BMS and main contactor

[Simi 60]

Originally Posted by hjohnson

On the other hand, the JBD BMSs don't integrate with anything, and can't do the signalling that's really needed for a good marine system.

Really?
You need networked electronic gadgetry to hold your hand on everything?
Take control.

To me basic and robust makes a good marine system.

[hjohnson]

Originally Posted by Simi 60

Really?
You need networked electronic gadgetry to hold your hand on everything?
Take control.

I don't need it, but I want it so that I don't have to worry about it, and screw with it every day. I want it to just work, with no worries. I'd rather sail than screw around with my power system. The whole thing looks after itself, and I can keep an eye on it (and the rest of my systems) from anywhere in the world. Why? because it's all integrated and it all communicates.

[s/v Jedi]

Originally Posted by hjohnson

If my BMS is no longer active, then my charging sources go into "limp mode" which I have set for 13.2v, which means most of them will stop pushing any power into the battery for any significant time.

Well, no, it's a Blue Sea 7713, so if you release the 12v line to it, it opens up just like a normal contactor. But again, if the BMS goes tango-uniform unexpectedly, all the charging sources (MPPTs, Alternator, Inverter/Charger) default to their preprogrammed voltage values, which I have set for 13.2v.

If a cell goes unbalanced, the BMS just orders the charging sources to drop the battery current to 2a or less via CAN, so it can balance the cells. If it's high temperature, It will order the charging sources to 0A and they'll all stop. It will also throw an alarm over CAN, which will cause the alternator to immediately shutdown.

If that's actually the case, then again, everything backs off and stops pushing power into the battery, even if it is connected. But also, again, the 7713 will act like a regular contactor, so for it to be a problem you would need a failure in both the 7713 and the BMS.

Also, these BlueSea latching contactors have full manual control, so when an alarm from a cell monitor or smart battery monitor is sounded, you can switch it off manually, just like it has been forever with LA batteries.

[hjohnson]

Originally Posted by s/v Jedi

Also, these BlueSea latching contactors have full manual control, so when an alarm from a cell monitor or smart battery monitor is sounded, you can switch it off manually, just like it has been forever with LA batteries.

Plus that’s assuming the BMS fails open. If the HVC is just being driven by a processor digital output, it’s entirely possible that it fails on rather than off. Though I would hope the designers are doing some sort of circuit that would require constant pulsing to keep alive.

[Statistical]

Originally Posted by hjohnson

It's not really an economizer in the traditional sense, the contactor is still just a bi-stable contactor, but has some additional electronics that make it operate like a standard contactor.

Regardless it is fail safe but has current draw which is what the OP wanted to avoid.

Well, no, it's a Blue Sea 7713, so if you release the 12v line to it, it opens up just like a normal contactor.

To be clear so we aren't talking past each other I never once said don't use Blue Sea they are the devil.

The OP wants to use a zero energy latching contactor to avoid the daily energy overhead. Yes I 100% agree if he wants a blue sea product he should use a 7713 over a 7700. Thanks for the correction that it isn't an economizer but a latching plus release mechanism. While not a true NO contactor w/ economizer I do think the need for constant signal provides similar safety. Personally I would go with a good NO contactor but I will adjust my language in the future to avoid absolute statement on latching contactors. Honestly given the continual powerdraw on the 7713 (but not on 7700) I just assumed they were NO w/ economizers. So again thanks for the correction. Learned something today and it is only 9AM.

As for the canbus comments they aren't foolproof. They are high level protocols. If they were then there would be no need for a contactor to begin with. The contactor is simple and hard to fail especially with auto-release. That is good for safety. Ideally with canbus messaging you never need to use the contactor but if you do you need it to work. It is similar to having a fuse. Technically the BMS will trip on over current but you should still have a fuse. A fuse is very simple and simple is good when it comes to safety.

[rgleason]

It is clever combining both fla and lfp in a smart way, but will not comply with abyc requirements.

[Nicholson58]

Originally Posted by sailingharry

My AGM house bank is pushing 10 years old. I personally have been murdering it for the last four, and no idea what the PO did. I did a capacity test in the winter of 21-22, and it had lost 30% of capacity. I think it goes to the grave this winter.

I've laid out much of the conceptual design, much of it aided by Jedi's input over the years.

A major stumbling block is the BMS and the main contactor.

I feel the BMS needs to get me four outputs.
1) HVC -- high voltage cut out that will trip the main contactor.
2) HVA -- high voltage alarm that will notify me of an impending HVC and also trip all charge sources. All charge sources will in theory have already shut off on their own.
3) LVA -- low voltage alarm that will notify me of an impending LVC and will also shut off the inverter. All other loads will be left to die at the LVC.
4) LVC -- low voltage cut out that will trip the same contactor as the HVC.

I should note that I intend (or hope!) to continue to use my Link 2000 for high level awareness, and hopefully use a smartphone to get detailed status. Most of these systems do not appear to allow distant monitoring, and the Link already provides current and SOC status.

I have looked at Chargery, Electrodacus, and REC as a BMS.

Chargery appears to give no external notification, and does not support a main contactor. Non starter.

Electrodacus doesn't seem to give a lot of flexibility (but it could be that it is so flexible that I don't understand that yet!). It also appears to want the shunt on the high side which I'm not particularly excited about.

REC currently looks like the winner. But again, it is complex and will take more digging to fully understand.

The main contactor is a big stumbling block. The Blue Seas remote switch looks like a brilliant solution, but no BMS provides direct control of a latching switch. A 500 amp relay with economizer is under $200, it looks really slick, but burns about 5 Ah per day. If there is no better answer, that's not a lot of power. Electrodocus recommends a relay with a trip shunt, but 500 amp breakers are expensive and his thoughts seem to imply that none have trip shunts that work on 12 volts (and I've found none at all with trip shunts!). Since this is a very rare event, I'd be happy with a trip shunt or similar auto trip manual reset device.

So, the question for the group. Or perhaps the question for Jedi! What is a good BMS, and what main contactor works well with it? While much easier to handle, I'd like to find a contactor for my charge sources as well (around 150A -- my Watt and Sea, some of my solar controllers, and an old Victron Centaur multi-voltage charger don't support a "disable" signal). These might work well on a solid state solution.

I did the conversion to LiFePo last year with Blue Heron. Hank George hank@starboardlanding.com Did the planning, selection of dongles, cables etc for reprogramming the Victron, Balmar charge controllers, solar MPPT. Also, Hank found links to software and firmware updates for everything. The BMS’s for each lithium battery are the shut off, no main contactor. We have a 630 AH house and 110 AH starting bank. All 24 volts and running in parallel as one big bank. The starting bank provides the necessary high amp inrush for our giant starter. If you have a smaller starter this might not be needed.

[Simi 60]

Originally Posted by hjohnson

I don't need it, but I want it so that I don't have to worry about it, and screw with it every day. .

I've had ours in for 18+ months and haven't worried about or screwed with it once.

Check the app is all I have done
All 24 cells within 0.005% of each other at any given time.

[sailingharry]

So, I've been quiet. But I've been reading the responses.


First, Jedi -- you need to develop a "Jedi's best" or some sort of link to all the really awesome stuff you've posted. Not the generally good stuff, but the awesome stuff. I just came across your post on pre-charge circuit. I'm pretty sure you've posted a circuit to make a latching relay respond to a on-off signal (this thread? I've already forgotten). So much really good stuff!


The main contactor question. I've been convinced that a solenoid with economizer is not a power concern. But the discussion on the Blue Seas RBS is interesting. I find that generally Blue Seas puts a staggering markup on industry products, but this one is unique and it provides some benefit for your extra $50 (West wants $270, but you can get it as low as $170). A nice recognized marine product, with the built-in circuitry to make it act like a relay, and a big knob on top to make it manual, and visual indication. If I can fit it (no known issues, but I haven't started that level of detail), it's probably in the design.


Integration. I need to make it super clear that I am NOT integrating. I'm not getting a CERBO GX. I am not getting a Wakespeed. I don't need CAN. My system is too entrenched, and I'm not replacing everything. I have:
* TWO Balmar regulators for two alternators. Yes, a single Wakespeed (or single Balmar) can easily and happily control both alternators, and I used to do that before I inherited a second, but TWO gives me redundancy as well as an installed spare (I can go back to one regulator).
* A Watt and Sea water generator. No external controls at all! No integration possible at all.
* 3 out of 5 solar controllers are Genasun, with no integration.
* A dumb old Victron Pegasus multi-voltage charger. I don't use it because I sail in North America, but it's ready if the boat ever goes back to a 220V country.


It's worth noting that all of my chargers SHOULD throttle back to zero charge before the BMS trips the charge control output (concurrent with the HVA). So it shouldn't ever trip. And since it will trip the regulator power supply (the alternators go to the main bus, not the charge bus), there won't be any negative impact if it does.


The LVA will trip the inverter (but it should already have tripped on its internal setting). In my view, the alarm will notify me to manage discharge, but if I don't, shortly after the LVC will open the main disconnect, and, in the words of the Navy, I'll be "cold, dark, and quiet."


The BMS.



I'm digging into the REC. It might be the ticket. It is FAR too complex, with all its integration with CERBO and Wakespeed and direct management of the charge profiles. But it "seems" like I can configure the outputs to simply give a LVC, LVA, HVA, and HVC based on individual cell voltages. I like the general form factor and construction, and programming complexity isn't a deal killer if I can make it do what I want. Price is not unreasonable.



I'll look again at the Electrodacus. I really like it's support and general design, but I'm even more concerned about the programming. The price is noteworthy.


Jedi, you mentioned in another thread the Daly, and using a super small size to control relays. If the power doesn't go through anything the BMS controls (either the BMS or a supported shunt), it has no idea about current -- but the only thing a good BMS does with current is track SOC. SOC is simply useful info to the operator, and has little value to the BMS internal programming. Since I'm intending to keep my Link2000 for user info on SOC (and start battery SOC), this may be an interesting approach. Have you posted on how to integrate a cheap SCR BMS into a robust LFP system? I'm thinking if the SCR output provides power to the main contactor, the cheap BMS will trip on HVC and LVC. That leaves LVA and HVA outputs to be addressed, as well as balancing (although many have opined that balancing in our low current applications, but charge and discharge, is of limited benefit).

[sailingharry]

A question regarding CAN. CAN is originally (??) a sophisticated generalized communication standard in cars. That makes it a logical BMS communication protocol. But it also is the foundation of N2K. Has anyone been able to link a CAN based BMS into a useful N2K output? It'd be wonderful to get data to the chart plotter, primarily SOC, voltage, and alarms. Seems to me it's mostly there, even if there has to be some hardware/transport layer conversion, as well as sentence structure.

[Statistical]

If this is a 12V system and you are using Rec BMS instead of putting the alternators on the discharge bus (which has its own risks) you can use the optocoupler 1 to safely turn the alternator regulators off via relay.

If the Charge optocoupler 1 hysteresis is set to 0, this digital optocoupler output functions like charger enable. Charge optocoupler 1 is turned ON until the last cell reaches END of charge voltage. If a single or multiple cell reach the voltage level between cell over-voltage switch-off and end of charge, output is turned OFF, until this/these cells are balanced down to end of charge voltage. Some of the errors
also turn the output off. See Error table 16

[sailingharry]

Originally Posted by Statistical

If this is a 12V system and you are using Rec BMS instead of putting the alternators on the discharge bus (which has its own risks) you can use the optocoupler 1 to safely turn the alternator regulators off via relay.

Thanks!


If I can get optocoupler 1 to work as an End of Charge signal (as indicated), that will serve as the HVA/charge enable part of my solution. That is perhaps the single biggest hurdle in my system.


I'll be using a single bus for both charge and discharge. As Jedi has opined, and convinced me, a charge and discharge bus is needlessly complicated. My alternators (270A combined rated output) are connected to my "Main Bus" which will be connected to the batteries by the main contactor. Splitting the bus would require double the number of large fuses and contactors. The inverter/charger will also be tripped by the HVA. The rest of my charge sources, totaling a max of 130A (the watt and sea won't be turning if the Pegasus is plugged in...) will be on a "charge bus" that is connected to the main bus by a contactor. But this won't need to be able to protect or handle the 500A that the main bus will be designed for. It will also be "one way" so can be a sold state solution (I think).


On further thought, I should probably wire the alternator regulators to shut down on LVA alarm as well as HVA. If the system gets low enough that the LVA is set (while the alternators are running!), there is a serious fault. But tripping the disconnect at LVC without first shutting down the regulators would be bad.

[sailingharry]

Originally Posted by Statistical

If this is a 12V system and you are using Rec BMS instead of putting the alternators on the discharge bus (which has its own risks) you can use the optocoupler 1 to safely turn the alternator regulators off via relay.

Statistical,


I've just finished reading through every manual I could find on the REC web site (https://rec-bms-na.com) and can't find the quote you posted anywhere.


More important than the quote itself, and what I was hoping to find when I found the quote, was detail on exactly how to connect and use the outputs, and how to configure them for various design intentions.


Can you point me to the source for the quote?


Meanwhile, I'm going to search out REC forums. I'm sure there is an avid (perhaps "rabid"?) forum or ten. LOL.

[rgleason]

Referring to X2 BMS

[Statistical]

Originally Posted by sailingharry

Statistical,
Can you point me to the source for the quote?

It is here on the international website. The international website has two versions of the manual one which says "wakespeed compatible" and one that doesn't. As far as I can tell there is only one BMS just two manuals depending on how it is used.

https://www.rec-bms.com/battery-management-system/
https://www.rec-bms.com/datasheet/UserManual_ABMS.pdf

Note this is only true on the ABMS (12V version). The 24v/48V version and the master slave one have different ports.


The manuals on the NA website have slightly different wording so I think they are the wakespeed version of the manual. They don't call it optocoupler 1 but instead "charge optocoupler" but it seems to indicate the same thing.

https://rec-bms-na.com/download/8/re...ible_v2_90.pdf

When the highest cell reaches the End of charging CHAR voltage setting,
charging current starts to ramp down to 1.1 A x Number of Inverter/Charger
Devices STRN until the last cell rises near the End of charging CHAR (CC/CV) – UBDI (End of charge unbalance difference). At that point the Maximum charging voltage allowed is set to Number of cells x (End of Charge Voltage per cell CHAR – Maximum Cell Float Voltage Coefficient CFVC x End of charging hysteresis per cell). End of charge SOC hysteresis SOCH and End of charge cell voltage hysteresis CHIS is set to prevent unwanted switching. SOC is calibrated to 100 % and Power LED lights ON 100 %. Charge optocoupler is turned off.

Maybe in later firmwares they limit optocoupler 1 to only charge function hence the change in language which would be fine in your case.

The rec forums should help to clarify.