AGM Batteries

[Conrad]

On 05/01/2022 at 11:57, nicknorman said:

These are the ones I bought 

https://blslifepo4battery.com/collections/3-2v-batteries/products/grade-a-calb-3-2v-200ah-lifepo4-rechargeable-batteries 

which admittedly would be £1160, but you could also get these ones https://blslifepo4battery.com/collections/3-2v-batteries/products/3-2v-200ah-lifepo4-battery?variant=32511661604944

for around £900. Of course this is just for the bare cells, you need to know what you are doing with regard to a BMS and charging.

Hi Nick,

 

Many thanks for your comment. I may switch from Rolls S12 AGM to Lithium with prices so good on that website. I am thinking about 200 Ah model:

https://blslifepo4battery.com/collections/12v/products/12v-200ah-lifepo4-battery?variant=33045844131920

Instead of going 50% discharge with AGMs I may get smaller capacity lithium battery discharged to 20% and get still more cycles...

 

Could you confirm that you are still happy with your purchase (quality of bateries and delivery, etc?)

 

All the best,

 

Conrad

[nicknorman]

46 minutes ago, Conrad said:

Hi Nick,

 

Many thanks for your comment. I may switch from Rolls S12 AGM to Lithium with prices so good on that website. I am thinking about 200 Ah model:

https://blslifepo4battery.com/collections/12v/products/12v-200ah-lifepo4-battery?variant=33045844131920

Instead of going 50% discharge with AGMs I may get smaller capacity lithium battery discharged to 20% and get still more cycles...

 

Could you confirm that you are still happy with your purchase (quality of bateries and delivery, etc?)

 

All the best,

 

Conrad

Yes I am still very happy with my purchase. But of course I bought bare cells and implemented my own BMS and charge controlling. The battery you are looking at presumably has its own internal BMS but there doesn’t seem to be much information about it. 

[IanD]

32 minutes ago, nicknorman said:

Yes I am still very happy with my purchase. But of course I bought bare cells and implemented my own BMS and charge controlling. The battery you are looking at presumably has its own internal BMS but there doesn’t seem to be much information about it. 

 

Before using a "drop-in" LiFePO4 battery with its own internal BMS -- or even "rolling your own" system like Nick did -- please (OP) read this if you haven't already:

 

https://marinehowto.com/lifepo4-batteries-on-boats/

 

"I do not believe LiFePO4 is ready for mass DIY prime time builds. Read with caution, and especially focus on the things that you don’t want to hear rather than only what you want to hear."

 

"Drop-in batteries will be a huge part of the future of LFP, and there are currently a few good manufacturers working to improve the marine specific shortcomings but, in my opinion, many of them are still not prime time ready, so purchase carefully."

Edited February 14, 2022 by IanD

[MtB]

Also, note this from Ian's link:

 

Since opening this article to the public we have now had what I consider a rather high number of LiFePO4 owners contact us who’ve ruined LiFePo4 batteries (not all marine based). In almost all of these cases of destroyed LiFePO4 batteries the resounding tone I hear come through is;

 

“But Rod, People on the internet made it sound so easy?“

[Conrad]

Thank you Gentlemen. I've read it and although the amperage consumption should not be problematic, my solar controller is quote old... The Morningstar mppt45 from 2010 may not have a proper switches combination for Lithium batteries. I wonder if the internal BMS covers it. Additionally, the website states the battery is in German warehouse but during checkout it shows China. 80 GBP delivery charge and potential custom duties mentioned. And lastly new electric terminal busbar for all connections would be needed and there is no space to fix it...

I will ask the seller for some technical information and then reconsider.

 

All the best!

[Alan de Enfield]

2 minutes ago, Conrad said:

Thank you Gentlemen. I've read it and although the amperage consumption should not be problematic, my solar controller is quote old... The Morningstar mppt45 from 2010 may not have a proper switches combination for Lithium batteries. I wonder if the internal BMS covers it. Additionally, the website states the battery is in German warehouse but during checkout it shows China. 80 GBP delivery charge and potential custom duties mentioned. And lastly new electric terminal busbar for all connections would be needed and there is no space to fix it...

I will ask the seller for some technical information and then reconsider.

 

All the best!

 

 

Do not forget that 20% VAT is also to be added from either Germany or China

[IanD]

6 minutes ago, Conrad said:

Thank you Gentlemen. I've read it and although the amperage consumption should not be problematic, my solar controller is quote old... The Morningstar mppt45 from 2010 may not have a proper switches combination for Lithium batteries. I wonder if the internal BMS covers it. Additionally, the website states the battery is in German warehouse but during checkout it shows China. 80 GBP delivery charge and potential custom duties mentioned. And lastly new electric terminal busbar for all connections would be needed and there is no space to fix it...

I will ask the seller for some technical information and then reconsider.

 

All the best!

 

If you're going lithium you really need the BMS to be the boss for all charging -- alternator, solar, shore -- to avoid killing your batteries or potentially destroying other parts of the system e.g. due to emergency disconnects.

 

It's what Nick (and other competent DIYers) did, and what the better commercially-installed systems do. Any bodges or shortcuts are likely to end badly and expensively... 😞

Edited February 14, 2022 by IanD

[Conrad]

Yes, thank you. I'll double check that BMS covers it but just for someone else looking for similar answers, here is a way to customise the mppt45 solar controler to work with lithium batteries:

kv7-iUBdyv8

 

All the best!

 

[nicknorman]

3 hours ago, Alan de Enfield said:

 

Do not forget that 20% VAT is also to be added from either Germany or China

No the prices from BLS included UK vat. I had nothing extra to pay when my batteries were delivered from china.

[Alan de Enfield]

5 minutes ago, nicknorman said:

No the prices from BLS included UK vat. I had nothing extra to pay when my batteries were delivered from china.

 

Thats good - I've been caught out a couple of times buying 'stuff' from Europe, and China to find that it has VAT added.

 

Last 3 items were a dive cylinder decanting / recharge hose, a pressure gauge (300 bar) and a dive cylinder carrying strap.

 

3 separate orders to 3 different suppliers, all in the last month and all had VAT added at the point of payment "check-out"

When they were just in the "basket" they were showing the advertised price which seemingly excludes VAT.

 

Backend of 2021 I bought an Anchor chain hook from Germany - that also had VAT added at checkout.

 

Last week I bought a SNUBA hose from Spain and asked them if VAT was to be added - they replied that their webpage in English had the Spanish VAT deducted and the UK VAT added so the price 'we' see is the price 'we' pay.

 

A new international agreement on 'etrade' came into force last year, previously any item of 'low value' (in the UK it was set at £15) would not be subject to VAT or duty and now it is.

 

 

Just pointing out that buying from overseas can result in increased prices due to duty and VAT.

[Tony1]

On 05/01/2022 at 18:10, nicknorman said:

Yes. Although if you look at Mr Cuthound’s intended usage it’s not something he would do very often. There has been a lot of talk about 80% to 20% or whatever, but I don’t really buy that and it’s not based on evidence, only opinion. I am more inclined to think that one just keeps off the knees. Once the cell voltage starts to get above say 3.4v (13.6v) you are very close to fully charged, say 97%. And on discharge when the voltage starts to fall rapidly (goes below 3v (12v) you are around 10% or less.

 

And anyway, how can you assess the SoC unless you synchronise the battery monitor from time to time, by charging to 100%? If you are planning to spend a couple of days without running the engine, that is the time to charge to 100% to synchronise the SoC.

 

Peterboat of this parish has supplied information that suggests that Valence batteries have different behaviour in terms of charge voltage vs SoC but I am unable to verify or refute that!

 

On the 80/20 thing, I do recall seeing various graphs seeming to show that the optimum SoC range (for prolonging their effective life) was 25-75%, but I remember that 20-80 was pretty close. 

Here's something I just found with a random search: 

https://www.researchgate.net/figure/Effect-of-other-SOC-ranges-0-to-20-80-to-100-and-0-to-100-on-the-cycling-life-of-a_fig2_261135878

For me personally, there is enough information out there (I'm sure I could call it hard evidence) to make me conservative about pushing their SoC limits (and especially as I cant monitor voltage for each individual cell, but rather only at battery level).

 

The other thing I take from the literature is that you dont want to run them daily between say 50-75% as I was doing for the first 8 months. 

It seems like its better (for a longer life) to let them run down to your chosen lower SoC every couple of days. Its a bit tricky for a CCer because you dont want to run them down to 20% at say 9pm, and then not be able to recharge them till the next morning.

So there is a need for a bit of messing about, to make sure you are regularly 'exercising' them through the full range, but also that you don't run out of charge overnight.

 

With mine, when I do a monthly full charge to synchronise the SoC and the BMV monitor, I am noticing that above 80% SoC, the voltage seems to start increasing more rapidly (assuming my SoC is reading accurately. So I think with mine, maybe the knee starts at 80-85%. So it makes sense, for me anyway, to use 85% as a day-to-day 'fill' point for the charging. 

 

On the voltage- it is very difficult to actually determine on a liveaboard boat because the batteries are never fully at rest, unless you leave the boat overnight. 

There is always a small charge coming out (wifi router, inverter, BEP switches, presumably the BMV712s use something, etc etc), or else the solar is putting something in. The batteries and the voltage are never static as such, for more than a few minutes anyway. 

And for hours after an engine charge, the voltage is artificially high anyway, so you cant read it then. 

 

The charging voltage also seems to depend on how much current is being put in. If the batteries are half full and I charge at say 60amps, the battery voltage will be around 13.6v. If I charge at 90amps, the battery voltage goes up to 13.8v, and and if the solar kicks another 30amps in, the voltage might go to 13.9v.

And this would all be with a SoC around say 60%. 

If I then disconnect the solar, the charging voltage goes back down a bit.

 

So its quite hard to be 100% sure what state the batteries are in, other than when I so a synchronisation (and for a while afterwards)- thats why I'm a bit cautious with them.  

 

 

[Tony1]

6 hours ago, Conrad said:

Hi Nick,

 

Many thanks for your comment. I may switch from Rolls S12 AGM to Lithium with prices so good on that website. I am thinking about 200 Ah model:

https://blslifepo4battery.com/collections/12v/products/12v-200ah-lifepo4-battery?variant=33045844131920

Instead of going 50% discharge with AGMs I may get smaller capacity lithium battery discharged to 20% and get still more cycles...

 

Could you confirm that you are still happy with your purchase (quality of bateries and delivery, etc?)

 

All the best,

 

Conrad

 

I hope you wont mind me suggesting something, as a lithium user myself. 

They are great batteries, and they accept and hold charge really well, but you will see a further benefit when they are teamed up with a strong charging system. 

Many narrowboat alternators are not actually capable of putting out their rated current on a prolonged basis. My domestic alternator is rated at 100amps, but if it gives out more than 50amps for 10 minutes, it overheats a lot. 

Good quality alternators seem to be less prone to this issue, but it would be worth taking a look at how much charge you can safely get out of your alternator(s), because ideally you want the lithiums to be charged pretty quickly so that you're not running the engine for hours, but you also dont want to overheat your alternator. 

 

 

 

[nicknorman]

25 minutes ago, Tony1 said:

 

On the 80/20 thing, I do recall seeing various graphs seeming to show that the optimum SoC range (for prolonging their effective life) was 25-75%, but I remember that 20-80 was pretty close. 

Here's something I just found with a random search: 

https://www.researchgate.net/figure/Effect-of-other-SOC-ranges-0-to-20-80-to-100-and-0-to-100-on-the-cycling-life-of-a_fig2_261135878

For me personally, there is enough information out there (I'm sure I could call it hard evidence) to make me conservative about pushing their SoC limits (and especially as I cant monitor voltage for each individual cell, but rather only at battery level).

 

The other thing I take from the literature is that you dont want to run them daily between say 50-75% as I was doing for the first 8 months. 

It seems like its better (for a longer life) to let them run down to your chosen lower SoC every couple of days. Its a bit tricky for a CCer because you dont want to run them down to 20% at say 9pm, and then not be able to recharge them till the next morning.

So there is a need for a bit of messing about, to make sure you are regularly 'exercising' them through the full range, but also that you don't run out of charge overnight.

 

With mine, when I do a monthly full charge to synchronise the SoC and the BMV monitor, I am noticing that above 80% SoC, the voltage seems to start increasing more rapidly (assuming my SoC is reading accurately. So I think with mine, maybe the knee starts at 80-85%. So it makes sense, for me anyway, to use 85% as a day-to-day 'fill' point for the charging. 

 

On the voltage- it is very difficult to actually determine on a liveaboard boat because the batteries are never fully at rest, unless you leave the boat overnight. 

There is always a small charge coming out (wifi router, inverter, BEP switches, presumably the BMV712s use something, etc etc), or else the solar is putting something in. The batteries and the voltage are never static as such, for more than a few minutes anyway. 

And for hours after an engine charge, the voltage is artificially high anyway, so you cant read it then. 

 

The charging voltage also seems to depend on how much current is being put in. If the batteries are half full and I charge at say 60amps, the battery voltage will be around 13.6v. If I charge at 90amps, the battery voltage goes up to 13.8v, and and if the solar kicks another 30amps in, the voltage might go to 13.9v.

And this would all be with a SoC around say 60%. 

If I then disconnect the solar, the charging voltage goes back down a bit.

 

So its quite hard to be 100% sure what state the batteries are in, other than when I so a synchronisation (and for a while afterwards)- thats why I'm a bit cautious with them.  

 

That research paper shows that cycling between 0 and 100% gives quite a lot fewer cycles than cycling 25% to 75%, the implication being that approaching either end of the SoC range is bad for the batteries. I think this is correct, but that is quite a coarse measure. What we really want to know is when the increased damage starts to occur. So it would be good to compare 25%-75%, 20-80, 15-85, 10-90, 5-95% my suspicion is that the accelerated damage only occurs quite near the ends, as the cell voltage enters the knee regions, ie in the last 5% or so, making say 10-90% a good regime. But I can’t prove that and neither does the paper shed any light on that.

 

The other thing to bear in mind is that what we are really interested in is the total (cumulative) number of Ah that can be extracted from the batteries before they hit say 80% of original capacity.

 

So one has to be careful when considering cycles vs DoD. Let’s say that the data shows that the battery can manage 2000 cycles when taken between 75% and 25%, but only 1000 cycles when taken between 100% and 0%. Wow, only half the number of cycles! BUT the overall charge supplied under the two regimes is identical. There is no advantage to cycling the batteries 75% to 25% every day, vs cycling them over 2 days between 100% and 0%. The batteries will still hit the 80% original capacity after the same number of days (years).

 

I suspect in reality the 100% DoD regime would give worse overall Ah delivered, but not by a massive amount. And I suspect that this loss only occurs pretty near the ends once the cells start to traverse the knees. But I can’t prove it!

[Conrad]

Thank you All for your comments.

Tony1 - 200 Ah bank should be enough for my needs as my daily usage is between 40-80 Ah. From April till October the solar panels (400W) should cope with this demand and during Winter my Honda gen will run an industrial charger 50A every 2nd day. It's limited to 14.4V and shows amperage so I should be able to monitor and switch the charger off when the current goes down. The solar controler also can be limited to 14.4 V (and remove the float phase) and I hope the integral BMS will cooperate with it.

Freezing temperatures may cause some troubles in the future but the specs say this battery can operate in minus 5 Celsius. 

I'm still considering 3x115Ah Rolls AGM that would be cheaper and easier to monitor but these lithium batteries may last longer (if treated kindly).

 

All the best.

[IanD]

43 minutes ago, Tony1 said:

 

On the 80/20 thing, I do recall seeing various graphs seeming to show that the optimum SoC range (for prolonging their effective life) was 25-75%, but I remember that 20-80 was pretty close. 

Here's something I just found with a random search: 

https://www.researchgate.net/figure/Effect-of-other-SOC-ranges-0-to-20-80-to-100-and-0-to-100-on-the-cycling-life-of-a_fig2_261135878

For me personally, there is enough information out there (I'm sure I could call it hard evidence) to make me conservative about pushing their SoC limits (and especially as I cant monitor voltage for each individual cell, but rather only at battery level).

 

The other thing I take from the literature is that you dont want to run them daily between say 50-75% as I was doing for the first 8 months. 

It seems like its better (for a longer life) to let them run down to your chosen lower SoC every couple of days. Its a bit tricky for a CCer because you dont want to run them down to 20% at say 9pm, and then not be able to recharge them till the next morning.

So there is a need for a bit of messing about, to make sure you are regularly 'exercising' them through the full range, but also that you don't run out of charge overnight.

 

With mine, when I do a monthly full charge to synchronise the SoC and the BMV monitor, I am noticing that above 80% SoC, the voltage seems to start increasing more rapidly (assuming my SoC is reading accurately. So I think with mine, maybe the knee starts at 80-85%. So it makes sense, for me anyway, to use 85% as a day-to-day 'fill' point for the charging. 

 

On the voltage- it is very difficult to actually determine on a liveaboard boat because the batteries are never fully at rest, unless you leave the boat overnight. 

There is always a small charge coming out (wifi router, inverter, BEP switches, presumably the BMV712s use something, etc etc), or else the solar is putting something in. The batteries and the voltage are never static as such, for more than a few minutes anyway. 

And for hours after an engine charge, the voltage is artificially high anyway, so you cant read it then. 

 

The charging voltage also seems to depend on how much current is being put in. If the batteries are half full and I charge at say 60amps, the battery voltage will be around 13.6v. If I charge at 90amps, the battery voltage goes up to 13.8v, and and if the solar kicks another 30amps in, the voltage might go to 13.9v.

And this would all be with a SoC around say 60%. 

If I then disconnect the solar, the charging voltage goes back down a bit.

 

So its quite hard to be 100% sure what state the batteries are in, other than when I so a synchronisation (and for a while afterwards)- thats why I'm a bit cautious with them.  

 

 

 

I suspect there's a lot of outdated information and FUD around about LFP SoC.

 

The newer battery/cell manufacturers who are also responsible for their own BMS (e.g. BYD) treat at least 10%-90% SoC as "normal" usage (sometimes even wider than this), and within this range the battery life is based on total energy charged and discharged -- for example the BYD LVL 15.4 is rated at 48MWh which is 3100 cycles at 0%-100%, 5200 cycles at 20%-80% and so on (and this is all logged by the BMS, and communicated back to BYD). The key is to not go into the regions right at the end of the SoC curves where voltage changes rapidly, which the inbuilt BMS will stop you doing -- as well as ensuring that the cells are correctly balanced.

 

Given that they guarantee lifetime based on this (so it would be expensive for them if they got it wrong, and they are one of the biggest LFP manufacturers in the world) there's no reason to think that any other LFP batteries behave any differently -- don't hit the overvoltage/undervoltage regions, keep the cells balanced, and it should make very little difference to total capacity (in MWh) over lifetime what SoC range you use.

 

This pretty much is what Nick said he suspected just above... 😉

Edited February 14, 2022 by IanD

[Martin Nicholas]

22 minutes ago, Tony1 said:

Many narrowboat alternators are not actually capable of putting out their rated current on a prolonged basis. My domestic alternator is rated at 100amps, but if it gives out more than 50amps for 10 minutes, it overheats a lot. 

 

You want a "hot rated" alternator - a 100A alternator will actually deliver 100A indefinitely. Automotive alternators are not hot rated (generally); indeed there is often no datasheet available for your average car alternator and thus are not suitable for a custom installation.

[IanD]

4 minutes ago, Martin Nicholas said:

You want a "hot rated" alternator - a 100A alternator will actually deliver 100A indefinitely. Automotive alternators are not hot rated (generally); indeed there is often no datasheet available for your average car alternator and thus are not suitable for a custom installation.

Actually a lot of them are "hot rated" because that's what the test standards require, see attached Iskra data sheet (which Beta sent me) -- but note that "hot rated" means "continuous output when the alternator has heated up at 25C ambient temperature", it doesn't mean "continuous output in a poorly ventilated hot engine compartment where the temperature is much higher than 25C"... 😉

200-05383 Iskra 24V 80A IA1150 technical data.pdf

[Tony1]

1 minute ago, Martin Nicholas said:

You want a "hot rated" alternator - a 100A alternator will actually deliver 100A indefinitely. Automotive alternators are not hot rated (generally); indeed there is often no datasheet available for your average car alternator and thus are not suitable for a custom installation.

 

Thank you Martin, and I must confess I hadn't even heard of hot rated alternators until now. 

Its an academic point for me, because I stumbled down the path of using B2Bs and ended up with a mish mash solution. 

 

I remember that Ed Shiers, who specialises in lithiums, alternators, and the required control systems for narrowboats, mentioned to me that he was aware of some good quality units that were rated at 160amps, but that could put out 100-120amps or more continuously at any rpm and with no overheating. 

 

 

[IanD]

3 minutes ago, Tony1 said:

 

Thank you Martin, and I must confess I hadn't even heard of hot rated alternators until now. 

Its an academic point for me, because I stumbled down the path of using B2Bs and ended up with a mish mash solution. 

 

I remember that Ed Shiers, who specialises in lithiums, alternators, and the required control systems for narrowboats, mentioned to me that he was aware of some good quality units that were rated at 160amps, but that could put out 100-120amps or more continuously at any rpm and with no overheating. 

 

 

...so long as the air around them in the (hopefully well-ventilated) engine compartment is reasonably cool, not at more than 50C... 😉

[nicknorman]

2 minutes ago, Tony1 said:

 

Thank you Martin, and I must confess I hadn't even heard of hot rated alternators until now. 

Its an academic point for me, because I stumbled down the path of using B2Bs and ended up with a mish mash solution. 

 

I remember that Ed Shiers, who specialises in lithiums, alternators, and the required control systems for narrowboats, mentioned to me that he was aware of some good quality units that were rated at 160amps, but that could put out 100-120amps or more continuously at any rpm and with no overheating. 

 

 

My 175A alternator can put out about 120A continuously with the temperature of the fan exit air at about 85C in a rather poorly ventilated engine bay. Obviously some parts of the internals will be hotter than that, but it certainly doesn’t seem overly hot. In fact the spec for the alternator says that the ambient temperature can be up to 110C

[Tony1]

13 minutes ago, IanD said:

 

I suspect there's a lot of outdated information and FUD around about LFP SoC.

 

The newer battery/cell manufacturers who are also responsible for their own BMS (e.g. BYD) treat at least 10%-90% SoC as "normal" usage (sometimes even wider than this), and within this range the battery life is based on total energy charged and discharged -- for example the BYD LVL 15.4 is rated at 48MWh which is 3100 cycles at 0%-100%, 5200 cycles at 20%-80% and so on (and this is all logged by the BMS, and communicated back to BYD). The key is to not go into the regions right at the end of the SoC curves where voltage changes rapidly, which the inbuilt BMS will stop you doing -- as well as ensuring that the cells are correctly balanced.

 

Given that they guarantee lifetime based on this (so it would be expensive for them if they got it wrong, and they are one of the biggest LFP manufacturers in the world) there's no reason to think that any other LFP batteries behave any differently -- don't hit the overvoltage/undervoltage regions, keep the cells balanced, and it should make very little difference to total capacity (in MWh) over lifetime what SoC range you use.

 

This pretty much is what Nick said he suspected just above... 😉

 

My objective is I think similar to yours, which is to avoid (routinely) going into the extreme ranges.

Nick feels that the 'knee' phase is significant in terms of increasing longevity.

 

Because I cant monitor at individual cell level, I feel I have to act more conservatively than the 'accepted' limits, so if a limit of 90% is recommend for day to day charging, my adopting 85% as a working day to day limit seems sensible in my particular case. 

 

 

 

 

 

 

 

[IanD]

Just now, nicknorman said:

My 175A alternator can put out about 120A continuously with the temperature of the fan exit air at about 85C in a rather poorly ventilated engine bay. Obviously some parts of the internals will be hotter than that, but it certainly doesn’t seem overly hot. In fact the spec for the alternator says that the ambient temperature can be up to 110C

 

...but not how much current it can provide when it's that hot 😉

[Tony1]

2 minutes ago, nicknorman said:

My 175A alternator can put out about 120A continuously with the temperature of the fan exit air at about 85C in a rather poorly ventilated engine bay. Obviously some parts of the internals will be hotter than that, but it certainly doesn’t seem overly hot. In fact the spec for the alternator says that the ambient temperature can be up to 110C

 

I'm sure that getting a beefier aftermarket alternator is going to become more common as the adoption of lithium batteries starts to increase. 

Just a damn shame that my poxy little V belt arrangement on the canaline 38 cant safely handle a big alternator.

 

 

[IanD]

8 minutes ago, Tony1 said:

 

My objective is I think similar to yours, which is to avoid (routinely) going into the extreme ranges.

Nick feels that the 'knee' phase is significant in terms of increasing longevity.

 

Because I cant monitor at individual cell level, I feel I have to act more conservatively than the 'accepted' limits, so if a limit of 90% is recommend for day to day charging, my adopting 85% as a working day to day limit seems sensible in my particular case. 

 

 

If you can't monitor individual cells, how do you know they're balanced -- or are these "drop-in" LFPs where you rely on the internal BMS to do this?

 

If you don't have anything to keep the cells balanced, even 85% reported SoC (based on overall battery voltage) could be risky, there's nothing to stop one cell being well above the safe limit so long as all the others are below it...

5 minutes ago, Tony1 said:

 

I'm sure that getting a beefier aftermarket alternator is going to become more common as the adoption of lithium batteries starts to increase. 

Just a damn shame that my poxy little V belt arrangement on the canaline 38 cant safely handle a big alternator.

 

A polyvee belt -- or even two! -- is pretty much essential if you want to use high-output alternators with LFP, but an external regulator with the correct settings (Wakespeed, Mastervolt) is also a must if you want to get maximum charging current while avoiding overvoltage.

 

Was a polyvee pulley ever available as an option, like it is for the Beta engines (for big alternators or Travelpower)? If so you might be able to retrofit one.

Edited February 14, 2022 by IanD

[Tony1]

11 minutes ago, IanD said:

 

If you can't monitor individual cells, how do you know they're balanced -- or are these "drop-in" LFPs where you rely on the internal BMS to do this?

 

If you don't have anything to keep the cells balanced, even 85% reported SoC (based on overall battery voltage) could be risky, there's nothing to stop one cell being well above the safe limit so long as all the others are below it...

 

Mine are the Valence type, so they have connecting cables which somehow help them to stay balanced, and also link to an external BMS box, which reportedly exist but has never been seen by mortal eye. 

 

The balancing cables do seem to be working- I periodically disconnect the three batteries after a full charge and measure their voltages separately (rather than as a single entity as the BMV units do), and so far the individual battery voltages have always been the same (to 2dp's anyway).  

But that said, there could still be minor issues with individual cells within a battery, that would be difficult to detect- which is why I stay a bit away from the extremes of the recommended SoC limits.

Its a bit belt and braces but fingers crossed, so far so good. 

 

ETA_ these dont have an internal BMS- the external black box was designed to do that job (they were designed for vehicle propulsion).

Hence why I have three BMV712s, two cable disconnects (one for loads and one for chargers), and for day to day control, I have individual control wires (from one of the BMVs) to remotely switch off the four B2B chargers and the two MPPTs, when the target 85% SoC is reached.

 

Heath Robinson doesnt even begin to describe it, but it works- just.

 

 

Edited February 14, 2022 by Tony1