LiFePO4 reference diagram, 12V version

[goboatingnow]

Originally Posted by s/v Jedi

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.

The blue sea L series is the exact same TE unit from the EV series. Blueses don’t make this stuff they oem it.

The L series is NOT latching

[s/v Jedi]

Originally Posted by wingssail

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.

If you want to de-energize the panel for maintenance then you can simply pull the fuse. If you want to do this when leaving the boat etc. then a switch is a good option.

[s/v Jedi]

Originally Posted by goboatingnow

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

GBN, you are wrong. When the BMS fails and power to the solenoid is interrupted then, as you say, the solenoid will switch off. This is correct. The RBS 7700 will not do that because it is pulse operated, but the 7713 does, this is what they call autorelease. The smaller BlueSea solenoid rgleason shows, also auto releases.

If you have the qualifications that you claim you have, then you must know that component selection is much more than just checking if the specs claim it will work. Matching suitability for the specific application is a key part of engineering design, and a big part of the profession.

[goboatingnow]

Originally Posted by s/v Jedi

GBN, you are wrong. When the BMS fails and power to the solenoid is interrupted then, as you say, the solenoid will switch off. This is correct. The RBS 7700 will not do that because it is pulse operated, but the 7713 does, this is what they call autorelease. The smaller BlueSea solenoid rgleason shows, also auto releases.



If you have the qualifications that you claim you have, then you must know that component selection is much more than just checking if the specs claim it will work. Matching suitability for the specific application is a key part of engineering design, and a big part of the profession.

Matching a $59 TE relay to my pocket as opposed to a $400 one is a big primary engineering design decision

As I understand it the 7713 will release if the control circuit is depowered. Ie the bms fails and hopefully the control circuit depower a

However no where does it say the 7713 will switch state when the primary 12v power feed Fails. If the battery voltage crashes the 7713 will not change state.

Hence it cannot be truely regarded as fail safe as it powers up in the state it powers down in.

[s/v Jedi]

Originally Posted by goboatingnow

Matching a $59 TE relay to my pocket as opposed to a $400 one is a big primary engineering design decision

As I understand it the 7713 will release if the control circuit is depowered. Ie the bms fails and hopefully the control circuit depower a

However no where does it say the 7713 will switch state when the primary 12v power feed Fails. If the battery voltage crashes the 7713 will not change state.

Hence it cannot be truely regarded as fail safe as it powers up in the state it powers down in.

Oh it’s making up reasons for going cheap does the TE have silver contacts?

I bet you never even had a BlueSea RBS in your hands, let alone tested one! You simply have no hands on experience with them at all.

[goboatingnow]

Originally Posted by s/v Jedi

Oh it’s making up reasons for going cheap does the TE have silver contacts?



I bet you never even had a BlueSea RBS in your hands, let alone tested one! You simply have no hands on experience with them at all.

The boat next to me has a Bluese unit and one of the five chandlers here has one on the shelf at over €450

The TE EV series lists the base contact as “
Copper “ it’s rated for 500A and versions upto to 2KV , nice version with aux contacts.

The TE ships through digi and mouser from $100-200 but it’s made in TE plant in China

Blue sea makes virtually nothing it OEMs most stuff including selling the L series TE relay at 2x TE Pricing while disguising it’s TE origins.

It’s just the same as it’s “ anchor “ cable. I get exactly the same or better speced cable from Germany and 1/3 the price.

So yes I’ve seen the BS big latching relay. Nope no BS stuff comes on my boat cause it’s outrageously priced.

That’s the way the cookie crumbles. Your mileage and pocket may be different.

[Baronkrak]

Originally Posted by fxykty

Here is our system design…

Nice but not versatile. I would consider that battery manufacturers are moving toward LFP packs and a 12/24 volts system is more viable.

[s/v Jedi]

Originally Posted by goboatingnow

The boat next to me has a Bluese unit and one of the five chandlers here has one on the shelf at over €450

The TE EV series lists the base contact as “
Copper “ it’s rated for 500A and versions upto to 2KV , nice version with aux contacts.

The TE ships through digi and mouser from $100-200 but it’s made in TE plant in China

Blue sea makes virtually nothing it OEMs most stuff including selling the L series TE relay at 2x TE Pricing while disguising it’s TE origins.

It’s just the same as it’s “ anchor “ cable. I get exactly the same or better speced cable from Germany and 1/3 the price.

So yes I’ve seen the BS big latching relay. Nope no BS stuff comes on my boat cause it’s outrageously priced.

That’s the way the cookie crumbles. Your mileage and pocket may be different.

Ah, you saw one on the shelf. I understand your pain, cost more than €450! We buy these for just over $100 here and well under $100 during sale. I have a number that I paid $50 for!

Copper contacts, yes, very much inferior to silver contacts. When switching often, the contact abrasion may rub the corrosion off, but for always-on use the silver contacts are excelling.

You claim TE manufactures the BlueSea solenoids? Maybe they do, just find the ones with equal specs and buy those to prevent the markup from you chandleries!

I wish you a fantastic time with those TE solenoids, I really do, but don’t try to talk yourself in believing it is a superior choice. Mine has been in use for years and even if it takes you another year or more to build, yours will still fail long before mine (buy spares! )

[goboatingnow]

Originally Posted by s/v Jedi

Ah, you saw one on the shelf. I understand your pain, cost more than €450! We buy these for just over $100 here and well under $100 during sale. I have a number that I paid $50 for!



Copper contacts, yes, very much inferior to silver contacts. When switching often, the contact abrasion may rub the corrosion off, but for always-on use the silver contacts are excelling.



You claim TE manufactures the BlueSea solenoids? Maybe they do, just find the ones with equal specs and buy those to prevent the markup from you chandleries!



I wish you a fantastic time with those TE solenoids, I really do, but don’t try to talk yourself in believing it is a superior choice. Mine has been in use for years and even if it takes you another year or more to build, yours will still fail long before mine (buy spares! )

Stuff I designed is still in use on the space station I’m sure mine will survive

I’m happy that for me the TE represents the best compromise of safety utility and cost , so yes I’m happy.





$50 , you must have got that sale price using a gun !!!!

[s/v Jedi]

Originally Posted by goboatingnow

Stuff I designed is still in use on the space station I’m sure mine will survive

I’m happy that for me the TE represents the best compromise of safety utility and cost , so yes I’m happy.

Attachment 265208

Attachment 265209

$50 , you must have got that sale price using a gun !!!!

None of those are on sale. Even the everyday price on Amazon is only $160 which is 1/3 of your $450+ price. https://www.amazon.com/Blue-Sea-Syst.../dp/B0016HRUSG

For good deals like I mentioned, you need these kind of places: Marine Connection Liquidators
yes, they have a bin full of Blue Sea RBS.

[fxykty]

Originally Posted by s/v Jedi

I modified the diagram for 12V house batteries. Asyou can see, much is the same. Changes:



1. House batteries from 4x 700Ah Winston cells, 9kWh each

2. BMS and Battery switch 12V versions

3. dc-dc converters are 12-12 versions

4. Inverter/charger is a 12V version

I am currently ordering 4 new 700Ah cells from Winston (via Julia Yu) so that I can create a second 12V 700Ah battery (4S) to put into parallel with my 2 year old 4S 12V 700Ah battery, per your diagram (though I’m not using DC-DC converters).

I’m getting pushback from the Winston factory, who are insisting that a 2P4S arrangement is superior (each 2P cell pair would have one old and one new cell). It only matters for the order in that a new 4S battery requires 2 compression plates and 8 compression straps that fit 4 cells, while buying 4 cells to make a 2P4S battery needs no additional compression plates but does need 8 compression straps to fit 8 cells plus an additional 10 terminal connectors to make the parallel connections.

This is a bit of a pain, as I don’t have enough knowledge to understand the Winston factory technician saying why a 2P4S arrangement is better than paralleled 4S batteries. This is what Julia last wrote me, quoting one of their factory technicians (I’ve written back to him directly explaining why I want the redundancy of two 12V 700Ah batteries rather than a single 2P4S artery).

“They (Winston factory technicians) think that if 12V700Ah then parallel, the final capacity is only twice of the old battery bank, the new bank will be slowed down by the old one; and if 2P4S with each parallel has one old cell and one new cell, the final capacity will be the old plus new cell.”

Does that make sense? Do I understand correctly that the new cells will have (slightly) more capacity than the two year old cells, so that the 2P4S battery will take advantage of the extra capacity, while as 4S the new battery capacity will be dragged down to the old battery capacity due to their parallel connection?

[s/v Jedi]

Originally Posted by fxykty

I am currently ordering 4 new 700Ah cells from Winston (via Julia Yu) so that I can create a second 12V 700Ah battery (4S) to put into parallel with my 2 year old 4S 12V 700Ah battery, per your diagram (though I’m not using DC-DC converters).

I’m getting pushback from the Winston factory, who are insisting that a 2P4S arrangement is superior (each 2P cell pair would have one old and one new cell). It only matters for the order in that a new 4S battery requires 2 compression plates and 8 compression straps that fit 4 cells, while buying 4 cells to make a 2P4S battery needs no additional compression plates but does need 8 compression straps to fit 8 cells plus an additional 10 terminal connectors to make the parallel connections.

This is a bit of a pain, as I don’t have enough knowledge to understand the Winston factory technician saying why a 2P4S arrangement is better than paralleled 4S batteries. This is what Julia last wrote me, quoting one of their factory technicians (I’ve written back to him directly explaining why I want the redundancy of two 12V 700Ah batteries rather than a single 2P4S artery).

“They (Winston factory technicians) think that if 12V700Ah then parallel, the final capacity is only twice of the old battery bank, the new bank will be slowed down by the old one; and if 2P4S with each parallel has one old cell and one new cell, the final capacity will be the old plus new cell.”

Does that make sense? Do I understand correctly that the new cells will have (slightly) more capacity than the two year old cells, so that the 2P4S battery will take advantage of the extra capacity, while as 4S the new battery capacity will be dragged down to the old battery capacity due to their parallel connection?

Well, I’m not sure why you even listen to that it’s BS.

There is no “slowing down” with batteries and the capacities of two parallel batteries don’t have to be equal, but still are cumulative.

The thing they don’t understand is that we have these for house batteries, not traction batteries. This means we don’t need to double current carrying capability but only want more capacity.

How this works for house battery application: the battery that has a higher SOC has a higher voltage. In that flat part of the graph there isn’t much difference so let’s say they both do 50% of the demand. But as soon as one starts nearing a low SOC, it’s voltage is dropping faster and now most of the demand is taken by the other battery… until that one comes down in voltage enough etc. etc. so both end up empty at the same time, but during the later phase of discharge, one battery does more than the other.

With charging it’s exactly the same: the lowest SOC battery takes most of the charge until out of the lower knee, then when the other battery reaches high SOC, it’s voltage increases more and most charge goes to the lower SOC battery again.

If you have cells that can do 1C discharge current continuous but you want to double that, then you need to parallel cells.

I think they also don’t understand you build two separate batteries and not two 4S strings that you want to parallel with one BMS.

I think Offgrid Garage Youtube channel did test this and confirmed this behavior like I described above

[fxykty]

Originally Posted by s/v Jedi

Well, I’m not sure why you even listen to that it’s BS.



There is no “slowing down” with batteries and the capacities of two parallel batteries don’t have to be equal, but still are cumulative.



The thing they don’t understand is that we have these for house batteries, not traction batteries. This means we don’t need to double current carrying capability but only want more capacity.



How this works for house battery application: the battery that has a higher SOC has a higher voltage. In that flat part of the graph there isn’t much difference so let’s say they both do 50% of the demand. But as soon as one starts nearing a low SOC, it’s voltage is dropping faster and now most of the demand is taken by the other battery… until that one comes down in voltage enough etc. etc. so both end up empty at the same time, but during the later phase of discharge, one battery does more than the other.



With charging it’s exactly the same: the lowest SOC battery takes most of the charge until out of the lower knee, then when the other battery reaches high SOC, it’s voltage increases more and most charge goes to the lower SOC battery again.



If you have cells that can do 1C discharge current continuous but you want to double that, then you need to parallel cells.



I think they also don’t understand you build two separate batteries and not two 4S strings that you want to parallel with one BMS.



I think Offgrid Garage Youtube channel did test this and confirmed this behavior like I described above

Thanks for your reply, that all makes sense. Correct, I won’t pull any more current out of the two batteries than I do out of the single one now. Max draw is about 0.6C and max charge lower than that.

I am adding a second BMS for the new 4S battery and will use the existing SmartShunt and Cerbo to monitor the system as a whole. Each battery will have its own BMS, but they will be setup as OR so that either one will start or stop charge for both batteries. If you’re interested I’ve attached our system diagram.


The other thing the Winston factory technician recommended was to increase the charging voltage to 14.6V, as he claims that with 13.8V I’m losing 10-15% of the actual capacity. I’m not sure of that, as I’ve seen plenty of references that relatively low charging voltages (down to 13.6V) held long enough can charge an LFP battery to 100%. I am going to stick with 13.8V.

[krid2000]

fxykty, what software did you use to draw this nice diagram?

Thanks!
Dirk

[s/v Jedi]

Originally Posted by fxykty

Thanks for your reply, that all makes sense. Correct, I won’t pull any more current out of the two batteries than I do out of the single one now. Max draw is about 0.6C and max charge lower than that.

I am adding a second BMS for the new 4S battery and will use the existing SmartShunt and Cerbo to monitor the system as a whole. Each battery will have its own BMS, but they will be setup as OR so that either one will start or stop charge for both batteries. If you’re interested I’ve attached our system diagram.
Attachment 272845

The other thing the Winston factory technician recommended was to increase the charging voltage to 14.6V, as he claims that with 13.8V I’m losing 10-15% of the actual capacity. I’m not sure of that, as I’ve seen plenty of references that relatively low charging voltages (down to 13.6V) held long enough can charge an LFP battery to 100%. I am going to stick with 13.8V.

Wow, you have your diagram down to the last lightbulb, impressive

What were you thinking when you saw people calling my diagrams “over the top” and “complex”?

The only thing I would like to see different is the house bank voltage. My preference would be 48V but I settled for 24V due to availability of parts I needed.

Also, keep an eye out for redundancy. How do you recover from a component failure for supplying power to electronics etc. Not sure if I saw a battery dedicated for that etc.

Edit: I went back to the diagram to check and see you don’t have that. I highly recommend to add this. Did you see my DC Main panel? In the lower left corner there is the power for electronics. I have a small AGM battery and the dc-dc converter is isolated like yours but it is set as a charger for the agm. Also, there are two of them. The two double pole breakers are in the outputs of those converters.