smart battery protect needed?

[Hr.brenner]

hello,

i am a beginner in this field and watched several videos carefully.
my question is regarding the video

(Complete LiFePO4 Solar Battery System Design (Updated Blueprint in Description).
In specific i would like to know if a Victron Smart BatteryProtect is necessary for direct connection of the inverter to the Battery, or can it be also solved with a strong relay which is controlled by the BMS.

thank you
ralph

 

[snoobler]

Smart BP is explicitly prohibited from use to act as inverter disconnect in the Victron documentation.

"This video is outdated. We now have BMS that can do everything! Also, do not use a battery protect with an inverter.check page below for update schematics"

 

[blutow]

Depeding on the inverter you are using, it should be smart enough to turn off when voltage drops beyond a specific level. If you have other DC loads coming off the battery, that is a good place to have a smart disconnect. While the battery BMS should ultimately disconnect each battery from everything at really low voltage (10v or so), that is a last resort to prevent you from ruining your battery. With the smart battery disconnnect, you can disconnect your significant DC loads at a more reasonable voltage floor (maybe 11v) and it has the option to sound an alarm at that point as well throug a relay. For around $50, I think It's worth including in a system, but I'm not an expert.

 

[Hr.brenner]

hello again and thank you for your answers. to the comment from snoobler. i understood to use a smart BP when the BMS does not support the demanded Amps. i thouth that the smart BP can be "controlled" by the BMS instead of using the smart BP set up to disconnect under a certain voltage. you mention that the video is outdated and a smart BP is explicitly prohibited. hmm ... ok. so i need to have a strong enough BMS and the setting as built up in the video is not accurate? i thougt this might be a solution to use a smaller BMS...

@ blutow. sure, the inverter will cut off when the voltage drops too low, but i am afraid that this is pre set and maybe too low to protect the battery with a clear value as defined with a smart BP or by the BMS. it is not that i dont want to spend 50$, I just would like to have a good working set up.

my planned project, 2 batteries, each 24V, 200Ah, around 1500WP solar panel, 3000W inverter.

 

[blutow]

hello again and thank you for your answers. to the comment from snoobler. i understood to use a smart BP when the BMS does not support the demanded Amps. i thouth that the smart BP can be "controlled" by the BMS instead of using the smart BP set up to disconnect under a certain voltage. you mention that the video is outdated and a smart BP is explicitly prohibited. hmm ... ok. so i need to have a strong enough BMS and the setting as built up in the video is not accurate? i thougt this might be a solution to use a smaller BMS...

@ blutow. sure, the inverter will cut off when the voltage drops too low, but i am afraid that this is pre set and maybe too low to protect the battery with a clear value as defined with a smart BP or by the BMS. it is not that i dont want to spend 50$, I just would like to have a good working set up.

my planned project, 2 batteries, each 24V, 200Ah, around 1500WP solar panel, 3000W inverter.

Nicer inverters will let you set the voltage for shutdown. The shutdown on the inverter and the smart disconnect shutdowns should be done before your BMS shutdown. That gives you some power to run any alarms, monitoring equipment, etc. that aren't downstream of the smart disconnect. You can use the smart disconnect controlled by something else (like an external BMS) basically as a relay, but I don't think you can use it between a battery and inverter/chager. The victron smart disconnect is a one-way device, so using with an inverter/charger would not work. If it's just an inverter, I don't know why that would be a problem, but it sounds like victron is saying not to do it. Maybe that are just assuming inverter/chargers when they talk inverters. I personally like the idea that the BMS is the last line of defense to avoid battery damage, but using the inverter setting and smart battery disconnect setting to avoid getting to the BMS disconnect point when possible.

 

[Hr.brenner]

hi. thank you for the answer. meanwhile, i am on page 5 reding the common/separate BMS port threat. ... and i am getting confused
in my setup i think i exceed the charging current with a separate port BMS. so i was "happy" to find the video (above) where unloading the cells is not balance controlled by the BMS. And charging is Ballance controlled....
the inverter i am looking at has a built in mpp charger, so it is a charger/inverter ... https://www.alibaba.com/product-det...81.html?spm=a2700.12243863.0.0.25a43e5f5Exz4G

so, if this video outdated, what would be the best setup for my system? can you give an advice?
my planned project: 2 batteries, each 24V, 200Ah, around 1500WP solar panel, 3000W inverter, 150A alternator from the truck engine,

 

[Hr.brenner]

is there a benefit in using separate devices instead of an all-in on one solution?