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Cheap LiFePO4 BMS?


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3 hours ago, Murflynn said:

that is 60% useful capacity ...........................   so there is not really a huge advantage in that respect over LA's that are used between 50% and 100%.

 

apart from the weight issue, I am again beginning to lose confidence in the alleged benefits of Lifepo4.

With an LA bank, (between 330Ah and 450Ah over the years), I used to have my genny running for 3 hours or more at least every other day, just to keep them full, so they didnt sulphate. The 3 hours was just to get the last 10% or so in and, during this time, I was seeing between 20A down to 3A or so going in..

 

Now, with a 530Ah Li bank, I cycle between 20% and 90-95% and can go 6 or 7 days with no sun, (depths of winter), and don't have to worry about the SOC. For the whole of the 6 or 7 hours it takes, I see 60A going in.

 

Given your view, (and your useage) I would suggest you stop thinking about an Li bank, and stick with what you've got.

 

Having said that, a month before I bought mine I said that there was no way I was going to spend the money on Li batteries :) 

 

ETA the bit in bold underlined

 

Edited by Richard10002
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Don't forget that with all these discussions about battery life, cars and boats are two very different cases. Cars have a real need to be able to use the maximum capacity for range but also have a life of many thousands of full-to-empty cycles, and are charged to full and run right down close to empty (or what the manufacturesrs define as full and empty) almost every time. So they avoid charging regularly to 100% or discharging to 0% because this would happen every time and shorten the life. OTOH they have expensive and sophisticated BM/balancing systems to allow (occasional) full charging to 100% and discharge to 0%, and battery packs that cost more than ten grand.

 

I doubt that any boat system would see anywhere near the number of full-to-empty cycles that a car does over lifetime, unless people cruise extensively almost every day and run washing machines etc almost every night -- cars batteries have a much harder life, and more severe temperature and lifetime requirements. So for most boaters worrying about losing some lifetime when it starts at several thousand complete cycles is probably the wrong thing to do (they might only last 10 years instead of 20, big deal...) if it gives a big reduction in net capacity (e.g. 20% to 80% range) given the cost of the batteries -- if you need a given capacity it's better to push them a bit harder than it is to install 50% more capacity in the first place. On most days the charge in/out will be far less than the maximum and the cycle life will be even longer (>5000? >10000?) so occasional excursions close to 100% and 0% will have very little effect on real lifetime.

 

But it's absolutely vital to ensure that they are properly balanced, don't sit at 100% (floated) for any great length of time, and *never* go outside the upper/lower cell voltage limits. The cost of a BM system to do this properly will be much lower than installing extra capacity (which is why car manufacturers do it), the problem is getting one and also the upfront cost -- boaters are usually cheapskates compared to car makers, they want to do a LiFePO4 system "on the cheap" and don't want to spend hundreds of pounds (or more) on a BM system, especially when lead-acids don't need one...

 

If you want a really big battery bank on a narrowboat for an electric-heavy lifestyle and have the space to put them (weight doesn't matter) either flooded traction cells or lead-carbon (depending on required capacity and cost) are probably still a better option today for most people (not all!) than LiFePO4, unless they're skilled enough to deal with the lithium issues themselves or rich enough to buy in a properly-designed commercial BM system.

 

This will change as LiFePO4 prices continue to fall, but what would make the biggest difference (by reducing the risk of killing the batteries) would be the availability of a good low-cost off-the-shelf lithium BM system targeted at the kind of systems narrowboats need.

 

But who's going to design/make/market one for a small market of cheapskates? They already exist for yachts where size/weight also matters, but are targeted at big expensive battery banks and yotties with deep pockets and aircon, and the market size as well as the acceptable BM unit price is much higher so it makes sense to develop one.

 

If you want a direct equivalent look at the Integrel system (replace onboard generator with massive HV alternator/charging system/inverter/battery bank) as a solution to the onboard power problem. At about 20 grand including batteries, compared to a generator-based solution it has big advantages and is not that expensive for what it is (and has cost several million to develop) but it's entirely targeted at yachts; it would of course work on a narrowboat as a (better?) alternative to a full-size encapsulated 1500rpm diesel generator based solution, but very few boaters need this level of power or have deep enough pockets to want to pay for such a system.

Edited by IanD
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That's why I think the smallest possible bank you can get away with and working it hard is the right approach. 

 

Take advantage of the benefits of lithium or you may as well stick with AGM lead which a lot of people argue is better for boats anyway where extra weight is not  a problem and existing charging systems are adequate. 

People who have bought Lithium batteries may be prone to choice bias. A similar thing happened with solar when if was £350 for 75w (I still have the two 75w panels (BP and Siemens) I paid £350 each for in the late 90s). 

 

 

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1 hour ago, IanD said:

Don't forget that with all these discussions about battery life, cars and boats are two very different cases. Cars have a real need to be able to use the maximum capacity for range but also have a life of many thousands of full-to-empty cycles, and are charged to full and run right down close to empty (or what the manufacturesrs define as full and empty) almost every time. So they avoid charging regularly to 100% or discharging to 0% because this would happen every time and shorten the life. OTOH they have expensive and sophisticated BM/balancing systems to allow (occasional) full charging to 100% and discharge to 0%, and battery packs that cost more than ten grand.

 

I doubt that any boat system would see anywhere near the number of full-to-empty cycles that a car does over lifetime, unless people cruise extensively almost every day and run washing machines etc almost every night -- cars batteries have a much harder life, and more severe temperature and lifetime requirements. So for most boaters worrying about losing some lifetime when it starts at several thousand complete cycles is probably the wrong thing to do (they might only last 10 years instead of 20, big deal...) if it gives a big reduction in net capacity (e.g. 20% to 80% range) given the cost of the batteries -- if you need a given capacity it's better to push them a bit harder than it is to install 50% more capacity in the first place. On most days the charge in/out will be far less than the maximum and the cycle life will be even longer (>5000? >10000?) so occasional excursions close to 100% and 0% will have very little effect on real lifetime.

 

But it's absolutely vital to ensure that they are properly balanced, don't sit at 100% (floated) for any great length of time, and *never* go outside the upper/lower cell voltage limits. The cost of a BM system to do this properly will be much lower than installing extra capacity (which is why car manufacturers do it), the problem is getting one and also the upfront cost -- boaters are usually cheapskates compared to car makers, they want to do a LiFePO4 system "on the cheap" and don't want to spend hundreds of pounds (or more) on a BM system, especially when lead-acids don't need one...

 

If you want a really big battery bank on a narrowboat for an electric-heavy lifestyle and have the space to put them (weight doesn't matter) either flooded traction cells or lead-carbon (depending on required capacity and cost) are probably still a better option today for most people (not all!) than LiFePO4, unless they're skilled enough to deal with the lithium issues themselves or rich enough to buy in a properly-designed commercial BM system.

 

This will change as LiFePO4 prices continue to fall, but what would make the biggest difference (by reducing the risk of killing the batteries) would be the availability of a good low-cost off-the-shelf lithium BM system targeted at the kind of systems narrowboats need.

 

But who's going to design/make/market one for a small market of cheapskates? They already exist for yachts where size/weight also matters, but are targeted at big expensive battery banks and yotties with deep pockets and aircon, and the market size as well as the acceptable BM unit price is much higher so it makes sense to develop one.

 

If you want a direct equivalent look at the Integrel system (replace onboard generator with massive HV alternator/charging system/inverter/battery bank) as a solution to the onboard power problem. At about 20 grand including batteries, compared to a generator-based solution it has big advantages and is not that expensive for what it is (and has cost several million to develop) but it's entirely targeted at yachts; it would of course work on a narrowboat as a (better?) alternative to a full-size encapsulated 1500rpm diesel generator based solution, but very few boaters need this level of power or have deep enough pockets to want to pay for such a system.

Battery balance boards are very cheap, £125 bought me 3 for three 48 volt batteries of 17.5 KWHs peanuts really

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1 hour ago, peterboat said:

Battery balance boards are very cheap, £125 bought me 3 for three 48 volt batteries of 17.5 KWHs peanuts really

It's not just the balancing, it's also over/undervoltage protection, monitoring, control, displaying status, error/fault checking, Raspberry Pi, software -- somebody with enough knowledge (I'm an electronics engineer) can roll their own system at the cost of significant time and development/debugging effort, but this is beyond the skills of most boaters who would just want something that works that they can connect up and go with. But also they don't want to pay what a commercially developed system to do all this would have to cost...

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7 hours ago, magnetman said:

Out of interest do you know what rating the EA charging points have at the moment? I've got a feeling it's a 6a thing but could well be more. 

 

It would make a difference to the viability of larger electric boats with lithium batteries / fast charge availability. 

actually I don't have a clue. 

my 20A charger fills my batteries overnight and only needs about 500watts.  I can use an electric kettle simultaneously but I have never needed to check the max available, but from that usage pattern I would reckon it must be more than 6A.. 

5 hours ago, Richard10002 said:

With an LA bank, (between 330Ah and 450Ah over the years), I used to have my genny running for 3 hours or more at least every other day, just to keep them full, so they didnt sulphate. The 3 hours was just to get the last 10% or so in and, during this time, I was seeing between 20A down to 3A or so going in..

 

Now, with a 530Ah Li bank, I cycle between 20% and 90-95% and can go 6 or 7 days with no sun, (depths of winter), and don't have to worry about the SOC. For the whole of the 6 or 7 hours it takes, I see 60A going in.

 

Given your view, (and your useage) I would suggest you stop thinking about an Li bank, and stick with what you've got.

 

Having said that, a month before I bought mine I said that there was no way I was going to spend the money on Li batteries :) 

 

ETA the bit in bold underlined

 

noted.  thanks.  :cheers:

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2 hours ago, IanD said:

It's not just the balancing, it's also over/undervoltage protection, monitoring, control, displaying status, error/fault checking, Raspberry Pi, software -- somebody with enough knowledge (I'm an electronics engineer) can roll their own system at the cost of significant time and development/debugging effort, but this is beyond the skills of most boaters who would just want something that works that they can connect up and go with. But also they don't want to pay what a commercially developed system to do all this would have to cost...

It is clear that someone skilled in the art can design a BMS that is fit for purpose for canal boats (MP has developed one and Nick has nearly got his system in place) but I dont think we will ever see a commercial system for someone using 2nd hand Li's from cars as every boat set up is different and to cover all eventualities (different solar, different alternators, different everything). It is however easily possible to put a system in based on off the shelf items which has multiple layers of safety (four of them) without the need for any programming or computer kit. That opens up the design of the system to anyone who understands LA batteries and how to look after them. Only minor soldering skills needed along with the ability to crimp connectors on battery size cables. That means the cost of a safe system is much less than the sort of prices that Victron are asking for their commercial system. One aspect of this though is that such as system works so much easier (and safer) by not going up to 100% charge each time - hence by giving up 10-15% capacity you can install a simple off the shelf solution.

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13 minutes ago, Richard10002 said:

Have you got a link to where you bought them?

Yes Richard ebay item 312871729322 they are for my lithium polymer batteries that I have made up for little electric car, they are 5P 15S with one board for each pack. I have 3 packs making up 17.5 KWHS 

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1 hour ago, Dr Bob said:

It is clear that someone skilled in the art can design a BMS that is fit for purpose for canal boats (MP has developed one and Nick has nearly got his system in place) but I dont think we will ever see a commercial system for someone using 2nd hand Li's from cars as every boat set up is different and to cover all eventualities (different solar, different alternators, different everything). It is however easily possible to put a system in based on off the shelf items which has multiple layers of safety (four of them) without the need for any programming or computer kit. That opens up the design of the system to anyone who understands LA batteries and how to look after them. Only minor soldering skills needed along with the ability to crimp connectors on battery size cables. That means the cost of a safe system is much less than the sort of prices that Victron are asking for their commercial system. One aspect of this though is that such as system works so much easier (and safer) by not going up to 100% charge each time - hence by giving up 10-15% capacity you can install a simple off the shelf solution.

As I said, give that many boaters have difficulty with simple conventional 12V lead-acid systems without killing their (cheap) batteries, this is all a step too far to get wide adoption -- you and MP and Peterboat and Nick and me may think it's obvious but it just isn't to most people, you need to put yourself in their shoes.

 

Even if somebody (like Nick) produced a comprehensive "Lithium for dummies" guide complete with a component list and instructions, if it made it seem easy then people would go for it, screw it up and kill their (expensive) batteries, then blame him (or whoever). They're just plain more finicky then lead-acid and need more care, and cost a lot more if you do kill them -- which people who don't understand them inevitably would unless the system prevented them, which means no possibility to override Vmin and Vmax, which means a closed system they can't mess with, which means not a DIY one.

 

I'm not saying that lithium isn't a good solution for people who see and understand the advantages and know how to use them, but right now they're just too expensive and fragile to put in the hands of people who can't even keep lead-acids alive...

Edited by IanD
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12 minutes ago, IanD said:

, but right now they're just too expensive and fragile to put in the hands of people who can't even keep lead-acids alive...

You wont get any argument from me on that one but for anyone who can keep their LA's alive and knows why they are managing them well - then there is no reason why Li's cant work. Therefore there are a large number of potential users. It really is not that difficult. They are not too expensive and fragile for anyone who knows how to look after lead acids.

18 months ago - I was in their shoes. In December 2018 I was interested and went to see MP and Tom &Bex. I was frightend at the complexity of MP's arduino box. I chose a simpler approach using off the shelf stuff and by just bolting on top of my LA system so didnt have to do major surgery on my battery wiring. I knew the basics of looking after LAs and had been very successful in keeping a large set of cheapo's alive....but my electrical skills were really just basic soldering. I had never crimpped a battery cable in my life.

Anybody reading this thread will think that Li's are really complex and only the 'clever' few can manage them (which is what people will think reading your post). That is clearly not the case. Anyone willing to learn and stick to new rules can do it. I did.

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54 minutes ago, peterboat said:

Yes Richard ebay item 312871729322 they are for my lithium polymer batteries that I have made up for little electric car, they are 5P 15S with one board for each pack. I have 3 packs making up 17.5 KWHS 

https://www.ebay.co.uk/itm/312871729322

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4 hours ago, IanD said:

It's not just the balancing, it's also over/undervoltage protection, monitoring, control, displaying status, error/fault checking, Raspberry Pi, software -- somebody with enough knowledge (I'm an electronics engineer) can roll their own system at the cost of significant time and development/debugging effort, but this is beyond the skills of most boaters who would just want something that works that they can connect up and go with. But also they don't want to pay what a commercially developed system to do all this would have to cost...

 

2 minutes ago, Dr Bob said:

You wont get any argument from me on that one but for anyone who can keep their LA's alive and knows why they are managing them well - then there is no reason why Li's cant work. Therefore there are a large number of potential users. It really is not that difficult. They are not too expensive and fragile for anyone who knows how to look after lead acids.

18 months ago - I was in their shoes. In December 2018 I was interested and went to see MP and Tom &Bex. I was frightend at the complexity of MP's arduino box. I chose a simpler approach using off the shelf stuff and by just bolting on top of my LA system so didnt have to do major surgery on my battery wiring. I knew the basics of looking after LAs and had been very successful in keeping a large set of cheapo's alive....but my electrical skills were really just basic soldering. I had never crimpped a battery cable in my life.

Anybody reading this thread will think that Li's are really complex and only the 'clever' few can manage them (which is what people will think reading your post). That is clearly not the case. Anyone willing to learn and stick to new rules can do it. I did.

Most boaters kill batteries by constantly under charging LifePo4s arnt bothered by that. Over charging is easily and cheaply sorted and a low voltage disconnect as well. Nick's board will sort out alternator charging.  As Bob knows I just use solar and the whispergen I have never fitted the protection board I bought. 3 years on still no issues and they are so much easier to live with than crap LAs 

2 minutes ago, WotEver said:

I bought 6 of them 3 for me and 3 for John who has the same batteries as me for his boat with a 48 volt inverter bit of discount and 125 squids for 3 ?

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1 hour ago, Dr Bob said:

but my electrical skills were really just basic soldering. I had never crimpped a battery cable in my life.

I’m frightened to death of soldering, yet can crimp battery cables from tiny to 70mm2.

 

Suppose I should practice soldering.... it can’t be that difficult?

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24 minutes ago, Richard10002 said:

Suppose I should practice soldering.... it can’t be that difficult?

The ‘secret’ to soldering is to have the cable and whatever you’re soldering it to scrupulously clean. Then wet the iron with a little solder (because it helps to transfer the heat), apply the iron to the wire and then apply the multi core solder to the wire. If everything is hot enough you’ll see the solder flow into the strands and around the terminal (or whatever). Remove the iron as soon as that happens and wait a while as it all cools. Don’t blow on it or do anything else that might speed up the cooling. 
 

Two more dont’s...

Don’t ‘carry’ the solder to the joint on the iron. The flux will burn off and it won’t flow. 
Don’t melt the solder on the iron, melt it on the joint (same reason). 


 

 


A little practise and you’ll soon get it. 

Edited by WotEver
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4 minutes ago, WotEver said:

The ‘secret’ to soldering is to have the cable and whatever you’re soldering it to scrupulously clean. Then wet the iron with a little solder (because it helps to transfer the heat), apply the iron to the wire and then apply the multi core solder to the wire. If everything is hot enough you’ll see the solder flow into the strands and around the terminal (or whatever). Remove the iron as soon as that happens and wait a while as it all cools. Don’t blow on it or do anything else that might speed up the cooling. 
 

Two more dont’s...

Don’t ‘carry’ the solder to the joint on the iron. The flux will burn off and it won’t flow. 
Don’t melt the solder on the iron, melt it on the joint (same reason). 


 

 

Hey, that's complicated.

I did say 'basic soldering'.

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Important!!!   Before you solder cable conductor ends, scrape them on the edge of the bench gently with a ''penknife blade is good'' until bright shiny copper, or your likely to get a rotton or dry joint. There is a kind of fine laquer on the wires which is there to help sheath it into the outer insulation at the factory, that's why they look dull when paring away the outer sheath.

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3 hours ago, IanD said:

 

 

They're just plain more finicky then lead-acid and need more care, and cost a lot more if you do kill them -- which people who don't understand them inevitably would unless the system prevented them, which means no possibility to override Vmin and Vmax, which means a closed system they can't mess with, which means not a DIY one.

 

I'm not saying that lithium isn't a good solution for people who see and understand the advantages and know how to use them, but right now they're just too expensive and fragile to put in the hands of people who can't even keep lead-acids alive...

I would disagree with that. I find ours much less finicky than LA. And living off grid, we struggled to get 12 months out of LA, despite hours and hours of generator running. Now we just run the engine for an hour or 2 every day or 2 depending on usage. We're also much more careless with our power usage than before, as it's so much easier to replace!

 

All components I used were "off the shelf" other than the alternator controller (which is now off the shelf, albeit at $500+!) No option to change max and min voltage settings on the BMS I've used. I think most of the complexity arises from alternator charging, and if you don't need this, it really is very easy indeed. 

 

No programming knowledge needed. Just the ability to safely connect a few wires. Our system will have definitely paid for itself by the end of this winter, if not already. Thinking about it, would have paid for itself just in saving cost of buying generator if I hadn't already bought it for endless hours charging LA batteries! Lithium would be a better investment, and cost less than a Honda generator. 

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12 hours ago, WotEver said:

The ‘secret’ to soldering is to have the cable and whatever you’re soldering it to scrupulously clean. Then wet the iron with a little solder (because it helps to transfer the heat), apply the iron to the wire and then apply the multi core solder to the wire. If everything is hot enough you’ll see the solder flow into the strands and around the terminal (or whatever). Remove the iron as soon as that happens and wait a while as it all cools. Don’t blow on it or do anything else that might speed up the cooling. 
 

Two more dont’s...

Don’t ‘carry’ the solder to the joint on the iron. The flux will burn off and it won’t flow. 
Don’t melt the solder on the iron, melt it on the joint (same reason). 


 

 


A little practise and you’ll soon get it. 

Having done hundreds if not thousands of LPG conversions which involved lots of soldering , i can safely say at times I lost the will to live doing it! The beauty is though soldered joints rarely fail and atr the best way of joining two or more wires. Spade terminals were also soldered much better than crimp connectors 

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11 hours ago, Tom and Bex said:

I think most of the complexity arises from alternator charging, and if you don't need this, it really is very easy indeed. 

 

 

I fully agree with all Tom says and if you do need the alternator then one 'off the shelf' approach is to use a Sterling AtoB which I did on my last boat or a Sterling BtoB as I am doing on this one.

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3 minutes ago, Dr Bob said:

I fully agree with all Tom says and if you do need the alternator then one 'off the shelf' approach is to use a Sterling AtoB which I did on my last boat or a Sterling BtoB as I am doing on this one.

The thing is all our systems suit us the designer, mine is simple because my 2 charging sources are quality items with realistic safe voltage limits. Yours is a compromise because the boat is under warranty, but your system is safe and has built in redundancy. Others have done the same and as yet no disasters reported, so they work and work well. I would not buy an off the shelf system as I know that the markup would be large so in most cases it would fail on uptake.  

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