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Cheap LiFePO4 BMS?


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16 hours ago, IanD said:

Far more difficult networking problems than this have been solved by the industry, including unique manufacturer and device addresses. You think this is hard, I'm currently working on 400Gbps optical transceivers which have to be interoperable...

Every Ethernet device is supposed to have a unique MAC address which defines the make the type and a serial number, OK some people spoof them and code in software but certainly in the 1990's and 2000' most were hard coded on the board so it is possible to get manufacturers to cooperate if the rewards are there, in the case of Ethernet, no MAC address you drop the package, so data will not pass from one device to another, so not really a network. 

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Another interview with the founders of Battleborn batteries.... not much to add to the Will Prowse one..... they seem to be trying not to disclose their upper and lower voltages and temperatures in the early part of the video but, later on, they say that their BMS cuts off charging a 25F and below, and that they cycle every cell and battery down to 2.2V per cell, and up to 3.65V per cell, to establish Ah capacity, and to match cells.

 

They then go on to say that in a 100Ah battery, they are quite happy for consumers to use all 100Ah of the battery so, presumably, from full down to 9V, in a 12V unit. They have no problem with a consumer charging at anything between 14.2V and 14.6V until full, and they seem happy for their batteries to float at 13.6V or less. They actually suggest that, during "absorption" charging, the cells balance so it seems important that this goes on for long enough to achieve that.

 

I'm not saying that we should push the limits, but everything I read and hear keeps telling me that we don't need to quite as worried as we are.

 

For me, I'm currently not going below about 12.7V when discharging, am reaching about 14.4V when charging, and leaving it there until the current falls to about 4% of capacity, (20Amps or so).

 

 

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1 hour ago, Richard10002 said:

......... but everything I read and hear keeps telling me that we don't need to quite as worried as we are.

 

 

 

1 hour ago, Richard10002 said:

 

 

 

Eh!

 

Everything you read!

You cant read very much then.

 

Whilst this battery manufacturer/vendor might push the limits ...to the limit.....users of batteries do not. You cannot have read the Tesla stuff then.....or the other EV manufactures

You are only listening to things that fit with your current views.

 

Nothing wrong with terminating charge when the tail current falls to 4%  but you will kill your batteries if you continue to charge after that point. Feel free to do that though. It wont be me that wrecks £1000+ of batteries.

 

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I watched it as well Bob and decided that I will believe Tesla GM etc. Who have  a vested interest in not paying for a bank of batteries! Clearly it's worked for GM as they sold of a load of the Chevy Volt spare batteries last year,  I was tempted but they were in the states 

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16 minutes ago, peterboat said:

I watched it as well Bob and decided that I will believe Tesla GM etc. Who have  a vested interest in not paying for a bank of batteries! Clearly it's worked for GM as they sold of a load of the Chevy Volt spare batteries last year,  I was tempted but they were in the states 

Yes. Its interesting to go back and look at the Nordkyn site (which I rate as one of the leading experts on Li batteries for botes) and the Marine How to site (which has good information). Both warn against the claims of the battery manufacturers who try to out do each other with claims that persuade the uninitiated to buy their superior product. Far more important to read info....which Richard obviously doesnt......from the users of Li batteries, the largest user being the EV automotive industry. They have no axe to grind and will give good information.

It is not about 'worrying' as Richard says. It is about doing the right thing to look after your investment.

Unfortunately, Richard just doesnt listen.

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59 minutes ago, Dr Bob said:

You are only listening to things that fit with your current views.

No.. I'm not.

59 minutes ago, Dr Bob said:

 

Nothing wrong with terminating charge when the tail current falls to 4%  but you will kill your batteries if you continue to charge after that point. Feel free to do that though. It wont be me that wrecks £1000+ of batteries.

 

All good then... I wont be wrecking £1,000+ of batteries either.

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18 hours ago, Dr Bob said:

Yes. Its interesting to go back and look at the Nordkyn site (which I rate as one of the leading experts on Li batteries for botes) and the Marine How to site (which has good information). Both warn against the claims of the battery manufacturers who try to out do each other with claims that persuade the uninitiated to buy their superior product. Far more important to read info....which Richard obviously doesnt......from the users of Li batteries, the largest user being the EV automotive industry. They have no axe to grind and will give good information.

It is not about 'worrying' as Richard says. It is about doing the right thing to look after your investment.

Unfortunately, Richard just doesnt listen.

I think there is a happy medium though. We all agree that charging up to 4.something volts is a bad idea. But equally, charging to only 80% SoC is perhaps unduly cautious. There is a happy medium somewhere in between!

 

Anyway I had a look at the Nordkyn site, which certainly has some good stuff despite a few technical faux pas. He does encourage great rigour in protection against “unexpected faults” and so I’m now wondering whether I’ve been clever enough in my design. He promotes the dual bus scheme (ie separate disconnects for charging and services) whereas I’d thought that just a battery disconnect and controlled alternator would be adequate.

 

Maybe I’m being over confident! In our case the charge sources are the alternator and the Combi. I wouldn’t really want to put the Combi on the charge bus because it would then stop inverting if there were a battery disconnect due to alternator over-voltage. I suppose a Combi in charge mode can develop a fault resulting in over-voltage but it’s pretty uncommon I think. Unless the Combi becomes totally goosed but still producing power, I’ll be able to turn off charging via CANBUS in the event of over-voltage.

 

Since I am breaking into the alternator to add the external regulator, it would be quite simple to add a relay in the field current wire that could open in the event of loss of control of the alternator regulation. Once the field current is cut, the alternator is effectively turned off in a benign way. I haven’t done the PCB layout for the regulator yet so I think I’ll add that capability.

Edited by nicknorman
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4 minutes ago, nicknorman said:

Since I am breaking into the alternator to add the external regulator, it would be quite simple to add a relay in the field current wire that could open in the event of loss of control of the alternator regulation. Once the field current is cut, the alternator is effectively turned off in a benign way. I haven’t done the PCB layout for the regulator yet so I think I’ll add that capability.

As it’s such a simple addition I agree that it would be foolish to not incorporate it. 

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45 minutes ago, nicknorman said:

The only down side is that every element you introduce is a potential source of a fault.

But there again, it would either fail safe or if it didn’t fail safe then it would be no different to not having it. 

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50 minutes ago, nicknorman said:

The only down side is that every element you introduce is a potential source of a fault.

As it only a relay you could join the wires together to start charging again, I have do doubt you would see the red light on the control panel, if the relay stopped the charging yet the meter wasnt showing overvoltage?

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32 minutes ago, peterboat said:

As it only a relay you could join the wires together to start charging again, I have do doubt you would see the red light on the control panel, if the relay stopped the charging yet the meter wasnt showing overvoltage?

It depends on where the failure occurred. I plan to take control of the charging light as the field will no longer be directly connected to the warning light - it wouldn’t work as it’s high side switched and when the engine is not running / no pulses from the field tapping, the regulator chip goes to sleep and no current would flow via the regulator to the field, hence the light wouldn’t come on. So the light will be controlled by a FET on the new regulator board. Of course if something bad happens to the alternator eg wire comes off / brushes lose contact etc, it’s going to be picked up by the microprocessor which can turn on the FET and thus bring on the warning. Unless the fault lies with the microprocessor of course!

 

The relay would really only be of use to deal with a wiring short or regulator chip failure whereby full voltage was applied to the field. Unless I have a completely independent means of operating the relay above a certain max voltage. But how many levels of “a monitoring system to monitor the monitoring system” should one have!

Edited by nicknorman
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2 minutes ago, nicknorman said:

It depends on where the failure occurred. I plan to take control of the charging light as the field will no longer be directly connected to the warning light - it wouldn’t work as it’s high side switched when the engine is not running / no pulses from the field tapping, the regulator chip goes to sleep and no current would flow via the regulator to the field, hence the light wouldn’t come on. So the light will be controlled by a FET on the new regulator board. Of course if something bad happens to the alternator eg wire comes off / brushes lose contact etc, it’s going to be picked up by the microprocessor which can turn on the FET and thus bring on the warning. Unless the fault lies with the microprocessor of course!

 

The relay would really only be of use to deal with a wiring short whereby full voltage was applied to the field. Unless I have a completely independent means of operating the relay above a certain max voltage. But how many levels of “a monitoring system to monitor the monitoring system” should one have!

Thats the problem isnt it? every levels introduces a potential fault point. Thats why my low voltage is taken care of by auto start on the whispergen, I do have an overvoltage cut off which I should fit a roundtuit keeps on getting in the way ?

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4 minutes ago, peterboat said:

Thats the problem isnt it? every levels introduces a potential fault point. Thats why my low voltage is taken care of by auto start on the whispergen, I do have an overvoltage cut off which I should fit a roundtuit keeps on getting in the way ?

What happens when the whispergen doesn’t start for some reason? Fault / out of fuel / turned off / trigger to turn on faulty etc. That seems quite an insecure defence against under voltage if that is all you have.

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42 minutes ago, nicknorman said:

What happens when the whispergen doesn’t start for some reason? Fault / out of fuel / turned off / trigger to turn on faulty etc. That seems quite an insecure defence against under voltage if that is all you have.

I live in hope! However I bought some 36 volt LifePo4 batteries which were flat, they have all taken a charge and the BMS reset and they are functioning well, it was a risk buying them but they were very cheap and just what I needed so I had a gamble

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1 hour ago, nicknorman said:

What happens when the whispergen doesn’t start for some reason? Fault / out of fuel / turned off / trigger to turn on faulty etc. That seems quite an insecure defence against under voltage if that is all you have.


Particularly as mine draws 20+Amps for 15-20 minutes before the Sterling engine runs fast enough to deliver a charge, and I’d expect Peter’s to do the same. Not good to be sucking that much energy from batts so heavily discharged already. 
 

 

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2 hours ago, nicknorman said:

 

 

Anyway I had a look at the Nordkyn site, which certainly has some good stuff despite a few technical faux pas. He does encourage great rigour in protection against “unexpected faults” and so I’m now wondering whether I’ve been clever enough in my design. He promotes the dual bus scheme (ie separate disconnects for charging and services) whereas I’d thought that just a battery disconnect and controlled alternator would be adequate.

 

 

The Nordkyn site is good reading but he is a bit 'half glass full'.

Tom and Bex installed a dual bus system, I think inspired by the site. Its all down to how much control you need/want to keep it all safe, but as you said above, every bit of stuff added is another bit of vunerability to go wrong.

On mine, I decided just to have one disconnect that isolates the Li's in the event of a problem ....but does not reconnect. I have to do the reconnection manually so have to investigate the problem and manually fix it. That works for me as I have the hybrid approach and the system just flips back to LA's only if the isolation switch trips.

It does get quite involved working out 'what happens if'. A good old fashioned 'Hazop' is needed.

 

 

 

@Tom and Bex

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3 minutes ago, Mike the Boilerman said:


Particularly as mine draws 20+Amps for 15-20 minutes before the Sterling engine runs fast enough to deliver a charge, and I’d expect Peter’s to do the same. Not good to be sucking that much energy from batts so heavily discharged already. 
 

 

Really? mine is up and running in five ish minutes ,it heats glow plug, then fuel added, stabalises flame, then heats up, fires up on bulk charge, glow plug then stops being used. I am using kero which has a lower flashpoint so I have reduced the glow plug heating time considerably. I probably have an advantage on you, in that when the pump turns on it pumps hot water from the heat store so it heats the whispergen up to start with? maybe reducing starting time as well?

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5 hours ago, nicknorman said:

I think there is a happy medium though. We all agree that charging up to 4.something volts is a bad idea. But equally, charging to only 80% SoC is perhaps unduly cautious. There is a happy medium somewhere in between!

Kind of where I am, I think :)

 

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19 hours ago, Richard10002 said:

Kind of where I am, I think :)

 

At last!

Some sense from Richard!

 

I am concerned that peeps reading this thread may be loosing track of a good charging strategy and not considering all the inputs. Peeps might be reading this info and the 3 articles that were published recently in the Canal Boat mag and then assuming it is fine to replicate the systems and charge to 'full voltage' and 4% tail current on every cycle. It might not be fine!

My system relies on a 4 level cut off for overcharging. Two audible alarms and two shut off systems when bank and cell voltage get too high. Fine. Well protected then? No. In my case, I am using a BEP motorised switch. How robust are they? Not a clue. However, I am following the guidance from the Nordkyn site which has a strategy of using the isolation switch/switches as an EMERGENCY system, to activate when things go badly wrong. In normal operation, I am below the bank/cell voltage that will cause a problem. In the 300 days my system has been operating, I HAVE NEVER triggered the disconnect or alarms. My charge sources are all set to back off voltage once a target is reached circa 90% SoC so I never get to the emergency cut off. It is also interesting that since installation, we rarely get to 90% anyway with our style of power usage. Maybe if we did 8 hour days motoring (we tend to do 2-3hrs) then our alternator controller would be backing off but our 20-80% usage is largely driven by our usage.

The Nordkyn site is emphatic about only using the auto disconnect as an emergency measure and that charge sources should normally be controlled to back off earlier. This makes the risk profile much better as you are not relying on the one final isolation relay to do your day to day protection. I am not sure how long my BEP switch would last if activating twice a day. I am happy it will last if checked and activated every few months.

Of the current users only @MoominPapa controls his charge based on voltage and tail current but he has designed his own system and knows it backwards. Only he though can decide on the risk of failure and is happy that he is in control. @nicknorman will likely have an all singing all dancing solution with charge sources backing off at the right time and an emergency system in case of emergencies. For the rest of us, we must design our DIY systems with appropriate levels of control. Using 'drop in' Li's may sound attractive but read the bumph on the Nordkyn site and the Marine how to site and look at the comments on what components are in the drop ins. Can you really rely on the kit that is inside them to protect you? My risk review tells me to have a level of normal operation and then an emergency only isolation when things go really wrong. It would be very wrong for someone to copy my system and then charge to 3.65V every cycle. A charging strategy is not about charging to a level that some CEO of a battery company suggests.....it is about understanding what you have and reducing risk to almost zero based on charging information PLUS the kit you have.

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4 minutes ago, Dr Bob said:

At last!

Some sense from Richard!

 

I am concerned that peeps reading this thread may be loosing track of a good charging strategy and not considering all the inputs. Peeps might be reading this info and the 3 articles that were published recently in the Canal Boat mag and then assuming it is fine to replicate the systems and charge to 'full voltage' and 4% tail current on every cycle. It might not be fine!

My system relies on a 4 level cut off for overcharging. Two audible alarms and two shut off systems when bank and cell voltage get too high. Fine. Well protected then? No. In my case, I am using a BEP motorised switch. How robust are they? Not a clue. However, I am following the guidance from the Nordkyn site which has a strategy of using the isolation switch/switches as an EMERGENCY system, to activate when things go badly wrong. In normal operation, I am below the bank/cell voltage that will cause a problem. In the 300 days my system has been operating, I HAVE NEVER triggered the disconnect or alarms. My charge sources are all set to back off voltage once a target is reached circa 90% SoC so I never get to the emergency cut off. It is also interesting that since installation, we rarely get to 90% anyway with our style of power usage. Maybe if we did 8 hour days motoring (we tend to do 2-3hrs) then our alternator controller would be backing off but our 20-80% usage is largely driven by our usage.

The Nordkyn site is emphatic about only using the auto disconnect as an emergency measure and that charge sources should normally be controlled to back off earlier. This makes the risk profile much better as you are not relying on the one final isolation relay to do your day to day protection. I am not sure how long my BEP switch would last if activating twice a day. I am happy it will last if checked and activated every few months.

Of the current users only @MoominPapa controls his charge based on voltage and tail current but he has designed his own system and knows it backwards. Only he though can decide on the risk of failure and is happy that he is in control. @nicknorman will likely have an all singing all dancing solution with charge sources backing off at the right time and an emergency system in case of emergencies. For the rest of us, we must design our DIY systems with appropriate levels of control. Using 'drop in' Li's may sound attractive but read the bumph on the Nordkyn site and the Marine how to site and look at the comments on what components are in the drop ins. Can you really rely on the kit that is inside them to protect you? My risk review tells me to have a level of normal operation and then an emergency only isolation when things go really wrong. It would be very wrong for someone to copy my system and then charge to 3.65V every cycle. A charging strategy is not about charging to a level that some CEO of a battery company suggests.....it is about understanding what you have and reducing risk to almost zero based on charging information PLUS the kit you have.

I rely on a top quality solar controllers to protect my batteries and the whispergen which has a clearly defined charging regime and will shut down if over voltage is detected, I paid for quality kit and it has worked very well in protecting the batteries, I have a disconnect board and should really get around to fitting it, problem is if it failed would it cook my solar controller?

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35 minutes ago, Dr Bob said:

At last!

Some sense from Richard!

 

I am concerned that peeps reading this thread may be loosing track of a good charging strategy and not considering all the inputs. Peeps might be reading this info and the 3 articles that were published recently in the Canal Boat mag and then assuming it is fine to replicate the systems and charge to 'full voltage' and 4% tail current on every cycle. It might not be fine!

My system relies on a 4 level cut off for overcharging. Two audible alarms and two shut off systems when bank and cell voltage get too high. Fine. Well protected then? No. In my case, I am using a BEP motorised switch. How robust are they? Not a clue. However, I am following the guidance from the Nordkyn site which has a strategy of using the isolation switch/switches as an EMERGENCY system, to activate when things go badly wrong. In normal operation, I am below the bank/cell voltage that will cause a problem. In the 300 days my system has been operating, I HAVE NEVER triggered the disconnect or alarms. My charge sources are all set to back off voltage once a target is reached circa 90% SoC so I never get to the emergency cut off. It is also interesting that since installation, we rarely get to 90% anyway with our style of power usage. Maybe if we did 8 hour days motoring (we tend to do 2-3hrs) then our alternator controller would be backing off but our 20-80% usage is largely driven by our usage.

The Nordkyn site is emphatic about only using the auto disconnect as an emergency measure and that charge sources should normally be controlled to back off earlier. This makes the risk profile much better as you are not relying on the one final isolation relay to do your day to day protection. I am not sure how long my BEP switch would last if activating twice a day. I am happy it will last if checked and activated every few months.

Of the current users only @MoominPapa controls his charge based on voltage and tail current but he has designed his own system and knows it backwards. Only he though can decide on the risk of failure and is happy that he is in control. @nicknorman will likely have an all singing all dancing solution with charge sources backing off at the right time and an emergency system in case of emergencies. For the rest of us, we must design our DIY systems with appropriate levels of control. Using 'drop in' Li's may sound attractive but read the bumph on the Nordkyn site and the Marine how to site and look at the comments on what components are in the drop ins. Can you really rely on the kit that is inside them to protect you? My risk review tells me to have a level of normal operation and then an emergency only isolation when things go really wrong. It would be very wrong for someone to copy my system and then charge to 3.65V every cycle. A charging strategy is not about charging to a level that some CEO of a battery company suggests.....it is about understanding what you have and reducing risk to almost zero based on charging information PLUS the kit you have.

A lot of good information there and anyone considering a lithium install would do well to read and make sure they understand all the points @Dr Bob is making. Particularly the point that the emergency disconnect is just that - for emergency use. If it activates at any time then something in your system has already failed and needs urgent further investigation. 

 

I'd also just like to point out that in addition to MP we also control charging based on voltage and tail current when alternator charging, although our solar charging is purely voltage based and therefore set more conservatively. 

 

The Nordkyn site is certainly a good source of information about system design, and we did copy several aspects of our system from there. The advantage of separate charge and load disconnect is the batteries will still charge back up (on solar if away). That way they'll not sit at very low soc (with the parasitic monitoring current drawing them lower) if they're allowed to get too low such as if we're away and left stuff on, or don't hear and/or react to any of the low SOC/voltage/cell voltage alarms!

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1 hour ago, Tom and Bex said:

 

 

I'd also just like to point out that in addition to MP we also control charging based on voltage and tail current when alternator charging, although our solar charging is purely voltage based and therefore set more conservatively. 

 

 

Apologies Tom. Yes I'd forgot you could were controlling the alternator charge.

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My PCBs arrived today. I am still mightily impressed to get 5 PCBs manufactured to my own design and shipped from China, all for £2. Let’s hope i didn’t get a free gift of coronavirus!

9BED6558-82C1-499D-9F80-8580D0F85D44.jpeg.e339dbcdc95bada885e3d5a5c52c3c8e.jpeg

 

the bit bottom left is to be cut off and mounted near the batteries, for the purpose of fusing the battery feeds to the board.

 

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