Small Boat BMS/LFP with backup

[Goboatingnow]

I wonder how much current these will use over 24hrs and how they compare to the more expensive Bluesea.

They are the exact same component. This TE product is the blue sea component.

The TE has the same “ economiser “ circuit which drops the current to 130 mA like the blue sea one

 

[Goboatingnow]

@Goboatingnow So is it a manual bypass switch for both relay coils CH "B" and DCH "C" or just one?

I would have at least one manual override for every remotely controlled or “smart “ disconnect device.

Where I had one combined disconnect ie CH and DCH , I would have two manual overrides to allow the CH bus to be reconnected while leaving off the CH bus.

 

[Tribune]

Really good content on here. This is going to help me huge while I plan my installation. I've been unable to find the TE contactors anywhere near $50. Would anyone have a link to provide.
Cheers

 

[Goboatingnow]

Really good content on here. This is going to help me huge while I plan my installation. I've been unable to find the TE contactors anywhere near $50. Would anyone have a link to provide.
Cheers

https://a.aliexpress.com/_mPQ9QVK. This is the 500A version smaller variants are a bit less , as you can see it’s the economiser version ( 130mA hold current )

 

[Tribune]

Perfect, thank you so much.

 

[Goboatingnow]

Perfect, thank you so much.

Shows you the blue sea markup for the exact same component !!

 

[Tribune]

Just ordered 4 with the aux contacts. Couple for the boat and couple for the plane I'm building.

 

[rgleason]

I would have at least one manual override for every remotely controlled or “smart “ disconnect device.

Where I had one combined disconnect ie CH and DCH , I would have two manual overrides to allow the CH bus to be reconnected while leaving off the CH bus.

Now understood. Thanks.

 

[Goboatingnow]

Now understood. Thanks.

I meant "leaving off the DCH bus" but I think you understood

 

[rgleason]

I would have at least one manual override for every remotely controlled or “smart “ disconnect device.
Where I had one combined disconnect ie CH and DCH , I would have two manual overrides to allow the CH bus to be reconnected while leaving off the CH bus.
I meant "leaving off the DCH bus" but I think you understood

Well when it comes to diagramming this, I find I need two relays! The two relay coils can operate together or separately. I need them in order to be able to have dual buses. Can you explain what you mean, so I can draw it?
Not comfortable with all the Bypass Switches, and the complicated Emergency FLA, but that's the way it is.

 

[svsagres]

Well when it comes to diagramming this, I find I need two relays! The two relay coils can operate together or separately. I need them in order to be able to have dual buses. Can you explain what you mean, so I can draw it?
Not comfortable with all the Bypass Switches, and the complicated Emergency FLA, but that's the way it is.


View attachment 108766

Actually, it's too bad you're not using the 7713 still, as you could do this even more simply. Just a switch on a jumper between your alternator and your starter, and a manual disconnect to the battery. If you want to swap over, just disconnect the battery, and then create the jump between the starter and alternator. Then your positives are all connected together and everything will run off your FLA. (you'd force the 7713 on manually in that situation).

That's basically what I have planned in mine, just that I have to manually install an 18" piece of 2awg.

 

[Goboatingnow]

Well when it comes to diagramming this, I find I need two relays! The two relay coils can operate together or separately. I need them in order to be able to have dual buses. Can you explain what you mean, so I can draw it?
Not comfortable with all the Bypass Switches, and the complicated Emergency FLA, but that's the way it is.


View attachment 108766

This is the correct way to do it , ( finally ) of you want redundancy and overrides. It offers the most flexibility and fail safe. The two busses CH and DCH can also be enabled remotely as both have contractor disconnects

The alternative is a single load and charge bus , with manual overrides that makes it into two busses CH and DCH. it offers most of the advantages but saves on a contractor and two switches

 

[Goboatingnow]

Actually, it's too bad you're not using the 7713 still, as you could do this even more simply. Just a switch on a jumper between your alternator and your starter, and a manual disconnect to the battery. If you want to swap over, just disconnect the battery, and then create the jump between the starter and alternator. Then your positives are all connected together and everything will run off your FLA. (you'd force the 7713 on manually in that situation).

That's basically what I have planned in mine, just that I have to manually install an 18" piece of 2awg.

Given the TE contactors are $40 and are fail safe ( the 7713 isn’t and costs a fortune ) the diagram offers the most flexibility and redundancy

Manual overrides should not simply attempt to “ force on “ the contactor . They should operate by bypassing it completely , for example if a bad surge took out the Electronics in the 7713 , the control circuit would be dead and the 7713 wouldn’t respond to a manual reconnect process. The manual bypass switch as shown is far superior

 

[rgleason]

I've made some changes and cleaned up the notes a little in this new diagram. I'd like to find a way to show the @svsagres alternatives for "B" Bluesea RMS Latching Switch and "C" Smart BatteryProtect 65 with some pro/con notes

1. Pro: Uses less LFP power (how much daily?) and has a built-in switch
   1. Blueseas ML-RBS 12vdc 7713 8mA when OFF, 13mA when ON, about 0.013a x 24 hours = 0.325 amps/day
   2. Victron Smart Battery Protect 65, on 1.5 mA, off 0.6 ma, 0.0015a x 24 hours = 0.036 amps/day
   3. Whereas the (2) Coil Powered Relay's 0.13a x 24 hours = 3.12amps/day x (2) = 6.24 amps/day, significantly more.
2. Con: May not meet strict/rote insurance adherence to ABYC & ISO. May not be quite as "fail safe" because a one is a mosfet and latching is used.
3. Con: Cost of Latching relay with switch Blueseas ML-RBS 12vdc 7713 $291

Diagram Changes:

1. Revise notes at bottom, alphanumeric id's
2. Clarify BMS Emergency operation and manual overrides and emergency switching.
3. Improve Emergency Switch for SLA, reducing it to one switch.

Questions outstanding directed towards @svsagres regarding operation, Please see Post #196 noting the Questions shown in Brown. Both of you have been outstandingly patient and helpful. Many Thanks.

PS: Regarding using short jumpers, you'll need two jumpers one heavy one and one lighter one for the DC Panel.

 

[rgleason]

@Goboatingnow wrote:

The two busses CH and DCH can also be enabled remotely as both have contractor disconnects

Yes, I suppose I could show a smaller 12v 6a bypass switch for each relay coil as well, but wouldn't that be overkill and somewhat confusing? Would these be powered from the LFP or not?

 

[Goboatingnow]

@Goboatingnow wrote:

Yes, I suppose I could show a smaller 12v 6a bypass switch for each relay coil as well, but wouldn't that be overkill and somewhat confusing? Would these be powered from the LFP or not?

I would not bother with coil based bypass switch , the full monty bypass manual is better

 

[Tribune]

Mbta?

 

[rgleason]

Mbta?

fuse type. Perhaps is should be changed to Mrbf Marine Rated Battery Fuse

Sites-WestMarine-Site

West Marine

www.westmarine.com

MRBF Terminal Fuse Block - 30 to 300A - Blue Sea Systems

Easily and economically satisfies ABYC 7 circuit protection rule by mounting on a 3/8 battery post, battery switch or bus bar.

www.bluesea.com

LATER: Have changed it. Thanks.

 

[Tribune]

Thank you sir.

 

[Goboatingnow]

I've made some changes and cleaned up the notes a little in this new diagram. I'd like to find a way to show the @svsagres alternatives for "B" Bluesea RMS Latching Switch and "C" Smart BatteryProtect 65 with some pro/con notes

1. Pro: Uses less LFP power (how much daily?) and has a built-in switch
   1. Blueseas ML-RBS 12vdc 7713 8mA when OFF, 13mA when ON, about 0.013a x 24 hours = 0.325 amps/day
   2. Victron Smart Battery Protect 65, on 1.5 mA, off 0.6 ma, 0.0015a x 24 hours = 0.036 amps/day
   3. Whereas the (2) Coil Powered Relay's 0.13a x 24 hours = 3.12amps/day x (2) = 6.24 amps/day, significantly more.
2. Con: May not meet strict/rote insurance adherence to ABYC & ISO. May not be quite as "fail safe" because a one is a mosfet and latching is used.
3. Con: Cost of Latching relay with switch Blueseas ML-RBS 12vdc 7713 $291

The TE relay is $45 , is fail safe and draws 130mA holding current , around 3AH per 24 hours.

Way better

Diagram Changes:

1. Revise notes at bottom, alphanumeric id's
2. Clarify BMS Emergency operation and manual overrides and emergency switching.
3. Improve Emergency Switch for SLA, reducing it to one switch.

Questions outstanding directed towards @svsagres regarding operation, Please see Post #196 noting the Questions shown in Brown. Both of you have been outstandingly patient and helpful. Many Thanks.

PS: Regarding using short jumpers, you'll need two jumpers one heavy one and one lighter one for the DC Panel.


View attachment 108822

 

[madmike]

1. A single fail safe contactor , activated by the BMS , disconnects the battery from both load and charge sources , the only remaining item left connected is the BMS.
2. By preference I would seperate load and charge busses , so option 1 needs a contactor on each bus , both contactors disconnect together on BMS safety trip

What about having a single contactor on the negative side of the battery? That way you only need one to break the circuits to both charge and discharge busses.

One each manual (normally closed) switch between the battery + and the charge and discharge busses will allow selecting what should be re-connected to the LFP battery when the contactor is closed (after fixing the BMS-detected problem or activating the manual bypass).

In other words, can "disconnect the battery" mean disconnecting the negative terminal instead of the positive?

 

[svsagres]

What about having a single contactor on the negative side of the battery? That way you only need one to break the circuits to both charge and discharge busses.

One each manual (normally closed) switch between the battery + and the charge and discharge busses will allow selecting what should be re-connected to the LFP battery when the contactor is closed (after fixing the BMS-detected problem or activating the manual bypass).

In other words, can "disconnect the battery" mean disconnecting the negative terminal instead of the positive?

That's how most FET based BMSs work.

However, the REC BMS, which is what @rgleason has settled on (and which I use) is setup/designed for dual high-side contactors.

 

[rgleason]

@svsagres Some questions from Post #196:

1. If the Emergency FLA switch is ON, with the alternator charging the FLA will Alternator be limited to 13.2v? How would you get it to charge SLA normally?
   1. svsagres: Yes the regulator will charge at 13.2v enough to get to a safe harbor.
2. Could CerboGX be powered from the DC Panel so that it will be powered in Emergency FLA mode? Also the GXcolor50 is powered by the CerboGX USB. When the DC panel has power, the CerboGX will work, but is there a better way to power the CerboGX?
   1. goboatingnow: When a BMS shutdown occurs the main resource for relevant information will be from the BMS.
   2. goboatingnow: CerboGX power will be from the DC Panel, which will go dark on a shutdown. Emergency SLA connection will repower it.
   3. svsagres: Not worth powering the CerboGX direct from LFP, the information may not be that relevant compared to the BMS.
3. REC BMS Monitering/Control via RS485/PC or Remote Panel
   1. While sailing, with occurrence of a BMS LFP shutdown, use of a PC and RS485 port is impractical.
   2. While sailing, with occurrence of a BMS LFP shutdown, a Remote Panel would be useful but is an expensive additional device.
   3. Can't the CerboGX + GXcolor50 be used?
      1. svsagres: The only time an LFP is really going to go in shutdown is if you really really abuse it, and you'll see the signs long before it really becomes a problem. In the mean time, do keep an eye on the Cerbo; make sure there is a reasonable SoC, and that it's doing what it should be doing.
4. Actions needed upon BMS LFP shutdown:
   1. Use the boat's multimeter to determine the state of the battery. Voltage of each cell? Total voltage?
   2. Check temperatures with an infrared device.
   3. If the CerboGX is powered will we have access to BMS and WS500 information?
   4. If both "B" CH and "C" DCH are failed "open", Turn on the Emergency FLA switch to power up the DC Panel and CerboGX.
   5. If just "B" CH is failed "open" then the discharge bus is still on so the DC Panel and CerboGX is powered. *
   6. If just "C" DCH is failed "open then there is no power to the DC Panel or CerboGX. Somehow force both "B" and "C" to fail open and only then Turn on the Emergency FLA switch to power up the DC Panel and CerboGX. *
   7. With BMS separated "B" and "C" action, you at least have some idea of what the shutdown failure was! *

Note * 5, 6 & 7 ABYC wants both of these relay coils to open for any BMS shutdown which, then obscures the reason for the shutdown and which then requires a more complete investigation for the shutdown.

svsagres:

1. Give the whole thing a visual inspection and sniff test. If something is overheating, it's going to smell.
2. Check the battery voltage with my DMM. If it's reasonable, cycle the REC off then back on again to see if it comes back
3. Assuming it's completely off, start my engine and head to safe space so I can deal with it without stress. I navigate with an iPad, and have a handheld vhf for the dinghy, so I can safely get to where I need to go.
4. If the battery voltage looks good, and reasonably balanced (verified with my DMM), I'll force my BatteryProtect back on and run without the BMS. At the fractional C my DC system draws, I can generally go 3 to 4 days on the battery alone without putting it in danger. Again, this is an emergency situation, but good enough to get me 3 days home from Desolation Sound or similar to my home marina where I can properly deal with the battery system. If the LFP battery itself is bad (low voltage, bad cells, etc...) I can fully disconnect the LFP, jumper my FLA starter over, and run on that in limp mode and get home that way.

Goboatingnow:

On bms trip
determine trip nature. The BMS must tell you why
(A) HVC , examine bms info or use multi meter to determine which cell or whole battery Examine cell. , activate manual DCH override to discharge battery. Reset bms. Suspect charge bus devices.
(B) LVC. again determine cell affected of if whole battery affected , manual override CH bus. Charge and re enable bms
( D ) overtemp
Examine battery. If serious evidence do not override bms. Do not reconnect DCH or CH. disable contactor
E) overcurrent , test load devices for shorts check fuses. , disconnect loads , enable BMS , selectively enable load while monitoring current
Note the manual overrides could be low cost latching relays controlled by a switch fed from the FLA. , this allows the relays to be mounted remotely and they take up less room.

 

[svsagres]

@svsagres Some questions from Post #196:

1. If the Emergency FLA switch is ON, with the alternator charging the FLA will Alternator be limited to 13.2v? How would you get it to charge SLA normally?

Yes, but in this case, we're in limp mode. It doesn't need to work perfectly, it just needs to work well enough to get to some place safe so that you can fix things properly. Yes, it's probably an "end of trip" situation, but you're still safe.

1. Could CerboGX be powered from the DC Panel so that it will be powered in Emergency FLA mode? Also the GXcolor50 is powered by the CerboGX USB. When the DC panel has power, the CerboGX will work, but is there a better way to power the CerboGX?

Sure, but you need to make sure that it doesn't think that it's monitoring/controlling the LFP at that point.

1. REC BMS Monitering/Control via RS485/PC or Remote Panel
   1. While sailing, with occurrence of a BMS LFP shutdown, I do find use of PC and RS485 practical.
   2. While sailing, with occurrence of a BMS LFP shutdown, a Remote Panel would be useful but an expensive additional device.
   3. Can't the CerboGX + GXcolor50 be used?

As long as you keep an eye on things, this is a situation that will never happen. I would say you have a greater chance of your fuel system failing, your mast breaking, or a through-hull breaking off. The only time an LFP is really going to go kaput is if you really really abuse it, and you'll see the signs long before it really becomes a problem. In the mean time, I do keep an eye on the Cerbo; make sure I have a reasonable SoC, and that it's doing what I think it should be doing.

• Actions needed upon BMS LFP shutdown:
  1. Use the boat's multimeter to determine the state of the battery. Voltage of each cell? Total voltage?
  2. Check temperatures with an infrared device.
  3. If the CerboGX is powered will we have access to BMS and WS500 information?
  4. If both "B" CH and "C" DCH are failed "open", Turn on the Emergency FLA switch to power up the DC Panel and CerboGX.
  5. If just "B" CH is failed "open" then the discharge bus is still on so the DC Panel and CerboGX is powered. *
  6. If just "C" DCH is failed "open then there is no power to the DC Panel or CerboGX. Somehow force both "B" and "C" to fail open and only then Turn on the Emergency FLA switch to power up the DC Panel and CerboGX. *
  7. With BMS separated "B" and "C" action, you at least have some idea of what the shutdown failure was! *

Note * 5, 6 & 7 ABYC wants both of these relay coils to open for any BMS shutdown which, then obscures the reason for the shutdown and which then requires a more complete investigation for the shutdown.

If I actually had a shutdown, it's going to be due to something weird. I'd probably do the following:

1. Give the whole thing a visual inspection and sniff test. If something is overheating, it's going to smell.
2. Check the battery voltage with my DMM. If it's reasonable, cycle the REC off then back on again to see if it comes back
3. Assuming it's completely off, start my engine and head to safe space so I can deal with it without stress. I navigate with an iPad, and have a handheld vhf for the dinghy, so I can safely get to where I need to go.
4. If the battery voltage looks good, and reasonably balanced (verified with my DMM), I'll force my BatteryProtect back on and run without the BMS. At the fractional C my DC system draws, I can generally go 3 to 4 days on the battery alone without putting it in danger. Again, this is an emergency situation, but good enough to get me 3 days home from Desolation Sound or similar to my home marina where I can properly deal with the battery system. If the LFP battery itself is bad (low voltage, bad cells, etc...) I can fully disconnect the LFP, jumper my FLA starter over, and run on that in limp mode and get home that way.

 

[rgleason]

@svsagres Thank you. That is a basic helpful emergency approach.

1. Is BMS power is directly connected to the LFP on the LFP side before the disconnects (otherwise it will shut itself off)?
2. Do you know what power the REC BMS draws?
3. Where do you power the CerboGX from?
4. Does it stay powered after a REC BMS shutdown?
5. I believe that CerboGX power (black & red connection at the lower right) is just for power, it has nothing to do with sensing. If that is true, it could be powered from the SLA!
6. After a BMS shutdown, if the CerboGX remains powered, will it provide more BMS / Wakespeed/ LFP information? (Obviously the other chargers, solar MPPT and Phoenix 120vdc charger are shut down so there is no information)