Question from one of your videos

[JonathanEdwards]

You mentioned that you should use a separate port bms to keep it from shutting down victron solar charge controller and damaging it if the system faulted. I recently bought a victron controller. I received a common port 200amp bms with the batteries I bought from china. I do not want to damage my controller and you mentioned that you would recommend one in your video comment section but I am not sure which one it is. Do you recommend a specific one? Also I bought the 200 amp battery protect to use on the system. Is it already out dated and there are a better way? Tks John

 

[Dzl]

You mentioned that you should use a separate port bms to keep it from shutting down victron solar charge controller and damaging it if the system faulted. I recently bought a victron controller. I received a common port 200amp bms with the batteries I bought from china. I do not want to damage my controller and you mentioned that you would recommend one in your video comment section but I am not sure which one it is. Do you recommend a specific one? Also I bought the 200 amp battery protect to use on the system. Is it already out dated and there are a better way? Tks John

If I understand what you are describing, you will not damage your Victron MPPT if your common port BMS disconnects (just as you wouldn't damage it if your separate port BMS disconnected). The trouble with a common port is that if a low voltage event triggers your BMS, it will disconnect loads and charging which is usually less than ideal. You will have to manually reset or charge somehow (not sure of the specifics).

What is your goal with the Victron Battery Protect? It is intended to be used as a low voltage disconnect for DC loads. There are two things it cannot do (1) be in between your battery bank and inverter (2) be bi-directional, current should only be allowed to flow one way through it.

 

[JonathanEdwards]

So if it is connected in-between the battery bank and the inverter then current would only be flowing in one direction correct. But actually now that I think more about it, the inverter has low voltage cutoff in it already so the battery protect would not be needed in this system but I can use it in another system. My biggest concern is where can I get a separate port bms, at least 200 amps, that will not cut the charging if you have a low voltage trigger?

 

[JonathanEdwards]

Actually since the inverter can also charge the battery bank the statement about the the current only flowing in one direction thought the battery protect is not correct I think but I will not be using it on this system anyways. I just need at least a 200A separate port BMS.

 

[Dzl]

So if it is connected in-between the battery bank and the inverter then current would only be flowing in one direction correct.

Actually since the inverter can also charge the battery bank the statement about the the current only flowing in one direction though the battery protect is not correct

It wouldn't matter either way because of point (1) a battery protect cannot be used directly between a battery and inverter.

My biggest concern is where can I get a separate port bms, at least 200 amps, that will not cut the charging if you have a low voltage trigger?

How much charge current do you need to accomodate? Daly has BMS' up to 250A which might be able to handle 200A continuous reliably, but on the separate port versions charge current is much lower.

At 200A a non FET based BMS (like the Chargery BMS) may be worthwhile. This is good all the way up to 600A and controls charging and discharging separately.

 

[JonathanEdwards]

Well, I will answer you first question last in my reply. I was thinking of the surge current the system would sometimes need to handle. So that is why I was looking to put a 200amp bms on the system. The added capacity can never hurt. It is just sometimes an added expense that may not be necessary, but in my case I think it is a good idea. My inverter has the charging ability from the grid as mentioned earlier and it has three charging settings low, med, high. I would have to contact Mppsolar about the specs on those because I am married now so shit is never where you put it last. Referring to my manual. I went to their websight but could not find my inverter now. But if you look at their instillation gallery you can see my system at the bottom of that page, last three pics from the bottom only one extra pic at bottom after my system. My system is one with cabinet and yellow inverter mounted on top. No longer using the deep cycle battery banks shown in pics. The Lifepo4 cells and bms is something I have not used, so I was trying to pick your brain to try an keep from screwing something up. I have learned a lot from your videos. You say the separate port bms has a lower charge current capacity than common port. Would you happen to know what the top current that might be? If my memory recall is correct I believe the charge current is 60, 80, and 100 amps depending which one you select. Low, med or High. I could keep it on low in order to use the separate port model if it can handle like 60 to 80amps. If you know of one, can you give me a link? Best regards and thanks for your help, John

PS. I take it that the only way to keep your charge controller charging if your bms faults from low voltage and cuts off is to use a separate port bms. Does that statement sound correct?

 

[Dzl]

I have learned a lot from your videos.

Just to clarify, I'm not Will. Just a fellow forum member trying to help you out where I can.

My inverter has the charging ability from the grid as mentioned earlier and it has three charging settings low, med, high. I would have to contact Mppsolar about the specs on those because I am married now so shit is never where you put it last.

This made me laugh

Well, I will answer you first question last in my reply. I was thinking of the surge current the system would sometimes need to handle. So that is why I was looking to put a 200amp bms on the system

Ahh okay, this makes sense. What is the continuous power output of your inverter?

You say the separate port bms has a lower charge current capacity than common port. Would you happen to know what the top current that might be? If my memory recall is correct I believe the charge current is 60, 80, and 100 amps depending which one you select.

It will depend on the model, I think this is something you would want to confirm with Daly directly. For separate port BMS' above 150A (the next sizes up are 200A and 250A) I believe you have to custom order, At least that's the impression I get from the Aliexpress page.
Often with separate port BMS, charge current is about 1/4 to 1/2 of discharge current.

There is also this BMS sold by overkill solar it is limited to 120A discharge current, but it can apparently handle 100A charge current

Then there is the chargery BMS which is more sophistcated. A lot of people on this forum have experience with it. Will did not find it to be very beginner friendly in his review of it, but many people like it. It can handle 200A (charge and discharge) easily using relays.

PS. I take it that the only way to keep your charge controller charging if your bms faults from low voltage and cuts off is to use a separate port bms. Does that statement sound correct?

Yes, I think that sounds correct (technically there are two types 'separate port' and what is called 'hybrid port' but basically they function mostly the same). Technically you can connect the charge controller to your battery bypassing your BMS, and then a common port BMS will only disconnect discharging, but then you lose the overcharge protection of the BMS. Some more experienced or old school (pre-affordable-BMS) lifepo4 folks do this, but I don't think that's advisable unless you are experienced or risk tolerant.

 

[JonathanEdwards]

I seen your video called solar inverter control w / optocoupler SSR and bms but unfortunately my system has a network cable connected to a remote module with the on off buttons etc. and like you said you have to hold down the button to get the inverter to start. Probably using microprocessor to scan switch so you must hold down for like 3 sec. I also used SSR and PLC to switch on and off ac input to inverter but eventually I believe noise or voltage spikes from switching SSR took out my temp. monitoring circuits for my batteries. ( They were 4 of them and they each had a control board with seven segment displays etc.) I am still trying to understand how to suppress the noise created by the switching SSR. If I could, I could make system improvements. Thanks for the ideas just the same and the video. You have a very advanced knowledge. Have you ever worked any with PLCs ? Do you have an engineering degree or something? Thanks again, John