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Cheap LiFePO4 BMS?


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1 minute ago, peterboat said:

Richard the BMS on out batteries will balance the cells over time, however, if you are forcing lots of amps in once past 13.9 volts, it will struggle to cope with some cells going over voltage and their lies the problem! Because we dont have the master BMS, which would turn off the charging source, giving batteries and cells time to balance. We if we are sensible, only charge to the 80%, saving ourselves lots of grief and big bills

Yes, I wasn't really asking for me. More for others who read the thread. I point people here occasionally as most things LiFePo4 have been covered.

 

I think if we had the Master BMS box, it would cycle the charge on and off between 14.8v and 14.75v in order to balance cells... At least that's what I recall from the manual.

 

As you suggest, according to the manual, if you keep them with a charge at about 13.8v, the internal BMS will attempt to balance them.

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2 minutes ago, Richard10002 said:

Yes, I wasn't really asking for me. More for others who read the thread. I point people here occasionally as most things LiFePo4 have been covered.

 

I think if we had the Master BMS box, it would cycle the charge on and off between 14.8v and 14.75v in order to balance cells... At least that's what I recall from the manual.

 

As you suggest, according to the manual, if you keep them with a charge at about 13.8v, the internal BMS will attempt to balance them.

I know it does, and so would you if you played like I did at the beginning

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2 minutes ago, peterboat said:

I know it does, and so would you if you played like I did at the beginning

I've been "playing" with them for a month or so now. Although after 5 to 6 hours of charging at 55A, I'm not inclined to leave them for long at 13.8v or so. When the sun comes out I'll probably set my controller to do it from time to time.

 

At the moment I'm charging them to around 85% and discharging to about 25%, which gives me about 310Ah between charges, about 4 days.

 

I used to think I used about 120Ah a day when on board, but it seems that it's only about 70Ah.

 

Much better than running the genny for hours every day or two just to get the last 10Ah into a bank of LAS :)

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1 minute ago, Richard10002 said:

I've been "playing" with them for a month or so now. Although after 5 to 6 hours of charging at 55A, I'm not inclined to leave them for long at 13.8v or so. When the sun comes out I'll probably set my controller to do it from time to time.

 

At the moment I'm charging them to around 85% and discharging to about 25%, which gives me about 310Ah between charges, about 4 days.

 

I used to think I used about 120Ah a day when on board, but it seems that it's only about 70Ah.

 

Much better than running the genny for hours every day or two just to get the last 10Ah into a bank of LAS :)

And you are safe as houses just doing that

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8 minutes ago, Richard10002 said:

I've been "playing" with them for a month or so now. Although after 5 to 6 hours of charging at 55A, I'm not inclined to leave them for long at 13.8v or so. When the sun comes out I'll probably set my controller to do it from time to time.

 

At the moment I'm charging them to around 85% and discharging to about 25%, which gives me about 310Ah between charges, about 4 days.

 

I used to think I used about 120Ah a day when on board, but it seems that it's only about 70Ah.

 

Much better than running the genny for hours every day or two just to get the last 10Ah into a bank of LAS :)

One of the advantages of lithium is the slightly higher voltage, so an Ah of lithium is worth more than an Ah of lead acid, by perhaps 10%. Many devices are “constant power”, ie they less current and charge to do the same job, if the voltage is higher.

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2 hours ago, Richard10002 said:

For the sake of clarity, what do you mean by overcharge?

If you are charging with a reasonable current i.e. 30A, then you should continue to charge until the current starts to decay and gets down to 4-5% of the bank capacity. Hence for a 480Ahr bank, you are full when current drops to 20A ish. If you are charging less than 20A, you can see it difficult to see when current drops!

If you are charging at low current i.e. 30A ish then your voltage is still likely to be rising as you approach full. If you are charging at 100A then that is outside my experience but others have said you may then be in constant voltage mode.

When you get to full you should remove the charge i.e. Reduce voltage to 13.4V Ish.

 

As Peter says, the complication here is that if you are not well balanced, when you get to 14.4V you may then exceed individual cell voltage targets and charging needs to stop. I don't take any of my cells over 3.65V absolute max.

 

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5 hours ago, Dr Bob said:

can then produce an extremely high temperature at a very small spot which can ignite the electrolyte without triggering the safety valve. This ignition can then heat the next set of molecules causing them to ignite and starts a thermal runaway.

Genuine question: the electrolyte is a flammable hydrocarbon, so if it vents the cell it can burn in air, but how can it burn inside the cell, without access to an oxidiser?

 

MP.

 

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AIUI The oxygen comes from the heat caused breakdown of the  lithium compound.  LiFePO4 is much harder to reduce than say LiCoO2, which gives up its Oxygen relatively easily.  That is why LFP batteries are safer.

N

 

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9 hours ago, MoominPapa said:

Genuine question: the electrolyte is a flammable hydrocarbon, so if it vents the cell it can burn in air, but how can it burn inside the cell, without access to an oxidiser?

 

I think the oxygen for a thermal runaway comes from the oxygen bound into the cathode. In The Li ion batteries, you basically have a lithium metal oxide...so the oxygen is bound into the metal oxide i.e. Co02. LiFePO4 are also classed as Li ion (I think) but the phosphate group (the PO4 bit) is much tightly bonded in and it is much more difficult to break the P-O bond than it is to break the Co-O bond.....much higher energy required....i.e. Heat.... You are talking maybe 500 C to break the P-O bond but you could get that if there was a very small short in a confined area. More 'general'  heat to get to those sort of temps would just blow the safety valve. For the other metal-O bonds, I guess the temps to break them and make the oxygen available are considerably lower, maybe 300C (but you'd have to find out the activation energies to see exactly......life too short for that!.....) so the will be much more prone to thermal runaway.

So all that says the LiFePO4s are much safer than phone batteries in catching fire BUT DONT OVERCHARGE.

Its also worth saying that the electrolyte used doesn't seem too flammable as in all these videos there don't seem to be many instances of them burning, even in the case of the last set of tests where they had a flame on them. The electrolyte just gassed off. The only real burning was in the first Li pol test where it looked like the battery was burning not the vented gas.....I am not sure these phone batteries have that safety feature to vent electrolyte when hot.

 

 

 

 

 

eta.  BEngo beat me tuit

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25 minutes ago, BEngo said:

AIUI The oxygen comes from the heat caused breakdown of the  lithium compound.  LiFePO4 is much harder to reduce than say LiCoO2, which gives up its Oxygen relatively easily.  That is why LFP batteries are safer.

N

 

I'm seriously handwaving with 30+ year old A-level chemistry now, but for this to happen at all requires that the energy from oxidising the organic electrolyte exceeds the energy in the P-O bonds in the phoshate, which feels unlikely. I'm sure you can make this stuff burn with a very reactive metal, but the only reactive metal on the scene is lithium, and that's already in the oxidised. state as Li+ ions. Unless it's been plated out as a metal due to abuse of the cells, of course, maybe that's the answer?

 

MP.

 

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3 minutes ago, MoominPapa said:

I'm seriously handwaving with 30+ year old A-level chemistry now, but for this to happen at all requires that the energy from oxidising the organic electrolyte exceeds the energy in the P-O bonds in the phoshate, which feels unlikely. I'm sure you can make this stuff burn with a very reactive metal, but the only reactive metal on the scene is lithium, and that's already in the oxidised. state as Li+ ions. Unless it's been plated out as a metal due to abuse of the cells, of course, maybe that's the answer?

 

MP.

 

That is correct. It is very difficult to get the P-O to give up its oxygen, but it can happen. You are right there is no reactive Li about but even that can't burn without the oxygen.  

It is likely it is not the energy from oxidising the electrolyte AIUI that breaks the P-O bond but the energy discharge when a micron thin Fe dendrite growing from the anode touches the cathode. That energy release could be very high in temp. As you say not likely to happen but for risk management there is a solution.

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As Dr Bob says, the extra energy to get the thermals self sustaining comes from discharging the battery.  If the energy in an LFP cell is released as a short circuit from mechanical damage it has to be quite localised in order to get things hot enough.  Hence edge damage to cells is more likely  to cause runaway than blunt trauma in the centre.  Even then it is hard to get LFP going.  The other consequence of the need to short the battery to release energy is the desired transportation charge level.  At 30% charge there is just not enough energy to get LFP thermal runaway started.

 

Other Li chemistries are different, and more likely to go, but we are not using them.

 

N

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Thanks to all contributors on this and the other threads, I think i have a plan to install lithiums

I bit the bullet and bought 3 low cycle 138ahr Valences from James in London

I plan on paralleling them with my domestics (4 @ 110ahr) isolated by a manual isolation switch @ 300A and BEP 701md motorised switch controlled by BMV712 

I have a 175a alternator for domestics {and a 50a for starter) and 500w solar controlled thru Victron easysolar which has a mppt100/50 in it

I think i can adjust the settings in the mppt to something suitable ie 13.9 bulk etc

The main alternator controller will be me with the BEP MD as the back up. I realise there are issues with this and maybe worth putting another alarm set a bit lower than the BMV for overvoltage protection

For undervoltage i will use the BMV and the BEP MD but maybe will put a Victron Battery 12/200 protect in too. 

They're going in the boat so temp shouldnt be huge issue. I intend to isolate them when away from boat.

Any suggestions on proposal ?

 

Peter and Richard, any chance you could point me in the direction of source for the cable/connectors to plug the Valences into pc ?

 

Dr-upthereds-Bob was the crimper that MP recommended something like this? https://www.ebay.co.uk/itm/10-Ton-Hydraulic-Crimper-Crimping-Tool-Dies-Wire-Battery-Cable-Hose-Lug-Terminal/163935559068?hash=item262b521d9c:g:95IAAOSwq-Bd-Gzu

 

Many thanks to all again

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2 minutes ago, redwing said:

Thanks to all contributors on this and the other threads, I think i have a plan to install lithiums

I bit the bullet and bought 3 low cycle 138ahr Valences from James in London

I plan on paralleling them with my domestics (4 @ 110ahr) isolated by a manual isolation switch @ 300A and BEP 701md motorised switch controlled by BMV712 

I have a 175a alternator for domestics {and a 50a for starter) and 500w solar controlled thru Victron easysolar which has a mppt100/50 in it

I think i can adjust the settings in the mppt to something suitable ie 13.9 bulk etc

The main alternator controller will be me with the BEP MD as the back up. I realise there are issues with this and maybe worth putting another alarm set a bit lower than the BMV for overvoltage protection

For undervoltage i will use the BMV and the BEP MD but maybe will put a Victron Battery 12/200 protect in too. 

They're going in the boat so temp shouldnt be huge issue. I intend to isolate them when away from boat.

Any suggestions on proposal ?

 

Peter and Richard, any chance you could point me in the direction of source for the cable/connectors to plug the Valences into pc ?

 

Dr-upthereds-Bob was the crimper that MP recommended something like this? https://www.ebay.co.uk/itm/10-Ton-Hydraulic-Crimper-Crimping-Tool-Dies-Wire-Battery-Cable-Hose-Lug-Terminal/163935559068?hash=item262b521d9c:g:95IAAOSwq-Bd-Gzu

 

Many thanks to all again

Did James give you the end to plug it in? Also have they got two leads each if so plug therm into each other according to a Geek on the tinternet they do talk. James also has the software and the lead I bought from Amazon. Well done with your purchase though

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2 minutes ago, peterboat said:

Did James give you the end to plug it in? Also have they got two leads each if so plug therm into each other according to a Geek on the tinternet they do talk. James also has the software and the lead I bought from Amazon. Well done with your purchase though

No Peter James didnt give me the end. Yes they have the 2 leads . I think Richard posted a link to the software and manual. Do you remember what the connector ends are called or do you have any spares left i could buy from you ? and what sort of lead from Amazon ? Cheers Peter. Im planning on sticking to the 20/80 charge and watching like a hawk when charging from alternator.

 

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38 minutes ago, redwing said:

That's the beastie, or it's in very good disguise.

 

MP.

 

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50 minutes ago, redwing said:

Peter and Richard, any chance you could point me in the direction of source for the cable/connectors to plug the Valences into pc ?

This is the connector that I bought to go on the bare end of the USB cable. A bit fiddly to fit and it's important to get the right coloured wires in the right holes.

 

https://www.ebay.co.uk/itm/SUPERSEAL-AMP-TYCO-WATERPROOF-ELECTRICAL-CONNECTOR-KIT-1-2-3-4-5-6-WAY-PIN-PLUG/271531088303?ssPageName=STRK%3AMEBIDX%3AIT&var=570361627716&_trksid=p2057872.m2749.l2649

 

I bought this as the USB gizmo that goes into the laptop, but it was a bit of a buy cheap buy twice thing... it worked after a lot of faffing, but I found better, (see below):

 

https://www.ebay.co.uk/itm/USB-to-RS485-Converter-FTDI-CCTV-EPOS-industrial-control-FT232RL-SP485-Adapt/132478019431?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649

 

This is a much more substantial USB - RS485 FTDI Chip connector, and is the one I now have permanently connected to the batteries, it was well worth the extra money!!

 

https://uk.rs-online.com/web/p/serial-converters-extenders/6877834/

 

The datasheet was helpful in terms of identifying which wire is which:

 

https://docs.rs-online.com/105f/0900766b80da71f7.pdf

 

I had to mess around a bit to get the right wires in the right holes of the Tyco connector... getting it wrong didnt cause any damage... the thing merely didnt communicate.

 

I found the Valence software on the web site of a youtuber. I'll see if I can find the video, and the link to his site and the software.

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38 minutes ago, MoominPapa said:

That's the beastie, or it's in very good disguise.

 

MP.

 

Thanks MP

10 minutes ago, Richard10002 said:

This is the connector that I bought to go on the bare end of the USB cable. A bit fiddly to fit and it's important to get the right coloured wires in the right holes.

 

...

Thanks v much Richard

Is this the vid ? 

 

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Here's the link to the video I watched, and a page from his web site which is actually more helpful:

 

https://www.yousun.org/archives/1269

 

 

This is the ling to the software.... it all looked a bit iffy at first glance and I think it might automatically download it to your PC... It has just done so on mine. Before clicking on it I found quite a few other people pointing to the same link from various forums on lithium batteries, and can confirm I have had no issues with it since downloading in November. Your risk if you click on it, but I'm reasonably sure it's fine.

 

You need a way to extraxt a .rar file, I think I used 7-zip:

 

https://onedrive.live.com/?cid=74a1e6e57afa4d2b&id=74A1E6E57AFA4D2B!119&authkey=!AGLt7EMehj39EJA

 

Here is the first video from a guy who goes through the process... I dont think he gets it quite right in this video, but does a follow up which I also attach:

 

 

 

 

Good Luck!!

 

 

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1 hour ago, redwing said:

Thanks to all contributors on this and the other threads, I think i have a plan to install lithiums

I bit the bullet and bought 3 low cycle 138ahr Valences from James in London

I plan on paralleling them with my domestics (4 @ 110ahr) isolated by a manual isolation switch @ 300A and BEP 701md motorised switch controlled by BMV712 

I have a 175a alternator for domestics {and a 50a for starter) and 500w solar controlled thru Victron easysolar which has a mppt100/50 in it

I think i can adjust the settings in the mppt to something suitable ie 13.9 bulk etc

The main alternator controller will be me with the BEP MD as the back up. I realise there are issues with this and maybe worth putting another alarm set a bit lower than the BMV for overvoltage protection

For undervoltage i will use the BMV and the BEP MD but maybe will put a Victron Battery 12/200 protect in too. 

They're going in the boat so temp shouldnt be huge issue. I intend to isolate them when away from boat.

Any suggestions on proposal ?

 

Peter and Richard, any chance you could point me in the direction of source for the cable/connectors to plug the Valences into pc ?

 

Dr-upthereds-Bob was the crimper that MP recommended something like this? https://www.ebay.co.uk/itm/10-Ton-Hydraulic-Crimper-Crimping-Tool-Dies-Wire-Battery-Cable-Hose-Lug-Terminal/163935559068?hash=item262b521d9c:g:95IAAOSwq-Bd-Gzu

 

Many thanks to all again

Redwing.

Well done on taking the decision to go forward. Keep us posted on how it goes.

I will be particularly keen to hear how you get on with charging via your 175A. Mine is only 90A and controlled via the AtoB but we are thinking about getting a newer boat and that is likely to have a 175A or even 240A alternator. I am not too bothered about the auto disconnect at high voltage but more interested in over cooking the alternator. Let us know what sort of power you are seeing from the alternator when charging  the Valences and if possible how hot the alternator is getting. The four or five of us on here only have 90A alternators so 175A is new ground.

Well worth while getting an infrequent red thermometer to monitor alternator temp. I followed Peter's advice and installed a cold air blower for <£50 taking cold air from the bottom of the engine bilge and blowing it on the electronics end of the alternator which works great (but it is still winter).

 

As MP says, that is the crimper we all seem to have bought. YNWA

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1 hour ago, redwing said:

The main alternator controller will be me with the BEP MD as the back up. I realise there are issues with this and maybe worth putting another alarm set a bit lower than the BMV for overvoltage protection

 

Any suggestions on proposal ?

 

 

Just a comment on the BMV alarms.

Victron screwed up last year with the firmware on the BMV 712 using 4Khz as the tone for the alarm which most of us cant hear. There was a firmware upgrade out just before Christmas which resolved this issue so you can now hear the BMV alarm. If your BMV is already installed, make sure you reload the new firmware.

Also, think through the logic of how you reconnect your BEP after an autodisconnect. I have a BMV on the LAs and a separate BMV on the Li's so can choose which meter I get to do the disconnect. My strategy is on disconnect, it doesnt re-connect again so that I have to go and find why the disconnect happened. Perhaps you will have it set so on isolation, you measure the voltage on the LA side and only re-connect when the LA circuit voltage drops to below 13.3V. Lots of options to think about.

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On 06/02/2020 at 13:42, Dr Bob said:

Just a comment on the BMV alarms.

Cheers Bob. Noted re BMV and alternator. I am away atm so wont get started for a few weeks. I am in a similar position to where Richard was ie flying by seat of pants but I'm hoping that once installed i'll have a better idea of whats what. . You all seem to be happy that theyre fairly easy to manage once you know and can set charge limits. Big alternator charging is the main concern and i'll be extra careful to start with. It may be that i'll have to have it modded like Peter suggests, get a smaller one or maybe something like Nick's wizardry will come along that can be fitted by muppet like me. I'm on a steep learning curve but hopefully slowly slowly wont catchy me a dead alternator.

 

 

Thanks Richard. Have ordered the cable from RS and the other bits.

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  • 2 weeks later...

Just ordered one of these beauties at a very discounted price.

https://www.ebay.co.uk/itm/223271777277

 

This will go with 8x aluminium cased 150ah 3.2v lifepo4 cells (12v/300ah) which I ordered from here

https://blslifepo4battery.com/

 

The bms is 120a with Bluetooth app to change parameters and functioning low temp sensor. I've ordered one and I will try with the whole bank and if it works well I'll order another one and split the bank so that should give me 240a continuous current draw for a 2kw inverter

https://www.ebay.com/itm/323971537785

https://www.ebay.com/itm/323860553131

 

I will also be ordering one of these which comes with a 500a shunt and programmable relay for dumping extra solar power onto a calorifier element

https://www.ebay.co.uk/itm/232941753068

 

A cheap but powerful solar setup is in the pipeline too ?

 

 

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38 minutes ago, Dre said:

Just ordered one of these beauties at a very discounted price.

https://www.ebay.co.uk/itm/223271777277

 

This will go with 8x aluminium cased 150ah 3.2v lifepo4 cells (12v/300ah) which I ordered from here

https://blslifepo4battery.com/

 

The bms is 120a with Bluetooth app to change parameters and functioning low temp sensor. I've ordered one and I will try with the whole bank and if it works well I'll order another one and split the bank so that should give me 240a continuous current draw for a 2kw inverter

https://www.ebay.com/itm/323971537785

https://www.ebay.com/itm/323860553131

 

I will also be ordering one of these which comes with a 500a shunt and programmable relay for dumping extra solar power onto a calorifier element

https://www.ebay.co.uk/itm/232941753068

 

A cheap but powerful solar setup is in the pipeline too ?

 

 

Very good glad to see someone else going the lifePo4 route 

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30 minutes ago, Dre said:

Just ordered one of these beauties at a very discounted price.

https://www.ebay.co.uk/itm/223271777277

 

This will go with 8x aluminium cased 150ah 3.2v lifepo4 cells (12v/300ah) which I ordered from here

https://blslifepo4battery.com/

 

The bms is 120a with Bluetooth app to change parameters and functioning low temp sensor. I've ordered one and I will try with the whole bank and if it works well I'll order another one and split the bank so that should give me 240a continuous current draw for a 2kw inverter

https://www.ebay.com/itm/323971537785

https://www.ebay.com/itm/323860553131

 

I will also be ordering one of these which comes with a 500a shunt and programmable relay for dumping extra solar power onto a calorifier element

https://www.ebay.co.uk/itm/232941753068

 

A cheap but powerful solar setup is in the pipeline too ?

 

 

Please let us know how the Sterling BtoB works. I have been looking at their BtoB's for charging at higher currents ie 100-200A but they are so expensive.

Watch out for what setting you put it on. I notice that the version you are buying is an older model (hence they are selling them cheap) but has a custom setting that can be set up to what you need. I am looking at the bigger 120A BtoB but it doesnt have the custom setting. I dont like the sound of the Sterling LiFePO4 setting as it has a bulk charge stage of 14.4V and then an absorption and float voltage of 13.8V. Once full ,13.8V is too high to float. Charging at 60A is a bit above what I do and this setting may work at that but I am not convinced. Charging my system at 30-40A then 14.4V is far too high and I would be up in the knee before it got past 14.3V.

Once you get it set up, if you try the LiFePO4 setting, let us know if your batteries get up into the voltage knee. If so, that is too agressive for me and likely to give balance issues if you do it as a norm (if you believe what your read on the internet). The one saving grace is that my experience with Sterling A to B's is that they switch to float well before they are rated to do so - these BtoBs may do the same so be fine on the lithium setting.

 

On the BMS, the balancing circuit current is very low so dont expect miracles on auto balancing. Try and manually balance them as best you can before you go 'live'.

 

Not sure about splitting the li banks so you get to 240A. That means you now have 8 cells to balance rather than 4. Let us know how you get on.

Very keen to hear how the BtoB works - how much power you get and what charging characteristics you get.

 

 

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