Jump to content

Monitoring lithium batteries


Dr Bob

Featured Posts

10 hours ago, Dr Bob said:

Is it possible the low voltage response is only to disconnect any load on the battery and leave in place any charge source which is needed on deep discharge.

That’s not my understanding. From what I’ve read, when the BMS disconnects it disconnects... but then again I’m unclear on how to get it to reconnect when charging - it probably just does so when it sees sufficient voltage on the terminal, but I’m not sure. There are also many, many variants of what a BMS does. 

Link to comment
Share on other sites

59 minutes ago, Mike the Boilerman said:

I suspect the Victron batteries have just four large cells inside so monitoring balance is both far easier and far more important. 

 

9 minutes ago, Robbo said:

Confirmed, the 12v ones have 4 cells.

See 4.1 here: https://www.victronenergy.com/upload/documents/Manual-Lithium-iron-phosphate-(LiFePO4)-battery-EN-NL-FR-DE-ES-A5.pdf

Link to comment
Share on other sites

9 minutes ago, WotEver said:

That’s not my understanding. From what I’ve read, when the BMS disconnects it disconnects... but then again I’m unclear on how to get it to reconnect when charging - it probably just does so when it sees sufficient voltage on the terminal, but I’m not sure. There are also many, many variants of what a BMS does. 

Reading the document I linked to in the above post it appears that the Victron BMS doesn’t completely disconnect the battery on low voltage as the document contains a dire warning in red about removing all loads following a low voltage disconnect. 

Link to comment
Share on other sites

39 minutes ago, WotEver said:

Reading the document I linked to in the above post it appears that the Victron BMS doesn’t completely disconnect the battery on low voltage as the document contains a dire warning in red about removing all loads following a low voltage disconnect. 

The standard VE.Bus BMS turn's off loads (and charging devices) remotely basically via a relay (Victron show a their "battery protect" product in their diagrams, but they also have a number of relays as well (https://www.victronenergy.com/upload/documents/Datasheet-Cyrix-Li-ion-230-A-EN.pdf).  If you wire a load directly to the battery the BMS won't have control over it, hence the warning.

Link to comment
Share on other sites

39 minutes ago, Robbo said:

The standard VE.Bus BMS turn's off loads (and charging devices) remotely basically via a relay (Victron show a their "battery protect" product in their diagrams, but they also have a number of relays as well (https://www.victronenergy.com/upload/documents/Datasheet-Cyrix-Li-ion-230-A-EN.pdf).  If you wire a load directly to the battery the BMS won't have control over it, hence the warning.

So in Victron’s case the external BMS does the disconnections leaving the internal BMSs to handle only reporting and balancing?

Link to comment
Share on other sites

I've not been reading the forums much recently as life and work have been getting in the way so missed this thread! Apologies if this post ends up a bit long but just finalising sourcing all the bits needed for upgrading to LiFePO4 batteries as I type, so here's my thoughts on some points raised in this thread. 

 

Firstly a general comment. There are still some people (not necessarily here, but certainly other boaters) who see lithium batteries as high risk and dangerous to use on boats. There are several types of lithium batteries, and the only type suitable for boats are LiFePO4. These are not at risk of exploding, fire, or thermal runaway if overcharged unlike other types, and many people believe them to be as safe or safer than lead acid. Having seen the results of a stray spark near a badly overcharged lead acid battery in my camper I'm inclined to agree - lead acid certainly has it's own dangers!

 

The main thing that damages these batteries is over charging, over discharging, and storing at full charge. I don't believe there is much harm to charging to 95-100% provided the batteries are in use and not kept at that level, or kept on float charge, although you do run the risk of over charging. In our type of low current usage they prove very resilient - remember they are designed (and all testing and specs are geared towards) electric vehicle use with far far higher change and discharge currents than ever likely to be seen on a narrowboat. 

 

The BMS in the type of battery that Peterboat has that is made up of multiple small cells, only monitors each bank of parallel cells. It's impossible to monitor each individual cell of a parallel group as they will always be at the same voltage. 

 

Now to my proposed setup. My budget is £1000 to include batteries and all extras. So far I'm looking like being slightly over this, but with slight increase in original planned capacity from 210ah to 320ah.

 

My charging will mainly be via solar and engine. Solar controller settings still to be decided on, but likely 13.6-13.8v bulk, dropping to 13.3ish float. Alternator charging will likely be at 14.0v until current drops to a set level, then charging will stop and voltage held at a level that provides 0A into or out of the batteries - thus powering all loads, but not putting any more charge in. This will be via external alternator controller. 

 

Monitoring will be of individual cell voltages with over and under voltage alarm, and charge level by AH counting gauge. There will be a BMS to monitor cell voltages, and provide a high voltage cut off for all charging sources, and low voltage cut for all loads. No automatic balancing. I expect them to stay fairly well balanced after initial top balance, but will monitor cell voltages and manually balance if required. 

 

The main decision still to be made is charging of the start battery. I'm concerned that just paralleling it during charging of the LiFePO4 will not result in high enough charge voltage. I have twin alternators but want to maximise their output to charge the LiFePO4 batteries (although currently only have a single controller). Not sure what will happen if I use the one controller for both alternators, but the designer can't see a reason it won't work and said to try it and see, but with the high probability of 1 alternator working harder than the other. Also not sure yet if either and/or both can even be modified to use just an external reg!

 

Current favourite is a battery to battery charger for the start battery, but this part of the install is still undecided. Part of me is tempted to eliminate the start battery completely and rely on just the lithiums, but think that's a step too far at this point!

 

Another option under consideration is one alternator connected to each battery, and parallel the banks for extra charging of the lithiums if required. The biggest problem with this option is overcharging. As the start alternator would be relying on usual regulator, would need to have a way to automatically split the banks again as the LiFePO4 batteries charged. 

 

The rest of the design and parts is pretty much finalised. 

 

If you've managed to read this far well done! It does help my thought processes to get ideas down in writing so hope I've not bored too many people!

 

If anyone has any questions or wants more details of the components I'm using just let me know. I'll post an update somewhere with my experiences when the install is complete, hopefully by the end of next month. 

Edited by Tom and Bex
  • Greenie 3
Link to comment
Share on other sites

6 hours ago, Tom and Bex said:

I've not been reading the forums much recently as life and work have been getting in the way so missed this thread! Apologies if this post ends up a bit long but just finalising sourcing all the bits needed for upgrading to LiFePO4 batteries as I type, so here's my thoughts on some points raised in this thread. 

 

Firstly a general comment. There are still some people (not necessarily here, but certainly other boaters) who see lithium batteries as high risk and dangerous to use on boats. There are several types of lithium batteries, and the only type suitable for boats are LiFePO4. These are not at risk of exploding, fire, or thermal runaway if overcharged unlike other types, and many people believe them to be as safe or safer than lead acid. Having seen the results of a stray spark near a badly overcharged lead acid battery in my camper I'm inclined to agree - lead acid certainly has it's own dangers!

 

The main thing that damages these batteries is over charging, over discharging, and storing at full charge. I don't believe there is much harm to charging to 95-100% provided the batteries are in use and not kept at that level, or kept on float charge, although you do run the risk of over charging. In our type of low current usage they prove very resilient - remember they are designed (and all testing and specs are geared towards) electric vehicle use with far far higher change and discharge currents than ever likely to be seen on a narrowboat. 

 

The BMS in the type of battery that Peterboat has that is made up of multiple small cells, only monitors each bank of parallel cells. It's impossible to monitor each individual cell of a parallel group as they will always be at the same voltage. 

 

Now to my proposed setup. My budget is £1000 to include batteries and all extras. So far I'm looking like being slightly over this, but with slight increase in original planned capacity from 210ah to 320ah.

 

My charging will mainly be via solar and engine. Solar controller settings still to be decided on, but likely 13.6-13.8v bulk, dropping to 13.3ish float. Alternator charging will likely be at 14.0v until current drops to a set level, then charging will stop and voltage held at a level that provides 0A into or out of the batteries - thus powering all loads, but not putting any more charge in. This will be via external alternator controller. 

 

Monitoring will be of individual cell voltages with over and under voltage alarm, and charge level by AH counting gauge. There will be a BMS to monitor cell voltages, and provide a high voltage cut off for all charging sources, and low voltage cut for all loads. No automatic balancing. I expect them to stay fairly well balanced after initial top balance, but will monitor cell voltages and manually balance if required. 

 

The main decision still to be made is charging of the start battery. I'm concerned that just paralleling it during charging of the LiFePO4 will not result in high enough charge voltage. I have twin alternators but want to maximise their output to charge the LiFePO4 batteries (although currently only have a single controller). Not sure what will happen if I use the one controller for both alternators, but the designer can't see a reason it won't work and said to try it and see, but with the high probability of 1 alternator working harder than the other. Also not sure yet if either and/or both can even be modified to use just an external reg!

 

Current favourite is a battery to battery charger for the start battery, but this part of the install is still undecided. Part of me is tempted to eliminate the start battery completely and rely on just the lithiums, but think that's a step too far at this point!

 

Another option under consideration is one alternator connected to each battery, and parallel the banks for extra charging of the lithiums if required. The biggest problem with this option is overcharging. As the start alternator would be relying on usual regulator, would need to have a way to automatically split the banks again as the LiFePO4 batteries charged. 

 

The rest of the design and parts is pretty much finalised. 

 

If you've managed to read this far well done! It does help my thought processes to get ideas down in writing so hope I've not bored too many people!

 

If anyone has any questions or wants more details of the components I'm using just let me know. I'll post an update somewhere with my experiences when the install is complete, hopefully by the end of next month. 

 

Fascinating, thanks for posting.

 

I too am considering a DIY LiFePO4 installation on one of my boats but i’ve only been idly considering it so far because I’ve yet to discover any firm in the uk supplying a voltage monitoring/high/low cut off device. Whose device are you planning to use or are you designing and building it yourself? 

 

Also, how do you plan to protect the alternator from damage if/when the charge current is disconnected on high voltage? And how will you monitor state of  charge during charging given your proposed charge voltage of 13.8v, when 13.6v represents 100% SoC of four single cells in series?

 

Thirdly, why bother with a lithium start battery? It makes thing far more complicated and for what end? Far simpler to just let one alternator charge the start batt and the other do the lithiums. 

 

And forthly you are clearly aware of the two different types of LiFePO4 batteries out there. Those made of four large single cells and those comprising hundreds of little cells. Which type will you be using, and why?

 

Edited by Mike the Boilerman
Link to comment
Share on other sites

6 hours ago, Tom and Bex said:

I've not been reading the forums much recently as life and work have been getting in the way so missed this thread! Apologies if this post ends up a bit long but just finalising sourcing all the bits needed for upgrading to LiFePO4 batteries as I type, so here's my thoughts on some points raised in this thread. 

 

Firstly a general comment. There are still some people (not necessarily here, but certainly other boaters) who see lithium batteries as high risk and dangerous to use on boats. There are several types of lithium batteries, and the only type suitable for boats are LiFePO4. These are not at risk of exploding, fire, or thermal runaway if overcharged unlike other types, and many people believe them to be as safe or safer than lead acid. Having seen the results of a stray spark near a badly overcharged lead acid battery in my camper I'm inclined to agree - lead acid certainly has it's own dangers!

 

The main thing that damages these batteries is over charging, over discharging, and storing at full charge. I don't believe there is much harm to charging to 95-100% provided the batteries are in use and not kept at that level, or kept on float charge, although you do run the risk of over charging. In our type of low current usage they prove very resilient - remember they are designed (and all testing and specs are geared towards) electric vehicle use with far far higher change and discharge currents than ever likely to be seen on a narrowboat. 

 

The BMS in the type of battery that Peterboat has that is made up of multiple small cells, only monitors each bank of parallel cells. It's impossible to monitor each individual cell of a parallel group as they will always be at the same voltage. 

 

Now to my proposed setup. My budget is £1000 to include batteries and all extras. So far I'm looking like being slightly over this, but with slight increase in original planned capacity from 210ah to 320ah.

 

My charging will mainly be via solar and engine. Solar controller settings still to be decided on, but likely 13.6-13.8v bulk, dropping to 13.3ish float. Alternator charging will likely be at 14.0v until current drops to a set level, then charging will stop and voltage held at a level that provides 0A into or out of the batteries - thus powering all loads, but not putting any more charge in. This will be via external alternator controller. 

 

Monitoring will be of individual cell voltages with over and under voltage alarm, and charge level by AH counting gauge. There will be a BMS to monitor cell voltages, and provide a high voltage cut off for all charging sources, and low voltage cut for all loads. No automatic balancing. I expect them to stay fairly well balanced after initial top balance, but will monitor cell voltages and manually balance if required. 

 

The main decision still to be made is charging of the start battery. I'm concerned that just paralleling it during charging of the LiFePO4 will not result in high enough charge voltage. I have twin alternators but want to maximise their output to charge the LiFePO4 batteries (although currently only have a single controller). Not sure what will happen if I use the one controller for both alternators, but the designer can't see a reason it won't work and said to try it and see, but with the high probability of 1 alternator working harder than the other. Also not sure yet if either and/or both can even be modified to use just an external reg!

 

Current favourite is a battery to battery charger for the start battery, but this part of the install is still undecided. Part of me is tempted to eliminate the start battery completely and rely on just the lithiums, but think that's a step too far at this point!

 

Another option under consideration is one alternator connected to each battery, and parallel the banks for extra charging of the lithiums if required. The biggest problem with this option is overcharging. As the start alternator would be relying on usual regulator, would need to have a way to automatically split the banks again as the LiFePO4 batteries charged. 

 

The rest of the design and parts is pretty much finalised. 

 

If you've managed to read this far well done! It does help my thought processes to get ideas down in writing so hope I've not bored too many people!

 

If anyone has any questions or wants more details of the components I'm using just let me know. I'll post an update somewhere with my experiences when the install is complete, hopefully by the end of next month. 

Very good. Please do let us know how you get on.

Link to comment
Share on other sites

6 minutes ago, Mike the Boilerman said:

 

Fascinating, thanks for posting.

 

I too am considering a DIY LiFePO4 installation on one of my boats but i’ve only been idly considering it so far because I’ve yet to discover any firm in the uk supplying a voltage monitoring/high/low cut off device. Which device are you planning to use or are you designing and building it yourself? 

 

Also, how do you plan to protect the alternator from damage if/when the charge current is disconnected on high voltage? And how will you monitor state of  charge during charging given your proposed charge voltage of 13.8v when 13.6v represents 100% SoC?

 

Thirdly, why bother with a lithium start battery? It makes thing far more complicated and for what end? Far simpler to just let one alternator charge the start batt and the other do the lithiums. 

An alternator controller can be set to cut off the charge current (or in this case reduce the voltage to float) without risk of damage. If the “backstop” over voltage trip operated, the charging mechanism would already have failed.

 

SoC monitored by AH counting as said.

 

I think the idea was not to have a separate LiFePO4 start battery, but just to have one battery used for both domestic and engine. A nearly-flat LI battery is quite capable of starting an engine. Not like LA!

 

If there are other means of charging (solar) then just having one battery is not a big risk.

  • Greenie 1
Link to comment
Share on other sites

2 minutes ago, nicknorman said:

An alternator controller can be set to cut off the charge current (or in this case reduce the voltage to float) without risk of damage. If the “backstop” over voltage trip operated, the charging mechanism would already have failed.

 

SoC monitored by AH counting as said.

 

 

Which alternator charge controller in particular do you gave in mind will do this, bearing in mind Tom’s declared budget of £1k to include sourcing the batteries?

 

 

Link to comment
Share on other sites

1 hour ago, Mike the Boilerman said:

I’ve yet to discover any firm in the uk supplying a voltage monitoring/high/low cut off device. Whose device are you planning to use

I've yet to find a supplier in this country too! Panning to use this BMS from an Australian company: 8-cell Battery Monitor Module V2 coupled to a BEP remote battery switch for low voltage cut, and a yet to be decided relay/contactor/switch for high voltage cut. 

 

Alternator regulator is this one: VSR Alternator Regulator. As Nick says, if it reaches high voltage cut then the charge device has already failed, the high voltage cut is a last ditch fail safe to protect the batteries from potentially dangerous overcharge. 

 

As Nick suggested, flat lithium would easily still start a diesel engine so one possible idea is to eliminate the start battery and just run from a single lithium bank. This would simplify the install, and with options to charge from solar and generator, very unlikely to leave us stranded. Just a thought at present, and most likely stick with FLA start battery for now. 

 

Planning on using 8 used Thundersky 160ah large format cells, as I believe this type of battery to be the most suited for off grid energy storage, but either battery type would probably suffice. These are costing £600. I was also considering 4 used CALB 210ah cells for £400.

 

Finally one potential supplier of new cells and monitoring is https://www.ev-power.eu. It's not UK based, but at least EU based so avoiding import duty and taxes (for now at least!). I particularly like their BMS123 Smart, a Bluetooth BMS system. Slightly out of my price range though.

 

Tom

 

  • Greenie 2
Link to comment
Share on other sites

7 hours ago, Tom and Bex said:

I've not been reading the forums much recently as life and work have been getting in the way so missed this thread! Apologies if this post ends up a bit long but just finalising sourcing all the bits needed for upgrading to LiFePO4 batteries as I type, so here's my thoughts on some points raised in this thread. 

 

Firstly a general comment. There are still some people (not necessarily here, but certainly other boaters) who see lithium batteries as high risk and dangerous to use on boats. There are several types of lithium batteries, and the only type suitable for boats are LiFePO4. These are not at risk of exploding, fire, or thermal runaway if overcharged unlike other types, and many people believe them to be as safe or safer than lead acid. Having seen the results of a stray spark near a badly overcharged lead acid battery in my camper I'm inclined to agree - lead acid certainly has it's own dangers!

 

The main thing that damages these batteries is over charging, over discharging, and storing at full charge. I don't believe there is much harm to charging to 95-100% provided the batteries are in use and not kept at that level, or kept on float charge, although you do run the risk of over charging. In our type of low current usage they prove very resilient - remember they are designed (and all testing and specs are geared towards) electric vehicle use with far far higher change and discharge currents than ever likely to be seen on a narrowboat. 

 

The BMS in the type of battery that Peterboat has that is made up of multiple small cells, only monitors each bank of parallel cells. It's impossible to monitor each individual cell of a parallel group as they will always be at the same voltage. 

 

Now to my proposed setup. My budget is £1000 to include batteries and all extras. So far I'm looking like being slightly over this, but with slight increase in original planned capacity from 210ah to 320ah.

 

My charging will mainly be via solar and engine. Solar controller settings still to be decided on, but likely 13.6-13.8v bulk, dropping to 13.3ish float. Alternator charging will likely be at 14.0v until current drops to a set level, then charging will stop and voltage held at a level that provides 0A into or out of the batteries - thus powering all loads, but not putting any more charge in. This will be via external alternator controller. 

 

Monitoring will be of individual cell voltages with over and under voltage alarm, and charge level by AH counting gauge. There will be a BMS to monitor cell voltages, and provide a high voltage cut off for all charging sources, and low voltage cut for all loads. No automatic balancing. I expect them to stay fairly well balanced after initial top balance, but will monitor cell voltages and manually balance if required. 

 

The main decision still to be made is charging of the start battery. I'm concerned that just paralleling it during charging of the LiFePO4 will not result in high enough charge voltage. I have twin alternators but want to maximise their output to charge the LiFePO4 batteries (although currently only have a single controller). Not sure what will happen if I use the one controller for both alternators, but the designer can't see a reason it won't work and said to try it and see, but with the high probability of 1 alternator working harder than the other. Also not sure yet if either and/or both can even be modified to use just an external reg!

 

Current favourite is a battery to battery charger for the start battery, but this part of the install is still undecided. Part of me is tempted to eliminate the start battery completely and rely on just the lithiums, but think that's a step too far at this point!

 

Another option under consideration is one alternator connected to each battery, and parallel the banks for extra charging of the lithiums if required. The biggest problem with this option is overcharging. As the start alternator would be relying on usual regulator, would need to have a way to automatically split the banks again as the LiFePO4 batteries charged. 

 

The rest of the design and parts is pretty much finalised. 

 

If you've managed to read this far well done! It does help my thought processes to get ideas down in writing so hope I've not bored too many people!

 

If anyone has any questions or wants more details of the components I'm using just let me know. I'll post an update somewhere with my experiences when the install is complete, hopefully by the end of next month. 

Great. Do let us know how you get on.

Link to comment
Share on other sites

If I hadnt had the source for the Valence batteries I would have maybe gone a different way, however Valence are a long established manufacturer, and supply to the USA forces, so their batteries are tried and tested much more rigorously than some of the others around, this is backed up with a very high price tag new!! I have a high voltage cut off it was knocked up for £15 from ebay and amazon, what I will have to do is program it for low voltage cutoff as well, it was an oversight on my part as I didnt think I would need it. 

As we speak I have done the washing machine the dishwasher is on 1860 watts of solar is producing 50 amps @ 24 volts so all is now well in my world. I did plug into the batteries after I took then down to 9.4 volts and they were still balanced, I will check them tonight to see if that is still the same now that they are at 13.6 volts

  • Greenie 2
Link to comment
Share on other sites

6 hours ago, peterboat said:

I have a high voltage cut off it was knocked up for £15 from ebay and amazon, what I will have to do is program it for low voltage cutoff as well

I'd be interested to hear what you've used for this. It's always good to see how others have tackled the same problem. Besides I've still time to change parts of my design!

 

As to the Valence batteries, they are certainly expensive new! Glad they are working well. I did look at these when they first became available used, and was very tempted, but was unsure as to how the inbuilt BMS would work without the (expensive) Valence external parts. 

 

Also wasn't really ready to move forward at that time, and since then most of the reading I have done about existing installations seem to relate to the large format prismatic cells, albeit with new not used.

 

Please keep us updated how they continue to perform, be interesting (to me at least!) to see if there is any difference long term between the 2 types. 

 

Tom

Link to comment
Share on other sites

16 hours ago, Tom and Bex said:

I'd be interested to hear what you've used for this. It's always good to see how others have tackled the same problem. Besides I've still time to change parts of my design!

 

As to the Valence batteries, they are certainly expensive new! Glad they are working well. I did look at these when they first became available used, and was very tempted, but was unsure as to how the inbuilt BMS would work without the (expensive) Valence external parts. 

 

Also wasn't really ready to move forward at that time, and since then most of the reading I have done about existing installations seem to relate to the large format prismatic cells, albeit with new not used.

 

Please keep us updated how they continue to perform, be interesting (to me at least!) to see if there is any difference long term between the 2 types. 

 

Tom

With our batteries you can either top or bottom balance, I chose top balancing as it was easier to achieve and is supposed to be better in our installations, as it happens I also did bottom balancing by accident! Since then I have connected the computer when the batteries were registering 13.8 volts and checked the balancing which was ok, however the very act of connecting the puter fully balances the cells so all is well in my world. My BM2 is also more in tune with batteries now as well, so no doubt over the winter it will fine tune itself.

Link to comment
Share on other sites

I have watched these videos in the past and after discussion between the 3 of us and in James case 1 year of testing why bother? we can connect and the battery balances, the batteries up to press havent been out of balance even after being nearly discharged to death? We dont normally go beyond 13.8 volts or below 12 volts so we arnt working the batteries hard. I would have to do 14 batteries and James a lot more and if it aint broke why change it?

Now if these were in cars with fast charging [all of us use solar] and we were ramming them full and running them flat, it would be a different thing altogether but we aint so we will stick to the occasional look at them see how it goes

Link to comment
Share on other sites

3 hours ago, peterboat said:

I have watched these videos in the past and after discussion between the 3 of us and in James case 1 year of testing why bother?

 

I thought the same. What is the point of buying an expensive proprietary battery then dismantling it and chucking away all the carefully designed and tested electronics?

Link to comment
Share on other sites

15 minutes ago, Mike the Boilerman said:

 

I thought the same. What is the point of buying an expensive proprietary battery then dismantling it and chucking away all the carefully designed and tested electronics?

I think the point was to avoid having to use the proprietary stuff to connect to the BMS. Anyway, it was interesting to see what was inside.

Link to comment
Share on other sites

Just now, nicknorman said:

I think the point was to avoid having to use the proprietary stuff to connect to the BMS. Anyway, it was interesting to see what was inside.

 

Yes but what was the point of wanting to avoid having to use the proprietary stuff to connect to the BMS?

 

What BMS anyway? Where those PCBs he levered out not BMS boards? This illustrates the lack of clarity about what "BMS" means. People just like saying it without really knowing quite what they mean by it, it seems to me. 

Link to comment
Share on other sites

BMS functions, as far as I can see:

 

Cell balancing

Temperature monitoring

High voltage emergency disconnection during charging

Low voltage emergency disconnection during discharge

AH counting in and out for SoC calculating

Disconnecting charge source at a predetermined (high) SoC

Disconnecting loads at predetermined (low) SoC

Supplying data for user display(s) 

 

Anything else for the list?

 

Edited by Mike the Boilerman
Link to comment
Share on other sites

8 minutes ago, Mike the Boilerman said:

 

Yes but what was the point of wanting to avoid having to use the proprietary stuff to connect to the BMS?

 

What BMS anyway? Where those PCBs he levered out not BMS boards? This illustrates the lack of clarity about what "BMS" means. People just like saying it without really knowing quite what they mean by it, it seems to me. 

That’s because BMS doesn’t have a very specific meaning. I would imagine the board was designed to be connected to a control system with contractors for connecting and disconnecting loads and charging devices, and signalling to charging devices to stop charging etc as a result of voltage or temperature approaching or out of limits.

4 minutes ago, Mike the Boilerman said:

BMS functions, as far as I can see:

 

Cell balancing

Temperature monitoring

High voltage disconnection during charging

Low voltage disconnection during discharge

AH counting in and out for SoC calculating

Disconnecting charge source at a predetermined (high) SoC

Disconnecting loads at predetermined (low) SoC

Supplying data for user display(s) 

 

Anything else for the list?

 

Yes, but there were no contactors inside the box, were there? Nor current shunts.

 

id include “signalling charging device to stop charging” as a first step. Disconnecting charge source is a second step.

Edited by nicknorman
Link to comment
Share on other sites

45 minutes ago, nicknorman said:

That’s because BMS doesn’t have a very specific meaning. I would imagine the board was designed to be connected to a control system with contractors for connecting and disconnecting loads and charging devices, and signalling to charging devices to stop charging etc as a result of voltage or temperature approaching or out of limits.

Yes, but there were no contactors inside the box, were there? Nor current shunts.

 

id include “signalling charging device to stop charging” as a first step. Disconnecting charge source is a second step.

 

Indeed, contactors to isolate the battery would have to be rated for the maximum likely current the battery is designed to supply, so would be pretty chunky things, as would shunt to allow ah counting.

 

These components are most likely to be external to the battery.

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.