BMV 700 settings ?

[Thatbloke]

Greetings all, first time posting so hope it is clear.
Briefly, having been inspired by T1 Terry i have finally got around to installing my very basic lifepo4 system in my ageing slide-on ( system is probably worth more than the slide-on ) it consists of a 200ah lifep04 battery an Enerdrive dc2dc charger and the BMV 700. It’s taken me some time to put together as this was my first attempt at 12 v power systems which was prompted by my need for a bigger fridge which i also had to install , so it has been a somewhat steep learning curve for me but all seems to be working ok after several days of testing.
Recently Terry posted some BMV settings in another post which i have used (many thanks) but i do have a question in regard to the relay function .
What i want to do is simply cut the power when the soc drops below a given %. Now as mentioned above i have used Terry’s suggestions but power is still flowing after my test setting of 60% soc.
I have set:

11. Realay Mode- Default
12. Invert relay -On
14. Min closed time . 0 min
15. Relay off delay. 0 min.

I have no charging connected at the moment as i just wanted to see if the relay setting for turning the power off was correct . All that has happened at the 60% setting is a that the word CHARGE has appeared on the BMV but the power is still being consumed when the fridge kicks in.

Have i misunderstood the operation of the relay function or just not set it correctly ?

Thanks for your help.
Ps if anyone would like a small 3 way fridge its yours for tha asking

[BruceS]

Welcome to the forum Sterling!! We hope you join in and help create some drama... !!!
There are quite a few LiFePO4 folks on here and I'm sure you'll get some info to help your install settle down.
What have you got plugged into the BMV relay facility?
Do you have some photos that may help at all?

[T1 Terry]

Hi Sterling and welcome to the forum. the Victron 700BMV has 2 push in wire connectors on the back of the gauge and these switch from closed circuit to open circuit with the relay function. This is only a driver circuit for a much higher capacity relay that does the actual switching on and off.
The next catch is the relay driver inside the Victron unit can't handle very much current, so it needs to drive a small low current relay that then drives the high current relay as these things have high current draw to pull them closed, far too much for the Victron 700 BMV relay contacts to handle and they would just fail the first time it turned on.

T1 Terry

[Thatbloke]

Ok, thanks guys, looks like i have completely misunderstood the relay operation. Adding extra relays starts to complicate thing for my simple mind . Might just go with a lvd , that’ll keep it simple.
Cheers and thanks

[T1 Terry]

Hi Sterling, are you using solar to charge the battery as well? What type of controller and what type of cell monitoring are you using?

T1 Terry

[Thatbloke]

Terry
I am only using the enerdrive which does my solar and alternator charging.
Now i know you might want to start pulling you hair out when i tell you that i’m using an all in one battery , supposed to have built in bms and cell balancing, not your thing i know but i decided to take a punt and see how it goes, been doing exactly what has been asked of it after sitting in the shed for the past few months

[T1 Terry]

Terry
I am only using the enerdrive which does my solar and alternator charging.
Now i know you might want to start pulling you hair out when i tell you that i’m using an all in one battery , supposed to have built in bms and cell balancing, not your thing i know but i decided to take a punt and see how it goes, been doing exactly what has been asked of it after sitting in the shed for the past few months

They are good like that eh What brand battery and just the one battery or multiple batteries in parallel?

T1 Terry

[Barboots]

Stirling you might find that getting an LVD with the right cut-off voltage is tricky. There's really not much added complexity using the BMV-700 and a solenoid/SSR/Gigavac.

What voltage does the battery's BMS call it quits at? Is it specified?

Cheers, Steve

[Thatbloke]

Terry
Single battery only, not sure i should mention the brand as you might call me a dill

Steve
I found this one on ebay which might do the trick . Not quite sure of the quit value but i think it might have been 10.9v. ‘Complexity’ is a subjective term
https://www.ebay.com.au/itm/Battery-Low ... W2cmPqSfqQ

[T1 Terry]

Terry
Single battery only, not sure i should mention the brand as you might call me a dill

Steve
I found this one on ebay which might do the trick . Not quite sure of the quit value but i think it might have been 10.9v. ‘Complexity’ is a subjective term
https://www.ebay.com.au/itm/Battery-Low ... W2cmPqSfqQ

Not that bad depending on just how much current you plan to run through it. The 80 amp model looks to be around the $120 mark AUD, set for around 12v and start at 0.5v back on and see if you get the flashing lights, adjust it up a bit till it settles down to either lights on or light off. Lithium batteries have quite a voltage bounce once the load is disconnected when they are close to fully exhausted so 0.5v or 12.5v back on might not be enough to cover the voltage bounce, but 13v is probably a bit much.

T1 Terry