ABYC and ISO Li reference diagram

[s/v Jedi]

Originally Posted by rgleason

I would be interested in exactly why you think this. I am certain that it is not just because its your design, but you've got to have some precise reasons to hold this opinion. So why not let us know your thinking? In the interest of learning... and not throwing bombs.

Small boats, which is the specific application for this design, tend to have small solar arrays and small battery banks. If the energy consumption of the solenoid is 3Ah/day and you only have 100-200Ah usable capacity, then it is a significant draw and people will object, I have seen that over and over with them shutting down fridges at night to save energy (it actually costs more but that’s another thread), using foot operated waterpumps instead of electric etc.
Also, they will notice that the solenoid gets hot. It may not feel so hot the first couple hours, but after days or a week it will get toasty. They are not going to like it, look at how they react to a Victron mppt or dc-dc converter getting warm. Now you give them an option to eliminate the power draw as well as the heat, simply by using the manual override. That is an incentive to use it, defeating the BMS. There should not be such a continuous penalty for using a BMS.

I have repeatedly stated this already, but it gets brushed off as ludicrous. I can assure you that an insurance expert will not find it ludicrous.

You simply have too much stuff going on between the battery and the busbars. There is a fuse, then a switch, then a solenoid, then a switch parallel to that. All those have heavy gauge cabling, terminals, contact resistance etc.

On that I agree with gbn: just keep some jumper cables at hand if you must, but don’t keep throwing switches at this.

[rgleason]

Originally Posted by s/v Jedi

Small boats, which is the specific application for this design, tend to have small solar arrays and small battery banks. If the energy consumption of the solenoid is 3Ah/day and you only have 100-200Ah usable capacity, then it is a significant draw and people will object, I have seen that over and over with them shutting down fridges at night to save energy (it actually costs more but that’s another thread), using foot operated waterpumps instead of electric etc.
Also, they will notice that the solenoid gets hot. It may not feel so hot the first couple hours, but after days or a week it will get toasty. They are not going to like it, look at how they react to a Victron mppt or dc-dc converter getting warm. Now you give them an option to eliminate the power draw as well as the heat, simply by using the manual override. That is an incentive to use it, defeating the BMS. There should not be such a continuous penalty for using a BMS.

I have repeatedly stated this already, but it gets brushed off as ludicrous. I can assure you that an insurance expert will not find it ludicrous.

You simply have too much stuff going on between the battery and the busbars. There is a fuse, then a switch, then a solenoid, then a switch parallel to that. All those have heavy gauge cabling, terminals, contact resistance etc.

On that I agree with gbn: just keep some jumper cables at hand if you must, but don’t keep throwing switches at this.

Your answer is very different than what I expected, however I still think that the ML-RBS manual switch is the same as an LFP Override essentially.

Jedi - I think you have a very good point here. I note that I have been concerned about the heat output of the DC-DC Charger, but I don't expect to turn it on very often because it is just being used as a starter. (In fact I may forgo it completely because I may not have room for it.)

I will give up the "LFP Bypass on the switch, because you have given me some very good reasons. I will make some sort vertical busbars with slide off protectors and a short busbar connection to slide on with an insulated handle. Perhaps there is something commercially made that does this. I know that for big rooftop AC equipment we use a similar type of service disconnect.

The small boat owner will decide to save energy and heat by overriding the relay with the LFP Bypass!

...when the LFP Bypass is only intended to be used on a very temporary basis to get the LFP charged and the battery back on line! That is why someone in another thread suggested something like a momentary contact or timed closing that has a limit.

Since we want "simple" I am just going to rework the diagram to eliminate the LFP Disconnect. I wonder if smaller commercial service disconnects are available?

Hopefully now you, Goboatingnow and ABYC will all be happy. At some point, on a stormy night the lights will go out and I will have to switch to SLA Emergency Feed & LFP Disconnect. At that point the lights and nav system will be operational. I will just have to study and investigate the LFP battery as is necessary in any case, fix any connections, and then perhaps deal will a jumper.

Now I have to ask, how else can I simplify this diagram and improve it?
Are any of the dam cables too big?

[rgleason]

I can't find any of the old style outdoor disconnects that I was considering. They all are too big and have switches or breakers in them. Also I think this is a bad idea because small boat owners will simply use them to override the BMS. So I am not going to show that either.


BTW Tao BMS website has a good comparison of BMS features that also includes the resolution of voltage sensing.
https://www.taoperf.com/2021/06/16/b...parison-chart/


Four BMS Comparison.

cell voltage resolution 0.1 mV 0.1 mV 1 mV ?

[rgleason]

The equipment list inlcuding batteries but without adding cable and connectors is about $4200

[s/v Jedi]

Okay, here is what I would change;

- at the house battery, attached straight to the positive terminal, this fuse block: https://www.bluesea.com/products/519...k_-_30_to_300A with this 250A fuse: https://www.bluesea.com/products/518...al_Fuse_-_250A

This eliminates a cable and brings the fuse as close to the battery as possible. All ABYC conform.

- from that fuse holder, a 2/0 cable, as short as possible, to this RBS: https://www.bluesea.com/products/770..._-_12V_DC_500A
followed by another 2/0 cable, straight to the Lynx distributor input terminal.
Note: this is the pulsed-control version, which can be found for less than $100 in places and ordered online for $160 every day or $120 during sale. To connect this to the REC BMS, you can use the very simple schematic developed by CatNewBee in his big LiFePO4 thread so that you don’t have to buy the adapter from REC.

Now you have “battery - fuse - cable - solenoid - cable - busbar” instead of “battery - cable - fuse - cable - switch - cable - solenoid - cable - manual switch - cable - cable - busbar”, eliminating 50% of components (only 6 instead of 12!)

Now for SLA:

- at SLA battery positive terminal, a short 1/0 cable to this fuse block: https://www.bluesea.com/products/519..._Common_Source

- from that fuse block same input terminal, another (2nd) short 1/0 cable to this switch: https://www.bluesea.com/products/600...th__Knob_-_Red and from that switch another 1/0 cable to the engine starter. Label switch as “engine start”
You can use a fuse for this circuit but traditionally it isn’t fused.

- on that same fuse block, a 250A fuse to a 1/0 cable to a second switch: https://www.bluesea.com/products/600...th__Knob_-_Red and from that switch another 1/0 cable to the Lynx distributor input terminal on the upper right side (like done for the negative cable) Label switch as “emergency parallel”

- on that same fuse block, a 30A fuse to a 6 AWG cable to an Orion Tr Smart 12-12 non-isolated. You do not have an isolated negative so no need for an isolated converter. This also eliminates one negative cable and you only need a thin diameter negative cable (input and output currents eliminate each other).

I guess this addresses the points?

[goboatingnow]

The point is if I understand you is the ML series has manual overrides which is exactly the same as a bypass switch.

I do not actually see the point of the argument. The contactor heat is a nonsense argument. Who the hell is switching to a 100Ah lithium setup.

I’m sorry this is “ reaching “ my usb chargers on the boat are running at 10 AH. To suggest 3AH is a problem is frankly nonsense. It’s in the noise !

I have one of these TE relays it does not get “ hot “ mildly warm at best.


A bypass switch marked in big red Letters “ emergency BMS bypass , warning etc “. Is more then enough in my view.

Secondly there is no evidence that this violates ABYC. As Nick says it’s very badly written anyway. Like him I couldn’t care tuppence about it.

I remain happy that RGleasons diagram is good a suitable “ balance “ between different demands. It especially avoids the inadvertent SLA Li paralleling.


Lastly. Despite what Nick claims I’m not against separate charge and discharge busses

But I see NO point in having two contractors , this suggests the bms can automatically reconnect systems after a critical safety trip event.

To me i fundamentally disagree with this concept. It’s simply NOT safe. Manual inspection must and should occur after a safety trip. ABYC is entirely missing on this point.

Finally te-13 is frankly an awful document. It conflated all forms of Li together , it’s poorly taught out and it’s technical backers should be hanging their heads in shame.

[goboatingnow]

Clearly on nicks boat he has all the manual activated fire extinguishers removes in case someone complains about the coffee being to hot. I mean it’s a serious concern that someone night reach for the nearby extinguisher and activate it.

I hope he has no manual engine stop system either. Someone might activate that cause the noise is too much.

[noelex 77]

Originally Posted by goboatingnow

I’m sorry this is “ reaching “ my usb chargers on the boat are running at 10 AH.

Parasitic draw is important when relying on solar. There is no need for a 10 AHr parasitic draw from USB chargers.

[goboatingnow]

Originally Posted by noelex 77

Parasitic draw is important when relying on solar. There is no need for a 10 AHr parasitic draw from USB chargers.

It’s not “ parasitic “ it’s merely a consumption for a given purpose. ( ie charging phones and tablets etc ) Just like my fridge is a 24h consumption for a specific gain

In my case with 300ΑH to kick around I’m more then happy to consume 3AH to have a completely fail safe contactor system protecting a huge power source.

Listen guys. I’m not interested in arguing nonsense. My design choices are just that “ mine”. Of course you may decide that aspects you would do will be different. I understand different people have different design priorities and therefore arrive at different conclusions.

There is NO BEST approach. There’s merely an approach that reflects the design priorities.

In my case I would be happy to trade 3Ah for complete fail safe operation and avoid a $200 relay that is not truely fail safe.

That’s my design criteria.

Secondly I’m firmly of the belief that an emergency bms override must exist. I have argued everything from jump leads to dedicated switching can be used , it’s up to the priorities of the designer to pick one. I completely reject the nonsense that someone will engage a clearly marked emergency switch to save 3AH I’m sorry it’s BS , as I said equally hide all your fire extinguishers too.

Thirdly I don’t have a view on charge or discharge busses. Have one or two contactors. To me it’s a nonsense decision

ABYC and iso require complete disconnection of a safety trip occurs. This is NOT the same as say a normal low SOC warning.

Hence after a safety trip complete disconnection must occur until a manual inspection can occur. Then and only then you can order reconnection either manual bypasses or via bms commands

I’m not for moving on this. It’s my safety first principle at work

[s/v Jedi]

Originally Posted by goboatingnow

The point is if I understand you is the ML series has manual overrides which is exactly the same as a bypass switch.

I do not actually see the point of the argument. The contactor heat is a nonsense argument. Who the hell is switching to a 100Ah lithium setup.

I’m sorry this is “ reaching “ my usb chargers on the boat are running at 10 AH. To suggest 3AH is a problem is frankly nonsense. It’s in the noise !

I have one of these TE relays it does not get “ hot “ mildly warm at best.


A bypass switch marked in big red Letters “ emergency BMS bypass , warning etc “. Is more then enough in my view.

Secondly there is no evidence that this violates ABYC. As Nick says it’s very badly written anyway. Like him I couldn’t care tuppence about it.

I remain happy that RGleasons diagram is good a suitable “ balance “ between different demands. It especially avoids the inadvertent SLA Li paralleling.


Lastly. Despite what Nick claims I’m not against separate charge and discharge busses

But I see NO point in having two contractors , this suggests the bms can automatically reconnect systems after a critical safety trip event.

To me i fundamentally disagree with this concept. It’s simply NOT safe. Manual inspection must and should occur after a safety trip. ABYC is entirely missing on this point.

Finally te-13 is frankly an awful document. It conflated all forms of Li together , it’s poorly taught out and it’s technical backers should be hanging their heads in shame.

No, it is not exactly the same. First of all, the diagram has a fuse, a manual switch, a solenoid, and another manual switch, all in the primary circuit between battery positive and main bus bar.

Second, the solenoid with manual switch in the diagram are two separate components, interconnected with two extra cables. That is four items, where the RBS replaces all that with just one item.

Third, the solenoid in the diagram has a 130mA power consumption 24x7. The RBS has 0mA (that is zero mA). Thatis a big difference.

Fourth, the combination of solenoid with manual override switch, provides an incentive to manually bypassing the BMS to stop that 130mA consumption. The RBS has no consumption, so that incentive isn’t there.

As other have written: for such situations a momentary switch that can’t be defeated by sticking something in to hold it without touching is used for that. I have that in my motorhome.

Show us you solenoid powered on continuously for a week, temperature measured with an IR tempgun. A picture, just like I post all the time.

If you have 10Ah parasitic draw and don’t care to throw in another 3Ah then really, something is wrong. I know you’re gonna be happy with that but you obviously can not understand that others are not. I have a big solar array and big batteries, but I still care about this and find it unacceptable. Smaller boats care more about it.

There are plenty boats with 100Ah or 200Ah LiFePO4 batteries. I have a much bigger battery as well, but I don’t see the need to ridicule thise with smaller batteries! Many cruisers don’t want to have much electric at all.

Anyway, I tried my best to help and actually put an hour of my time into it. I wonder why I bothered.

[noelex 77]

Originally Posted by goboatingnow

It’s not “ parasitic “ it’s merely a consumption for a given purpose. ( ie charging phones and tablets etc )

OK. The energy consumed when actively charging phones/tablets etc is a productive use of energy.

In contrast the energy needed to keep a relay closed is a purely parasitic load that transfers no energy to other devices.

Equating productive loads with parasitic loads is not sensible.

[s/v Jedi]

Originally Posted by goboatingnow

Clearly on nicks boat he has all the manual activated fire extinguishers removes in case someone complains about the coffee being to hot. I mean it’s a serious concern that someone night reach for the nearby extinguisher and activate it.

I hope he has no manual engine stop system either. Someone might activate that cause the noise is too much.

I think you have lost it.

[goboatingnow]

Originally Posted by s/v Jedi

No, it is not exactly the same. First of all, the diagram has a fuse, a manual switch, a solenoid, and another manual switch, all in the primary circuit between battery positive and main bus bar.


Second, the solenoid with manual switch in the diagram are two separate components, interconnected with two extra cables. That is four items, where the RBS replaces all that with just one item.

There are two switches , one is a two way switch which doubles as a bms bypass the second position switched in the SLA

Secondly that switch uses it AFD contacts to trigger a relay to electrically interlock the bms contactor from ever being powered up while the SLA is switched in.

Hence its a very simple and elegant design

None of the that functionality can be provided by the ML series relay.

Third, the solenoid in the diagram has a 130mA power consumption 24x7. The RBS has 0mA (that is zero mA). Thatis a big difference.



Fourth, the combination of solenoid with manual override switch, provides an incentive to manually bypassing the BMS to stop that 130mA consumption. The RBS has no consumption, so that incentive isn’t there.

This is an absurd argument. You could equally argue that the user would feel compelled to start the engine. To suggest a 3Ah draw would have people reaching for a big switch marked “ emergency “ is nonsense

Equally they could just as easily bring the SLA battery into play. That will kill the contactor power consumption too.

Sorry it’s a BS argument rather as I said , people could equally reach for a fire extinguisher because their coffee was too hot.


By the way the second switch , which was added lately is there as a complete safety first disconnect in the event of a BMS failure

As other have written: for such situations a momentary switch that can’t be defeated by sticking something in to hold it without touching is used for that. I have that in my motorhome.

Show us you solenoid powered on continuously for a week, temperature measured with an IR tempgun. A picture, just like I post all the time.

The TE relay is specifically designed as a battery connect disconnect. It’s designed to operate for long long periods. It gets mildly warm. The use of safety first powered relays is extremely common in industrial applications.

Latched relays cannot be regarded as inherently fail safe.

If you have 10Ah parasitic draw and don’t care to throw in another 3Ah then really, something is wrong. I know you’re gonna be happy with that but you obviously can not understand that others are not. I have a big solar array and big batteries, but I still care about this and find it unacceptable. Smaller boats care more about it.

There are plenty boats with 100Ah or 200Ah LiFePO4 batteries. I have a much bigger battery as well, but I don’t see the need to ridicule thise with smaller batteries! Many cruisers don’t want to have much electric at all.

Anyway, I tried my best to help and actually put an hour of my time into it. I wonder why I bothered.

I don’t have a 10Ah parasitic draw. I never used the term “parasitic. “. I consume 10AH charging things via USB. Hence I would consume 3Ah ensuring I have a failsafe disconnect on a big 300Ah lithium battery.

To me that’s good “ safety first “ engineering

You put your time on just like I do. Your opinions are valuable when accompanied by cogent arguments but just because you speak doesn’t mean you are right !!! You have opinions others equally have opinions. There’s no exact “ perfect “ here.

The point is it’s a trade off you might personally not like the trade off that doesn’t make it wrong.

[goboatingnow]

Originally Posted by s/v Jedi

I think you have lost it.

I’m in good company with the guy switching a big labelled “emergency bypass “ switch cause he feels a relay is slightly warm.

[goboatingnow]

Originally Posted by noelex 77

OK. Charging phones/tablets etc is a productive use of energy.

In contrast the energy needed to keep a relay closed is a purely parasitic load.

Equating productive loads with parasitic loads is not sensible.

It’s not a parasitic load. It’s enabling a completely fail safe device that’s disconnects the big lithium for any number of reasons. The current has a purpose.

Hence the load isn’t parasitic it’s serving a function

Hey you don’t have to like it but don’t misrepresent it.

Equally you could regard the BMS operating current as “ parasitic “ are you going round disabling that. Or the standby current in the BmV battery monitor , my co2 and gas alarms , my bilge led, my wifi to nmea gateways or the 446 MHz receivers in my outdoor lights.

Every boat has a quiescent Ah figure this is just another component to it.

It’s not parasitic the correct term is “ quiescent “