Lifepo4 battery too cheap?

[n-baj]

11 minutes ago, Tony1 said:

 

If you can confirm the B2B never draws more than 45 amps that will help, but the lead acid may also take in some charge, especially during the first 10-15 minutes of charging, so I don't know if you can assume that the 45 amps for the B2B is the total current draw throughout the charging process....

But I understand that lead acid batteries rapidly build up a resistance to charging after the first 10-15 mins, that issue might not be a problem. You might see 60 amps total draw initially if the lead acid battery needs some charging, but maybe you'll only see that for 10 minutes, and then it might go down to a safer level.

 

I hate to say this because I've been there myself with limited capacity alternators, but it might that your alternator (at engine tickover) just cant put out more than 40amps without going above 100 degrees. 

When my engine is charging at tickover (which happens often during cruising), I limit the current draw to 30 amps from each alternator, by setting the B2Bs onto half power mode. But when moored up and charging, I can up the revs and safely draw more current from the alternators.

But I have a separate B2B and lead acid for each alternator, and its a fair bit of faff/expense tbh. Not recommended.

Maybe you can set the Renogy B2B to half power when cruising, in case it spends long periods at tickover etc, but when moored up you can run the engine at say 1300rpm to cool the alternator a bit, and in that scenario maybe switch it to full power?

This is why I suggested testing alternator temp vs output current at different rpm. 

 

 

The alternator can give the full 110A for the first few minutes as everything is cool so the first 30 minutes or so I’m not too concerned, it’s hour after hour when everything is warm.

 

this is going to sound daft but I cannot create a load that takes 50A from the alternator. It just so happens it maxes out at around 50A on tick over so I’ve just been operating the microwave on half power (half power being the magnetron switching on and off, not halving the power) so the alternator was outputting 50A or thereabouts all the time, if I increased the revs the output will increase. It’s still a useful test as it’s testing worse case, therefore a higher speed at 50A will be better for the alternator 

[Tony1]

14 minutes ago, n-baj said:

The alternator can give the full 110A for the first few minutes as everything is cool so the first 30 minutes or so I’m not too concerned, it’s hour after hour when everything is warm.

 

this is going to sound daft but I cannot create a load that takes 50A from the alternator. It just so happens it maxes out at around 50A on tick over so I’ve just been operating the microwave on half power (half power being the magnetron switching on and off, not halving the power) so the alternator was outputting 50A or thereabouts all the time, if I increased the revs the output will increase. It’s still a useful test as it’s testing worse case, therefore a higher speed at 50A will be better for the alternator 

 

The way I controlled the alternator output current was to insert a length of cable after the alternator (or maybe after the lead acid, I cant be sure).

I think the cable was 10mm sq, and if you start with say 10 or 15 metres of it, it will throttle down the current a lot- probably below 40 amps.

Then you chop a measured length of it off and as you make it a bit shorter, it allows more current through. And in that way you can test the alternator at fairly precise current outputs.

Lot of faffing, but you only have to do it once! 

 

ETA- the results for my alternators were very disappointing. At tickover, my 100 amp alternator could only put out 35 amps before it started going over 100 degrees, and even at a steady 1300rpm it could only manage 45-50 amps before getting too hot. 

 

2nd ETA- I would really think about investing in some more solar though as I know you're full time liveaboard. 

As an example, today has been bright but not very sunny, and I've had 105Ah worth of charge from the panels, so no engine or genny running needed at all today- and at the moment that's the case about two thirds of the time. 

 

 

Edited February 16, 2023 by Tony1

[n-baj]

14 minutes ago, rusty69 said:

I can't speak for all BMS types, but my one has user programmable settings that you can set an upper cell voltage disconnect, and an overall voltage disconnect. I believe if the BMS is activated that discharge can still take place as long as none of the discharge parameters have been triggered.

 

The solar controller(s), as well as an absorption and float voltage setting also have an over voltage disconnect and a charge limit.

 

I set my solar controller so that it goes into float well before the BMS cuts in. I am one of those that believe the BMS should not be used as a charge control device, but that the charging sources, if using a homebrew system should be set accordingly.

Thanks Rusty I think when I physically get the battery I’ll need to play around with the voltages from the charging sources. I had it in my head that I can instruct the bms to stop accepting charge at a soc of my choosing but it does make more sense to set the bulk/abs voltage at say 14.0 and treat the bms as an back up to that.

 

setting the solar mppt correctly is critical as I’ll most likely be away from the boat and that does allow a full customised range of voltage settings. B2B is less critical as I’ll be around when the engine is running but I don’t want to nanny it.
 

The third charging source is the mains charger. There’s no lithium setting only lead acid voltages for sealed, flooded, gel, agm, etc but the only time I use that is via a genny in the winter months but I can just turn the genny off when I feel the batteries don’t need anymore. On the very rare occasion I’m on grid power I’ll just isolate the lithiums, isolate the solar panel and use the battery charger to power the dc system

[n-baj]

12 minutes ago, Tony1 said:

 

The way I controlled the alternator output current was to insert a length of cable after the alternator (or maybe after the lead acid, I cant be sure).

I think the cable was 10mm sq, and if you start with say 10 or 15 metres of it, it will throttle down the current a lot- probably below 40 amps.

Then you chop a measured length of it off and as you make it a bit shorter, it allows more current through. And in that way you can test the alternator at fairly precise current outputs.

Lot of faffing, but you only have to do it once! 

 

ETA- the results for my alternators were very disappointing. At tickover, my 100 amp alternator could only put out 35 amps before it started going over 100 degrees, and even at a steady 1300rpm it could only manage 45-50 amps before getting too hot. 

 

2nd ETA- I would really think about investing in some more solar though as I know you're full time liveaboard. 

As an example, today has been bright but not very sunny, and I've had 105Ah worth of charge from the panels, so no engine or genny running needed at all today- and at the moment that's the case about two thirds of the time. 

 

 

Oh yeah of course I have loads of arctic blue wire for shoreline could have used that but means I’d be cutting bits off to set the current output. 
 

the solar controller has capacity for another 370w panel as I’ve purposely oversized it as I didn’t know how I’d get on with 370w but I like to get a tonne of coal at the start of winter for bulk pricing as I burn through about a tonne so need the roof space, although it would be nice as with frugal use the lithiums might allows me to ride out the dark days with the odd sunny day and moving day and not have to fully charge every 3 days or so so the noisy yellow Jen will be surplus to requirements 😃

[rusty69]

12 minutes ago, n-baj said:

setting the solar mppt correctly is critical as I’ll most likely be away from the boat and that does allow a full customised range of voltage settings. B2B is less critical as I’ll be around when the engine is running but I don’t want to nanny it.

The best bet is to start conservatively whilst monitoring it. If leaving the boat unattended for long periods, leave the SOC of the lithiums low to middling and isolate the solar.

12 minutes ago, n-baj said:

The third charging source is the mains charger. There’s no lithium setting only lead acid voltages for sealed, flooded, gel, agm, etc but the only time I use that is via a genny in the winter months but I can just turn the genny off when I feel the batteries don’t need anymore. On the very rare occasion I’m on grid power I’ll just isolate the lithiums, isolate the solar panel and use the battery charger to power the dc system

I use a standard battery charger on mine, but am very careful not to let it go into float.

Edited February 16, 2023 by rusty69

[n-baj]

2 minutes ago, rusty69 said:

 

I use a standard battery charger on mine, but am very careful not to let it go into float.

How come you don’t let it go into float? Mine goes into float 1 hour after continuous voltage 

[TheBiscuits]

3 minutes ago, n-baj said:

so the noisy yellow Jen will be surplus to requirements 😃

 

Oi!  @Jen-in-Wellies is blue, not yellow!

[Tony1]

1 minute ago, n-baj said:

Oh yeah of course I have loads of arctic blue wire for shoreline could have used that but means I’d be cutting bits off to set the current output. 
 

the solar controller has capacity for another 370w panel as I’ve purposely oversized it as I didn’t know how I’d get on with 370w but I like to get a tonne of coal at the start of winter for bulk pricing as I burn through about a tonne so need the roof space, although it would be nice as with frugal use the lithiums might allows me to ride out the dark days with the odd sunny day and moving day and not have to fully charge every 3 days or so so the noisy yellow Jen will be surplus to requirements 😃

 

I do get the thing about space for the coal.

I've had up to 12 bags on my roof at times, but I stack them on top of each other so I can just about manage- although it can be a faff if the centre lines go in between the bags etc. 

I guess its all about where we individually see our priorities. I feel as if I'm saving so much on diesel costs by having the solar that its worth the hassle of all the panels taking up a lot of my roof, but that wont be the case for everyone.  

 

 

[TheBiscuits]

8 minutes ago, n-baj said:

I have loads of arctic blue wire for shoreline could have used that

 

It's likely to be 2.5 sq mm or smaller though.  Conductor cross sectional area, not including insulation.

 

 

[Tony1]

39 minutes ago, n-baj said:

Thanks Rusty I think when I physically get the battery I’ll need to play around with the voltages from the charging sources. I had it in my head that I can instruct the bms to stop accepting charge at a soc of my choosing but it does make more sense to set the bulk/abs voltage at say 14.0 and treat the bms as an back up to that.

 

setting the solar mppt correctly is critical as I’ll most likely be away from the boat and that does allow a full customised range of voltage settings. B2B is less critical as I’ll be around when the engine is running but I don’t want to nanny it.
 

The third charging source is the mains charger. There’s no lithium setting only lead acid voltages for sealed, flooded, gel, agm, etc but the only time I use that is via a genny in the winter months but I can just turn the genny off when I feel the batteries don’t need anymore. On the very rare occasion I’m on grid power I’ll just isolate the lithiums, isolate the solar panel and use the battery charger to power the dc system

 

Just a thought, but there is an interesting thing you see with lithiums  (and its a behaviour that you'll observe as you get more used to them) :- if you charge at a low current level, they will get to a higher SoC before the charger goes into float (or stops), than if you charge at a high current.

For example, I found that if I charged my lithiums at a high current level of say 100-120 amps (with both MPPTs going plus some engine charging with the B2Bs), they only got to about 75% full before the chargers all went into float. 

But if I charge at say 30 amps, the SoC can get up to 90% or more before the charger go to float. 

Most of the long term lithium users here go for a bulk charge voltage of 13.8/13.9v or so.

So bear in mind when selecting a bulk charge voltage for the MPPT, that on some sunny days, because higher charging currents will push up the voltage compared to lower charging currents, you might end up with a slightly less full battery when you get home, in terms of the SoC it reached. 

(And our lithium expert Nick has confirmed this is a thing, its not just my fevered imagination).

 

Strictly speaking this is part of the 5 hour lithium lecture, which I will be touring around the towpaths of Cheshire this Spring and Summer. Book your tickets early.   

 

 

 

Edited February 16, 2023 by Tony1

[rusty69]

1 minute ago, Tony1 said:

Strictly speaking this is part of the 5 hour lithium lecture, which I will be touring around the towpaths of Cheshire this Spring and Summer. Book your tickets early.   

 

Will you be supplying the lithium tablets, or do we need to bring our own?

[Tony1]

Just now, rusty69 said:

Will you be supplying the lithium tablets, or do we need to bring our own?

 

I think cyanide tablets might be the preferred option once we get 3 hours into the lecture. 

 

 

[TheBiscuits]

3 minutes ago, Tony1 said:

Strictly speaking this is part of the 5 hour lithium lecture, which I will be touring around the towpaths of Cheshire this Spring and Summer.

 

Oh, you're only doing the introduction then not the full presentation?

[IanD]

5 minutes ago, Tony1 said:

 

Just a thought, but there is an interesting thing you see with lithiums  (and its a behaviour that you'll observe as you get more used to them) :- if you charge at a low current level, they will get to a higher SoC before the charger goes into float (or stops), than if you charge at a high current.

For example, I found that if I charged my lithiums at a high current level of say 100-120 amps (with both MPPTs going plus some engine charging with the B2Bs), they only got to about 75% full before the chargers all went into float. 

But if I charge at say 30 amps, the SoC can get up to 90% or more before the charger go to float. 

So bear in mind when selecting a bulk charge voltage for the MPPT, that on some sunny days, because higher charging currents will push up the voltage compared to lower charging currents, you might end up with a slightly less full battery when you get home, in terms of the SoC it reached. 

(And our lithium expert Nick has confirmed this is a thing, its not just my fevered imagination).

 

Strictly speaking this is part of the 5 hour lithium lecture, which I will be touring around the towpaths of Cheshire this Spring and Summer. Book your tickets early.   

 

 

This is true for all batteries of all chemistries -- actually LFP are less prone to it than LA at high charge rates because the internal resistance is lower...

[Tony1]

1 minute ago, IanD said:

 

This is true for all batteries of all chemistries -- actually LFP are less prone to it than LA at high charge rates because the internal resistance is lower...

 

You do realise I now have to rewrite an entire chapter of my lithium lecture????

 

[IanD]

3 minutes ago, Tony1 said:

 

You do realise I now have to rewrite an entire chapter of my lithium lecture????

 

Sorry... 😉

 

It does show up with LFP though when people start to charge at high rates they'd never consider using with LA.

[Tony1]

24 minutes ago, TheBiscuits said:

 

Oh, you're only doing the introduction then not the full presentation?

 

I have a new section on the mating habits of lithium batteries.

Its sad that in this day and age, there is still a stigma attached to people who form an emotional relationship with a battery.

 

[Tony Brooks]

2 hours ago, Tony1 said:

they only got to about 75% full before the chargers all went into float. 

 

I think we are back with the vagaries of "adaptive charging". I would be interested if this was still the case if adaptive charging was turned off. However, if you did that or if you set float to the "absorption" voltage, you may have to manually terminate charging. Really just thinking out loud.

[Tony1]

31 minutes ago, Tony Brooks said:

 

I think we are back with the vagaries of "adaptive charging". I would be interested if this was still the case if adaptive charging was turned off. However, if you did that or if you set float to the "absorption" voltage, you may have to manually terminate charging. Really just thinking out loud.

 

I must confess Tony I don't know enough about adaptive charging to say if that's a factor in this scenario. The MPPTs are victron 100/50 units, and I just set the bulk charge to 14.6v, and rely on my SoC monitor to stop them charging at the correct point.

 

I have a very unusual system for controlling the daily charging, which evolved  largely by accident, through my own ignorance, because I wrongly assumed SoC was the best way to manage lithium charging.

I ended up having a spare BMV712, so I set that up to monitor the state of charge, and when my batteries' SoC gets to 85% (or whatever I set it for), the BMV712 is then able to switch off the various chargers, since they all have a 'BMS input' socket. It uses a very thin wire, that carry a 12v signal from the BMV712 unit to the various chargers.

 

What it means is that I always use the bulk charging phase, and I charge flat out until the batteries get up to 85% SoC, regardless of how high or low the charging voltage is.

The normal method as you know is for the MPPT to rely on the voltage to make its decision on when to go into float, or to stop.

That time they got charged to 75% SoC was just a test to see how things went if I didnt use my SoC monitor. 

The only charger that is not managed by my SoC monitor is the shoreline charger. 

I used it for 10 days or so in December when  I was in Llangollen, and I did find that it was difficult to set the charging voltage in a way that would get the batteries up to a consistent SoC. 

Sometimes it would charge them to over 90%, and sometimes less than 80%.

But that's not a problem, nearly all lithium users rely on charging voltage to make sure they get the batteries up to a good SoC, and they aren't bothered if the SoC gets to 75% or 95%.

And who knows, maybe its better for the batteries if you introduce more variability to the SoC, instead of reaching a consistent 85% SoC every day like I do. 

Essentially my SoC monitor is overkill, but now that I've set it up, I'll carry on using it. 

 

 

Edited February 16, 2023 by Tony1

[nicknorman]

4 hours ago, n-baj said:

Thanks Rusty I think when I physically get the battery I’ll need to play around with the voltages from the charging sources. I had it in my head that I can instruct the bms to stop accepting charge at a soc of my choosing but it does make more sense to set the bulk/abs voltage at say 14.0 and treat the bms as an back up to that.

 

setting the solar mppt correctly is critical as I’ll most likely be away from the boat and that does allow a full customised range of voltage settings. B2B is less critical as I’ll be around when the engine is running but I don’t want to nanny it.
 

The third charging source is the mains charger. There’s no lithium setting only lead acid voltages for sealed, flooded, gel, agm, etc but the only time I use that is via a genny in the winter months but I can just turn the genny off when I feel the batteries don’t need anymore. On the very rare occasion I’m on grid power I’ll just isolate the lithiums, isolate the solar panel and use the battery charger to power the dc system

A problem with charging lithium optimally and not too hard, is that one really needs to know the charge current. Unlike lead acid, Li will charge at the maximum current the charge device can provide, until it is very nearly full. When the voltage finally becomes constant, and at the sorts of charge currents we are talking about, the current drops off very quickly perhaps only taking 5 mins to drop to the 5% of capacity one is looking for to terminate charge. The nominal “5 minutes” obviously varies somewhat depending on the charge rate as a % of capacity.

 

Without knowing the charge current, any charge device has to guess how long to hold the absorption phase before going to float. What is best avoided is a long period of holding the charge voltage up near the maximum, with very little current flowing into the battery. Golden rule for charging Li is charge to the specified voltage, up to 3.65v/cell, and then STOP charging as soon as the current decreases to 5% of capacity! Of course if the charger goes to float and the float voltage is such that it matches the resting voltage of the battery (around 13.2 or 13.3v) then fair enough - the battery doesn’t realise there is a float voltage being held. But IMO a good design is one that doesn’t hold the voltage up at 13.8v or more once the charge current has fallen off.

[Jen-in-Wellies]

16 hours ago, TheBiscuits said:

 

Oi!  @Jen-in-Wellies is blue, not yellow!

I'm proud of my Morlock heritage. 💙

There are so few blue emojis available in the list that aren't expressing negative emotions. Some subtle discrimination going on there...

[n-baj]

On 16/02/2023 at 20:55, nicknorman said:

Golden rule for charging Li is charge to the specified voltage, up to 3.65v/cell, and then STOP charging as soon as the current decreases to 5% of capacity! Of course if the charger goes to float and the float voltage is such that it matches the resting voltage of the battery (around 13.2 or 13.3v) then fair enough - the battery doesn’t realise there is a float voltage being held. But IMO a good design is one that doesn’t hold the voltage up at 13.8v or more once the charge current has fallen off.

Thanks Nicknorman, I think it’s going to be a case of just playing around with the voltages and see what happens. I personally cannot see myself charging at 14.6v as I would like to be a little conservative. If I don’t use say the top 40ah in a 460ah battery and the battery lasts longer then so be it, I’ve coped fine with 480ah lead acids (probably not 480ah now) I’m only thinking of going for that 460ah battery as it’s the cheapest per ah.

[n-baj]

Okay I’ve had a reply from Barrus about not cooking my alternator from Mr Cooke and he states around 120 deg c max and a warning about not being suitable for lithium charging.
 

So in theory it’s okay and sounds like there’s not going to be any immediate failures running at <50A at tick over however I think this may shorten the alternators life over the long term as it is running hotter.

 

He did offer that there’s several options and will send me details next week. If one of the option is an all singing and dancing alternator with disconnect protection, ability to alter voltages, reduces output with temperature and a straight swap for the current alternator for around £400 then I might go down that route and completely bin off lead acids but if it’s a dinky £30 regulator box for that price because it has the word ‘marine’ in the description then I’ll probably stick with the original plan with the B2B and just stick the engine on higher revs in neutral when in locks, etc.

[Tony1]

16 minutes ago, n-baj said:

Thanks Nicknorman, I think it’s going to be a case of just playing around with the voltages and see what happens. I personally cannot see myself charging at 14.6v as I would like to be a little conservative. If I don’t use say the top 40ah in a 460ah battery and the battery lasts longer then so be it, I’ve coped fine with 480ah lead acids (probably not 480ah now) I’m only thinking of going for that 460ah battery as it’s the cheapest per ah.

 

I suspect what you'll find when charging at a relatively low rate of about 40 amps (plus some from the solar) is that during the charge, the battery voltage won't get up anywhere near the nominated charging voltage for a long time. 

For example, I have my MPPTs set to charge at 14.4v, but in winter the battery never gets anywhere that voltage, until the end of the charge and when the batteries are over 85% full.

Its different when I charge in high summer, with the MPPTs putting in say 90 amps. 

So charging at a higher current seems to push up the battery voltage more quickly than charging at low current, and you reach your end point a bit sooner. 

 

I find that the charging voltage is a sort of target/end point figure, and you set it according to how full you want the batteries to get. 

So if I set my bulk charge voltage at 14.6, the batteries will get above 95% full before the chargers go in to float. If I set the charging voltage at say 13.8v, the batteries get to about 80% full before the float stage starts. 

Maybe think of the bulk charge voltage as the thing that determines how full you want the batteries to get. 

 

 

 

 

Edited February 19, 2023 by Tony1

[MtB]

All this chat about float charging on lithiums is asking for trouble AIUI. As Nick says, one needs to STOP charging when any one cell gets up to 3.65V.

 

For the most comprehensive seemingly knowledgable article I've ever read about LiFePO4 batteries in boats, this chap is well worth reading. The link has not been posted on this forum for a while now so it's time it had another outing. 

https://nordkyndesign.com/protection-and-management-of-marine-lithium-battery-banks/

 

Li batts in boats still strike me as immature technology, mainly because Li batts like to be cycled over a wide range (not kept well charged like LA batts) and most Li users still seem to have the LA mentality engaged and write in ways that imply they keep their Li batts constantly charged. E.g. using a charger with a 'float' setting. One really should not be doing this. Charge them, then discharge them low before re-charging almost fully. Don't put them on float so they get recharged after a small discharge. 

 

What the boating world needs is some devices that monitor the SOC somehow and keep the charge sources disconnected until it falls to a low value, then reconnects until charged to a high SOC, then disconnects, etc etc.