Using Classic low bat disc to switch outback VFX inverters

[SolarMusher]

Hi all,
Is that possible to use Classic Aux1 Low Bat Disconnect (dry contact) to switch Outback inverters off as a safety/LBCO for LFP batteries and avoid discharge deeper than 80% DOD ?
Thanks,
Erik

[boB]

Yes, that should work just fine if adjusted just the way you want.

Good usage !

boB

[SolarMusher]

Hey boB,
Hope you're doing well!
Thanks,
Erik

[boB]

Hey boB,
Hope you're doing well!
Thanks,
Erik

Hi Erik !   Doing OK.

Working warmly in AZ for a few weeks on inverter stuff.

Back to the cold and freezing PNW in a couple weeks.

boB

[mahendra]

Hi all,
Is that possible to use Classic Aux1 Low Bat Disconnect (dry contact) to switch Outback inverters off as a safety/LBCO for LFP batteries and avoid discharge deeper than 80% DOD ?
Thanks,
Erik

Yes ,definitely but you must have the wbjr. Set up on the classic
I have been using this on an exact model

[SolarMusher]

I already have a WBjr installed + Trimetric with big red numbers!
Batteries are 2x Volthium LFP 48Vdc 200Ah (auto heating for low temp) and I would like to keep my old VFX3648 (x2). I plan to use only 300Ah on these batteries.
It should be ok as I never used more than 200Ah from the Rolls 750Ah bank.
I guess that I don't really need HBCO but would like to build a LBCO (on voltage) from the Classic for battery longevity and deal with 80% max DOD.
Anyway, I think it's time for a switch to LFP.
A+,
Erik

[SolarMusher]

Mahendra,
Did you make your LBCO with dry contact ( classic switch) or did you add an external relay to get the job done?
Was it accurate enough for you?
Volthium number for 20% SOC is 50.85Vdc at 50A discharge so I was thinking to add a 5 minutes delay to be ok.
What is your LBCO voltage?
A+,
Erik 

[mahendra]

Mahendra,
Did you make your LBCO with dry contact ( classic switch) or did you add an external relay to get the job done?
Was it accurate enough for you?
Volthium number for 20% SOC is 50.85Vdc at 50A discharge so I was thinking to add a 5 minutes delay to be ok.
What is your LBCO voltage?
A+,
Erik

I used the classic dry contact aux low battery disconnect with wbjr soc to operate the Outback vfx aux to turn off or on based on soc.
I don't have voltium batteries .
I have calb.
I am using an overkill solar bms which is.set to 80% dod
Classic /wbjr is set at 60%.dod that's.my preference.

I just don't want the overkill bms shutting down everything thus the reason for the difference in wbjr and overkill.
So just the inverter.would shut down in the event of low battery based on user.setting.

I would say both are pretty accurate since they are just about 1 to 2 % off at any one time.

I use state of.charge not voltage for battery disconnect.
Outback low battery disconnect cannot be raised beyond 48vdc.So I used that.

Voltium 50.8 sound ok.Delay is good also.

[SolarMusher]

I read somewhere that SOC wasn't so great with LFP batteries, That's why I was thinking to use voltage instead.
Did you test this battery disconnect on SOC? Does it work as it should?
Thanks,
Erik

[mahendra]

Yes .definitely had it turned off a couple time during bad weather.
It may not be extremely accurate but it beats judging battery state using voltage

[SolarMusher]

Any idea for a normally closed DC relay that would do the job and would not be too expensive?
Thanks,
Erik

[boB]

Any idea for a normally closed DC relay that would do the job and would not be too expensive?
Thanks,
Erik

Have you done a parametric search on digikey.com  or  mouser.com ?

That is where I would go first.

boB

[SolarMusher]

Yes, but NC relays seem to be rare and back order for a long time, the few crydom I found yesterday were above $200 and up.
Covid/inflation/poutine, we are living a wonderful time!
Anyway, these batteries are great.
A+,
Erik

[boB]

Yes, but NC relays seem to be rare and back order for a long time, the few crydom I found yesterday were above $200 and up.
Covid/inflation/poutine, we are living a wonderful time!
Anyway, these batteries are great.
A+,
Erik

Normally Closed will be hard to find in a DC  SSR.

An AC SSR might be easier because they can just trigger themselves and a signal sent to them to turn OFF would just keep them from turning themselves on.  That's how I would design an AC SSR anyway.

I'm not sure if anybody makes a Normally On SSR, AC or DC ?

boB

[SolarMusher]

boB, I'm gonna try it with a simple 12 Vdc 5 pins relay with NC, it should work.
I would have prefered an SSR for quality and peace of mind but anyway it will only work a few times a year for a short time.
All the 12Vdc relays I've used for venting from Classic aux in 48Vdc systems are still working after 10 years.
Thanks,
Erik