# Automatic Battery Bank switching?



## mightybooboo (Feb 10, 2004)

Here's the question.

Lets say you have 2 individual solar setups,each powering its own Bank of 24v configured batteries.1 set 440/ah and the other 800/ah battery bank.To a trace DR2424 inverter.

I can see where you could manually switch between which bank powers the inverter,but does an automatic switch for this exist? Links? Experience?


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## wind power (Sep 29, 2010)

Hi Mighty,
I know someone who is using a relay and a 55 dollar coleman air controller to do just that, he juggles his wind turbine from 24 -12 volt banks.
He has a buss setup which has 12 volts positive and negative buss bars coming from his batteries...he then makes jumpers at the buss for what ever voltage he needs.
He clamis it equalizes the batteries much better when in use...amps are not being drained off the end batteries while the middle portion of batteries are darined much less...in a long series/parallel run. 

Anyway, here is his video:
[ame]http://www.youtube.com/user/DairylandWindpower?feature=mhum#p/a/u/0/sQS7HrfJiD8[/ame]

I know the guy hes a pretty smart cookie...you could essentially do the same thing with battery banks of the same voltage


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## mightybooboo (Feb 10, 2004)

So he is juggling which bank gets charged? I want to juggle which of the 2 separate systems will send power from its battery bank to the inverter.1 system is lead acid,the other is AGM.

Ie,bank one hits 25.2 volts or something it will switch inverter to the other charged up bank.By itself. Of course it can be done manually with a battery switch,but we want to set it up so when gone for 2 weeks,poor sun or snow,whatever.... if one gets low the other will power the house and freezer,refer,etc.


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## wind power (Sep 29, 2010)

OK Mighty,
I see what you are saying...sorry about that!
Ok, So you essentially need a low voltage dump...something that will switch off one battery bank and switch on another one.
The only think I could think of would be 2 Ghurd controllers setup for low voltage dump, on both banks which would trigger a relay to switch back and forth on the DC side of the inverter....and I'm not sure if that would work!
I use the Ghurd controllers for High voltage dumps, but they can be configured either way.

Or try contacting Craig at Coleman air and see if he's got something that could work


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## mightybooboo (Feb 10, 2004)

Thanks for idea Wp,much appreciated.


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## Jim-mi (May 15, 2002)

Could be done using high/low programable voltage switches powering 100amp mercury contactors....


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## mightybooboo (Feb 10, 2004)

Jim-mi said:


> Could be done using high/low programable voltage switches powering 100amp mercury contactors....


LOOSIE,You got some 'splainin' to do!! :teehee:

Total Greek to me,can you send me some links on whats involved?[prophead]

Thanks.


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## cowboy joe (Sep 14, 2003)

Typcially this is done (it simple terms) with a comparator & a relay or solid state switch. The 'comparator' compares the levels of the two battery banks & switches when one is almost depleted (depleted meaning preset level before damage occurs to the battery). I did a quick search & found this:

http://bluesea.com/viewresource/69

I'm not certain if it would handle the load (you didn't specify) but you could always add a relay with higher amperage contacts.


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## Jim-mi (May 15, 2002)

There are voltage controlled switches --where you program the high or low setpoints . . .At these set points this unit triggers a built in 30A relay. Sounded like your "load" was/is going to exceed 30A . .so I would use that 30A relay to power/trip big 100A mercury contactors. 
Hysteresis of these setpoints can be as little as .2 volts.

The reason for the mercury contactors is that if your switching a big load like a inverter you don't need to worry about switch/relay contact arcing . . .. 
Arcing would be a big problem with any 'dry' contacts (with any amount of load) 

I use a high volt switch (with a outboard relay) to switch on/off a electric resistance heater . . . .All this for when my system is generating excess power .......


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## mightybooboo (Feb 10, 2004)

Gentlemen,is this the switch that would take care and keep separate the 2 battery banks?

http://www.solar-electric.com/volconswit.html


In lieu of a mercury switch would this work? I havent found the mercury yet but this is 450 amp continuous

http://bluesea.com/category/1/productline/8


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## wind power (Sep 29, 2010)

Hi Mighty,
That appears to be DC switching, which means it will have to go in before the inverter. Is this what you are wanting to do? then this should be an easy fix:lookout:
-----
Thinking out loud here:

Does your inverter have multiple DC hook up posts?
IF so, lets say you could hook up on battery bank to one set of posts and the other bank to the other posts and have an On-Off DC battery monitoring switch like you have shown there.

Or...

Could you wire each battery bank for you inverter voltage ( 24v?) and take each battery cable ( both positives) and hook them to the same posts? and ( both) the Negatives too? Then your DC HVD/LVD dump you listed could work....but you might need two...i dont know...havent fully grasped the operation of the thing yet...maybe just one
----
Still thinking out loud here:

Now if you want to break the load on the AC side you would need a dc fired-AC relay to break say an AC positive line while the negative line flowed straight to your source....you can get Solid State relays off of ebay fairly cheap....usually you can get them which will fire the "contacts" at 3-32 volt DC and will close the AC side with a failry good amp load....

It seems easier to do the switching on the DC side....

-----

That selonoid you have listed would probably do...just figue all your appliance/inveter amp draws and ther you have it...440 amps is a lot...wheeeew...but is good to have a relay which can handle before you let the magic smoke out.
I agree with Jim....that dc controller with its smaller relay could fire that bigger relay


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## mightybooboo (Feb 10, 2004)

Batt Bank 1- 440 amp/24 volt lead acid,800 watts solar,bluesky 3024 controller
Batt Bank 2-800 amp/24 volt AGM,1200 watts solar Tristar-60 controller

So the banks cant tie together as different batteries and controllers.Plan is to let Bank one be primary load with the 10 year old exide batteries until they crap out,and be replaced with L-16's in dry storage when the time comes.

Inverter Tr2424 pulling 120 amps at 24 volt input side

We want to switch inverter from Bank 1 when voltage goes below a set point over to Bank 2 automatically.When Bank 1 is charged back up we want it to switch back.Hopefully not too often(dont know how often really as a 2nd freezer and a refer is being added when system 2 is brought online),and to do so if bank 1 goes dead while system unattended.Gonna be a lot of meat in those 2 freezers he wants to protect.

So I found this 50,000 cycles at 200 amp solenoid for 112 dollars here
http://www.grainger.com/Grainger/WHITERODGERS-DC-Power-Solenoid-6C025

Or this cheaper one,an Ametek that doesnt have a known cycle life rating,also 24 v 200amp continuous
15-141
SAS-4401
Your Cost
$53.50
At this site right side,2nd down
http://www.texasindustrialelectric.com/relays.asp

So we would need 2 solenoids,now how does that LVD relay work,we need one or two of those,Im confused too.


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## Jim-mi (May 15, 2002)

Yes booboo that would be the voltage switch I spoke of...

Yes two contactors are needed . .one for each bat bank.
You fire a outboard DPDT relay.
Energized it holds one contactor 'closed'
When unenergized the other contactor is 'closed'
very simple circuit . .........

I still think wet contacts are much better.
If Bat 'one' is being drawn down to "that low level" .. that means that the tR inverter is under 'load' . .and drawing lots of current . .therefore much arcing . .NOT good on contacts.


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## mightybooboo (Feb 10, 2004)

The load on the inverter is generally pretty low,I doubt its ever running at 120 amps dc. It would be like the 440 a/hr system has suffered thru several days no charging and run down. The switch claiming 50,000 switches at 200 amps,thats a pretty tuff switch,it would surely outlast him at 135 year life expectancy with a switch daily at 200 amps which isnt going to happen.No? And Im having problems deciphering the mercury switches and coming up with 24 volt/200 amp continuous.What mercury switch would work here at what price,and price sensitivity matters,this is a retired guy,not much cash.

BRB,need to wrap my brain around the switching explanation,Im really befuddled with learning new terms to boot.My knowledge on wiring runs like this.Use heavier wire than called for,use disconnects and fusing where appropriate,and ground as called for. When we start talking switches its greek to me,I think I understand the difference between the switches but not how they function so humor me here.....

IF we used DPST it wouldnt work? Wouldnt the top switch be closed when powered,then open when power off to it and power applied to the bottom switch it would close,completing the circuit. If the banks had their neg wires combined all I would have to do is power a positive to each of the switches,correct? Or is it powered applied to this switch closes BOTH contacts and power off opens both?









Now how does the DPDT get wired? Is each switch getting individual power and working independently? Is that why its called a double throw? OK,reread your post,so power on 1 switch open,other closed.When power off its the reverse,correct?









Yes,a simple picture sure would help,I can grasp a diagram.


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## PD-Riverman (May 24, 2007)

Mightybooboo, when these banks switch want your inverter cut of for a Second? Will it restart after the switch? I have a inverter that if it cuts off under a load because of weak batteries then fresh batteries are hooked up, it has to be cut off manually then turned back on to reset it. Then I have others that come right back on.


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## PD-Riverman (May 24, 2007)

mightybooboo said:


> The load on the inverter is generally pretty low,I doubt its ever running at 120 amps dc. It would be like the 440 a/hr system has suffered thru several days no charging and run down. The switch claiming 50,000 switches at 200 amps,thats a pretty tuff switch,it would surely outlast him at 135 year life expectancy with a switch daily at 200 amps which isnt going to happen.
> 
> BRB,need to wrap my brain around the switching explanation,Im really befuddled with learning new terms to boot.My knowledge on wiring runs like this.Use heavier wire than called for,use disconnects and fusing where appropriate,and ground as called for. When we start talking switches its greek to me,I think I understand the difference between the switches so humor me here.....
> 
> ...


You got me confused---LOL. A DPDT switches from two contact to the two other. If you are using the circuit mentioned above----you would have the positive and negative hooked to the center---then when the switch is one way it will activate 1 solenoid, the other way ---solenoid 2.

Yes you can switch the positive only and could use a SPDT.


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## mightybooboo (Feb 10, 2004)

Lets try this.....










Each lightbulb is instead a battery bank,battery is instead the inverter,A and B are both positive wires,and the negatives of the bank are tied together.

I would have A,B and the tied negative pigtailed off to the LVD. When the switch(edit-solenoid) isnt receiving current from the LVD then circuit A would be completed to the inverter. When LVD sends current to switch(solenoid) in a low voltage situation circuit B would close instead and that circuit would now feed the positive juice to the inverter?


As for the DPDT,how would that wire to the inverter? How are the battery banks wired in?


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## mightybooboo (Feb 10, 2004)

PD-Riverman said:


> Mightybooboo, when these banks switch want your inverter cut of for a Second? Will it restart after the switch? I have a inverter that if it cuts off under a load because of weak batteries then fresh batteries are hooked up, it has to be cut off manually then turned back on to reset it. Then I have others that come right back on.


Thats a very good point,have to check.


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## PD-Riverman (May 24, 2007)

mightybooboo said:


> Lets try this.....
> 
> 
> 
> ...


Booboo, you seem to be thinking about wiring your inverter and battery banks to these switch illustrations. You would be wiring your solenoids to THESE Switch and both outputs of these solenods would be hooked to your inverter. The DPDT/SPDT switches would turn on one or the other solenoids. The Switches are NOT heavy enough to do what you want so thats why you are going to use a solenoid.


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## mightybooboo (Feb 10, 2004)

Correct,and its looking like the 200 amp 24 volt solenoid SPDT is the answer,I cant even find a 24 volt DPDT solenoid.We would use this,7th down on the right
http://www.texasindustrialelectric.com/relays.asp

15-381
SBD-5401
Your Cost
$85.00
---------------------------------------
So,the spdt,lvd and wired as per posted spdt diagram and explanation in post 17,would that work,looks good to me so something must be wrong,LOL!


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## mightybooboo (Feb 10, 2004)

PD-Riverman said:


> Mightybooboo, when these banks switch want your inverter cut of for a Second? Will it restart after the switch? I have a inverter that if it cuts off under a load because of weak batteries then fresh batteries are hooked up, it has to be cut off manually then turned back on to reset it. Then I have others that come right back on.


He THINKS it resets by itself but doesnt have manual with him.Let me look it up....


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## PD-Riverman (May 24, 2007)

OK, Booboo, I think I caught up with you------You have been talking about using a SPDT solenoid-----thought you were still on the DPDT switch mentioned above. I believe I would go with a SPST, get 2 of them, using one on each line---Then again---I would have to think about that----Hmmmm, Well I know I would because I set here a few minutes earlier and sketched out a flip/flop relay design that with 2 of the soleonids and a few relays I already have would work great for my set-up so I don't have to switch banks manually. Just thought about it I got some 300 amp and 600amp (I think thats what they are rated) HUGE relays I bought a few years back. So I just need to get busy, but I am not ready to build this yet---LOL. 





mightybooboo said:


> Correct,and its looking like the 200 amp 24 volt solenoid SPDT is the answer,I cant even find a 24 volt DPDT solenoid.We would use this,7th down on the right
> http://www.texasindustrialelectric.com/relays.asp
> 
> 15-381
> ...


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## Jim-mi (May 15, 2002)

With the circuit done right (and mercury contactors) the amount of "OFF" time would be so little that the inverter would likely not 'see' it


I've got to question the duty cycle of those solenoids . . .can it be kept on for days at a time . .?????


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## wind power (Sep 29, 2010)

Hi Jim-mi,
I'm using a soleniod rated for 440 amps...its suppose to have silver contacts
buts thats anybodys guess, I haven't been inside of it.
It does ok, dumping at 2500 watts into a bank of resistors sometimes off and on throughout the day at 10 mins a pop....But if that puppy ever welds shut....then I will have a DOA battery bank completely flat-lined on voltage.
So far its working good, but I'm about to start dumping into a water heater element on the AC side of the inverter with a SS relay.

I really like that idea of that hi/low programable mercury switching...those selonoids like Im using do have a bit of an amp draw from what I'm told...so there is a bit of loss.

I would have to agree, your argument is right on spot! Its a completely different ball game when a selonoid is used toggling back and forth for short periods of time as in my application as opposed to when Mighty's might be used for hours on end....if that relay fails....



Likewise, just to keep those selonoids closed does eat away at your overall power useage


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## Jim-mi (May 15, 2002)

You had silver contacts . . .lol
If you have been 'welding' with that much current for long . .what you have now is any bodys guess . . lol .. . .
With the MC's you will not have welded shut contacts.
Ever look at a good sized relay that has failed . .?? The contacts are more that ugly . . . .more times than not the coil is ok but the contacts are the reason for failure.

Are not those solenoids rated for "intermittent" duty . .?

The 100 amp MC I have . its coil only uses between 17-20 ma.


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## wind power (Sep 29, 2010)

Hi Mighty, Jim...everyone.
I just tried something it about my changeover to the AC dump side...but it might alos be applicable to Mightys situation too.

I took one of those Ghurd controllers a second ago:

http://www.ghurd.info

I took the fet side wire of the controller and hooked it to the positive DC side of a SS relay then I hooked the negative DC side of the relay to the negative side of the battery..as I adjusted the pot to kick on the dump light ( yellow led) it sent enough voltage ( 10 VDC) to the DC relay to open or close it off on the AC relay side.

Could not Mighty also use this same setup with your mercury switch relay to open and close the positive line DC cable going to his inverter?...I guess it would be best to open and close both the negative and positive inverter cables at the same time, but I'm far from a relay guru....is there such a beast?


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## mightybooboo (Feb 10, 2004)

Jimmi,yes,these are continous duty 200 amp switches,and again,its 120 amp MAX when inverter on full,RARE!

Will read up on rest,yes,they have silver contact ones. 

Golf carts use these solenoids and they push heavy amps.More than we will be pushing continous and again,we are maxing at 120 on 200 amp solenoids,thats not much load.

Jimmi,find me a link on those mercs,certainly willing to consider.

About the inverter resetting,yes,that may be the bottleneck in the whole plan,going to have to see about that,I'd like to know how fast these solenids switch,know my home inverter does it fast enough to not effect the digital clocks at home

Thank you everyone on the ideas,you really came thru!!


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## mightybooboo (Feb 10, 2004)

wind power said:


> I would have to agree, your argument is right on spot! Its a completely different ball game when a selonoid is used toggling back and forth for short periods of time as in my application as opposed to when Mighty's might be used for hours on end....if that relay fails....
> 
> 
> 
> Likewise, just to keep those selonoids closed does eat away at your overall power useage


Good points.

If ours failed all it would do is either leave the bank connected or not,worse case combining the 2 banks,so not a catastrophic welding failure just at worse case combining banks of different voltage,28.8 with 29.6,agms wouldnt be happy.

Yup,dont like the waste of current running the solenoids,yep,about 700ma it appears


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## Jim-mi (May 15, 2002)

I know a bit about electrical stuff.....
I am a puter dumby.........
So cutting and pasting and all that crap is beyond me..........

Just giggle "Mercury Contactor'

The top item that came up was all I needed to look at......

100A- 24vdc coil- 72 bucks..............good stuff.


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## mightybooboo (Feb 10, 2004)

Jim-mi said:


> I know a bit about electrical stuff.....
> I am a puter dumby.........
> So cutting and pasting and all that crap is beyond me..........
> 
> ...


AWESOME,I was googling solenoid for em,thanks Jimmi!!


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## mightybooboo (Feb 10, 2004)

Will check back tomorrow AM,Jimmi,look at this link,only one I see on a quick look,(no time) and tell me which one(s)

http://www.sordselectric.com/Merchant2/merchant.mv?Screen=CTGY&Store_Code=SE&Category_Code=CON24D

Thanks.


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## wind power (Sep 29, 2010)

Hi Mighty,
Here's someone bascially asking the same thing as your situation to the guy who came up with those tiny Ghurd controllers. I guess it might be of some use:
http://fieldlines.com/board/index.php/topic,144968.0.html


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## mightybooboo (Feb 10, 2004)

Thanks WP,I will check link and that controller


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## mightybooboo (Feb 10, 2004)

So I joined,commented on their thread,asked their opinions of OUR thread,only to return and Find my comments deleted.

Friendly bunch,eh? They got issues with this forum or something,or freaked over links to others?


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## wind power (Sep 29, 2010)

Hi Mighty I dont know about that one.
I dont htink they have any issues over other forums...they might have wanted to make thing tidy....they also have a rule of no advertising on the initial post.....something to do with spammers.

Usually they are a swell bunch over there....very helpful too, only on occassions does somenbody come along and tries to do some trolling.

They might have seen your question as something within these possible realms
just about every moderator over there is a-ok

Tell you what, give it another shot, list your Question in "Controls" or piggy back off that response I sent you a link too and explain your situation...surely someone will ring out to you


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## Jim-mi (May 15, 2002)

I went back and giggled MC again . . . . .wow . . . sure is a bunch of suppliers.....
One is www.sordselectric.com
there is many more.......
If you go this route remember to order:
One ---NO- (normally open)
One----NC- (normally closed)


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## mightybooboo (Feb 10, 2004)

I would need 2 of these,one NO,one NC.Correct? I cant afford to be wrong,nor can the owner of the system.

http://www.sordselectric.com/Mercha...Product_Code=CON100NO24D&Category_Code=CON24D

MDI 100NO24D, 100 amp Mercury Contactor, Single Pole, 24vdc Coil, 600 max volts	
Price: $87.00
Shipping Weight: 3.00 pounds


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## mightybooboo (Feb 10, 2004)

WP,I think I will pass on em. They could have at least said SOMETHING to me,whatever,not going back.Dont like the initial first impression.Right or wrong.


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## PD-Riverman (May 24, 2007)

Why would you need a N.O. and a N.C.??? I would think you would need 2-- N.O.. Somebody explain!! Thanks!!





mightybooboo said:


> I would need 2 of these,one NO,one NC.Correct? I cant afford to be wrong,nor can the owner of the system.
> 
> http://www.sordselectric.com/Mercha...Product_Code=CON100NO24D&Category_Code=CON24D
> 
> ...


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## Jim-mi (May 15, 2002)

Yes the info on your post is correct.

Feel free to bop around on the giggle MC 'list' for 'price'


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## Jim-mi (May 15, 2002)

The default position is bat one powering the load through the NC contactor.
When the voltage switch reaches the preset "low" voltage the switch triggers the relay which triggers the coils on both M contactors.
bat one--opens the bat circuit.
bat two-- closes taking up the "load"

It will stay that way until bat one comes back up to and above the return voltage setting pre set on the V switch.

quite simple actually...........


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## mightybooboo (Feb 10, 2004)

But Gentlemen,is the link I posted the CORRECT mc,the ones we would need? Thats all I need to grasp to fully understand. I would write compnay,tell em I need that model,1 NO,1 NC and be good to go with the correct,BEST switches for the application we could get?


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## Jim-mi (May 15, 2002)

booboo you must have missed my post above..........
Yes . . correct info.


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## mightybooboo (Feb 10, 2004)

Jim-mi said:


> booboo you must have missed my post above..........
> Yes . . correct info.


OK,its the correct switch and good to go then,thanks!


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