BMS common port vs seperate port

[JanVJ]

I prefer common port, less wires to fix to the BMS, easier to change around.

The 200A JK bms in my current project do separate the charge and discharge.
No extra wire connections.
Its all done with app controlled internal mosfets

 

[John Frum]

I am.... using a BMS with separate port capability.... in my current project.

In my project I am using a JK 200A BMS (B2A8S20P)

To my knowledge the BMS could handle 200A in both directions.
And both charge and discharge directions could be separate controlled from app.

Please provide a product link to the bms in question.

I found this one and i appears to be a common port bms not separate.

134.21US $ |Jikong 2a Active Balance Bms 150a Canbus Rs485 Bt 36v 48v 60v Li-ion Lto Battery 18650 Battery Lifepo4 Battery Storage - Battery Accessories & Charger Accessories - AliExpress

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[JanVJ]

Please provide a product link to the bms in question.

I found this one and i appears to be a common port bms not separate.

134.21US $ |Jikong 2a Active Balance Bms 150a Canbus Rs485 Bt 36v 48v 60v Li-ion Lto Battery 18650 Battery Lifepo4 Battery Storage - Battery Accessories & Charger Accessories - AliExpress

Smarter Shopping, Better Living! Aliexpress.com

www.aliexpress.com

I bought the B2A8S20P (200A)

Its a common physical connection,
But you can separate control the two directions
You can enable or disable charge (or discharge) in app

Hope I did not misunderstand the functions or the definition of a «common port»


JK BMS 1A 2A 5A Balance Current 8S 12S 13S 14S 16S 17S 20S 24S Smart JK Bms 60A 80A 100A 150A 200A 600A Lifepo4 Li-Ion Battery

45.94US $ 29% OFF|Jk Bms 1a 2a 5a Balance Current 8s 12s 13s 14s 16s 17s 20s 24s Smart Jk Bms 60a 80a 100a 150a 200a 600a Lifepo4 Li-ion Battery - Battery Accessories & Charger Accessories - AliExpress

Smarter Shopping, Better Living! Aliexpress.com

a.aliexpress.com

 

[John Frum]

I bought the B2A8S20P (200A)

Its a common physical connection,
But you can separate control the two directions
You can enable or disable charge (or discharge) in app

Hope I did not misunderstand the functions or the definition of a «common port»


JK BMS 1A 2A 5A Balance Current 8S 12S 13S 14S 16S 17S 20S 24S Smart JK Bms 60A 80A 100A 150A 200A 600A Lifepo4 Li-Ion Battery

45.94US $ 29% OFF|Jk Bms 1a 2a 5a Balance Current 8s 12s 13s 14s 16s 17s 20s 24s Smart Jk Bms 60a 80a 100a 150a 200a 600a Lifepo4 Li-ion Battery - Battery Accessories & Charger Accessories - AliExpress

Smarter Shopping, Better Living! Aliexpress.com

a.aliexpress.com

Single Port BMS MOSFETs Explained

Single Port BMS MOSFETs Explained

diysolarforum.com

 

[JanVJ]

Single Port BMS MOSFETs Explained

Single Port BMS MOSFETs Explained

diysolarforum.com

For sure I did misunderstood the definition of "separate" and "common" port....

 

[Tex]

The only commodity BMS I'm aware of that has separate port capability is Daly.
Its low current and dumb(non configurable).
Just about nobody on this forum is making new projects with a commodity separate port BMS.
I wonder why this thread continues to accumulate.

That was a long time ago, Daly's now have Bluetooth and will do 100 amps easily (but you must specify).
Their ordering systems and communications is crap though.

 

[John Frum]

That was a long time ago, Daly's now have Bluetooth and will do 100 amps easily (but you must specify).
Their ordering systems and communications is crap though.

Link please.

 

[fratermus]

https://www.amazon.com/DALY-LiFePo4-Bluetooth-Module-Common/dp/B09797CJTF here's one one amazon that appears to fit the description

 

[John Frum]

https://www.amazon.com/DALY-LiFePo4-Bluetooth-Module-Common/dp/B09797CJTF here's one one amazon that appears to fit the description

That is a common port bms.

 

[BigBrosMo]

@GXMnow in post #109 and subsequently you mentioned that your JK BMS still kept your SCC alive during a LVD so that it could still charge your bank. Are you certain? Which BMS? I think that might have been momentary/situational.

The reason I ask is because I have a JK (the 8s200a) and I ran into the problem the other day where it disabled discharge under UVP and the SCC turned off because of it. Subsequently the next day the SCC did not come back on until I was able to manually intervene.

@smoothJoey might find this interesting as we are discussing in another thread but my latest testing has shown that if BMS disables discharge BUT the solar is working the SCC stays on. As soon as the solar stops the SCC powers off. Oddly... In the condition that I have BMS discharge off, but the SCC is running because there is PV input, if I disconnect the positive battery input, it shuts off immediately. I don't understand that one.

 

[John Frum]

In the condition that I have BMS discharge off, but the SCC is running because there is PV input, if I disconnect the positive battery input, it shuts off immediately.

You mean the solar charge controller shuts off?
Does it recover when you reconnect the battery input?

 

[HRTKD]

@smoothJoey might find this interesting as we are discussing in another thread but my latest testing has shown that if BMS disables discharge BUT the solar is working the SCC stays on. As soon as the solar stops the SCC powers off. Oddly... In the condition that I have BMS discharge off, but the SCC is running because there is PV input, if I disconnect the positive battery input, it shuts off immediately. I don't understand that one.

I've seen the same thing. I turned off my system using the switch at the battery bank and forgot to turn off power from the PV before doing that. I was left scratching my head trying to figure out why my stuff was still running. Eventually the lightbulb lit up (dimly though).

 

[John Frum]

I guess some solar charge controllers that auto-detect voltage need to see battery voltage during initialization.
After they switch to run-time they should continue to work in absence of system side voltage.
If there is a way to hard code the system voltage they probably can get past this step in initialization.

 

[BigBrosMo]

You mean the solar charge controller shuts off?
Does it recover when you reconnect the battery input?

Yes the SCC shuts off as soon as I remove its Batt +, even if there is PV input. No it does not recover when I reconnect it unless I give it 24v (or 12v I assume).

 

[John Frum]

Yes the SCC shuts off as soon as I remove its Batt +, even if there is PV input. No it does not recover when I reconnect it unless I give it 24v (or 12v I assume).

Is there a way to hard code the system voltage in the solar charge controller?
It may just be an initialization thing and not a run-time thing.

 

[GXMnow]

@GXMnow in post #109 and subsequently you mentioned that your JK BMS still kept your SCC alive during a LVD so that it could still charge your bank. Are you certain? Which BMS? I think that might have been momentary/situational.

The reason I ask is because I have a JK (the 8s200a) and I ran into the problem the other day where it disabled discharge under UVP and the SCC turned off because of it. Subsequently the next day the SCC did not come back on until I was able to manually intervene.

@smoothJoey might find this interesting as we are discussing in another thread but my latest testing has shown that if BMS disables discharge BUT the solar is working the SCC stays on. As soon as the solar stops the SCC powers off. Oddly... In the condition that I have BMS discharge off, but the SCC is running because there is PV input, if I disconnect the positive battery input, it shuts off immediately. I don't understand that one.

I don't have a solar charge controller in my system at this time, but when I was setting up my battery I did a few tests. When I would turn on just the charge mosfets in the app, the battery would take charge from my 600 watt mains powered charger, but if I put any load on the output, the voltage would just fall. The BMS would not put out current, but it would take current in. It acts exactly like a diode was in series with the battery.

When I flipped it, and had just the discharge mosfet on, I could pull current out of the battery, but if I tried to charge, the voltage would go right up to 58.8 volts, and the 600 watt charger measured no amps going into the battery. When I went back into the app and turned on the charge mosfets, it went right back to charging.

The solar charge controller may be a bit more picky than a dumb CC CV mains charger. @smothJoey basically just said the same thing I am thinking.

In your case, I am guessing the load drew he voltage too low when the discharge mosfets turned off. The SCC might see the battery as too low to accept a charge. What was the load that caused it to hit low voltage protection? If the system is setup properly, the BMS should never go into a protect mode. That should only happen when something goes very wrong. If your charge controller needs to see the battery voltage with a little load on it, then you will have this condition with any common port BMS. Depending on how much current it applies to test, you might be able to put a resistor or something in parallel with the BMS to get it to start charging. I would not recommend having it always connected though, as that could keep draining the battery even after the BMS shut it off. Maybe add a button to force it to start when you know there is decent sun on the solar panels. Once the SCC it pushing current, you should be able to release the button and let it keep charging up. If this is a 12 volt system, a 12 volt incandescent light bulb like a car tail light will probably pull enough current to wake it up. If it is 24 or 48 volts, then you can probably do it with a couple in series. I have used a 100 watt 120 volt bulb to pre-charge the caps in my inverter on my 48 volt system. But a little less resistance would work better.

You really should figure out what caused the low voltage shut down and fix that. If your loads do not have a low voltage shut off, I would add something like the Victron battery protect. That will cut power to loads like DC lights before the battery BMS goes into protect shut down.

 

[BigBrosMo]

Is there a way to hard code the system voltage in the solar charge controller?
It may just be an initialization thing and not a run-time thing.

It does not appear that that matters. In the battery parameter settings of the SCC I had already specifically put it as 24v from the drop down. So it is "hard coded" in that sense. There was no autosense option in the drop down.

 

[John Frum]

It does not appear that that matters. In the battery parameter settings of the SCC I had already specifically put it as 24v from the drop down. So it is "hard coded" in that sense. There was no autosense option in the drop down.

Ok I'm confused.
I understood from this

My JK and my meat

I actually found in my testing today to your questions that 1) As long as there is sun, when I disable "discharge" and/or "charge" on the BMS, the SCC stays on and keeps powering the inverter! I thought it would shut off in the absence of the battery. As soon as I turn off the PV input, the SCC...

diysolarforum.com

That no scenarios required manual intervention.

 

[BigBrosMo]

Ok I'm confused.
I understood from this

My JK and my meat

I actually found in my testing today to your questions that 1) As long as there is sun, when I disable "discharge" and/or "charge" on the BMS, the SCC stays on and keeps powering the inverter! I thought it would shut off in the absence of the battery. As soon as I turn off the PV input, the SCC...

diysolarforum.com

That no scenarios required manual intervention.

If the discharge is enabled, no manual intervention needed. ie if I disable and re-enable discharge it comes back on. In the absence of discharge being enabled (like under LVD), the SCC stays on as long as there is PV power. If there isn't it shuts off. I can jump it to start with a 24v source once the sun comes out again, and then it will stay on if I remove the source since the PV is pulling power.

 

[Henderson]

The big problem with separate port BMS is the current is extremely limited. Not uncommon for a 100a separate port bms to have a charge line that can only handle 8-15 amps. If you are building a system for solar, use a common port for your loads, and connect the SCC directly to the battery.

Hi Will, I'm new to the forum a few months now. I'm now seeing your post in 2022 which you wrote in 2019. I know alot has changed in the last 2 to 3 years, and I'm wondering if you're still recommending same port BMS for the reason that they have/had low charging current. I'm looking to build quite a large AH lifepo4 battery and trying to finalize my BMS of choice. They are so many options to choose from but I am really warming up to a relay type BMS.