Cheap LiFePO4 BMS?

[nicknorman]

20 minutes ago, stuart said:

Thanks for the info, looks like a similar replacement device for the AD7280A is the LTC6803-3.

 

Just double the cost and out of stock everywhere!

Farnell has 13 AD7280A in stock at the moment if you just want it for a one-off hobby project.

[redwing]

Boaters' Update on lithiums

 https://canalrivertrust.org.uk/enjoy-the-waterways/boating/boating-blogs-and-features/the-boaters-update/boaters-update-19-nov-2021

 

(bottom of page)

 

 

[IanD]

21 minutes ago, redwing said:

Boaters' Update on lithiums

 https://canalrivertrust.org.uk/enjoy-the-waterways/boating/boating-blogs-and-features/the-boaters-update/boaters-update-19-nov-2021

 

(bottom of page)

 

All true as written, but note that on cost he compared LFP with AGM lead-acids, which most people don't use because of the high cost.

 

Comparing LFP to conventional cheap LA (for smaller battery banks) or flooded traction LA (for larger banks changes the numbers -- but then so does using cheaper LFP cells with external BMS, or big LFPs which are cheaper per kWh than small ones.

 

It's true that the higher installation cost of LFPs is balanced out by more usable capacity, longer lifetime and shorter generator running times, and in most cases LFPs will work out cheaper over lifetime -- always assuming your pockets are deep enough to buy them in the first place -- but the numbers are different for different installations. Also if you're not going to keep the boat for a long time, it's the following owner who gets the LFP lifetime/cost benefits you've paid for...

 

What is certainly correct is that the biggest advantages by far are the ability to use LFP at almost any SoC and not needing to equalise them for hours like LA, so maybe halving generator running times -- this alone is a very good reason to use them for many boaters, and it seems that most who have switched are very happy with them 🙂

Edited November 30, 2021 by IanD

[BEngo]

A nicely balanced summary, with the exception that he did not address the effects  of continuous high output on a typical ex-automotive alternator.  The in battery BMS doesn't help nor does a LA load-dump battery solve this.

 

N

[IanD]

8 minutes ago, BEngo said:

A nicely balanced summary, with the exception that he did not address the effects  of continuous high output on a typical ex-automotive alternator.  The in battery BMS doesn't help nor does a LA load-dump battery solve this.

 

N

LFP with a side order of fried alternator... 😞

[Phoenix_V]

I notice Beta marine are now offering an Optional 12V Lithium Ion Battery Charger Alternator (in Lieu of Secondary) on new motors,not clear what bells and whistles it has or whether it is just the standard derated in some way

[IanD]

38 minutes ago, Phoenix_V said:

I notice Beta marine are now offering an Optional 12V Lithium Ion Battery Charger Alternator (in Lieu of Secondary) on new motors,not clear what bells and whistles it has or whether it is just the standard derated in some way

I think it has an external alternator controller to speed up charging and meet LFP voltage requirements while also stopping the alternator from frying.

[nicknorman]

55 minutes ago, BEngo said:

A nicely balanced summary, with the exception that he did not address the effects  of continuous high output on a typical ex-automotive alternator.  The in battery BMS doesn't help nor does a LA load-dump battery solve this.

 

N

In fact he specifically said that B2B solutions to this issue were a pointless waste of money. Clearly he has never actually tried charging a lithium battery from an alternator. But don’t waste your breath trying to persuade him - he runs a 12v boating closed group on Facebook. I foolishly joined. On day 2 there was mention of measuring specific gravity and I said that I’d found a refractometer to be a good way of doing it. But apparently refractometers are useless and the only way is to use a floating thing. When I disagreed, I was immediately banned from his closed group little empire of drones. Which was a merciful outcome!

4 minutes ago, IanD said:

I think it has an external alternator controller to speed up charging and meet LFP voltage requirements while also stopping the alternator from frying.

For many years Beta supplied engines with an external controller so I would presume this is just an updated version of that concept. I wonder if it has a float mode though - one requirement for cruising boats is to charge the batteries and then stop charging and go to float whereby the batteries think they have been disconnected from the charging source, eg 14.4v to charge and 13.4v to float so that the alternator supplies any loads whilst not subjecting the batteries to any stress.

[IanD]

15 minutes ago, nicknorman said:

[snip]

For many years Beta supplied engines with an external controller so I would presume this is just an updated version of that concept. I wonder if it has a float mode though - one requirement for cruising boats is to charge the batteries and then stop charging and go to float whereby the batteries think they have been disconnected from the charging source, eg 14.4v to charge and 13.4v to float so that the alternator supplies any loads whilst not subjecting the batteries to any stress.

 

Beta supplied engines with alternators configured with a brush box (internal regulator removed) to allow external controllers to be used (I talked to them a lot about this last year) but I don't think they supplied or supported the controllers, that was down to the end user. It now looks like they're supplying a preconfigured solution, presumably (tbc) with proper charging control to suit lithium batteries -- because otherwise they'll get lots of complaints from people that Beta have killed their expensive batteries...

 

N.B They do specifically say "lithium ion", which in theory LFP are but this isn't the term normally used to describe them. I'm sure a quick phone call to them would reveal all... 😉

Edited November 30, 2021 by IanD

[nicknorman]

12 minutes ago, IanD said:

 

Beta supplied engines with alternators configured with a brush box (internal regulator removed) to allow external controllers to be used (I talked to them a lot about this last year) but I don't think they supplied or supported the controllers, that was down to the end user. It now looks like they're supplying a preconfigured solution, presumably (tbc) with proper charging control to suit lithium batteries -- because otherwise they'll get lots of complaints from people that Beta have killed their expensive batteries...

 

N.B They do specifically say "lithium ion", which in theory LFP are but this isn't the term normally used to describe them. I'm sure a quick phone call to them would reveal all... 😉

I’ve never seen one in person but I got the idea from this forum that the controllers were badged “Beta” - although of course they didn’t design or make them.

 

Of course it could be something as crap as inserting a 2 ohm resistor into the field circuit to reduce the max field current and thus limit the max output to a non-melting one. Coincidentally (or not) the mentioned 130A is pretty much what an Iskra 175A alternator can put out continuously without frying itself.

Edited November 30, 2021 by nicknorman

[IanD]

3 minutes ago, nicknorman said:

I’ve never seen one in person but I got the idea from this forum that the controllers were badged “Beta” - although of course they didn’t design or make them.

 

Of course it could be something as crap as inserting a 2 ohm resistor into the field circuit to reduce the max field current and thus limit the max output to a non-melting one. Coincidentally (or not) the mentioned 130A is pretty much what an Iskra 175A alternator can put out continuously without frying itself.

I'd certainly hope that Beta haven't done anything as crude as that; using a standard alternator (no external "intelligent" controller) with lithium batteries is a recipe for disaster given the soft and temperature-dependent alternator current/voltage limiting, either not enough voltage to guarantee fully charging them or too much for too long after 100% SoC to destroy them through overcharging -- or even both... 😞

 

I suspect their solution is a downrated Iskra 175A alternator with a brush box, hopefully a temperature sensor, and a properly designed/configured external controller. Anything else would leave Beta liable to expensive warranty claims for dead batteries...

[nicknorman]

2 minutes ago, IanD said:

I'd certainly hope that Beta haven't done anything as crude as that; using a standard alternator (no external "intelligent" controller) with lithium batteries is a recipe for disaster given the soft and temperature-dependent alternator current/voltage limiting, either not enough voltage to guarantee fully charging them or too much for too long after 100% SoC to destroy them through overcharging -- or even both... 😞

 

I suspect their solution is a downrated Iskra 175A alternator with a brush box, hopefully a temperature sensor, and a properly designed/configured external controller. Anything else would leave Beta liable to expensive warranty claims for dead batteries...

You’d like to think so. But if they have made a decent solution why didn’t they put a little bit of info about it on their website?

[IanD]

12 minutes ago, nicknorman said:

You’d like to think so. But if they have made a decent solution why didn’t they put a little bit of info about it on their website?

Their website is not exactly the most informative one in the world. However I've found them very helpful and responsive when asked questions by email or phone.

 

If I was still looking at high-power alternators and big battery banks that's what I'd do, but I'm not any more...

 

It's also possible that they only really want to support this solution -- at least for now -- with new engine installations, rather than getting swamped with "can I retrofit this to my engine, how about pulleys, how do I connect it up, oh my god it's destroyed my batteries" enquiries from people who want to retrofit this but don't have the knowledge on how to do it properly...

 

(same thing with the brush-box/external controller alternators, and fitting 2x 24V 100A alternators to a Beta 43 -- both possible but not on the website, but if you contact them and sound like you know what you're doing they'll happily supply them fitted to a new engine)

Edited November 30, 2021 by IanD

[nicknorman]

Back in the Marina now, I thought I’d better exercise the lower part of the Li batteries, having not had them below about 40%. So yesterday as we set off from the Plough I set the alternator controller to 50% SoC so we arrived at the Marina at that. Didn’t plug the shore power in. Last night electric kettle, tv, lots of lighting, usual stuff. This morning toaster, electric kettle etc and batteries were still at 25% so I thought I’d give them something to do - immersion heater on, 1kw which is just under 100A. I felt like such a naughty boy!

 

Some time later the SoC got down to 5%, and, with the 100A drain still on, the BMS finally started to chirp its low cell voltage warning as the bottom cell hit 2.9v. Shut off is 2.5v but there didn’t seem any point in stressing them too much so I terminated the discharge there and plugged in the shore power/Combi to charge them.

 

 So in summary Li batteries are quite usable down to 5% SoC and I’m sure if the load was a more normal 5 - 10A or so, I could have got down to 2 or 3% before hitting 2.9v. I did wonder if I should add a current term into the low voltage cutoff algorithm (ie so the alarms and shutoff would be at a lower voltage if there was heavy discharge) but it doesn’t seem necessary.

[IanD]

4 minutes ago, nicknorman said:

Back in the Marina now, I thought I’d better exercise the lower part of the Li batteries, having not had them below about 40%. So yesterday as we set off from the Plough I set the alternator controller to 50% SoC so we arrived at the Marina at that. Didn’t plug the shore power in. Last night electric kettle, tv, lots of lighting, usual stuff. This morning toaster, electric kettle etc and batteries were still at 25% so I thought I’d give them something to do - immersion heater on, 1kw which is just under 100A. I felt like such a naughty boy!

 

Some time later the SoC got down to 5%, and, with the 100A drain still on, the BMS finally started to chirp its low cell voltage warning as the bottom cell hit 2.9v. Shut off is 2.5v but there didn’t seem any point in stressing them too much so I terminated the discharge there and plugged in the shore power/Combi to charge them.

 

 So in summary Li batteries are quite usable down to 5% SoC and I’m sure if the load was a more normal 5 - 10A or so, I could have got down to 2 or 3% before hitting 2.9v. I did wonder if I should add a current term into the low voltage cutoff algorithm (ie so the alarms and shutoff would be at a lower voltage if there was heavy discharge) but it doesn’t seem necessary.

10% to 90% SoC (or even 5% to 95%) is what many reputable LFP manufacturers now define as "normal operating range".

[nicknorman]

1 hour ago, IanD said:

10% to 90% SoC (or even 5% to 95%) is what many reputable LFP manufacturers now define as "normal operating range".

Yes. It’s just such a massive paradigm shift after decades of lead acid battery usage! And 100% for me is only 14.3v not the 14.6v I could go up to ( not that it adds many Ah)

[IanD]

6 minutes ago, nicknorman said:

Yes. It’s just such a massive paradigm shift after decades of lead acid battery usage! And 100% for me is only 14.3v not the 14.6v I could go up to ( not that it adds many Ah)

Better not hold the batteries at 14.3V for any length of time (and certainly not 14.6V, 3.65V/cell) if you want to maximise lifetime. There's no significant capacity above 13.8V charge voltage (3.45V per cell)...

[nicknorman]

39 minutes ago, IanD said:

Better not hold the batteries at 14.3V for any length of time (and certainly not 14.6V, 3.65V/cell) if you want to maximise lifetime. There's no significant capacity above 13.8V charge voltage (3.45V per cell)...

Correct. My alternator controller charges at (up to) 14.3v. Of course if the selected SoC is 50% or 80%, it stops charging when the BMV SoC gets there (long before 14.3 is reached) and reverts to a float of 13.2v or 13.3v which puts no more current into the batteries but will run any boat services.  If the selected SoC is 100% it charges to 14.3v and once the current falls to 4% of capacity and a couple of minutes has elapsed, it goes to a float of 13.4v

 

The charging profiles for the Combi are the same, controlled by the BMS over Masterbus (CANBUS) and using the same SoC selector switch in the alternator controller. The Combi will only go into charge mode when the charge rate switch on the alternator controller is moved to “fast” with aC power present (shore or Travelpower) and it’s a one-off charge, after which it reverts to float until the operator resets the rate switch to “slow” and then “fast” again. This being because when on shore power, 99.99% of time wil be spent on float. The need to charge, instead of float, from the Combi is only either to prepare for a cruise (batteries having been floated at 50% for long term storage), or to assist the alternator with a fast charge when out and about, via the Travelpower.

 

So from an operator point of view, the whole shebang is controlled by the two switches on the alternator controller, a 3-way one for target SoC selection and a slow/fast rate switch.

Edited December 1, 2021 by nicknorman

[peterboat]

2 minutes ago, nicknorman said:

Correct. My alternator controller charges at (up to) 14.3v. Of course if the selected SoC is 50% or 80%, it stops charging when the BMV SoC gets there (long before 14.3 is reached) and reverts to a float of 13.2v or 13.3v which puts no more current into the batteries but will run any boat services.  If the selected SoC is 100% it charges to 14.3v and once the current falls to 4% of capacity it goes to a float of 13.4v

 

The charging profiles for the Combi are the same, controlled by the BMS over Masterbus (CANBUS) and using the same SoC selector switch in the alternator controller. The Combi will only go into charge mode when the charge rate switch on the alternator controller is moved to “fast” and it’s a one-off charge, after which it reverts to float until the operator resets the rate switch to “slow” and then “fast” again. This being because when on shore power, 99.99% of time wil be spent on float. The need to charge, instead of float, from the Combi is only either to prepare for a cruise (batteries having been floated at 50% for long term storage), or to assist the alternator with a fast charge when out and about, via the Travelpower.

 

So from an operator point of view, the whole shebang is controlled by the two switches on the alternator controller, a 3-way one for target SoC selection and a slow/fast rate switch.

My solar controller works the same except top voltage in is 13.9, dropping to 13.6 absorb then 13.4 float has worked well for years, as Ian says pointless going for to high a voltage on bulk charging as it does nowt

[IanD]

3 minutes ago, nicknorman said:

Correct. My alternator controller charges at (up to) 14.3v. Of course if the selected SoC is 50% or 80%, it stops charging when the BMV SoC gets there (long before 14.3 is reached) and reverts to a float of 13.2v or 13.3v which puts no more current into the batteries but will run any boat services.  If the selected SoC is 100% it charges to 14.3v and once the current falls to 4% of capacity and a couple of minutes has elapsed, it goes to a float of 13.4v

 

The charging profiles for the Combi are the same, controlled by the BMS over Masterbus (CANBUS) and using the same SoC selector switch in the alternator controller. The Combi will only go into charge mode when the charge rate switch on the alternator controller is moved to “fast” and it’s a one-off charge, after which it reverts to float until the operator resets the rate switch to “slow” and then “fast” again. This being because when on shore power, 99.99% of time wil be spent on float. The need to charge, instead of float, from the Combi is only either to prepare for a cruise (batteries having been floated at 50% for long term storage), or to assist the alternator with a fast charge when out and about, via the Travelpower.

 

So from an operator point of view, the whole shebang is controlled by the two switches on the alternator controller, a 3-way one for target SoC selection and a slow/fast rate switch.

I know that you know all this, I was just trying to stop LFP newbies seeing your post mentioning 14.3V or 14.6V (like in some of the videos) and then going off and destroying their batteries... 😉

[nicknorman]

1 minute ago, peterboat said:

My solar controller works the same except top voltage in is 13.9, dropping to 13.6 absorb then 13.4 float has worked well for years, as Ian says pointless going for to high a voltage on bulk charging as it does nowt

It depends on the rate of charge. If you charge slowly then by the time you get to 13.9 you are effectively fully charged. But if you charge fast, approaching 1C, and stop charging when you reach 13.9, the SoC will be a fair way away from 100%. Obviously solar is relatively slow, well not approaching 1C anyway!

[IanD]

2 minutes ago, nicknorman said:

It depends on the rate of charge. If you charge slowly then by the time you get to 13.9 you are effectively fully charged. But if you charge fast, approaching 1C, and stop charging when you reach 13.9, the SoC will be a fair way away from 100%. Obviously solar is relatively slow, well not approaching 1C anyway!

I think most boats with decent-sized LFP batteries are "fractional-C" and have no chance of ever getting anywhere close to 1C charging -- I'd need a 700A charger which is 35kW...

[nicknorman]

1 hour ago, IanD said:

I think most boats with decent-sized LFP batteries are "fractional-C" and have no chance of ever getting anywhere close to 1C charging -- I'd need a 700A charger which is 35kW...

Yes but there are fractions and then there are fractions! I can hit 275A which is nearly C/2 (we have 600Ah) and stopping charge at 13.9v would be unnecessarily pessimistic.

Edited December 1, 2021 by nicknorman

[Col_T]

4 hours ago, nicknorman said:

The need to charge, instead of float, from the Combi is only either to prepare for a cruise (batteries having been floated at 50% for long term storage),

 

May I ask why you would do this, as surely the Lithiums would get more than adequately charged just by cruising? Note - this isn't intended as a criticism; I don't have lithiums, and probably never will, so am just curious.

[nicknorman]

23 minutes ago, Col_T said:

 

May I ask why you would do this, as surely the Lithiums would get more than adequately charged just by cruising? Note - this isn't intended as a criticism; I don't have lithiums, and probably never will, so am just curious.

It’s a fair question. Firstly it depends on how far one is intending to cruise on the first day. For example, we might just be off to Kingsbury water park, about 1 hr away but very peaceful! In normal (slow) charging mode we get about 90A so if we start at 50% SoC, after an hour cruising we would only be at 65%. Well yes ok that is plenty for one night but…

 

And secondly, although we are not talking big bucks, electricity from the bollard is cheaper than electricity generated by a Diesel engine / alternator. Cheaper because it’s more efficient, and that is good (well better, anyway) for the planet.

 

Of course if we didn’t do this, it would be no big deal, but bearing in mind it’s just a question of flicking a couple of switches and then forgetting it, why not?

Edited December 1, 2021 by nicknorman