Monitoring lithium batteries

[eid]

15 minutes ago, Robbo said:

You can use the BMS12/200 in addition to the VE Bus BMS, in this mode the 12/200 acts as a current restrictor when needed.

 

https://www.victronenergy.com/upload/documents/VE.Bus-BMS-to-BMS-12-1200-alternator-control-cable-EN.pdf

I thought this just restricts the current to 80% of the value of the fuse?

 

I want to know "how to turn off alternator to avoid too long a charge at acceptable voltage level"

 

ETA: sorry, I should have read your link. Apparently it does also stop the charge in case of an alarm. Do you know if these alarms are configurable?

Edited November 28, 2018 by eid

[nicknorman]

47 minutes ago, eid said:

I thought this just restricts the current to 80% of the value of the fuse?

 

I want to know "how to turn off alternator to avoid too long a charge at acceptable voltage level"

 

ETA: sorry, I should have read your link. Apparently it does also stop the charge in case of an alarm. Do you know if these alarms are configurable?

If you look at Tom and Bex’s posts, you’ll see he’s using an Arduino based (programmable) external alternator. This seems to me to be the way to go. You can set it to bulk charge to a specified voltage and then drop to float so that the batteries are not charged further, whilst the alternator can continue to supply any boat loads. The over voltage and undervoltage shutoffs should be for failure situation, not for routine use.

[eid]

6 minutes ago, nicknorman said:

If you look at Tom and Bex’s posts, you’ll see he’s using an Arduino based (programmable) external alternator. This seems to me to be the way to go. You can set it to bulk charge to a specified voltage and then drop to float so that the batteries are not charged further, whilst the alternator can continue to supply any boat loads.

Thanks Nick, I'll look into that.

8 minutes ago, nicknorman said:

The over voltage and undervoltage shutoffs should be for failure situation, not for routine use.

I was given a quote for a Victron install which would have done exactly the above. I didn't get the job done mainly because of the warnings in Jono's videos. I've been trying to understand the Victron setup but their documentation seems to require a lot of prior knowledge, or something.

 

According to the BMS12/200 data sheet, "A LFP cell will be damaged if the voltage over the cell increases to more than 4,2V", so I assume this is when it shuts off the charge. From everything I've read elsewhere, this is far too high.

 

 

 

[eid]

44 minutes ago, nicknorman said:

The over voltage and undervoltage shutoffs should be for failure situation, not for routine use.

What is the reason for this?

 

Are you saying the current should be cut off at the alternator?

[nicknorman]

23 minutes ago, eid said:

Thanks Nick, I'll look into that.

I was given a quote for a Victron install which would have done exactly the above. I didn't get the job done mainly because of the warnings in Jono's videos. I've been trying to understand the Victron setup but their documentation seems to require a lot of prior knowledge, or something.

 

According to the BMS12/200 data sheet, "A LFP cell will be damaged if the voltage over the cell increases to more than 4,2V", so I assume this is when it shuts off the charge. From everything I've read elsewhere, this is far too high.

 

Not quite sure where you are in your understanding so excuse me if I’m doing the sucking eggs thing, however...

 

One can take cell voltages up fairly high for short periods without accumulating much damage ((though cycle life will always be reduced if you charge to 100% rather than say 80%). However one has 4 cells in series and thus it is less about the total voltage across all cells, than about the voltage across each individual cell. Taking the overall voltage up near the the limit of the product of max cell voltage and number of cells, risks getting one or more cells above the max voltage whilst the other cells remain below it - cell imbalance. If a battery has built in cell balancing this is less of an issue, and I think pre- made batteries tend to have this. If you are building your own system from individual cells the you either need a cell balancing system, or to avoid getting near the max overall voltage.

 

Anyway, damage from hi voltage is progressive and cumulative so it depends on where you want to strike the compromise between maximising capacity and maximising cycle life.

[nicknorman]

9 minutes ago, eid said:

What is the reason for this?

 

Are you saying the current should be cut off at the alternator?

Because they are at the limits of tolerable damage. Routinely hitting these limits will significantly shorten the battery’s life.

yes either the current should be cut off at the alternator (by means of reducing the alternator output voltage), or an alternator regulated voltage should be less than a value which will come close to or exceed the maximum voltage. The latter is the easy way to do it but it means the charge current railing off significant as the final voltage is approached. The former will give much quicker charging but of course is more complex.

Edited November 28, 2018 by nicknorman

[eid]

23 minutes ago, nicknorman said:

Not quite sure where you are in your understanding so excuse me if I’m doing the sucking eggs thing, however...

 

Don't worry about that, you explain things very well and a comprehensive explanation is exactly what I need (even if it's only refreshing what I already read).

 

I don't know if you have watched Jono's vlog but IF I understand them, he uses the relay on the Victron battery monitor to cut the positive feed to (I think) the BMS12/200, thereby cutting the charge at a user-set voltage. I'm a bit confused as I think the load also connects to the BMS so wouldn't this also be disabled by cutting the feed?

[Robbo]

4 minutes ago, eid said:

 

Don't worry about that, you explain things very well and a comprehensive explanation is exactly what I need (even if it's only refreshing what I already read).

 

I don't know if you have watched Jono's vlog but IF I understand them, he uses the relay on the Victron battery monitor to cut the positive feed to (I think) the BMS12/200, thereby cutting the charge at a user-set voltage. I'm a bit confused as I think the load also connects to the BMS so wouldn't this also be disabled by cutting the feed?

The 12/200 basically has a on/off switch that’s usually connected to the other BMS, Jono I think uses that.

 

The load side of the 12/200 isn’t connected when using the 12/200 as just a alternator controller controlled by the other BMs

Edited November 28, 2018 by Robbo

[eid]

1 hour ago, Robbo said:

The 12/200 basically has a on/off switch that’s usually connected to the other BMS, Jono I think uses that.

 

The load side of the 12/200 isn’t connected when using the 12/200 as just a alternator controller controlled by the other BMs

So if I wanted to use the BMS12/200 as a BMS, is there some kind of powered isolation switch that I could put between the alternator and the BMS which I can control with the battery monitor's relay?

 

ETA: Is there any reason I shouldn't do this?

Edited November 28, 2018 by eid

[Robbo]

12 minutes ago, eid said:

So if I wanted to use the BMS12/200 as a BMS, is there some kind of powered isolation switch that I could put between the alternator and the BMS which I can control with the battery monitor's relay?

 

ETA: Is there any reason I shouldn't do this?

Have a look at the VEBus BMS diagrams, they have devices for turning the link off between the “alternator” battery bank and the lithium house bank.   Basically just a spilt charge relay controlled by the BMS, but you could probably also control via a BMV as well.  

 

I’m not sure why you would want to tho? What BMV are you needed?  Is the 12/200 enough for you are do you need the VE bus version?  If the 12/200 is what you going to use you could use a BMV and split charge relay as well, but it does seem overkill!

Edited November 28, 2018 by Robbo

[Robbo]

I think this was mentioned before regarding Victron releasing a update for the batteries so won’t charge under 5°, but as the blog entry has been posted thought it worth a link to it if you have these batteries.

 

Blog entry here; https://www.victronenergy.com/blog/2018/11/28/victronconnect-now-with-smart-lithium-update/

Edited November 28, 2018 by Robbo

[nicknorman]

3 hours ago, eid said:

 

Don't worry about that, you explain things very well and a comprehensive explanation is exactly what I need (even if it's only refreshing what I already read).

 

I don't know if you have watched Jono's vlog but IF I understand them, he uses the relay on the Victron battery monitor to cut the positive feed to (I think) the BMS12/200, thereby cutting the charge at a user-set voltage. I'm a bit confused as I think the load also connects to the BMS so wouldn't this also be disabled by cutting the feed?

I should give a general caveat that I’ve never played with any of this stuff! But as I understand it, one way is to isolate the alternator from the battery once it’s fully charged. But then you are left with the battery powering the boat services if you continue to run the engine (ie you are cruising, not just statically charging). Or I suppose you could cut off the battery altogether and just leave the alternator connected direct to the boat services. But neither of these schemes seem elegant to me, they all involve contactors with moving parts and probable momentary power interruptions.

 

A much more elegant system seems to be the one in use by Tom whereby the alternator voltage is reduced to a non-damaging float value once the battery approaches fully charged. Everything is left in circuit and any boat loads are provided by the alternator. Over voltage trip relays are reserved for failure conditions.

That is certainly the way I would do it (will do it, once our Trojans die).

Edited November 28, 2018 by nicknorman

[peterboat]

23 minutes ago, nicknorman said:

I should give a general caveat that I’ve never played with any of this stuff! But as I understand it, one way is to isolate the alternator from the battery once it’s fully charged. But then you are left with the battery powering the boat services if you continue to run the engine (ie you are cruising, not just statically charging). Or I suppose you could cut off the battery altogether and just leave the alternator connected direct to the boat services. But neither of these schemes seem elegant to me, they all involve contactors with moving parts and probable momentary power interruptions.

 

A much more elegant system seems to be the one in use by Tom whereby the alternator voltage is reduced to a non-damaging float value once the battery approaches fully charged. Everything is left in circuit and any boat loads are provided by the alternator. Over voltage trip relays are reserved for failure conditions.

That is certainly the way I would do it (will do it, once our Trojans die).

I am with you Nick, I chose the simplest solution to my system which is an over/under voltage cutoff board and set the MPPT controller at the correct voltage. As I have a fridge and a fan in the composting toilet, the batteries are safe from over charging on a day to day basis.

I did however have a look at the batteries to day with the puter, and all is well, the cells are balanced which for me vindicates my no more than 80% charging routine

[eid]

1 hour ago, nicknorman said:

I should give a general caveat that I’ve never played with any of this stuff! But as I understand it, one way is to isolate the alternator from the battery once it’s fully charged. But then you are left with the battery powering the boat services if you continue to run the engine (ie you are cruising, not just statically charging). Or I suppose you could cut off the battery altogether and just leave the alternator connected direct to the boat services. But neither of these schemes seem elegant to me, they all involve contactors with moving parts and probable momentary power interruptions.

 

A much more elegant system seems to be the one in use by Tom whereby the alternator voltage is reduced to a non-damaging float value once the battery approaches fully charged. Everything is left in circuit and any boat loads are provided by the alternator. Over voltage trip relays are reserved for failure conditions.

That is certainly the way I would do it (will do it, once our Trojans die).

I hadn't thought of that, and I agree with you that Tom's sounds more elegant. I'll read up a bit and see if I can understand it at all.

I did have a quick look earlier at Arduino based regulators. I came to a page with pictures of bare PCB's (not even in a box!) and talk of FOSS, which kind of put me off as it is beyond me completely. I shall persevere though, as it did look interesting. I will likely pay someone to install it, though I would like some level of understanding before I do so.

Edited November 28, 2018 by eid
grammer

[MtB]

Bear in mind Tom writes about using alarms to indicate cell imbalance and over-voltage. An audio alarm (or even a red light) is much easier to arrange than a disconnecting relay and less inconvenient to have trigger too. Granted alarms require user intervention but if you are interested in your installation, you will intervene and neither cell imbalance nor initial over-voltage needs instantaneous cut-off. 

[eid]

2 hours ago, Robbo said:

Have a look at the VEBus BMS diagrams, they have devices for turning the link off between the “alternator” battery bank and the lithium house bank.   Basically just a spilt charge relay controlled by the BMS, but you could probably also control via a BMV as well.  

 

I’m not sure why you would want to tho? What BMV are you needed?  Is the 12/200 enough for you are do you need the VE bus version?  If the 12/200 is what you going to use you could use a BMV and split charge relay as well, but it does seem overkill!

 

The reason is that I have read in several places (Nick said it a few posts above), that you should not rely on the BMS' cut off functions for your daily use but for emergencies only. Also, I would like the ability to stop charging at 80% which everyone seems to think will make the batteries last longer.

 

 

1 hour ago, Robbo said:

I think this was mentioned before regarding Victron releasing a update for the batteries so won’t charge under 5°, but as the blog entry has been posted thought it worth a link to it if you have these batteries.

 

Blog entry here; https://www.victronenergy.com/blog/2018/11/28/victronconnect-now-with-smart-lithium-update/

Yes I saw that in the Victron Connect update. That's one less thing to deal with anyway.

 

3 minutes ago, Mike the Boilerman said:

Bear in mind Tom writes about using alarms to indicate cell imbalance and over-voltage. An audio alarm (or even a red light) is much easier to arrange than a disconnecting relay and less inconvenient to have trigger too. Granted alarms require user intervention but if you are interested in your installation, you will intervene and neither cell imbalance nor initial over-voltage needs instantaneous cut-off. 

 

In this example would I need to use a manual isolator when the alarm goes off (while I'm cruising)?

[MtB]

9 minutes ago, eid said:

 

In this example would I need to use a manual isolator when the alarm goes off (while I'm cruising)?

 

I gave two examples actually

 

In the case of over-voltage you could just look at the volt meter and make a judgement about how much over the voltage is, and balance this with with how much longer you need to cruise before stopping. If you see fit, you could just moor up and stop the engine immediately.

 

If cell imbalance is indicated you would just make a note of it, then next weekend disconnect your bank and use a bench power supply to accurately charge each cell individually to precisely the same voltage, put the bank back together again and carry on for a few more years before it needs doing again. 

 

 

 

 

 

Edited November 28, 2018 by Mike the Boilerman
Improve clarity

[peterboat]

19 minutes ago, Mike the Boilerman said:

 

I gave two examples actually

 

In the case of over-voltage you could just look at the volt meter and make a judgement about how much over the voltage is, and balance this with with how much longer you need to cruise before stopping. If you see fit, you could just moor up and stop the engine immediately.

 

If cell imbalance is indicated you would just make a note of it, then next weekend disconnect your bank and use a bench power supply to accurately charge each cell individually to precisely the same voltage, put the bank back together again and carry on for a few more years before it needs doing again. 

 

 

 

 

 

Stop making it tooooo simple Mike, however are vitron etc going to make a fortune? if they dont scare people into spending thousands and thousands

[Robbo]

1 hour ago, eid said:

 

The reason is that I have read in several places (Nick said it a few posts above), that you should not rely on the BMS' cut off functions for your daily use but for emergencies only. Also, I would like the ability to stop charging at 80% which everyone seems to think will make the batteries last longer.

It looks like You can use the BMV with alarm output to disconnect the 12/200, if this disconnects the load as well (I don’t know if it does) and you use this then you can use the BMV to disconnect a relay (like one of Victrons).  This is how the other victron BMS’s do it (the BMS is connected to the relay to disconnect the alternator)

 

The other BMS’s that Victron have basically just turn off/on devices via “alarm outputs”, this then either turns off/on chargers/MTTPs/alternators or loads.  A BMV can do the same with its alarm output to what ever you set it to do.

 

basically the yellow cAbles from the BMS are the “alarm” outputs to control the loads/chargers.  Victron have just releSe a mini BMS which I think doesn’t have the bus to the combi so if you don’t need that have a look at that one.

Edited November 28, 2018 by Robbo

[peterboat]

4 hours ago, Robbo said:

It looks like You can use the BMV with alarm output to disconnect the 12/200, if this disconnects the load as well (I don’t know if it does) and you use this then you can use the BMV to disconnect a relay (like one of Victrons).  This is how the other victron BMS’s do it (the BMS is connected to the relay to disconnect the alternator)

 

The other BMS’s that Victron have basically just turn off/on devices via “alarm outputs”, this then either turns off/on chargers/MTTPs/alternators or loads.  A BMV can do the same with its alarm output to what ever you set it to do.

 

basically the yellow cAbles from the BMS are the “alarm” outputs to control the loads/chargers.  Victron have just releSe a mini BMS which I think doesn’t have the bus to the combi so if you don’t need that have a look at that one.

That looks very expensive glad James, John  and I didnt bother

[nicknorman]

44 minutes ago, peterboat said:

That looks very expensive glad James, John  and I didnt bother

Well a little, but whilst we agree on how to control the alternator charging, we also have to have a strategy for dealing with the shore powered charger for boats like ours that are on shore power quite a bit. In my case I would use the Masterbus system as we already have a Mastershunt that can be set to send a command when the SoC reaches some preset values including 60%, 80% and 100%. Also over and under voltage alarms (programmable voltage). This can be linked to a command on the Combi. BUT UNFORTUNATELY our present Combi doesn't have a command to switch it to float. That command is available in the latest Combi Ultra. So all this will have to wait until our present Combi blows up and I can get a new one. 8 years and still waiting...

 

I suppose ultimately, for non-full-time live-aboard, one wants an easy means to select between say charging to only 50% (for long term lurking empty in the marina) and charging to near 100% (when out and about off shore power). So if/when I ever go to Lithiums, I can see a bit of a complicated system being developed. I've recently been practicing my C programming!

[peterboat]

18 minutes ago, nicknorman said:

Well a little, but whilst we agree on how to control the alternator charging, we also have to have a strategy for dealing with the shore powered charger for boats like ours that are on shore power quite a bit. In my case I would use the Masterbus system as we already have a Mastershunt that can be set to send a command when the SoC reaches some preset values including 60%, 80% and 100%. Also over and under voltage alarms (programmable voltage). This can be linked to a command on the Combi. BUT UNFORTUNATELY our present Combi doesn't have a command to switch it to float. That command is available in the latest Combi Ultra. So all this will have to wait until our present Combi blows up and I can get a new one. 8 years and still waiting...

 

I suppose ultimately, for non-full-time live-aboard, one wants an easy means to select between say charging to only 50% (for long term lurking empty in the marina) and charging to near 100% (when out and about off shore power). So if/when I ever go to Lithiums, I can see a bit of a complicated system being developed. I've recently been practicing my C programming!

I use a 24 volt CTEK charger it knocks off at 27.2 volts and just floats at 26.8 volts, it automatically went for these settings. I at the moment seem to be using it one day in five, although if I go away the solar copes with the fridge freezer and composting toilet.

Seriously Nick keep it simple, if the charger cant go above the safe voltages [apart from developing a fault] thats the best way of doing the job, I do have the low/high voltage cutoffs as an emergency fingers crossed I dont need them

[nicknorman]

4 minutes ago, peterboat said:

I use a 24 volt CTEK charger it knocks off at 27.2 volts and just floats at 26.8 volts, it automatically went for these settings. I at the moment seem to be using it one day in five, although if I go away the solar copes with the fridge freezer and composting toilet.

Seriously Nick keep it simple, if the charger cant go above the safe voltages [apart from developing a fault] thats the best way of doing the job, I do have the low/high voltage cutoffs as an emergency fingers crossed I dont need them

Well I hear what you say but there is a difference between requirements for a liveaboard vs a leisure user, in that when not in use it’s best to keep the batteries at a medium SoC. I can effortlessly set bulk, absorb and float voltage for the Combi but in order to differentiate between wanting the batteries in “storage mode” vs wanting them fully charged prior to detaching from shore power umbilical, there would have to be a means to achieve that. Obviously this could be done manually but as you know, I do like gadgets!

 

I could for example use the GSM receiver to inject a Mastervolt command into the CANBUS (Masterbus) system to modify the set charging voltages in the Combi, so I’d just have to remember to send it a text. Etc etc. Probably will never happen though, so don’t fret!

[peterboat]

2 minutes ago, nicknorman said:

Well I hear what you say but there is a difference between requirements for a liveaboard vs a leisure user, in that when not in use it’s best to keep the batteries at a medium SoC. I can effortlessly set bulk, absorb and float voltage for the Combi but in order to differentiate between wanting the batteries in “storage mode” vs wanting them fully charged prior to detaching from shore power umbilical, there would have to be a means to achieve that. Obviously this could be done manually but as you know, I do like gadgets!

 

I could for example use the GSM receiver to inject a Mastervolt command into the CANBUS (Masterbus) system to modify the set charging voltages in the Combi, so I’d just have to remember to send it a text. Etc etc. Probably will never happen though, so don’t fret!

Yes you do like gadgets, but why bother? I take it everything is off in the boat when you moor it up in the marina? if so make sure that batteries are at 60% when you leave and 2 months later they will be the same of that I can assure you I have 10 sat around just like that. When you fire the boat up the batteries will be up to 13.8 in no time at all. Its the kiss principle and it really works Jame has been doing it for well over a year with total success, John and I under a year and apart from my solar panel fault all is working well

[eid]

15 hours ago, Robbo said:

It looks like You can use the BMV with alarm output to disconnect the 12/200, if this disconnects the load as well (I don’t know if it does) and you use this then you can use the BMV to disconnect a relay (like one of Victrons).  This is how the other victron BMS’s do it (the BMS is connected to the relay to disconnect the alternator)

 

The other BMS’s that Victron have basically just turn off/on devices via “alarm outputs”, this then either turns off/on chargers/MTTPs/alternators or loads.  A BMV can do the same with its alarm output to what ever you set it to do.

 

basically the yellow cAbles from the BMS are the “alarm” outputs to control the loads/chargers.  Victron have just releSe a mini BMS which I think doesn’t have the bus to the combi so if you don’t need that have a look at that one.

 

Sorry for these very basic questions but I really want to understand this.

 

How exactly would you connect up the BMV's relay in the above diagram. Since it's basically a controlled switch, where in that circuit would you connect the in/out?

 

Also, when you say Victron relay, do you mean the Cyrix?

 

Thanks

 

 

Edited November 29, 2018 by eid