LiFePO4 reference diagram, 12V version

[goboatingnow]

Originally Posted by s/v Jedi

Keep in mind that any component can fail. I see the argument that when the BMS fails, the non-latching solenoid will open, protecting the battery. This argument is brought like if it is an advantage. Now imagine a battery that is 100% okay and the BMS fails, taking this good battery offline preventing you from hauling anchor during a violent squall that threatens to throw you on the rocks. The supposedly safety mechanism has turned into a disaster.



With the RBS, you can manually switch it off.

100% good but on BMS fail you activate the manual relay override switch whether this is the TE version of the ML version both these can be setup to have manual override of the BMS


No problem. I would agree a way around the BMS is needed. But I would prefer the system failed sAfe “ first “ then you investigate and activate manual overrides as required.

Very dangerous to allow a LI battery to remain connected with the bms dead. Hence safety first demands a trip and then a manual intervention

No different from hauling that anchor and the windlass breaker trips. A run to the ships panel. A quick scan and re enable the windless breaker ( or Li manual override )

Rocks avoided , battery failed safe

Likewise, instead of the BMS failing, the solenoid can fail. Imagine a massive power draw from the inverter and the BMS detects low voltage in cells and triggers LVC, but the solenoid contacts fuse together as they try to interrupt the large current.

Use a decent relay with good interrupting ability.

The TE relay has a very high interrupt capacity , is by a well know brand and is designed precisely for high power interior.

For MOSFET based BMS’s it’s the same because MOSFETs normally fail in a shorted state.



Dealing with failing technology is a thing to consider. I like the RBS because it allows manual operation, even a lockout function, as well as remote switch and remote control by microcontroller. I also like the switch indicator signal that allows the microcontroller to learn the switch state. You can write a software routine that closes or opens the switch intelligently, instead of just sending a signal and pray it works.

I notice you tend to get “ fixated “ on your own solution and promote it without regard to reasonable argument. ( sea cocks too ) this is dogma not engineering.

Positive operation of a contactor am be simply verified by sending the battery voltage on the output of the contactor. There are also versions of the TE relay with mechanical auxiliary contacts. This can also be used

Everyone can postulate increasingly hypothetical failure modes it it’s largely just a debating point not an engineering one.

From a safety perspective I want full “ fail safe “ operation. If the contactor coil supply is interrupted by any means the contactor will open

Secondly the contactor will always power up in a disconnected state

Latching relays cannot be “ fail safe “

So failsafe operation for 130 mA and $50 or 13mS, $180 and not fully failsafe

You takes your choices. One is not better then the other it’s a matter of design priorities and cost.

Note large voltage/ current will cause Mosfets to blow clean of the board hence open !!!

[s/v Jedi]

Originally Posted by goboatingnow

Te $50 and 130mA is hard to beat simple one wire coil circuit. Completely fail safe.

The ML series is a manual battery disconnect it’s not a safety device imho.

Please stop, make your own thread about how bad these are and how unhappy REC BMS users are who have them. Then we can discuss it there instead of in this thread which is about a complete system to help people who have no idea where to begin.

[rgleason]

Just to followup on your insistant post about bypass of protection relays, https://www.cruisersforum.com/forums....php?p=3684658

I believe the RBS switch does the same thing. If so, what should we believe?

Have seen nothing from you about this aspect of your design, is it flawed or is it ok?

Nick, I would be very interested in your thoughts about your engineered diagram at this point.

Just like design, I find engineering is an exploratory and iterative process, learning what is possible, what works and most of all what doesn't. Which reminds me of my favorite Physics teacher. It should be cerebral, not emotional.

[s/v Jedi]

Originally Posted by rgleason

Just to followup on your insistant post about bypass of protection relays, https://www.cruisersforum.com/forums....php?p=3684658

I believe the RBS switch does the same thing. If so, what should we believe?

Have seen nothing from you about this aspect of your design, is it flawed or is it ok?

Nick, I would be very interested in your thoughts about your engineered diagram at this point.

Just like design, I find engineering is an exploratory and iterative process, learning what is possible, what works and most of all what doesn't. Which reminds me of my favorite Physics teacher. It should be cerebral, not emotional.

Yes, I was waiting for your message (gbn already did). When yours didn’t come, I posted on your thread that I thought it was okay to have the manual override, because it is for extraordinary circumstances and it may well enable actions to increase the safety aboard.

My problem with your setup is the power consumption and heat generation from the regular non-latching solenoid. Not only could those attribute to a person opting to use the override instead of the BMS, but I have found many failures with these solenoids when used for always-on operation. Even in our motorhome, where we used to have one that was only energized when driving, failure rate was high (they fail open, promoting manual override again and reluctance to keep replacing) and the solution was to install a BlueSea ML-ACR (https://www.bluesea.com/products/cat...Relays/ML-ACRs) which is the same product as the ML-RBS, just with different code running inside.

All that said, you can still use a 7718 model which brings it to the letter of ABYC even when disregarding any “extraordinary circumstances”. https://www.bluesea.com/products/7718/Solenoid_ML_12V
(8mA when off, 13mA when on)

I think that, while I bring my BMS from prototype to something more accessible, you will find that you too may prefer to build and program your own BMS so that you get complete control over it. This complete control allows emergency modes to be simply programmed. I kept changing things for months, just because I can and believed I could improve it. This is wonderful.

[s/v Jedi]

Originally Posted by goboatingnow

From a safety perspective I want full “ fail safe “ operation. If the contactor coil supply is interrupted by any means the contactor will open

Secondly the contactor will always power up in a disconnected state

Latching relays cannot be “ fail safe “

So failsafe operation for 130 mA and $50 or 13mS, $180 and not fully failsafe

You takes your choices. One is not better then the other it’s a matter of design priorities and cost.

Note large voltage/ current will cause Mosfets to blow clean of the board hence open !!!

This is simply not true, your design is not fail safe, even if the solenoid would be. These solenoids are not good for always-on situations, even when they are continuous duty. The fact that you need a continuous duty model already hints at that.

In my opinion and in my experience, the Blue Sea Systems ML family of solenoids are far superior to most solenoids on the market. I have never experienced a failure, nor have I ever heard of a failure with one. I bet you never heard of that either.

The auto-releasing versions do exactly what you need and are 100% reliable in this application. In the x-files rated chance that they stay closed because they lose power (which hasn’t been proven to happen), it is okay for them to stay closed, because the battery is dead. As long as the battery has enough power to switch the RBS, it will switch off, even when the BMS fails.

In your setup, your BMS could fail and keep the solenoid closed. Or you have a hard short circuit, the BMS tries to open the solenoid but it’s contacts are welded together while trying to separate. A user could override and forget they did so, completely disabling the BMS. Where is the indicator that they used the override (yes, the RBS will show that). There is so much more that can fail that it makes no sense to use a solenoid with NO contact for an application where the contact needs to be closed all the time.

Also, you say that the RBS is a battery disconnect and not a safety device. A remotely operated battery disconnect is exactly what you need here and this is by definition a safety device. It is the whole reason for it’s existence.

[rgleason]

Jedi (Nick) posted

.. I posted on your thread that I thought it was okay to have the manual override, because it is for extraordinary circumstances and it may well enable actions to increase the safety aboard.

Sorry I missed that or missed the connection or reference.

Thanks for the anticdotal camper van experience. I've got to say that anything man makes will eventually fail, but the mean time between failure may differ between components. Prehaps there are some records for this somewhere?

[s/v Jedi]

Originally Posted by rgleason

Jedi (Nick) posted

.. I posted on your thread that I thought it was okay to have the manual override, because it is for extraordinary circumstances and it may well enable actions to increase the safety aboard.

Sorry I missed that or missed the connection or reference.

Thanks for the anticdotal camper van experience. I've got to say that anything man makes will eventually fail, but the mean time between failure may differ between components. Prehaps there are some records for this somewhere?

Solenoids are best for applications where they are energized a small part of the time. Look at applications and you will find things like starter motors, pump switches, electric toilets etc., all with a low duty cycle.

This use for a BMS is the opposite and when engineering a system, we are trained to look for components that best fit for the application, not for ill fitting components and bruce forcing them in. This case is a good example, just like we got in college to illustrate this aspect of proper engineering. Make it easy for the components to succeed.

This is why we did the motorhome modification like that and we reported this to the manufacturer who then copied it…. with a cheaper component but at least a latching version that kept working.

[rgleason]

Manufacturer ratings

Bluesea RBS 7713 Mechanical Endurance 100,000 Cycles
Bluesea L-Series 250A 9012 https://www.bluesea.com/products/901..._-_250A_12_24V

[s/v Jedi]

Originally Posted by rgleason

Manufacturer ratings

Bluesea RBS 7713 Mechanical Endurance 100,000 Cycles
Bluesea L-Series 250A 9012 https://www.bluesea.com/products/901..._-_250A_12_24V

That second one is the same latching solenoid but with smaller contacts. It has the same 8mA / 13mA consumption figures so the same control hardware.

All these are suitable for a BMS. Study how a sear works in a gun trigger: the sear requires very little power to move, but it will hold the spring tension under control. It is done exactly the same with these solenoids. When you remove the “close contact” signal, the sear will let go and the spring opens the solenoid just like in a regular solenoid. The addition is a mechanical latch (sear) so that the big spring doesn’t need to be compressed by the coil all the time.

I am sure cheaper brands must exist… probably won’t come with silver contacts but hopefully almost never need to open a highly loaded circuit so if cost is the driving factor, there will be other options.
The thing with these BlueSea units is that the pulsed versions can be found at great deals while most of the others not and thus are far more expensive. And the pulsed one is better for microcontroller because of the easy LED feedback… the others start flashing patterns etc.

[rgleason]

Originally Posted by rgleason

Manufacturer ratings

Bluesea RBS 7713 Mechanical Endurance 100,000 Cycles
Bluesea L-Series 250A 9012 https://www.bluesea.com/products/901..._-_250A_12_24V

Tyco TE Kilovac EV200AAANA 12/24V/500A 1618002-7 New energy electric vehicle contactor high voltage DC Relay $35

Mechanical life 1 million cycles shown in the spec sheet
Electrical life specs on second page.

Mouser link to specs

"TE Connectivity / Kilovac EV200 Contactors feature 1 Form X contacts rated at 500+A carry with 2000A interrupt at 320VDC. They are hermetically sealed for operation in explosive/harsh environments. The series provides versatile coil/power connections"

[s/v Jedi]

Originally Posted by rgleason

Tyco TE Kilovac EV200AAANA 12/24V/500A 1618002-7 New energy electric vehicle contactor high voltage DC Relay $35

Mechanical life 1 million cycles shown in the spec sheet
Electrical life specs on second page.

Mouser link to specs

"TE Connectivity / Kilovac EV200 Contactors feature 1 Form X contacts rated at 500+A carry with 2000A interrupt at 320VDC. They are hermetically sealed for operation in explosive/harsh environments. The series provides versatile coil/power connections"

Yes, I had the Tyco in our previous motorhome, as well as White Rodgers. They all failed but the Tyco, despite being cheaper, lasted longer.

I see you are looking at cycle life? A regular solenoid has a much higher cycle life because it is just the center piston being moved back and forth by the electromagnet. A latching solenoid has the additional mechanical parts that I described before: those are more complex and wear out much quicker.

But that is okay. For this application we’re looking at a couple dozen or maybe a couple hundred cycles during the lifespan of the system. I will probably cycle once per year, maybe an extra test each year but probably not. So a latching solenoid with 100.000 cycles life is more than enough.

A non latching solenoid must have a higher cycle life because it is used in applications that cycle much more: every time you flush the toilet, start the engine etc.

BTW: you never get to see the cycles of this rating, because this is for a cycle without any current on the contacts. I believe BlueSea lists 10,000 cycles when under load of a couple hundred amperes.
Also, with a non-latching solenoid in an always-on application like this, the solenoid will fail because the coil burns out. Some solenoids allow you to replace the coil but it’s a bad deal to make a replacement routine like a new coil every year; much better to source a latching solenoid for that application.

[wingssail]

Good job on your refence diagram. I don't need an electrical circuit diagram, it's pretty obvious from the reference diagram what is going where and why.

I've been following the discussions but frankly I couldn't follow all of the components and routes originally, but I think with the latest version I've finally figured out what everything is and what it does, thank you.

But I do have a question:

What exactly are the two grey boxes at the bottom of the diagram. They look like fuse boxes. Are there not switches on those lines as well?

Because if not, I don't see how you can or could manually turn off power from either house or service battery banks to the distribution panel.

[s/v Jedi]

Originally Posted by wingssail

Good job on your refence diagram. I don't need an electrical circuit diagram, it's pretty obvious from the reference diagram what is going where and why.

I've been following the discussions but frankly I couldn't follow all of the components and routes originally, but I think with the latest version I've finally figured out what everything is and what it does, thank you.

But I do have a question:

What exactly are the two grey boxes at the bottom of the diagram. They look like fuse boxes. Are there not switches on those lines as well?

Because if not, I don't see how you can or could manually turn off power from either house or service battery banks to the distribution panel.

Thank you! Yes, those are BlueSea SafetyHub 150’s: https://www.bluesea.com/products/774...150_Fuse_Block
which are basically boxes with 10 fuses, up to 200A.

I find there is no need to turn off power to the distribution panel, but many have a master switch or breaker right on that distribution panel to do so. My DC distribution is so simple that I just switch everything off there so I don’t even have a master switch.

Of course every battery has it’s own main switch.

I attached impressions of my main and distribution dc panels to get an idea

[wingssail]

Originally Posted by s/v Jedi

Thank you! Yes, those are BlueSea SafetyHub 150’s: https://www.bluesea.com/products/774...150_Fuse_Block
which are basically boxes with 10 fuses, up to 200A.

I find there is no need to turn off power to the distribution panel, but many have a master switch or breaker right on that distribution panel to do so. My DC distribution is so simple that I just switch everything off there so I don’t even have a master switch.

Of course every battery has it’s own main switch.

I attached impressions of my main and distribution dc panels to get an idea

Yes, I see that every battery has a switch, and a switch at the panel is a possibility, plus I understand your opinion that it isn't needed. But I note that if you did want to turn off power to the distribution panel you'd have to switch off all batteries, then you could not charge your batteries or start your engine.

I think I'd have a switch to the distribution panel or on the panel as I have.

[goboatingnow]

Originally Posted by rgleason

Tyco TE Kilovac EV200AAANA 12/24V/500A 1618002-7 New energy electric vehicle contactor high voltage DC Relay $35

Mechanical life 1 million cycles shown in the spec sheet
Electrical life specs on second page.

Mouser link to specs

"TE Connectivity / Kilovac EV200 Contactors feature 1 Form X contacts rated at 500+A carry with 2000A interrupt at 320VDC. They are hermetically sealed for operation in explosive/harsh environments. The series provides versatile coil/power connections"

Nick always “ reaches “ and stretches conclusions to drive a point

The TE relay is a high reliability device rated for continuous operation. High interrupt capacity.

They are robust and rugged

Blueses is a marine company which simply means everything is 3x pricing

TE is a extremely reliable supplier

Again any “ latching “ relay cannot fail safe

The TE relay is absolutely failsafe. If the BMS fails on the battery voltage collapses the TE relay will automatically open.

This is absolutely what you want the contactor is not a battery disconnect ( ABYC AND ISO suggest separate disconnects ) ITS A SAFETY device.

It must and does therefore “ fail safe “

Nick this is like your external sea cock thread. My point is I can accept your Choice , it’s simply not my choice. You seem unwilling to accept anything other then your own perspective.

Continuously powered contractors are used everywhere in power control applications precisely because they are fail safe and revert to a known position on power failure.

A latching relay can never have this definition