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Cheap LiFePO4 BMS?


jetzi

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14 minutes ago, MtB said:

 

Or even attach an overheat thermostat to it, wired up to sound a buzzer if it trips. Plenty of boiler thermostats around that trip at about 90c.

Well in my case I’d add another Onewire temperature sensor to the alternator controller so that it shut down if the relay temperature became excessive.

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1 hour ago, rusty69 said:

He's not here frequently any more 

 

.....er how can I be here frequently if the last post before this current round was 2nd July? I frequently look for infrequent postings but frequently am disappointed.

My infrequent red thermometer has been infrequently used since May as the stove has been in dormant mode awaiting the injection of some solid fuel and an ignition source. That cant be more than 3 or 4 weeks away....EEK!!!!

 

Sorry to hear about Tom's blow out but 2 blown alternators sounds expensive.

I'm using the BEP switch for charging and discharging (rather than the latching relay) but my strategy is for the charging source to back off or be isolated before the isolation switch activated so it is only to be used in an emergency. I do test it from time to time (infrequently - every 3 months or so) and do have an audible alarm if there was a failure.

 

Tom, why did the alternator blow? When the tyco activates, the 12V LA in your system takes the surge. What happened when the relay blew?

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16 hours ago, Tony1 said:

 

 

We know that the 'long wire' parallel/lead acid method works ok for charging them with an existing alternator, as proven by several knowledgeable members here, so at this point I'm starting to think its as good as chance for electrical novices to get into lithiums as we're likely to see for a couple of years.

 

 

Well said.

A simple hybrid system is working very well for me. Li's at £500 for 100Ah brings the price to a decent point. I've lost touch with the 2nd Li's from the EV market - interested to hear what the current pricing is - and where those batteries (ie LiFePO's) come from - Peter?

 

 

15 hours ago, TheBiscuits said:

Just a warning that if you don't connect the Sterling batteries via a battery-to-battery charger the 5 year warranty is invalidated.

 

It'll probably work fine, but you "pays your money and takes your chances."

 

In related news they are about to have a very good 150Ah one going cheap on their clearance section - it was mine and the Bluetooth module died, so they simply replaced the battery with a brand new one under the warranty.  The cells are fine and the BMS works fine, you just can't monitor it over Bluetooth.

 

That does worry me a bit. If the Bluetooth module dies, what else is suspect? I'm glad I have my bare Thundersky's where I know exactly what is attached and I can put a number of layers of protection on them. For me, the main area of weakness in my system is the BMV battery monitor - which is my main way of monitoring the system - but these seem pretty bulletproof... well done Victron.

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2 minutes ago, Dr Bob said:

Well said.

A simple hybrid system is working very well for me. Li's at £500 for 100Ah brings the price to a decent point. I've lost touch with the 2nd Li's from the EV market - interested to hear what the current pricing is - and where those batteries (ie LiFePO's) come from - Peter?

 

 

 

That does worry me a bit. If the Bluetooth module dies, what else is suspect? I'm glad I have my bare Thundersky's where I know exactly what is attached and I can put a number of layers of protection on them. For me, the main area of weakness in my system is the BMV battery monitor - which is my main way of monitoring the system - but these seem pretty bulletproof... well done Victron.

My BMS BT module packed up after a couple of months. Fortunately, they are relatively inexpensive. I think I had 2 more delivered Inc postage from China for less than 10 quid

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1 minute ago, Dr Bob said:

That does worry me a bit. If the Bluetooth module dies, what else is suspect?

 

Nah, the Daly bluetooth module is known to be flaky.  I did mention that I'd prefer the hardwired version for monitoring and control, and Sterling said "Watch this space ..." 

 

Just now, rusty69 said:

My BMS BT module packed up after a couple of months. Fortunately, they are relatively inexpensive. I think I had 2 more delivered Inc postage from China for less than 10 quid

 

Yeah that.

 

The issue is that I didn't want to invalidate the remaining four-and-a-half year warranty by cutting the casing open to get to it!

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43 minutes ago, Dr Bob said:

Well said.

A simple hybrid system is working very well for me. Li's at £500 for 100Ah brings the price to a decent point. I've lost touch with the 2nd Li's from the EV market - interested to hear what the current pricing is - and where those batteries (ie LiFePO's) come from - Peter?

 

That does worry me a bit. If the Bluetooth module dies, what else is suspect? I'm glad I have my bare Thundersky's where I know exactly what is attached and I can put a number of layers of protection on them. For me, the main area of weakness in my system is the BMV battery monitor - which is my main way of monitoring the system - but these seem pretty bulletproof... well done Victron.

 

Almost all the secondhand EV lithium batteries from cars today are NCO chemistry or similar, definitely *not* recommended for boats due to fire risk (LFP are fine). You might possibly find LFPs from early installations in vans and buses (like Peter did) but this was before EVs took off -- there will be more secondhand EV LFPs in future because Tesla are starting to use them in some models, but it's very unlikely to find these secondhand yet...

 

Victron gear is pretty good (though obviously *nothing* is 100% reliable...) but it's a lot more expensive than the no-name/straight-from-China stuff, some of which is cheap badly-designed badly-built unreliable junk... 😉

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5 minutes ago, IanD said:

Almost all the secondhand EV lithium batteries from cars today are NCO chemistry or similar, definitely *not* recommended for boats due to fire risk (LFP are fine).

You might possibly find LFPs from early installations in vans and buses (like Peter did) but this was before EVs took off --  😉

I didnt ask for sources of LiFePO's from cars. It's obvious that the new car sources are out of the question. You do realise do you that there were a number on here before you got interested that sourced Li's from the EV market - not just Peter? That is why I asked Peter (who knows about the sources) rather than you (who doesnt know about the sources). Those sources are still there with batteries 4 years older - and likely in much larger quantity as they are now 4 years older.

 

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1 hour ago, Dr Bob said:

I didnt ask for sources of LiFePO's from cars. It's obvious that the new car sources are out of the question. You do realise do you that there were a number on here before you got interested that sourced Li's from the EV market - not just Peter? That is why I asked Peter (who knows about the sources) rather than you (who doesnt know about the sources). Those sources are still there with batteries 4 years older - and likely in much larger quantity as they are now 4 years older.

 

You said "I've lost touch with the 2nd Li's from the EV market" and asked "where those batteries (ie LiFePO's) come from", I just answered your questions -- no need to be so aggressive 😉

 

Of course I know other people got into Li batteries for boats before I did, and I'd be interested to know if the sources that were around 4 years ago are still there, because most of the secondhand EV batteries on the web are from cars and aren't LFP -- I'm sure Peter will come along with his answer soon... 🙂

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17 minutes ago, Richard10002 said:

I bought 4 x 135Ah Valence batteries, which seemed to be readily available in 2019.

 

I might like one or two more, but haven't seen any for sake for a while. 

 

 

Valence are LiFeMgPO4 lithium iron magnesium phosphate, according to my notes.

 

Dunno how much difference that makes. 

 

 

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34 minutes ago, rusty69 said:

I'm pretty sure the guy I got my cells from (40Ahr Thundersky) said they were from some kind of UPS for a computer server. He had hundreds of them that had not been put into active use. 

Thundersky/Winston and Valence are both (safe) LFP.

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42 minutes ago, rusty69 said:

Pretty sure the early victron lithium batteries contained Thundersky cells (LiFeYPO4)

I believe the current Victron ones use Winston, similar to Thundersky.

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6 hours ago, Dr Bob said:

Well said.

A simple hybrid system is working very well for me. Li's at £500 for 100Ah brings the price to a decent point. I've lost touch with the 2nd Li's from the EV market - interested to hear what the current pricing is - and where those batteries (ie LiFePO's) come from - Peter?

 

 

 

That does worry me a bit. If the Bluetooth module dies, what else is suspect? I'm glad I have my bare Thundersky's where I know exactly what is attached and I can put a number of layers of protection on them. For me, the main area of weakness in my system is the BMV battery monitor - which is my main way of monitoring the system - but these seem pretty bulletproof... well done Victron.

I got some for a mate recently 200ah lifepo4s individual cells at 110 squid each brand new, he built a 48 volt system with them fitted a BMS and Bob's your uncle 

3 hours ago, Richard10002 said:

I bought 4 x 135Ah Valence batteries, which seemed to be readily available in 2019.

 

I might like one or two more, but haven't seen any for sake for a while. 

James still has some or did the other month 

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8 hours ago, Dr Bob said:

Well said.

A simple hybrid system is working very well for me. Li's at £500 for 100Ah brings the price to a decent point. I've lost touch with the 2nd Li's from the EV market - interested to hear what the current pricing is - and where those batteries (ie LiFePO's) come from - Peter?

 

 

 

That does worry me a bit. If the Bluetooth module dies, what else is suspect? I'm glad I have my bare Thundersky's where I know exactly what is attached and I can put a number of layers of protection on them. For me, the main area of weakness in my system is the BMV battery monitor - which is my main way of monitoring the system - but these seem pretty bulletproof... well done Victron.

 

Many will consider this overkill, and I dont have a good enough understanding of the risks to know one way or the other, but I've ended up with three BMV712s monitoring my batteries.

The day to day management is done by a BMV-712 that is set to switch off the various chargers when the battery SoC gets to 80%, via a tiny cable that feeds into their BMS inputs. When the SoC falls below 55%, the MPPTs are switched back on again automatically.

I don't entirely trust the SoC measurement as I know it can drift a bit over time, so the second level of protection is the more normal one, which is based on the charge profile of the MPPTS and B2Bs that I'm using. 

Its the MPPTs that do all the charging between April and end of Sept, and they go into float when the batteries reach 13.8v, which generally happens when they  are about 85% full.

So from April to Oct, the SoC monitor is usually the first thing to kick in and switch off the MPPTs at 80% SoC.

But if that doesnt work as expected (eg the measured SoC value might display 80%, but the true SoC might be say 90%+, due to error creeping in over time), then the charge profile will cause the MPPTs to go into float when the batteries reach 13.8v- so the batteries should be safe even if the SoC measurement drifts over time. 

The third protection level, which is the emergency last resort, is a victron battery protect unit which is triggered by a BMV-712 so that it will disconnect all the chargers from the batteries if the voltage goes above 14.6v. 

I bought it intending to use it as a low-voltage disconnect, but then I read that it doesnt work with inverters, which makes it useless on most boats. 

So I pressed it into service as the high-voltage disconnect, and the BEP switch that I was using for that purpose was swapped over, and that now works as the emergency low voltage disconnect (since my valences dont come with a built-in BMS).

That needs a third B<V712, specifically monitoring low voltage and low SoC events. 

It feels like all this may be overkill, and its evolved in a sporadic and clumsy way without an original design in mind, and its turned out to be a right dogs breakfast in terms of complexity, but on the plus side I do feel that I'm well protected from extreme voltages. 

My temp protection is not so good (in fact the MPPTs dont even have a temp sensor on the batteries, but that's a problem for another day.  I'm hoping that being conservative about SoC and battery voltages will provide the protection I need against high temps. 

 

 

Edited by Tony1
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1 hour ago, Tony1 said:

 

Many will consider this overkill, and I dont have a good enough understanding of the risks to know one way or the other, but I've ended up with three BMV712s monitoring my batteries.

The day to day management is done by a BMV-712 that is set to switch off the various chargers when the battery SoC gets to 80%, via a tiny cable that feeds into their BMS inputs. When the SoC falls below 55%, the MPPTs are switched back on again automatically.

I don't entirely trust the SoC measurement as I know it can drift a bit over time, so the second level of protection is the more normal one, which is based on the charge profile of the MPPTS and B2Bs that I'm using. 

Its the MPPTs that do all the charging between April and end of Sept, and they go into float when the batteries reach 13.8v, which generally happens when they  are about 85% full.

So from April to Oct, the SoC monitor is usually the first thing to kick in and switch off the MPPTs at 80% SoC.

But if that doesnt work as expected (eg the measured SoC value might display 80%, but the true SoC might be say 90%+, due to error creeping in over time), then the charge profile will cause the MPPTs to go into float when the batteries reach 13.8v- so the batteries should be safe even if the SoC measurement drifts over time. 

The third protection level, which is the emergency last resort, is a victron battery protect unit which is triggered by a BMV-712 so that it will disconnect all the chargers from the batteries if the voltage goes above 14.6v. 

I bought it intending to use it as a low-voltage disconnect, but then I read that it doesnt work with inverters, which makes it useless on most boats. 

So I pressed it into service as the high-voltage disconnect, and the BEP switch that I was using for that purpose was swapped over, and that now works as the emergency low voltage disconnect (since my valences dont come with a built-in BMS).

That needs a third B<V712, specifically monitoring low voltage and low SoC events. 

It feels like all this may be overkill, and its evolved in a sporadic and clumsy way without an original design in mind, and its turned out to be a right dogs breakfast in terms of complexity, but on the plus side I do feel that I'm well protected from extreme voltages. 

My temp protection is not so good (in fact the MPPTs dont even have a temp sensor on the batteries, but that's a problem for another day.  I'm hoping that being conservative about SoC and battery voltages will provide the protection I need against high temps. 

 

 

Tony it will be fine, I have had my batteries right down and back up again without problems. 

My 36volt drive batteries came in various states of charge, I fully charged them reset the BMS and 3 years later still flashing green and working great

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2 hours ago, Naughty Cal said:

Some of you have some incredibly overly complicated systems in play 😵💫

 

Guilty as charged your honour, the only reason I explain all the gory detail is so that people can see they don't really need all that stuff.  

My setup evolved like Fronkenstein's monster, due to ignorance about electrics, and about what were the real risks involved. 

In hindsight a bigger alternator plus a clever regulator would have been a far simpler and better solution, but the price scared me, and the straw that broke the camel's back was that my canaline 38 wont accept a poly V alternator, which is the type needed if you want a bigger current output. It needed some kind of crank upgrade. The original upgrade kits were no longer available, and there was some uncertainty about whether the new kits would fit my engine. 

Nobody involved was able to give a 100% guarantee that it would fit together, so after much thought, I very reluctantly decided I couldn't take the risk of splashing out close to £1500 to get it all done.  

 

 

Edited by Tony1
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13 hours ago, Tony1 said:

 

Many will consider this overkill, and I dont have a good enough understanding of the risks to know one way or the other, but I've ended up with three BMV712s monitoring my batteries.

The day to day management is done by a BMV-712 that is set to switch off the various chargers when the battery SoC gets to 80%, via a tiny cable that feeds into their BMS inputs. When the SoC falls below 55%, the MPPTs are switched back on again automatically.

I don't entirely trust the SoC measurement as I know it can drift a bit over time, so the second level of protection is the more normal one, which is based on the charge profile of the MPPTS and B2Bs that I'm using. 

I

 

Tony, I am probably one of the few people with direct experience of what you are doing as I have a very similar system, a hybrid LA/Li set up with B2B's, long wires controlled by a BMV 713 and a BEP switch. I do think you are overcomplicating it a tad! There is two sides to this i) the technical set up and ii) how it is operated in practice. Lets look at these separately.

Firstly the technical bit. For me the first level of control has to be the charge source reducing its input when a set level is reached, rather than the isolation switch activated. You say your first line of defence is the isolation activated when you get to 80% SoC. If you are using solar, then the MPPT will work fine to turn down to float so your isolation switch will never be needed. If you are on the alternator for charge then the B2B's will turn down once the set level is needed. I assume your isolation switch is the BEP. In the 4 years I have operated my system, my BEP has not activated once (on its own). I test it infrequently. For me the first level must not rely on the isolation switch.

You then say you need 3 BMVs. Why are you controlling on SoC? On my BMV, SoC is pretty useless after a couple of weeks since sync. Why not use voltage? My BMV is set to trigger the relay for high voltage at 13.9V. This is an absolute value. My state of charge limit is always the same – when the alternator gets to 13.9v at circa 50A (drops from 120A at start). The SoC reading could be anything. One advantage of using voltage is that the BMV has a high level and low level relay so the one BMV does both. That removes your 2nd BMV, and also allows your charge sources to shut down rather than relying on the BEP.

The BMV voltage is my second line of defence but as above it is never normally triggered. My third defence is the BMV sounding an audible (just) alarm at 14.0V volts, then a fourth - a cell monitoring device that activates the BEP if an individual cell goes above 3.8V and then a final audible alarm if the whole lot goes over 14.4V. The automated isolation is all via the BEP switch which is a vulnerability in the way Tom's Tyco bipolar relay could fail, but shutting down the charge sources in normal operation has to be the way to do it.

I think though that you have to look at normal operation. I very rarely get anywhere near isolation events. I see 2 modes of operation, moving and stationary. An example from this summers 3 months trip out. In the stationary mode, we are tied up not going anywhere. Our 200Ah of power has gone out overnight (and previous 24hrs) and the BMV is showing -200Ahrs. The sun starts charging, we run the engine for an hour to warm the water (putting circa 100Ahr back in). The sun does the rest and the mppt goes into float at the end of the afternoon. No intervention at all. No B2B running – just straight from the solar to Li's. Lack of sun one day and I run the engine for an extra 30 mins. Never any chance of getting near full charge with the engine. I will turn it off after the time I estimate. If I died in the interim, the BEP would isolate it. In moving mode, we are down -200Ahrs at the start of the day. I know we will be charged enough after circa 60 mins and the B2B will shut down the charge then. In practice though I have given up with the B2B's (2* 60A) as they consume so much power and heat up the boat! …..and I just manually isolate the Li's when the voltage gets to circa 13.8V. If I want it automatic then the B2Bs are fine but I am always watching the instruments as we idle along so spending 10 secs to turn a switch is not a chore. It really is so simple.

Now the solar is loosing its efficiency, when stationary, we just run the engine for 90 mins instead of 60 – but we are a very heavy power user.

I do use 2 BMVs, one on the Li system that does all the controlling and one on the LA system. Both are needed to understand battery health for the two banks.

Anyway, well done on setting up your system. It sounds complicated to the non initiated but it isnt. I would certainly encourage you to move to isolating the charge sources at source and then using voltage to control the BMV rather than SoC in an emergency situation.

 

How do you monitor your system with the 3 BMVs? I have mine wired into a Raspberry Pi which dumps all the data to the Victron server (data 24/7) so can see all of the data from the last year from my armchair.

 

For peeps new on here who dont know me, (who can you trust on the internet these days?)my electrical knowledge is significantly lacking when compared to Nick and Simon (MP) so my system was developed from a 'user' approach rather than a technical approach and one where I could marry 2nd hand Li's to a new boat where I didnt want to void any warranties – hence the hybrid. I do however consider myself an expert on Li batteries, particularly in their safety as I am director of a company working closely with the aviation industry setting standards (via destruction testing) on their transport on passenger aeroplanes and also developing new technology for early warning of battery failure leading to ignition or explosions (ie during dendrite failure).

 

 

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6 minutes ago, Dr Bob said:

 

Tony, I am probably one of the few people with direct experience of what you are doing as I have a very similar system, a hybrid LA/Li set up with B2B's, long wires controlled by a BMV 713 and a BEP switch. I do think you are overcomplicating it a tad! There is two sides to this i) the technical set up and ii) how it is operated in practice. Lets look at these separately.

Firstly the technical bit. For me the first level of control has to be the charge source reducing its input when a set level is reached, rather than the isolation switch activated. You say your first line of defence is the isolation activated when you get to 80% SoC. If you are using solar, then the MPPT will work fine to turn down to float so your isolation switch will never be needed. If you are on the alternator for charge then the B2B's will turn down once the set level is needed. I assume your isolation switch is the BEP. In the 4 years I have operated my system, my BEP has not activated once (on its own). I test it infrequently. For me the first level must not rely on the isolation switch.

You then say you need 3 BMVs. Why are you controlling on SoC? On my BMV, SoC is pretty useless after a couple of weeks since sync. Why not use voltage? My BMV is set to trigger the relay for high voltage at 13.9V. This is an absolute value. My state of charge limit is always the same – when the alternator gets to 13.9v at circa 50A (drops from 120A at start). The SoC reading could be anything. One advantage of using voltage is that the BMV has a high level and low level relay so the one BMV does both. That removes your 2nd BMV, and also allows your charge sources to shut down rather than relying on the BEP.

The BMV voltage is my second line of defence but as above it is never normally triggered. My third defence is the BMV sounding an audible (just) alarm at 14.0V volts, then a fourth - a cell monitoring device that activates the BEP if an individual cell goes above 3.8V and then a final audible alarm if the whole lot goes over 14.4V. The automated isolation is all via the BEP switch which is a vulnerability in the way Tom's Tyco bipolar relay could fail, but shutting down the charge sources in normal operation has to be the way to do it.

I think though that you have to look at normal operation. I very rarely get anywhere near isolation events. I see 2 modes of operation, moving and stationary. An example from this summers 3 months trip out. In the stationary mode, we are tied up not going anywhere. Our 200Ah of power has gone out overnight (and previous 24hrs) and the BMV is showing -200Ahrs. The sun starts charging, we run the engine for an hour to warm the water (putting circa 100Ahr back in). The sun does the rest and the mppt goes into float at the end of the afternoon. No intervention at all. No B2B running – just straight from the solar to Li's. Lack of sun one day and I run the engine for an extra 30 mins. Never any chance of getting near full charge with the engine. I will turn it off after the time I estimate. If I died in the interim, the BEP would isolate it. In moving mode, we are down -200Ahrs at the start of the day. I know we will be charged enough after circa 60 mins and the B2B will shut down the charge then. In practice though I have given up with the B2B's (2* 60A) as they consume so much power and heat up the boat! …..and I just manually isolate the Li's when the voltage gets to circa 13.8V. If I want it automatic then the B2Bs are fine but I am always watching the instruments as we idle along so spending 10 secs to turn a switch is not a chore. It really is so simple.

Now the solar is loosing its efficiency, when stationary, we just run the engine for 90 mins instead of 60 – but we are a very heavy power user.

I do use 2 BMVs, one on the Li system that does all the controlling and one on the LA system. Both are needed to understand battery health for the two banks.

Anyway, well done on setting up your system. It sounds complicated to the non initiated but it isnt. I would certainly encourage you to move to isolating the charge sources at source and then using voltage to control the BMV rather than SoC in an emergency situation.

 

How do you monitor your system with the 3 BMVs? I have mine wired into a Raspberry Pi which dumps all the data to the Victron server (data 24/7) so can see all of the data from the last year from my armchair.

 

For peeps new on here who dont know me, (who can you trust on the internet these days?)my electrical knowledge is significantly lacking when compared to Nick and Simon (MP) so my system was developed from a 'user' approach rather than a technical approach and one where I could marry 2nd hand Li's to a new boat where I didnt want to void any warranties – hence the hybrid. I do however consider myself an expert on Li batteries, particularly in their safety as I am director of a company working closely with the aviation industry setting standards (via destruction testing) on their transport on passenger aeroplanes and also developing new technology for early warning of battery failure leading to ignition or explosions (ie during dendrite failure).

 

 

I have always said it's down to voltage on Lifepo4s it's worked for years for me

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17 minutes ago, Dr Bob said:

 

 

For peeps new on here who dont know me, (who can you trust on the internet these days?) 

 

 

 

Never trust a muppet. They lack kermit-ment. 

Edited by rusty69
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