Small Boat BMS/LFP with backup

[Goboatingnow]

I can only give you some general comments on this because the basis of the system is a battery and BMS combo that we don't sell.

That’s fine but it doesn’t mean alternatives are worse they could easily be better

Here are a few things I noted on your drawing:

You have an unusually low value for your main fuse. 160 amps is the rated output of your alternator. Its quite possible for it to put out more than its rated output for a brief period and that alone would blow the main fuse. You also have lots of other things connected which could contribute to this situation. If the main fuse blows the alternator will be toast.

Well it’s a call. If there is a serious risk of that type of current. Then the fuses needs to be upped. If your design calculations are due less then that then the fuse is there to protect the cable. If ( and it’s an if ) it goes the alternator may not survive. Either you up the cable massively and not fuse or fuse and evaluate the risks.

Your system has a BMS designed to stop charging if any cell gets too high a voltage and stop loads if any cell gets too low a voltage. The BMS is just a simple processor, it has to act on the system to be effective. How does it disconnect your DC loads in the event of a low cell? There doesn't seem to be any way for it to achieve this.

Bms as defined by ABYC and ISO is not required to disconnect loads selectively. It’s required to shutdown the battery in the event of LVE HVE , overtemp over over current. That’s it.
Most boats have no comprehensive battery low protection this is not LVE LVE should be set at the lowest manufacturers cell voltage of SOC. battery Soc disconnects are separate and if fitted shoujd trigger above LVE.

I have to question how the BMS acts for the other load and charge devices too. Perhaps it can communicate with the Cerbo to achieve this electronically with connected devices using DVCC but you would have to verify that the integration works.

It can communicate or you can have seperafe “ battery saver “ disconnects. Your diagram has neither

Your Cerbo does not have its own way of measuring current or voltage, you would have to establish that the BMS is communicating that information to the Cerbo.

Again this is a claim. The REC can relay current and voltage to the Cerbo.

ABYC standards call for the system monitoring equipment to stay active in the event of a BMS shutdown. Have you taken care of this in your system?

No such statement exists in TE-13 to my knowledge.

There isn't much support for this kind of system. Neither Victron nor I will support this, you have put yourself in the hands of the tinkerers. Official support extends to the individual Victron devices themselves, not for integration with third party products. Support for this will have to be from other tinkerers and you will find lots on the Victron Community Forum

That’s an unjust claim. Victron supports all normal use cases. The Victron community is there to support you.

The tinkers comment is unwarranted. Every lithium install on a boat is a “ tinkering “ cause nobody has all the components of a fully interconnected system with all charge sources controller and loads managed.

The last paragraph makes me question his whole answer.

 

[rgleason]

Either you up the cable massively and not fuse or fuse and evaluate the risks.

Perhaps I should increase all the Alternator to Battery cables to 2/0 AWG and change the Alternator Lynx fuse to 200a and increase the LFP Battery fuse to 200a mrbf (this size fuse is just 2a more than the ampacity). I understand that the T-fuse has an extremely fast short circuit response and is the type of fuse we need on the battery, of course that fast characteristic jeopardizes the Alternator but protects the system.

John Harries suggests sizing the alternator fuse at 120% of the rated capacity and then sizing the wire for that.
160A x 120% = 192A so 200A should be ok.

Most boats have no comprehensive battery low protection, this is not LVE. LVE should be set at the lowest manufacturers cell voltage of SOC. Battery Soc disconnects are separate and if fitted shoud trigger above LVE.

I believe @svsagres uses a Victron Smart Battery Protect 65 in the bus to the DC Panel Loads with an automatic disconnect at some voltage greater than the LVE disconnect voltage. Is this a device that I should have on the feed from the Lynx to the DC Panel ? I understand this is a system separate from the BMS for "comprehensive battery low voltage protection".

Peter Kennedy wrote:

I have to question how the BMS acts for the other load and charge devices too. Perhaps it can communicate with the Cerbo to achieve this electronically with connected devices using DVCC but you would have to verify that the integration works.

@Goboatingnow wrote:

It can communicate or you can have separate “ battery saver “ disconnects. Your diagram has neither

I thought that @svagres had all Victron devices like Solar MPPT and Phoenix 120vac charger connected to the CerboGX and via VE.direct so that the CerboGX would control them appropriately. I have shown these VE.direct cable connections in the diagram as 1,2 & 3 (inside a small circle). Won't the CerboGX control these devices so that they don't overcharge and shut off, and charge when the LFP is low?
LATER: Refer to @Goboatingnow Post #280

You can run DVCC on the Cerbo Gx and Control all Mppt and alternator charge sources , allowing central control What would be nice would to add the ability in the Cerbo to instruct the REC to reconnect the battery , this would even allow remote ( via victron VRM ) ability to reengage charge sources etc. I must study the Ve.can integration of the REC to see what it’s possibilities are.

Also by adding a Victron Smart Battery Protect 65 in front of the DC Panel loads we wouldn't we then have a better battery protection?

First see Post #86

2. Smart disconnect. If u intend to use this as a disconnect device it must be next to the battery. No other devices except the bms must remain connected and provision must be contained within the bms to not discharge the li completely either. Hence as it is the smart switch is not compliant with ABYC or ISO.

In reviewing the past posts in the thread we have had a number of discussions about having a Smart Battery Disconnect 65. I believe that Goboatingnow does not recommend having one of these devices for several reasons.

The remaining device to consider is then the Alternator and Regulator (Wakespeed) which has an Balmar APD (to perhaps help) and the regulator is interlinked via Canbus to the REC Active BMS and VE.canbus to the CerboGX and is then controlled by the CerboGX to shutdown in advance of a BMS HVD or HVE (High voltage event)?

Post #361 svsagres - nice.

Without BMS control, the Wakespeed will set its voltage out to limit to a configured value. On my boat, I have it at the default limp mode at 13.2v, but unless things go really bad, I’ll just run the lfp without the bms.

Also I believe that the Wakespeed has its own high voltage setting which stops the alternator from charging which would be set at a lower voltage than HVDisconnect or HVEvent setting. In addition, I think the CerboGX will control other charge devices like the Solar MPPT?

Post #369 svsagres -nice!

In regards to the solar, it’s all managed by the Cerbo GX. So the MPPTs themselves can be programmed for lead acid. This will be overridden when they’re connected to the cerbo and being remote controlled. (The Cerbo takes in the voltage/current limits and measurements from the BMS, and translates them to the MPPTs. Without the remote control, the MPPTs will revert to their internally measured voltage set points.

Alternator protection when switching
Should the Alternator brown or the field wire be run through the 1-off-2 switch AFD to protect the alternator when switching, or should we just shut the engine down before touching the switch? --NO
LATER: No that isn't going to work,

• When switch is at OFF "Normal LFP" we want the alternator to be able to charge.
• When we switch to "LFP Disconnect & SLA Emergency Feed", if the engine is running, hopefully the alternator/regulator will adjust to the "limp home" setting (13.8-13.2v).
• When we switch to LFP Override, if the engine is running, then we may want the alternator to be charging or may not depending on the state of the battery!
• Does this need further attention? - No, not going to do.

LATER: Regarding PK question about keeping the BMS powered after shutdown.
Post #184

BMS draws its power from the sense leads connected to the (LFP) battery, so it will always be powered.

Additionally, the CerboGX is powered from the SLA battery so it will continue to function with Victron equipment (MPPT, Orion-Tr) and with the Wakespeed, and the BMS since it continues to be powered from the LFP.

Svsagres wrote:

For me, if I’m not aboard, I put the boat into hibernation mode. That drops my load to 20W or so (Cerbo, Instrumentation, AIS, and LTE left on). With my battery that gives me about 20 days to respond to something gone wrong with charging.

If I’m just leaving the boat for an afternoon, I really don’t care, since I’m fully operational mode (refrigeration, devices, laptops, etc…) I still have about 4 or 5 days until I really need a charge.

 

[rgleason]

Post #93 Summary ABYC and Major Requirements

Post #247

The key point both under ABYC and ISO is the presence of a BMS , a complete disconnection of the Battery from both loads and charge sources , and advance warning of such an action

Post #280

I do not think dual bus systems , ie CH and DCH buses , despite was Bruce Swarb suggested , will appear In ABYC or the more prescriptive ISO standards simple because both are focused on battery safety first not overall system design. As you easily retrofitted. With you components , ie. REC BMS , you have very fine control over charging limits , especially as you can run DVCC on the Cerbo Gx and Control all Mppt and alternator charge sources , allowing central control What would be nice would to add the ability in the Cerbo to instruct the REC to reconnect the battery , this would even allow remote ( via victron VRM ) ability to reengage charge sources etc. I must study the Ve.can integration of the REC to see what it’s possibilities are

See Post #383 John Harries checked, a response to Bruce Schwab's...

13.7.2.1A BMS shall respond to any conditions outside the SOE by activating the output disconnect device.

See Post #383 John Harries wrote: All that said, if it were me I would consider installing an all Victron or Lithionics system with duel busses and then hide behind:

13.6.1.2 No electrical connections shall be made directly to a battery that would bypass a BMS or any battery protection circuits. EXCEPTION: Connections made specifically per the battery manufacturer’s instructions.

Post #261

At the end of the day Li is just a battery doing the same thing in a boat as the lead acid did. All we have added is a safety system that acts in “ last moment “ events to protect the battery. Arguably we should have had some of it in LA systems.
Hence I ( and ABYC) don’t require anything else , no complex charge and load bus separation etc.

Offgridsolutions Post #10 Benv Comments

ISO 13297 9.3: Remote controlled battery disconnect switches, if used, shall also permit safe manual operation.

1. If never paralleled than all is ok.
As I mention I didn't read all the details.

2. With 2 relays there is also a complete disconnect!!!
They rules don't say it need to be one contactor. It only says disconnect completely, when needed thats done with 2 contactors!!
Off course it is good to have in the ""user manual"" a comment about this. That the system has 2 contactors..
Name the contactor like main contactor, 1/2 and 2/2 as example and labeled like that.

Dont forget this part from the rules.
ISO 13297 9.3 says:
""Remote controlled battery disconnect switches, if used, shall also permit safe manual operation.""

The contactor in your system can be seeing as a remotely controlled contactor?.
This means there need a manual control from the contactors also!!!
This means if there is a faulty BMS, you can still operated the system.
ONLY in case off a fault in equipment, and NEVER for normally use!!!. It should labeled as this also!!

This seams contradiction with other rules, BUT I see this as a extra safety if lightning damage a processor in the BMS. You can have long discussions with technician about this which rules overrules another rule or not!!

3. What is the exact discretion from BMS?
Battery Management System.
In your setup the REC AND the CERBO together are the battery management system.
I interpreted the Rules like that.

Yes the REC has the name, BMS, the Cerbo, is named different. BUT only together the have the function from a complete battery management system.

What they like to say, in my personal interpretation, as example, don't connect any other equipment like chargers, mppt direct to the battery without discontactor.

About settings: Every device has settings, not that difficult, but if you are new in this, it is lot off reading.

I hope this info will help you. Ben

Post #256

Not suggesting that people don’t do this , what I saying is that fron a basic safety perspective , compliant to ABYC or ISO , there’s no point in dual disconnects( load and charge ) and complex manual overrides and so forth.

Sure fit them , knock yourself out. But again a simple all load and charge source disconnect and a man with a pair of jump leads is all you really need in extremis .

Post #390 Goboatingnow

Again yes if you want a CH and a DCH bus great use two contactors but the bms should kill both in lve and hve

Post #242 Panbo identification of ABYC E-13 items:

E-13.7 requires a BMS on all lithium batteries installed on boats.
E-13.8.1 Battery Manufacturer will provide a manual that provides information...
Notes at the end E-13.7 (serve as recommendations but don’t carry the same requirements as items in the main body of the standard).
Note 1 recommends alternative power sources for critical systems (engine starting, propulsion, navigation lights, etc) . It’s worth noting, another lithium battery is acceptable as a redundant power source.
Note 2 BMS should give an audible or visual signal when a disconnect condition is approaching.
Note 3 A BMS may suddenly and unexpectedly disconnect a battery from charge and load sources.

Also the standard says that dissimilar batteries should not be paralleled.

Post CF #65

ISO says
4.9 In normal operation, different battery chemistries should not be connected in parallel or in series.
Interesting while Broadly similar ABYC te-13 omits that sentence.
Bit the oft repeated issues of connecting LFP to SLA means safety is best served by preventing paralleling. It’s been standard practice in most designs to use dc dc to separate the batteries.
Neither ABYC or ISO support operation of the batteries outside manufacturers reccomendations
So can you point to a LFP battery manu that supports direct paralleling. I have not seen one .

Post #349 and Post #340

ABYC 13.5.3 Consideration should be given to providing alternative power for critical systems (e.g., engine starting,
navigation lights, etc) if a BMS shuts down the battery.

CF Post #48
Originally Posted by s/v Jedi View Post

I held the diagram against ABYC recommendations and it appears that the manual switch violates 13.7.7
13.7.7 No electrical connections should be made directly to a lithium ion battery that would bypass a BMS or the protection relays.
The switch clearly bypasses the protection relays.

Goboatingnow wrote:

Firstly an open switch is not connected to the battery. That’s in plain sight.
Secondly both iso and ABYC recognise the need for overrides
“13.5.3 Consideration should be given to providing alternative power for critical systems (e.g., engine starting,
navigation lights, etc) if a BMS shuts down the battery.“
Thirdly the RBS ML has a integrated override that in theory violates your pedantry

Post #339

ABYC 13.7.7 No electrical connections should be made directly to a lithium ion battery that would bypass a BMS or the protection relays.

Post #160

ABYC TE-13 and ISO 23625 you cannot have anything remaining connected after safety LVC disconnect except the BMS , nothing must be wired on the battery side of round the safety disconnect breaker . On disconnect EVERYTHING must be disconnected

Post #92

Iso and ABYC standards require that a safety LI disconnect disconnects all devices from the battery bus including charge sources , nothing should remain powered by the bus expect the BMS. provision should be then made to reconnect the charge sources but only if the Li has not discharged completely.

Post #141

just to be clear ABYC does not require fail safe operation AFAIK, in other words if the BMS dies, the system is unprotected

 

[Goboatingnow]

Post 141

ABYC doesnt really address component failure or bypass systems TE-13 is far too vague on what happens as systems fail.

Hence we are on our own in this regard.

I think the manual override approach is good. But I would not bother protecting the alternator from the consequences of inappropriate manual switching

 

[rgleason]

Diagram Changes to make:

1. Add a note to the manual Switch Diagram SK-2, "Engine (Alternator) must be "Off" when switching" or if there is a separate alternator field disconnect switch, it should be off. -Done
2. Increase all the Alternator to LFP Battery cables to 2/0 AWG and change the Alternator Lynx fuse to 200a and increase the LFP Battery fuse to 200a mrbf (this size fuse is just 2a more than the ampacity).
   1. John Harries suggested Alternator output 160a x 120% = 192a fuse, then size the wire. He also says that if this fuse blows then the alternator diodes are probably damaged, so a 250a fuse might be better than 200a. - Done 250a and 2/0 AWG
3. at Starter Battery
   1. Main disconnect switch needed (Benv) -Is this really needed? Where between SLA and bus bar? Could a 250mbta suffice?
   2. Fuse needed marinehowto about starter fuse sizing #1AWG, 10' 250mbta
   3. Size for ample capacity wire, and ABYC does not require a fuse for the starter motor (Goboatingnow). -Done Increased to 1 AWG, no fuse
4. Add a note somewhere to disconnect the Solar panels at the M4 connectors before disconnecting from the batteries.
5. Add "SLA Emergency Feed (LFP Disconnected)" to the red dashed wire because people don't get the operation and are confused. -Done
6. New Victron documentation for Wakespeed WS500 (svsagres wrote below)
   1. Separate current shunt in the Alternator black - cable to the Lynx bus for current sensors. -Done
   2. Pick parameter "current sensors at Alt" (to be done)
   3. Temp sensor on alternator - Done
   4. Show sense + at the 1-off-2 switch and sense - at the shunt. -Done
   5. Change WS500 to cerboGX from VE-bus to VE-CAN. (Benv & svsagres) -Done
   6. Change REC to WS500 BMS can, to VE-CAN (Victon has BMS-CAN and VE-CAN, you need to use VE-CAN). (Benv & svsagres) -Done
   7. WS500 can share a shunt, but you need to set CerboGX to "SVS" shared voltage sense. Read the CerboGX manual. -not doing that.
   8. 13. Wakespeed WS500 support www.victronenergy.com
7. https://www.offgridsoftwaresolution...nd-wakespeed-on-bms-can-on-cerbo/#postid-1061
   1. VenusOS firmware v2.90 or higher installed on your GX device
   2. Wakespeed WS500 firmware 2.5.0 or higher installed on the WS500 controller
   3. The WS500 must connect to the VE.Can port of the GX device. It is not possible to monitor the WS500 when connected to the BMS-Can port of a Cerbo GX.

Just Considering these changes:

I think perhaps I should consider powering a few of the essential and low power loads from the SLA in the rare event a BMS/LFP shutdown occurs:

1. Nav lights (masthead) - separate dedicated switches located on the DC panel
2. Bilge pumps - separate small panel for fuse and switches
3. Cabin lights - currently uses DC circuit breaker
4. Instruments - currently uses DC circuit breaker (also part of nmea2k and nav system)

#1 & #2 could be easily done by connecting to a small 6 fuse panel powered from the SLA.
#3 & #4 are somewhat problematical because the Cabin lights need a switch, and the instruments are really part of the nav system.
Perhaps moving the Cabin lights to SLA are a priority.

See Goboatingnow comment below. Not going to make any changes about this, to complicated.

 

[Goboatingnow]

I will add a note to the manual Switch Diagram SK-2, "Engine & Alternator Off when switching".

I think perhaps I should consider powering a few of the essential and low power loads from the SLA in the rare event a BMS/LFP shutdown occurs:

1. Nav lights (masthead) - separate dedicated switches located on the DC panel
2. Bilge pumps - separate small panel for fuse and switches
3. Cabin lights - currently uses DC circuit breaker
4. Instruments - currently uses DC circuit breaker (also part of nmea2k and nav system)

#1 & #2 could be easily done by connecting to a small 6 fuse panel powered from the SLA.
#3 & #4 are somewhat problematical because the Cabin lights need a switch, and the instruments are really part of the nav system.
Perhaps moving the Cabin lights to SLA are a priority.

Add a note somewhere to disconnect the Solar panels at the M4 connectors before disconnecting from the batteries.

Remember if every wet Wednesday you’re finding you have to switch in the SLA something has gone badly wrong.

Hence given it’s a system only designed to be used occasionally and manually I see no point in spending money to direct the SLA at particular loads. After all you can just selectively trip them out manually at the panel.

Hence just power up the boat completely from the SLA. This is the simplest electrically.

Then depending on whether you are facing a long period of “ bypass” or a short period you can decide to selectively manually kill certain loads.

It’s a mistake to complex engineer a costly system that almost never gets used.

 

[rgleason]

Post #4 and #5 by Benv from offgridsolar.com forum REC-BMS and WS500 Smart Regulator Users forum.
He makes some observations about the diagram.
I have added a few revisions to the list #380

Also re Wakespeed WS500 new developments Sept 14 2022.
I found the new Victron documentation for Wakespeed WS500 and it is showing a separate current shunt in the Alternator red cable to the Lynx bus. The temp sensor goes on the alternator and it does appear we should use VE.bus. Also now has alternator voltage, current and temp on the VRM portal.

13. Wakespeed WS500 support

www.victronenergy.com

Why the red cable? Can't we use the same shunt as the REC Active BMS which is closer to the battery and on the black cable?


From Wakespeed WS500 Technical Docs

Remote sensing / Port Expander: The WS500 Alternator Regulator is able to take advantage of the CAN communications capability to transfer real-time battery status: voltage, amperage, and temperature as well as operational status (e.g., off-line in the case of a LiFeP04). By using this capability wiring and installations may be simplified.

Self healing / fail over: Ability to self-recover from a failed, removed, or turned off device. The system continuously monitors all devices and adjusts as needed.

‘Get-Home’ total system failure mode: In the event of a catastrophic total system communications failures, the WS500 Alternator Regulator will fail-to-safe and operate in a stand-alone mode. Allowing for continued charging, but perhaps with less optimization and longer times needed

WS500 and REC BMS use SMA: The ‘Sunny’ SMA CAN protocol an 11-bit message commonly used in the Solar and Electric Vehicle industry. It allows for a BMS to tell charging sources to start, stop, and which goals to utilize. Often know as the SMA protocol, it is also reflective of the Victron 11-bit BMS protocol, though at a different CAN speed

WS500 has the ability to manage an optional external DC-DC converter and control the transfer of power between two separate DC busses. Page 69
WS500 User Manual has a wiring diagram on page 8 showing the shunt on the negative, so I believe the REC BMS and WS500 can share that shunt.

WS500 with REC BMS Active and Q Pdf

 

[rgleason]

After my comment:

I note that Bruce Schwab, who prefers dual bus configurations, hopes that ABYC will evolve to support separate shutdown of the charge bus and discharge bus.

John Harries "Attainable Adventure Cruising" thread "Seamanlike Lithium Battery System" reports:

Hi Rick,
I’m sure he does, me too!
Just read the standard and you are right:

13.7.2.1A BMS shall respond to any conditions outside the SOE by activating the output disconnect device.

My guess is that this is probably the result of poor drafting, rather than intended. The problem, of course, is the word output.
Just another way in which ABYC E13 is, in my view, deeply flawed.
All the said, if it were me I would consider installing an all Victron or Lithionics system with duel busses and then hide behind:

13.6.1.2 No electrical connections shall be made directly to a battery that would bypass a BMS or any battery protection circuits. EXCEPTION: Connections made specifically per the battery manufacturer’s instructions.

(As I remember Victron manuals for their higher end BMSs show duel busses, so I would file that and feel comfortable.
Anyway, I’m 100% with Stein on this, in my view, compelling the BMS to dump the loads just because of an overcharge does not increase safety, it decreases it since load dumps are dangerous in and of themselves and overcharge is the most likely scenario to cause a disconnect.

My response to him:

I actually agree, but am trying to keep it really simple and follow ABYC requirements. REC BMS Active supports dual bus and several additional relays and integrates well with WS500 and CerboGX via VE.CAN and Canbus. So what would it cost for dual bus? Another relay?

Although dual bus increases cost somewhat there are many advantages to a dual bus that works as one would expect,
A. Disconnecting the charge bus on HVE ,
B. Disconnecting the discharge or load bus on LVE.

The lights won’t go out on “A” as the loads reduce the battery SOC,
and for "B" the alternator and chargers remain connected to recharge the LFP.

Also I am planning a rather small LFP 240-300ah, not having the additional small load of the NO relay does help, although our 100w solar would help, when we aren’t on board and on the mooring.

Thanks for checking.

 

[svsagres]

Also re Wakespeed WS500 new developments Sept 14 2022.
I found the new Victron documentation for Wakespeed WS500 and it is showing a separate current shunt in the Alternator red cable to the Lynx bus. The temp sensor goes on the alternator and it does appear we should use VE.bus. Also now has alternator voltage, current and temp on the VRM portal.

It’s on the VE.Can interface, not VE.Bus. (I have this setup working for a couple months now). VE.Bus is an older RS485 based bus, primarily used by Victron for communicating with their Multiplus inverter/chargers and related equipment. VE.Bus isn’t relevant to your configuration as you don’t have a multiplus. I also have this tied into my NMEA 2000 network, as it puts all the information from my power system and engine (thanks to the ws500) onto the N2K bus for my instrumentation.

At the same time, it also lets me see all my boat’s instrumentation remotely, and also export it via signal-k to my phone, watch, etc… Having a live readout of the depth sounder on my apple watch, while up on the foredeck and prepping to drop anchor is remarkably handy. Conversely, it’s great to be able to look at all of that stuff quickly from my phone while in my bunk for the piece of mind of knowing I haven’t moved, and that I have enough depth under the keel.

13. Wakespeed WS500 support

www.victronenergy.com

Why the red cable? Can't we use the same shunt as the REC Active BMS which is closer to the battery and on the black cable?

The point is to measure the alternator current independently. I‘m using an old shunt left over from my Link 10 battery monitor that has long since died. In my case, though, since my alternator is isolated ground, I actually have it on the low side of the alternator rather than the high side. However, the electronics in the WS500 can also handle a high-side shunt which is nice, given that most alternators are not isolated ground.

From Wakespeed WS500 Technical Docs


WS500 has the ability to manage an optional external DC-DC converter and control the transfer of power between two separate DC busses. Page 69
WS500 User Manual has a wiring diagram on page 8 showing the shunt on the negative, so I believe the REC BMS and WS500 can share that shunt.

WS500 with REC BMS Active and Q Pdf

They can, but you’re better off, in my opinion, to be able to know the actual current out of the alternator, rather than the net in/out of the battery. When building your wakespeed configuration, it’s the difference between “shunt at battery” and “Shunt at alt” in the appropriate command string.

 

[Goboatingnow]

13.6.1.2 No electrical connections shall be made directly to a battery that would bypass a BMS or any battery protection circuits. EXCEPTION: Connections made specifically per the battery manufacturer’s instructions.

(As I remember Victron manuals for their higher end BMSs show duel busses, so I would file that and feel comfortable.
Anyway, I’m 100% with Stein on this, in my view, compelling the BMS to dump the loads just because of an overcharge does not increase safety, it decreases it since load dumps are dangerous in and of themselves and overcharge is the most likely scenario to cause a disconnect.

My response to him:

I actually agree, but am trying to keep it really simple and follow ABYC requirements. REC BMS Active supports dual bus and several additional relays and integrates well with WS500 and CerboGX via VE.CAN and Canbus. So what would it cost for dual bus? Another relay?

Although dual bus increases cost somewhat there are many advantages to a dual bus that works as one would expect,
A. Disconnecting the charge bus on HVE ,
B. Disconnecting the discharge or load bus on LVE

I could not disagree more with this philosophy

Since HVE and LVE are critical safety trips I would not condone leaving anything connected after a trip. Loads and charge sources should be disconnected.

Manual inspection will then occur and then and only then can either selective loads or charge sources be manually reinstated.

A bms does not know “ WHY “ a HVE , or an LVE occurred. it should not make connection decisions based on not knowing what Is wrong.

People need to stop seeing LVE or HVE as somehow “ normal “ and that the battery system remains operational at such events.

In particular reconnecting charge sources on lve is inherently dangerous and never occur automatically.

 

[rgleason]

I could not disagree more with this philosophy

Since HVE and LVE are critical safety trips I would not condone leaving anything connected after a trip. Loads and charge sources should be disconnected.

Manual inspection will then occur and then and only then can either selective loads or charge sources be manually reinstated.

A bms does not know “ WHY “ a HVE , or an LVE occurred. it should not make connection decisions based on not knowing what Is wrong.

People need to stop seeing LVE or HVE as somehow “ normal “ and that the battery system remains operational at such events.

In particular reconnecting charge sources on lve is inherently dangerous and never occur automatically.

There is a slow learner here, forgive me. Your explanation is good. It is the reason we have a single relay.
I suppose that the second relay and bus only offer the advantage, after manual inspection, of connecting the charge bus to recharge a LVE or connecting the load bus to deplete an HVE.

After a BMS/LFP failure and shutdown:

1. Manual inspection to determine the problem. The BMS will still have power. The CerboGX is powered from SLA so provided the SLA is not dead, it will still work.
2. LVE determined. Switch off the main DC Panel breaker.
3. HVE determined. Switch off the chargers use the on/off terminals of the MPPT and a field wire switch for the Alternator?
4. These would all have to be set properly before moving the switch from LFP Disconnect & SLA Emergency to LFP Override to recover the LFP Battery and BMS.

 

[rgleason]

It’s on the VE.Can interface, not VE.Bus. (I have this setup working for a couple months now). VE.Bus is an older RS485 based bus, primarily used by Victron for communicating with their Multiplus inverter/chargers and related equipment. VE.Bus isn’t relevant to your configuration as you don’t have a multiplus. I also have this tied into my NMEA 2000 network, as it puts all the information from my power system and engine (thanks to the ws500) onto the N2K bus for my instrumentation.

At the same time, it also lets me see all my boat’s instrumentation remotely, and also export it via signal-k to my phone, watch, etc… Having a live readout of the depth sounder on my apple watch, while up on the foredeck and prepping to drop anchor is remarkably handy. Conversely, it’s great to be able to look at all of that stuff quickly from my phone while in my bunk for the piece of mind of knowing I haven’t moved, and that I have enough depth under the keel.



The point is to measure the alternator current independently. I‘m using an old shunt left over from my Link 10 battery monitor that has long since died. In my case, though, since my alternator is isolated ground, I actually have it on the low side of the alternator rather than the high side. However, the electronics in the WS500 can also handle a high-side shunt which is nice, given that most alternators are not isolated ground.


They can, but you’re better off, in my opinion, to be able to know the actual current out of the alternator, rather than the net in/out of the battery. When building your wakespeed configuration, it’s the difference between “shunt at battery” and “Shunt at alt” in the appropriate command string.

I also have a failed Link10 right now . I could use that shunt for the alternator, in the black neg line to the Lynx bus, for "shunt at alt" setting. I believe my converted to external regulator Delco Remy SI28 12V 160A that I am going to field limit to 100a is not isolated ground. Thanks.

Will change to VE.CAN

 

[rgleason]

Revision 10-2-2022
See Post #380 Diagram Changes to make
I have two open questions that I know of:
1. Have I shown the REC BMS VE.CAN and WS500 VE.CAN correctly?
2. At the starter battery, do I need an on/off switch between the battery and the bus bar? If so, would a 250A mbta suffice?

I am hoping that I am almost finished with this!
I need to complete the list of equipment.

 

[rgleason]

Offgridsolutions Post #8 Benv

ISO TE13: NOTES: If batteries are paralleled in an unbalanced state, extremely high paralleling currents can flow. If used automatic paralleling devised or on/of switches, should have an appropriate current limiting capability.
Manual switch 1, 2 both and automatic parallel systems MAY NOT BE appropriate.

(Rick) Is the last line above actually Ben's comment?

Ben then wrote:

As example, your starter battery is empty and you use the "emergency switch" is good to know that the amp limiting from the resistant in the cable is enough, to not blow the fuses.
That why I wrote do some tests.

I am trying to understand why this is necessary if we are not paralleling the batteries? Does he not understand it?

 

[Goboatingnow]

There is a slow learner here, forgive me. Your explanation is good. It is the reason we have a single relay.
I suppose that the second relay and bus only offer the advantage, after manual inspection, of connecting the charge bus to recharge a LVE or connecting the load bus to deplete an HVE.

After a BMS/LFP failure and shutdown:

1. Manual inspection to determine the problem. The BMS will still have power. The CerboGX is powered from SLA so provided the SLA is not dead, it will still work.
2. LVE determined. Switch off the main DC Panel breaker.
3. HVE determined. Switch off the chargers use the on/off terminals of the MPPT and a field wire switch for the Alternator?
4. These would all have to be set properly before moving the switch from LFP Disconnect & SLA Emergency to LFP Override to recover the LFP Battery and BMS.

Again the Victron mppt has Bluetooth on off so you can disable charge via this of using the Cerbo or using the remote on off. It’s up to you.

Again yes if you want a CH and a DCH bus great use two contactors but the bms should kill both in lve and hve

 

[Goboatingnow]

Offgridsolutions Post #8 Benv


(Rick) Is the last line above actually Ben's comment?

Ben then wrote:

I am trying to understand why this is necessary if we are not paralleling the batteries? Does he not understand it?

Yes his comment makes no sense

 

[Goboatingnow]

By the way one thing worth adding is a LI last ditch manual disconnect switch.

 

[rgleason]

Ok, is that in case relay contact weld, for example.
Would the disconnect be between the LFP and relay?

Should I also have one at the SLA?

 

[Goboatingnow]

Ok, is that in case relay contact weld, for example.
Would the disconnect be between the LFP and relay?

Should I also have one at the SLA?

I would always reccomend a simple single pole switch before the bms contactor and yes also on the SLA output.

In things like fire , or other emergencies you just want to kill the batteries. Also useful where you need to work upstream and want the security of an electrically dead system.

 

[svsagres]

I would always reccomend a simple single pole switch before the bms contactor and yes also on the SLA output.

In things like fire , or other emergencies you just want to kill the batteries. Also useful where you need to work upstream and want the security of an electrically dead system.

Yep, this is something I've brought up before... on both my batteries, I have a full disconnect. On my LFP, it goes Battery+ -> Class-T Fuse -> Disconnect -> Unswitched positive bus (which in turn feeds my load and charge contactors). If I want to kill the system dead, to work on it, say changing the class t, or re-working the wiring, I can fully disconnect the battery manually.

One of the key safety things, though, is that I have my wiring laid out such that there is no way the unfused heavy wires from the + of the battery can physically reach anything connected to the negative bus. It's all kept deliberately short.

On the Lead Acid Starter side of my system, I also have a main battery disconnect primarily so that I can kill my engine dead. This is both theft protection, and safety when working on the engine. It's not full lockout/tagout (as you can't lock the Blue Sea 6006), but its good enough for my purposes.

With both disconnects open, the only thing that will remain powered on in the system is the BMS on the LFP, and the monitor on my starter battery. Everything else is completely dead.

 

[svsagres]

Revision 10-2-2022
See Post #380 Diagram Changes to make
I have two open questions that I know of:
1. Have I shown the REC BMS VE.CAN and WS500 VE.CAN correctly?
2. At the starter battery, do I need an on/off switch between the battery and the bus bar? If so, would a 250A mbta suffice?

I am hoping that I am almost finished with this!
I need to complete the list of equipment.

View attachment 114564View attachment 114565

Very minor correction, you'll want to move the alternator shunt to the positive (B+) side of the alternator, as your alternator isn't an isolated return model. WS500 is fine with a high side shunt. Also, because the REC is designed for dual channel operation, if you want to run it with a single contactor, you'll need to wire both CH and DCH relays outputs in series to make a "Wired AND" circuit. The BMS really is intended for dual bus operation.

 

[rgleason]

Very minor correction, you'll want to move the alternator shunt to the positive (B+) side of the alternator, as your alternator isn't an isolated return model. WS500 is fine with a high side shunt. Also, because the REC is designed for dual channel operation, if you want to run it with a single contactor, you'll need to wire both CH and DCH relays outputs in series to make a "Wired AND" circuit. The BMS really is intended for dual bus operation.

Thanks I was wondering about the BMS relays, thats a good solution.

On the diagram will note the alternator Delco Remy 28SI 12v 160a #360312 - dual fan, negative ground, J180 short hinge mount, rotation clockwise, temp rating 125°C / 257°F, 10000 rpm continuous. Modified for external regulator. It just has a ground screw on the casing so it is not isolated ground.

 

[rgleason]

Post #93 Summary ABYC and Major Requirements

Post #247

Post #280

See Post #383 John Harries checked, a response to Bruce Schwab's...

See Post #383 John Harries wrote: All that said, if it were me I would consider installing an all Victron or Lithionics system with duel busses and then hide behind:

Post #261

Offgridsolutions Post #10 Benv Comments



Post #256


Post #390 Goboatingnow


Post #242 Panbo identification of ABYC E-13 items:


Post CF #65


Post #349 and Post #340


CF Post #48
Originally Posted by s/v Jedi View Post

Goboatingnow wrote:


Post #339

Post #160

Post #92

Post #141

Summary ABYC and Major Requirements - continued from Post #378
We've run out of space for adding to this reply, so I've added another reply in order to continue.

Offgridsoftwaresolutions.com Post #11 by @Goboatingnow

One point I feel very excercised on and I see it pop up across many forums

HVE and LVE should be configured to be serious safety trip points and if they occur should be treated so. Both should NEVER occur in a properly functioning Li system. Low SOC alarms should trigger well before LVE and charge stop should occur well below HVE

Hence consistent with ABYC and ISO I would argue on these events the battery is disconnected from all load and charge sources.

Then after manual inspection and cause determination should the appropriate overrides be activated which can (a) switch in alternative power sources (b) reconnect charge sources ( c) reconnect loads.

A bms should NEVER decide to allow charge sources to remain connected on LVE or loads on HVE. The BMS HAS NO IDEA what caused the lve or hve and hence to have it leave charge sources or loads connected on any combination of these safety trips is not “ safety first. “

We must get away from the false notion that LVE or HVE are benign common situations in a normal system. They are not . On HVE LVE over temp and over current which all result in complete LI disconnect, no automatic re connection should occur without manual inspection and then manual intervention process depending on what’s discovered.

For me, a definitive statement that should dispel any of my wayward ideas. Thank you.

 

[Goboatingnow]

Summary ABYC and Major Requirements - continued from Post #378
We've run out of space for adding to this reply, so I've added another reply in order to continue.

Offgridsoftwaresolutions.com Post #11 by @Goboatingnow

For me, a definitive statement that should dispel and of my wayward ideas. Thank you.

Forgive me if I come across as “ prescriptive “ but I feel the whole point of ABYC and ISO and also a safety first perspective should pertain , and that everything else should fall in line

 

[rgleason]

Revision 10-3-2022 adding disconnects at both batteries, moving alternator shunt to positive.
Hopefully this is 98% complete. Thank you Goboatingnow, svsagres and wholybee. I could not have gotten this far without all your help! It is a great feeling to have some confidence about this diagram due help from to my excellent teachers!