Lifepo4 battery too cheap?

[rusty69]

21 minutes ago, IanD said:

They're now officially supported by Victron too...

Lots of people are doing this, and it works fine in the short term. In the long term it's almost certain to reduce battery life, which given their cost seems like unwise penny-pinching to me.

 

AFAIK none of the FB bods have had a hybrid setup running long enough for this to show up...

The unknown answer is by how much? If they can get 4 years out of say a 280Ah drop in lithium battery at say 800 quid, that may be no where near what is achievable, but it's how comparable with the lead acid alternative that is more important, and the cost saving in charging them.

 

The facebook lot have put their faith totally in the BMS, and I guess not many people will be brave enough to admit they have wrecked their precious batteries.

 

With 4 cheapy 110Ah lead acids nearing 300 quid, with a typical lifespan of two years, the price gap, I would suggest is closing, and possibly worth the punt.

 

There are people on here with 4 year old lithium setups, but none that I know of have actually said they have killed them yet.

 

I am only a year into mine,so they need to last another few years to be as 'good' as the cheap LA batteries that I previously favoured.

[IanD]

2 minutes ago, rusty69 said:

The unknown answer is by how much? If they can get 4 years out of say a 280Ah drop in lithium battery at say 800 quid, that may be no where near what is achievable, but it's how comparable with the lead acid alternative that is more important, and the cost saving in charging them.

 

The facebook lot have put their faith totally in the BMS, and I guess not many people will be brave enough to admit they have wrecked their precious batteries.

 

With 4 cheapy 110Ah lead acids nearing 300 quid, with a typical lifespan of two years, the price gap, I would suggest is closing, and possibly worth the punt.

 

There are people on here with 4 year old lithium setups, but none that I know of have actually said they have killed them yet.

 

I am only a year into mine,so they need to last another few years to be as 'good' as the cheap LA batteries that I previously favoured.

 

Of course if a simple hybrid setup like this halves the life of an 800 quid LFP battery and you have to then replace it, it would have been a lot cheaper to use a proper BMS in the first place... 😉

 

Maybe this is the difference between 4 years life and 8 years (in which case it's probably a false economy), or the difference between 10 years and 20 years (which is so long anyway nobody will care) -- and obviously it depends on how intensively the battery is used, a full-time all-year-round liveaboard will work them much harder than a part-time or holiday boater.

[rusty69]

5 minutes ago, IanD said:

 

Of course if a simple hybrid setup like this halves the life of an 800 quid LFP battery and you have to then replace it, it would have been a lot cheaper to use a proper BMS in the first place... 😉

 

Maybe this is the difference between 4 years life and 8 years (in which case it's probably a false economy), or the difference between 10 years and 20 years (which is so long anyway nobody will care) -- and obviously it depends on how intensively the battery is used, a full-time all-year-round liveaboard will work them much harder than a part-time or holiday boater.

What are you calling a proper BMS, and what is the typical cost of one?

 

Got any links? 

[MtB]

3 minutes ago, rusty69 said:

What are you calling a proper BMS, and what is the typical cost of one?

 

Got any links? 

i was wondering the same. The bms inside drop-ins is perfectly good afaics, save for the lack of redundancy 

[Tony1]

22 hours ago, nicknorman said:

 So if for example you charge at 14.0v all the time you are out on a day’s cruise, then you will still be 99.9%SoC and you will still have been holding the battery there for hours, which is not good.

 

I'm sure I'm missing something here, but I wanted to check- in the OPs case he is charging at a modest 40 amps,

So even if he sets his charging voltage at 14.0v, his battery voltage will not actually reach 14v until the battery is say 90% full, surely? And when it reaches that point, wont his charger go into float mode? 

And if he restarts his engine after a stop, the B2B will detect the battery voltage is already high, and it will stay in float, right?

Thats the way mine seem to work, at least from observing them.

When I charge at 40amps or so, the battery voltage doesnt even go above 13.8 until well into the charge, when the batteries are at about 70 to 80% full.

My MPPTs are set to charge at 14.6v, but in reality the batteries stay around 13.4 or 13.5, increasing very slowly, until they are 70% full.  

In my experience, the bulk charge voltage seems to be an end point or target that is used to decide when to go into float, right? It's not a voltage that is sustained throughout the charge. 

I guess with your alternator charging at 160amps or more, you do see a really significant voltage rise as soon as you start charging, but I dont see that (until summer), and I dont think the OP will.  

I'm not sure if I've asked a question in all that! 😁

 

Edited February 20, 2023 by Tony1

[rusty69]

1 minute ago, MtB said:

i was wondering the same. The bms inside drop-ins is perfectly good afaics, save for the lack of redundancy 

I suspect the answer will lie in the hallowed nordkyn and marine know how websites. 

[IanD]

12 minutes ago, rusty69 said:

What are you calling a proper BMS, and what is the typical cost of one?

 

Got any links? 

 

One of the setups built with separate cells and which includes an LFP-specific BMS with active balancing -- plenty about, here are a couple of examples:

 

https://shop.gwl.eu/Battery-Management/BMS123-Smart/BMS123-Smart-Gen3-Complete-Set-4-cells-with-Bluetooth-4-0.html

https://www.rec-bms.com/

 

Unsurprisingly "proper" BMS like this cost more than cheap ones, but are a lot better at managing and protecting the cells, especially if they work together with the rest of the boat system.

Edited February 20, 2023 by IanD

[IanD]

2 minutes ago, MtB said:

i was wondering the same. The bms inside drop-ins is perfectly good afaics, save for the lack of redundancy 

 

Inside *some* drop-ins, yes. If there's more than one drop-in (either in series or parallel) then they need a way to synchronise the BMS inside each one; some (more expensive) ones do that, most don't. Ones that do often also allow external monitoring (e.g. via Bluetooth) and/or integration into the electrical system on the boat, for example controlling an inverter/charger and/or MPPT controllers.

 

https://www.victronenergy.com/live/battery_compatibility:start

[MtB]

Aha, some goalpost moving going on here! Yes using multiple drop ins adds complexity over using one the correct size in the first place. 

[rusty69]

6 minutes ago, IanD said:

 

One of the setups built with separate cells and which includes an LFP-specific BMS with active balancing -- plenty about, here are a couple of examples:

 

https://shop.gwl.eu/Battery-Management/BMS123-Smart/BMS123-Smart-Gen3-Complete-Set-4-cells-with-Bluetooth-4-0.html

https://www.rec-bms.com/

 

Unsurprisingly "proper" BMS like this cost more than cheap ones, but are a lot better at managing and protecting the cells, especially if they work together with the rest of the boat system.

They do look very nice, and maybe well suited in some environments. I'm not sure a boat is necessarily the best place for all those open circuit boards though. 

[IanD]

4 minutes ago, rusty69 said:

They do look very nice, and maybe well suited in some environments. I'm not sure a boat is necessarily the best place for all those open circuit boards though. 

 

You asked for examples -- the REC BMS is probably better suited for a boat, as you say.

 

Anyway you'd normally box in the batteries -- a good idea given the enormous short-circuit currents LFP can provide, especially when you drop a spanner on them... 😞

[rusty69]

2 minutes ago, IanD said:

 

You asked for examples -- the REC BMS is probably better suited for a boat, as you say.

 

Anyway you'd normally box in the batteries -- a good idea given the enormous short-circuit currents LFP can provide, especially when you drop a spanner on them... 😞

Fair enough. I didn't see the second link. 

[IanD]

12 minutes ago, MtB said:

Aha, some goalpost moving going on here! Yes using multiple drop ins adds complexity over using one the correct size in the first place. 

There are few drop-ins big enough for the size of battery banks that a lot of canal boaters use, so using more than one drop-in is quite common.

 

There are also plenty of cheapo drop-ins which are not really up to the job for boats with relatively high currents, see here... (I know you've read it but it's worth posting again)

 

https://marinehowto.com/drop-in-lifepo4-be-an-educated-consumer/

Edited February 20, 2023 by IanD

[nicknorman]

2 hours ago, Tony1 said:

 

I'm sure I'm missing something here, but I wanted to check- in the OPs case he is charging at a modest 40 amps,

So even if he sets his charging voltage at 14.0v, his battery voltage will not actually reach 14v until the battery is say 90% full, surely? And when it reaches that point, wont his charger go into float mode? 

And if he restarts his engine after a stop, the B2B will detect the battery voltage is already high, and it will stay in float, right?

Thats the way mine seem to work, at least from observing them.

When I charge at 40amps or so, the battery voltage doesnt even go above 13.8 until well into the charge, when the batteries are at about 70 to 80% full.

My MPPTs are set to charge at 14.6v, but in reality the batteries stay around 13.4 or 13.5, increasing very slowly, until they are 70% full.  

In my experience, the bulk charge voltage seems to be an end point or target that is used to decide when to go into float, right? It's not a voltage that is sustained throughout the charge. 

I guess with your alternator charging at 160amps or more, you do see a really significant voltage rise as soon as you start charging, but I dont see that (until summer), and I dont think the OP will.  

I'm not sure if I've asked a question in all that! 😁

 

Charging a typical boat battery of say 200-300Ah at 40A will mean it is about 99% charged by the time the voltage gets to 14.0v. When you stop the voltage will drop back to 13.4v or so. So when you start again surely it will go back to trying to achieve 14v? And when it does so, now the SoC will be 99.5% or some such.

 

I would say that when you get to 13.8v at a moderate rate of charge, you are something north of 95%SoC. Well, that is how mine behave anyway. Bear in mind that holding 13.8v will eventually give you 99.9% SoC, so the charge current as a proportion of the capacity is an important factor in these sorts of discussions. Once it gets above 13.6v it is getting close to the knee and probably about 90%. Maybe it depends on where you are measuring the voltage - I am measuring it at the cell terminals, not upstream of the charge wiring.

 

We normally charge at around 95A but it is a 600Ah bank so not that dissimilar relationship between current and capacity to you.

Edited February 20, 2023 by nicknorman

[Tony1]

48 minutes ago, nicknorman said:

Charging a typical boat battery of say 200-300Ah at 40A will mean it is about 99% charged by the time the voltage gets to 14.0v. When you stop the voltage will drop back to 13.4v or so. So when you start again surely it will go back to trying to achieve 14v? And when it does so, now the SoC will be 99.5% or some such.

 

I would say that when you get to 13.8v at a moderate rate of charge, you are something north of 95%SoC. Well, that is how mine behave anyway. Bear in mind that holding 13.8v will eventually give you 99.9% SoC, so the charge current as a proportion of the capacity is an important factor in these sorts of discussions. Once it gets above 13.6v it is getting close to the knee and probably about 90%. Maybe it depends on where you are measuring the voltage - I am measuring it at the cell terminals, not upstream of the charge wiring.

 

We normally charge at around 95A but it is a 600Ah bank so not that dissimilar relationship between current and capacity to you.

 

What I'm trying to clarify is more for new lithium users, and its not so much about the specific charge voltage you choose (in fact I agree with your suggested values for a prolonged charge). 

My issue is this- I think potential new lithium users might get the idea that if they set their MPPT to bulk charge at 14.6v, then as soon as the sun appears above the horizon and a few amps trickle in, their battery voltage reading will jump to 14.6v, and it will stay there as the battery fills up, until the MPPT goes into float.

 

But what actually happens, as you obviously know, is that the battery voltage increases very slowly.

If 20 amps are coming in, for example, my battery voltage will stay under 13.3v for a long time. If I charge at 60 or 70 amps, the battery voltage will be maybe 13.4 or 13.5.

I dont use voltage to manage the charging like almost everyone else does- but (to make it more pertinent to newbies) if I did use voltage, my battery voltage would creep up very slowly until it reached the bulk charge voltage value (lets say 13.8v), at which point the chargers would go into float.

 

So my point was just to clarify that when people set a bulk charging voltage, that voltage will take time to be reached. And when it is reached, the charger will go into float. 

In other words, the bulk charge voltage, is an 'end point' voltage, it is not a voltage that is maintained throughout the charge. 

I dont think a lot of lithium newbies are clear about that. 

 

 

 

 

 

[ditchcrawler]

10 hours ago, rusty69 said:

I get the impression every man and his dog has lithium batteries on their boat now. I reckon the trailblazers are those that installed them 5 years ago. 

 

You just need to look on the 12V boating Facebook page to see hundreds of people adopting the hybrid approach and relying on the BMS and a long length of cable (unfused?) to do all the work. 

Is the cable from your alternator to your batteries fused?

[nicknorman]

40 minutes ago, Tony1 said:

 

What I'm trying to clarify is more for new lithium users, and its not so much about the specific charge voltage you choose (in fact I agree with your suggested values for a prolonged charge). 

My issue is this- I think potential new lithium users might get the idea that if they set their MPPT to bulk charge at 14.6v, then as soon as the sun appears above the horizon and a few amps trickle in, their battery voltage reading will jump to 14.6v, and it will stay there as the battery fills up, until the MPPT goes into float.

 

But what actually happens, as you obviously know, is that the battery voltage increases very slowly.

If 20 amps are coming in, for example, my battery voltage will stay under 13.3v for a long time. If I charge at 60 or 70 amps, the battery voltage will be maybe 13.4 or 13.5.

I dont use voltage to manage the charging like almost everyone else does- but (to make it more pertinent to newbies) if I did use voltage, my battery voltage would creep up very slowly until it reached the bulk charge voltage value (lets say 13.8v), at which point the chargers would go into float.

 

So my point was just to clarify that when people set a bulk charging voltage, that voltage will take time to be reached. And when it is reached, the charger will go into float. 

In other words, the bulk charge voltage, is an 'end point' voltage, it is not a voltage that is maintained throughout the charge. 

I dont think a lot of lithium newbies are clear about that. 

 

 

Yes. I suppose my main point is to say that charging to some desired SoC less than 100% is not easily done by setting a specific charge voltage.

[rusty69]

4 minutes ago, ditchcrawler said:

Is the cable from your alternator to your batteries fused?

No

[Tony1]

3 minutes ago, nicknorman said:

Yes. I suppose my main point is to say that charging to some desired SoC less than 100% is not easily done by setting a specific charge voltage.

 

I definitely agree with that. 

My charging voltages vary wildly, from 5 amps of solar in mid December, around 75 amps with the engine running, up to potentially 170 amps in summer with MPPTs and B2Bs all running. So it would be impossible in my case to set a voltage that could always guarantee you that you stop charging at a chosen SoC. 

By coincidence, I had to rely on voltage to manage charging for the ten days I spent in Llangollen, as my shore charger doesnt have an input for a remote BMS switch off, so my BMV712 couldnt be used to control it. 

And it was quite tricky. I tried 13.8v and found that the SoC was going well over 90% before it went into float. Then I tried 13.7v, and then it only charged to 70% before stopping. It was tricky to find a good setting with it. 

 

 

[MtB]

2 minutes ago, Tony1 said:

And it was quite tricky. I tried 13.8v and found that the SoC was going well over 90% before it went into float.

 

Off at a tangent I know, but can we clarify this term "float" you are using please? 

 

Do you mean "float charge"? I.e. a voltage high enough still to maintain some current into the batteries as in "trickle charge" a lead acid? 

 

Or do you mean a voltage so low that zero current flows and charging is effectively turned OFF? 

 

Or something else?

 

Much obliged! 

 

 

[Tony1]

15 minutes ago, MtB said:

 

Off at a tangent I know, but can we clarify this term "float" you are using please? 

 

Do you mean "float charge"? I.e. a voltage high enough still to maintain some current into the batteries as in "trickle charge" a lead acid? 

 

Or do you mean a voltage so low that zero current flows and charging is effectively turned OFF? 

 

Or something else?

 

Much obliged! 

 

 

 

You know what- the truth is I dont know- at least in the sense that I dont know exactly what the chargers are doing to the batteries during the float phase. 

I never use the float phase in reality, since I switch the chargers off at 85% SoC. 

I've messed around with the float phase a few times (eg in Llangollen), and my impression is that although the charger is not charging as such, it is sort of 'leaning' on the batteries, checking the voltage in case they need a bit more charge. And if the battery voltage drops a bit below the nominated float voltage, the charger seemed to kick in and start doing some limited charging.

That was the 6 year old shore charger mind. I dont know how other units and MPPTs etc behave. 

I agree with you (from the things I've read) that the ideal treatment for lithiums is to just charge them and leave them alone, ie switch off the charger altogether. No float charge needed. Thats why I like my SoC-based charge management using the BMV712.

It seems odd that such a basic principle- something that a relative newbie like me realised very early on in my usage- still isnt being built into the charging products that we are seeing come onto the market. 

My solution is to set the float voltage at 12.7v, and in fact I may go even lower. 

 

 

Edited February 20, 2023 by Tony1

[Tony1]

 

Apologies to the OP for banging on about solar again, as I know its been mentioned, but it is worth reiterating for a liveaboard.

On 12 of the last 15 days I've had enough solar to run most of the electrics, and if I didnt run a fridge it would have been every single day.

Today I got over 1700Wh of charge (charging at about 13.35v), so if I understand it right that means I got around 127Ah of charge, which is my full days usage in winter.

It was a bright day, but not sunny all day long. And I am overlooked  by trees to the north and east, so its not even the ideal spot for solar. 

If I'm already getting 130Ah of charge in a half decent day around mid Feb, that says to me that that its worth you rearranging the coal storage on the roof (ie pile the bags up higher), and getting some more panels installed. 

If you were getting that same amount of charge (charging with a genny or a B2B at say 40 amps), that's three hours of engine or genny running saved, in terms of fuel costs. And that's just one day. When we get into Spring the solar will go ballistic

I never heard of a single liveaboard boater who regretted installing more panels. 

 

 

Edited February 20, 2023 by Tony1

[nicknorman]

1 hour ago, MtB said:

 

Off at a tangent I know, but can we clarify this term "float" you are using please? 

 

Do you mean "float charge"? I.e. a voltage high enough still to maintain some current into the batteries as in "trickle charge" a lead acid? 

 

Or do you mean a voltage so low that zero current flows and charging is effectively turned OFF? 

 

Or something else?

 

Much obliged! 

 

 

 

Well I think that float charge and trickle charge are not the same thing. When we had LAs, the Combi was permanently connected to shore power when we were away from the boat, voltage set to 13.25v. When I got back to the boat, current into the batteries was to all intents and purposes zero. That is floating - no current flowing either way. Same for Lis now. Whereas trickle charge is a low current slow charge.

[cuthound]

18 hours ago, nicknorman said:

 

Well I think that float charge and trickle charge are not the same thing. When we had LAs, the Combi was permanently connected to shore power when we were away from the boat, voltage set to 13.25v. When I got back to the boat, current into the batteries was to all intents and purposes zero. That is floating - no current flowing either way. Same for Lis now. Whereas trickle charge is a low current slow charge.

 

That has always been my understanding too.

 

Perhaps the term "holding charge" would be better to explain a charge that holds a battery at a pre-set SoC, rather than "float"?

Edited February 21, 2023 by cuthound
To insert a missing space

[nicknorman]

Yes holding charge could be it. MtB missed out on that one! But it isn't quite as simple as that because when we are in the marina on shore power, the Combi is set to the "holding voltage" but when we turn stuff on in the boat, the charger supplies the juice rather than it coming from the batteries. And ditto when we are cruising after the batteries have reached the target SoC, the alternator remains available to supply any additional loads from the boat. So "holds" the SoC but also powers the loads.