LiFePo4 High Level Schematic

[Steve_C]

Originally Posted by ronstory

I noticed you are setting up separate charge and discharge busses, but have an inverter/charger connected to the discharge bus. If you want to keep the charge and discharge busses, you will likely need a dedicated charger and separate inverter.

Or you can just combine charge / discharge sources/sinks but managing the HVC and LVC gets tricky. That said, you have canbus, so there may be some cool thresholds you can do with the I/C but make sure that critical DC items like bilge pump will still get power.

Will you have a backup battery?

Yeah I really was in a quandary about that for a while and with a device that can be both a load and a charger it can very confusing. I actually have a third ML-RBS that I could use as a main contactor to disconnect everything, but I don't think I need it.

The primary control for all of the charge and discharge functions should be handled by the settings of the BMS and communicated between the BMS, The Iverter-Charger and the other charging devices by the CAN bus and the VE Con connections. The HVC and LVC switches are for backup in case the others don't work as they are supposed to. The switch for the Load (Dis-Charge) bus is there to disconnect all loads in case voltage is low, and if this happens I am assuming the Inverter/Charger is NOT charging, but could be pulling load as an inverter so I want it disconnected. The Solar array and the alternator would still be connected to provide charging at this point.

If the voltage is getting high, I also may need to disconnect the Inverter/Charger. First I would disconnect the Charge bus and if the voltage was still climbing, the Main disconnect setting could also be tied to the LVC to open it. At this point the Bank would be isolated and safe.

I will also have an alarm and a LED light to alert me if there is a HV or LV issue.

I also want to be able to manually connect or disconnect at this point because something would be malfunctioning and I may need to manually control things till I can get it fixed.

Let me know if my logic sounds right, I appreciate anyone trying to help me find flaws in my layout especially now while its just a drawing!

[Steve_C]

The BMS, (I am leaning towards the Orion Jr 2) (https://www.orionbms.com/products/orion-jr2-bms/) uses signal outputs that are negatives (draw to ground). This enables them to work with multiple voltages. There are other safety factors as well, but you can read about that in their wiring guide. https://www.orionbms.com/manuals/pdf...ing_manual.pdf

Since I need a positive 24 volt output for my Blue Sea RBS switches, and I want manual and override and remote capability. I designed a small relay interface that would not only achieve what I need, but would also allow me to use the main contactor output from the BMS to provide the 24 volt Line voltage to both the HVC and LVC relays.

By doing this, the HVC and LVC can only be closed if the Main Contactor circuit is energized. If that circuit is de-energized, both switches would open and isolate the bank. You will also see I added a circuit to go out to the "Override" switches that would enable me to remotely open or close the main contactor circuit, or just close the HVC or LVC switches.

Please let me know if I am missing something.

[ronstory]

With the inverter/charger in the system, you may be better off just merging all the charge sources and discharge devices into a single bus. Then you would just need one contactor to 'pull the plug' on HVC or LVC event.

I would think about having the bilge pump wired directly to the battery so if the out of range voltage happens, you can still keep the boat afloat.

Alternatively, you could add a backup battery and keep it healthy through a Battery-to-Battery charger and wire the bilge pump to that.

Our boat has an gasoline atomic 4 motor, so with 6.3:1 compression... I just need 9ish volts to get the ignition to fire. Since it comes with a hand crank and it's really easy to get to hand start... I'm thinking about eliminating the backup battery. However, I would not do that it we had a diesel.

[mbartosch]

Originally Posted by Steve_C

Yeah I really was in a quandary about that for a while and with a device that can be both a load and a charger it can very confusing.

You were given an answer with a simple and low-tech solution, yet you choose to ignore it. Ah, the Internet.

[CatNewBee]

Originally Posted by Steve_C

The BMS, (I am leaning towards the Orion Jr 2) (https://www.orionbms.com/products/orion-jr2-bms/) uses signal outputs that are negatives (draw to ground). This enables them to work with multiple voltages. There are other safety factors as well, but you can read about that in their wiring guide. https://www.orionbms.com/manuals/pdf...ing_manual.pdf

Since I need a positive 24 volt output for my Blue Sea RBS switches, and I want manual and override and remote capability. I designed a small relay interface that would not only achieve what I need, but would also allow me to use the main contactor output from the BMS to provide the 24 volt Line voltage to both the HVC and LVC relays.

By doing this, the HVC and LVC can only be closed if the Main Contactor circuit is energized. If that circuit is de-energized, both switches would open and isolate the bank. You will also see I added a circuit to go out to the "Override" switches that would enable me to remotely open or close the main contactor circuit, or just close the HVC or LVC switches.

Please let me know if I am missing something.

The auto-reset blue sea solenoids draw always 10+ mA power, no matter if open or closed. Just keep this in mind. The REC ABMS has potential free relay outputs, no need to add another relay inbetween, also an impulse creation is then meaningless. You can also use a simple transistor to invert the signal, no need for a relay.

[Wood]

Originally Posted by Steve_C

Yeah I really was in a quandary about that for a while and with a device that can be both a load and a charger it can very confusing. I actually have a third ML-RBS that I could use as a main contactor to disconnect everything, but I don't think I need it.

Why not a HVD relay on the 110v charger supply?

[Steve_C]

Originally Posted by ronstory

With the inverter/charger in the system, you may be better off just merging all the charge sources and discharge devices into a single bus. Then you would just need one contactor to 'pull the plug' on HVC or LVC event.

I would prefer to be able to disconnect the Charge Source (Solar and/or Alternator) and keep the Dis-Charge connected to allow for the DC to operate and use power. Having a second contactor seems a minor addition to have this capability.

I would think about having the bilge pump wired directly to the battery so if the out of range voltage happens, you can still keep the boat afloat.

Alternatively, you could add a backup battery and keep it healthy through a Battery-to-Battery charger and wire the bilge pump to that.

Definitely, I will have the bilge pumps powered no matter what. I will determine my exact method later, for now I am trying to just make sure I sort out the Main house bank protection and charging scheme

Our boat has an gasoline atomic 4 motor, so with 6.3:1 compression... I just need 9ish volts to get the ignition to fire. Since it comes with a hand crank and it's really easy to get to hand start... I'm thinking about eliminating the backup battery. However, I would not do that it we had a diesel.

Thanks for the Feedback!

[Steve_C]

Originally Posted by mbartosch

You were given an answer with a simple and low-tech solution, yet you choose to ignore it. Ah, the Internet.

Hi mbartosch,

I actually didn't really get your earlier post because it was so short, I got distracted and meant to go back and give it some attention. I re-read it and gave it some thought and see that it is indeed very clean and simple.

I would still need a LVC for the load buss (between the bus and the bank), a second HVC for the Solar and alternator, and a third for AC input of the I/C??

Sorry if I need more clarification, I am indeed open to any simpler solution.

Thanks for helping me understand what you are proposing!

[Steve_C]

Originally Posted by CatNewBee

The auto-reset blue sea solenoids draw always 10+ mA power, no matter if open or closed. Just keep this in mind. The REC ABMS has potential free relay outputs, no need to add another relay inbetween, also an impulse creation is then meaningless. You can also use a simple transistor to invert the signal, no need for a relay.

I actually called and talked to Blue Sea about this, the tech said that the 24 volt version actually only uses about 3 mA when not switching and about 10 mA when changing state on the control circuit. He said its higher than that for the 12 volt. Apparently that's why they use the <13 mA in the specs to be conservative. I am actually going to test and verify that later today. I plan to measure both with and without the LED. I will report back what I find with the 7717 current draw.

Since I am going with 24 volt, I would be forced to use a different REC BMS than the "REC Active" as that is only 12V and 4 cell only. The REC Q 16s is very different and has only one relay and two digital optic ports available. There are other limitations as well compared to the active. I have been talking to Maja at REC and learned they are working on a new version of the REC Q 16s but it wont be out for a long time and he can't release the specs yet because they are still working on them. He did verify that the new one will still have only one relay and the same optical ports.

Thanks CatNewBee!

[mbartosch]

Originally Posted by Steve_C

I would still need a LVC for the load buss (between the bus and the bank), a second HVC for the Solar and alternator, and a third for AC input of the I/C??

You can normally attach all loads to a single load bus, no special requirements here.

All non-inductive DC charging sources which can be just "switched off" can be attached to a common charge bus controlled by a single HVC relay/contactor. This could apply to sources like solar chargers or fuel cells. Check with the documentation of the charge source if it is OK to drop the load.

The challenge is typically properly shutting down inductive charging sources. Note that there is nothing wrong with having multiple HVC relays, each performing the special task to shut down a charging source. This often makes the overall design much simpler or even possible at all.

Alternator: cut regulator power or ignition signal. A dedicated NC HVC relay for this purpose may be the proper answer.

Inverter/charger: as mentioned, load side can be attached to load bus. For the AC side use a similar trick as for the alternator, but of course with a different relay, as it carries high voltage AC.

Similar approaches for other charging sources.

I am reluctant to plug Entropy's design again, but a lot of these issues have been elaborately explained on this blog post.

[Steve_C]

Originally Posted by Wood

Why not a HVD relay on the 110v charger supply?

I would still need one also on the load bus as well as the Solar/Alternator input, so that would be 3 total!

[mbartosch]

Originally Posted by Steve_C

I would still need one also on the load bus as well as the Solar/Alternator input, so that would be 3 total!

Yes. Where's the problem?

[Wood]

Originally Posted by Wood

Why not a HVD relay on the 110v charger supply?

Yup. Someone will correct me if I'm wrong but I think the REC ABMS can have more than one relay on the HDV & LVD.

[Steve_C]

Originally Posted by mbartosch

You can normally attach all loads to a single load bus, no special requirements here.

All non-inductive DC charging sources which can be just "switched off" can be attached to a common charge bus controlled by a single HVC relay/contactor. This could apply to sources like solar chargers or fuel cells. Check with the documentation of the charge source if it is OK to drop the load.

The challenge is typically properly shutting down inductive charging sources. Note that there is nothing wrong with having multiple HVC relays, each performing the special task to shut down a charging source. This often makes the overall design much simpler or even possible at all.

Alternator: cut regulator power or ignition signal. A dedicated NC HVC relay for this purpose may be the proper answer.

Inverter/charger: as mentioned, load side can be attached to load bus. For the AC side use a similar trick as for the alternator, but of course with a different relay, as it carries high voltage AC.

Similar approaches for other charging sources.

I am reluctant to plug Entropy's design again, but a lot of these issues have been elaborately explained on this blog post.

I am studying the link to Entropy you sent, Its very helpful but I need some time with it (It is a work day for me) It does not seem drastically different. It's a little harder to completely interpret due to the way the schematics are drawn and some of the symbols used.

One of the reasons I am doing what I am with my schematic is the level of frustration I have had trying to find a simple clear representation of a design that's easy to understand and directly apply to my situation. That's why I started simple and will add details as I go. I am hoping the end product will be useful to others. There are SO MANY posts out there, and SO MUCH information its actually confusing.

I am very visual, and I REALLY need to make sure I can see and follow each circuit and think thru each scenario as I finalize my plan.

I also want to make sure to have a very clear document to use later as a reference to my own system. I have seen a lot of early designs on CF and then discussions about how they have changed their minds and are altering the design, but they never actually create a schematic for the final design, or at least never share it.

I really like the idea of an additional HVC to cut the AC input of the I/C. Although I will be living on-board and actually will rarely be connected to AC power. I am initially not planning on having a generator at all.

As I move forward I will focus more on the HO Altenator, and will plan on using the output from the Victron BVM to inteligently shut down the alternator output well before any HVC action occurs. In my mind the HVC is a last ditch emergency action to protect the bank. In practice I hope it never actually gets used. I would see it being used to isolate the bank for system work and safety far more often than anything. Thats one of the things I like about the Blue Sea switches is that I can lock them out (Open) while doing any work on the system.

Thanks for the info and input!

[mbartosch]

Originally Posted by Steve_C

As I move forward I will focus more on the HO Altenator, and will plan on using the output from the Victron BVM to inteligently shut down the alternator output well before any HVC action occurs. In my mind the HVC is a last ditch emergency action to protect the bank. In practice I hope it never actually gets used.

Think outside the box.

You will have a LiFePO4 bank which enjoys being held in the middle SoC ranges and which does not like being held near full SoC. Sure, when cruising you want to store and use every Joule of energy your solar cells produce, but at anchor the story may be different. At least we noticed that is the case for us.

When in "at anchor mode" for prolonged time I found it very useful to be able to completely shut down charging sources administratively, to keep the bank e. g. below 80 % even though the sun is shining.

If I am not mistaken, the BMS you plan to use pulls HVC output to ground if HVC is active, so you can adopt the same idea:

You can pull BMC HVC output to ground externally (e. g. with a switch or a relay) and thus simulate a HVC to cut off all charging sources. If the system is properly designed you can do this in all operation modes without damaging your system.

I have a manual 3-way switch at the console labeled "Normal charging" - "Stop charging" - "Lazy charging".
"Stop charging" connects the HVC output of the BMS to ground, forcing a simulated HVC.
"Lazy charging" connects ground to the BMV700 relay which in turn is connected to HVC output of the BMV700. Then the BMV700 can turn charging off at, say, 80% and on again at, say 60 % SoC. Actually we use "Lazy charging" a lot when at anchor.