranch · February 2013

Re: Surrette Batteries power British Isles

Right, I looked at that small pic , saw there were 24 in a row but did not see that there were 2 wires per 2 cell battery, each side is 1/2 of the 2 parallel 48v strings. simple...

Blackcherry04 · February 2013

Re: Surrette Batteries power British Isles

Wow, I guess there is no other Charge regimen besides the 3 Stage + Equalization. All of this started with Heart Interface, Trace, Xantrex and their off spring, OutBack and Magnum that were originally designed for Grid/Generator. All the Inverters and Chargers and Charge Controllers they have Manufactured followed the same mindset since the late 80's-90's and into the Solar Market. There are other charging profiles that work and RE is just a small segment of the Battery storage market. I for one am looking forward to seeing some options in equipment in the future and something the Battery Manufacturers understand and Solar will work with.

Vic · February 2013

Re: Surrette Batteries power British Isles

Hi Bc..04,

sthephandv has been doing some interesting things with small Microcomputers, as have others. He would be the best person to give an overview, there are some Threads on this topic here, and some on the MidNite Forum. Will try to pull some more together -- this ia a derailment of this Thread for sure, but to get you going, if you have not seen this:

http://midnitesolar.com/smf_forum/index.php?topic=967.0

EDIT: Here is a Thread on this Forum, where stephendv discusses more about managing data and controlling a Classic CC, see post#12:
http://forum.solar-electric.com/showthread.php?18380-Fun-and-games-with-industrial-control-software

EDIT#2: Another Thread from the MidNite Forum is any are interested:
http://midnitesolar.com/smf_forum/index.php?topic=721.msg4707#msg4707

if any US company did enhance the range of CC charge profiles, would bet that it would be MidNite. Although, it is possible that this range of extended charging function would really belong in a Battery Monitor/Controller, or an accessory controller of some kind. There are limits on what functions can/should be built into CCs. It requires a lot of Engineering time to code and test the extended functions, AND supporting customer's questions/issues with these functions might be very costly, and so on.

Will try to find some Threads here, but stephan is one of the hot-shots on this ... I am definitely NOT. Vic

stephendv · February 2013

Re: Surrette Batteries power British Isles

I can't find the SMA doc that describes their charge management system... seems they re-arranged the website and lost it. I think they discuss it very briefly in the user manual though.
There's another new MPPT controller available this side of the pond that has some interesting features (http://www.studer-inno.com/?cat=mppt_solar_charge_controller&id=2094&tab=2) , but it's still predominantly based on the old faithful bulk-absorb-float routine, the interesting things they've added are:

- A separate end amps value can finish EQ
- A separate current limit value only for EQ
- Choose to EQ before or after absorb (This would be very handy to mimic an IUIa curve that some batteries seem to like)
- Skip bulk-absorb and go straight to float if the battery doesn't go below a preset voltage level for a preset time.

NorthGuy · February 2013

Re: Surrette Batteries power British Isles

stephendv wrote: »

There's another new MPPT controller available this side of the pond that has some interesting features.

Looked at their manual. Thy offer these settings, but they don't discuss pros and cons of the settings you can choose.

stephendv wrote: »

Choose to EQ before or after absorb

Xantrex has a similar setting, but only before absorption. They call it "boost charge". You set a voltage and they keep it for the first hour of absorption, then drop down to regular voltage. They say this is good against sulphation and stratification.

As to real equalization, Xantrex only allow to do it manually, and only after absorption is done. Trojan also says in all their manuals that absorption must be complete before you equalize.

They all swear that if you don't follow their ruls, your batteries will die. But this all lacks explanations. Very little studies are done on charging methods.

Blackcherry04 · February 2013

Re: Surrette Batteries power British Isles

NorthGuy wrote: »

Xantrex has a similar setting, but only before absorption. They call it "boost charge". You set a voltage and they keep it for the first hour of absorption, then drop down to regular voltage. They say this is good against sulphation and stratification.

As to real equalization, Xantrex only allow to do it manually, and only after absorption is done. Trojan also says in all their manuals that absorption must be complete before you equalize.

They all swear that if you don't follow their ruls, your batteries will die. But this all lacks explanations. Very little studies are done on charging methods.

My guess would be after years of dealing with them and the ones they came from that they never found a way to deal with varying Amp hour capacity of battery banks. Their minimum use to be 400 Amp hrs and 1900 amps maximum for the bank settings, of course back then they only made 12 V and later 24 V inverters. So to start them all equal, they run a full charge and then a Equalize charge for a hour. The boost just seems to be a variation of a 3 stage charge.

A lot of people must like it, I see it posted as " Rule of Thumb " in here all the time.

Cariboocoot · February 2013

Re: Surrette Batteries power British Isles

Batteries rarely drop dead suddenly no matter what you do to them. It's a matter of trying to extend their life as much as possible.

I really do not think battery manufacturers have caught up with the way solar functions and they are still just pushing what they've got as being suitable for RE. By the same token, the charging ability of controllers are not entirely suitable for the batteries that are available.

So yes, we use rules-of-thumb to try and short-cut to a balanced system and most of the time they work. Just not always.

Blackcherry04 · February 2013

Re: Surrette Batteries power British Isles

Cariboocoot wrote: »

Batteries rarely drop dead suddenly no matter what you do to them. It's a matter of trying to extend their life as much as possible.

I really do not think battery manufacturers have caught up with the way solar functions and they are still just pushing what they've got as being suitable for RE. By the same token, the charging ability of controllers are not entirely suitable for the batteries that are available.

So yes, we use rules-of-thumb to try and short-cut to a balanced system and most of the time they work. Just not always.

I think you guys do a great job of working with the variables in helping people. My comment was about the Topic of Equalization and where a Full charge was necessary before doing equalization and where it came from . My opinion is a battery does not care if it's 12.5 V and you put in 15.5 volts and go to Equalization or if you give it 14.5v for 2-4 hours and let it get hot, then a hour of Equalization at 15.5 v. The results of if it's working is in the SG's, if they are not rising, either way your wasting your time.

Cariboocoot · February 2013

Re: Surrette Batteries power British Isles

Blackcherry04 wrote: »

I think you guys do a great job of working with the variables in helping people. My comment was about the Topic of Equalization and where a Full charge was necessary before doing equalization and where it came from . My opinion is a battery does not care if it's 12.5 V and you put in 15.5 volts and go to Equalization or if you give it 14.5v for 2-4 hours and let it get hot, then a hour of Equalization at 15.5 v. The results of if it's working is in the SG's, if they are not rising, either way your wasting your time.

Well, not quite. Since EQ is done at a high Voltage than Absorb the batteries have to be brought up through Absorb anyway, and whether they spend 2 hours at Absorb Voltage or 2 hours at EQ Voltage the result is the same.

The point is that if they are fully charged at the normal Absorb Voltage that is less time spent at the higher EQ Voltage and so less stress on the battery.

Batteries that are fully charged with proper V and T for Absorb tend not to need EQ as often, or even ever. Trouble is most of the time the target Voltage for Absorb is set too low (by manufacturers who don't seem to understand the process) and the Absorb time is a bit of a guessing game, even if End Amps is used.

Frankly, none of us follow the prescribed EQ method because it's impractical for a system in use. Charging instructions are written for batteries that are not in service at the time, which is useless for RE. How many actually shut their system down to recharge and EQ if needed? Not very practical is it? So we have to try and "adopt, adapt, and improve" to get a regime that will work "on the fly".

Frustrating as all get-out.

Surrette Batteries power British Isles

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