Bmv712 settings for lithium SOC control

[the1andonly]

I have votronics mppt and b2b controllers, currently use an issolator on battery negative for winterization.
Now the bmv712 has a relay that can be controlled by SOC level. Heres an experiment, Pick a level to switch on external relay. I start at 59% (solar on relay closed) set come on at 61 off at 62% . Once solar takes level to 63% (relay open) switch off solar put on lights. The drain takes soc down slowly, then it hits 61%. Im expecting the relay to go open to close nope some time later ( at least 8 mims) it does goto close. no relay delay setup, relay mode is set to default. I cant see anything relevant in the manual.
From photos bellow note time remaining and relay state. ( what is namm?)
Anyone know or done simular?
Im assuming the simplest method to go from summer to winter to max use is to change the % settings.

Still waiting delivery of a relay to try in practice.

 

[autorouter]

'nan' is what you get when a computer calculation goes wrong. For example dividing by zero. It means 'not a number'. I think the 'm' is automatically added as the units (minutes). Somebody didn't test the software for all possible erroneous inputs.

 

[the1andonly]

'nan' is what you get when a computer calculation goes wrong. For example dividing by zero. It means 'not a number'. I think the 'm' is automatically added as the units (minutes). Somebody didn't test the software for all possible erroneous inputs.

everyday a school day eh. In all my programing days never came accross that (pherhaps i did and my memory is really worse than i think). at least their error trapping worked.
is what im trying to do sensible?

 

[the1andonly]

Well these settings work. Using a std automotive mechanical relay. But 200ma drain too much need to find a latching or low power ssr for a sensible price. First look £220 , nah i need 2@ 30A.(really 30 and 20)
Basically i have 2 chanels one 220w controller with SB trickle charged as 2nd battery, relay after controller. 2nd has one 330w panel, relay before controller (to stop ramming all that power into controller with no where to go.)

 

[Raul]

I’m not sure what exactly you trying to do, but I do use a cheap generic Chinese 40a ssr, triggered by the solar controller relay, When it hits float, delay 5 mins and closes. It opens at fixed voltage under float. It powers a socket for the immersion heater. I get hot water when in float, otherwise energy is wasted. This is at the house on 48v system. The bmv relay can work on soc, handy for loads off, but I never used it.

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[autorouter]

I think all these outputs controlled by soc levels and voltage levels have inbuilt delays to avoid rapidly switching on and off as the voltage/soc jitters around the threshold level. I was going to suggest trying the 55% and 65% levels instead of the 61% and 62%, thinking they might be too close together for the software to distinguish meaningfully between them. But if it's working OK, then great.

 

[the1andonly]

autorouter the 61 2nd 62% levels were set purely as a test. My intention is to use much broader values eg 30-70%.
Raul The main purpose of this is to essentially winterize the battery without over charging or physicaly issolating the battery.
Have you any details on the 40a ssr youve used or any appropriate one?

 

[Raul]

I use one of these

Solid State Relay Module SSR-40DA 40A, 3-32V DC to 24-380V AC. | eBay

Solid State Relay Module SSR-40DA 40A 250V 3-32V DC Input 24-380V AC Output. Load Current: 40A. Quantity: 1 Pc.

www.ebay.co.uk

But my load is barely 10A AC, you will need a very expensive high power DC rating like Crydon ssr. They are 200 quid up. I would try a latching relay or a argodiode, or a victron battery protect. They come in 100A 12-24-48v dc, and have a very low few milliamps draw.
On the high soc you will want the solar cut off, not the controller. I just set the chargers for winter when I live the house, and have a freezer to draw some. On the van I have a load at all times, and just adjust for winter settings. If you can set float low enough, like 13,35v and have a camera or router on, the battery will never gonna get to full, even with 600w solar. I was floating at 13,40v and bulk 13,60, and I could not exceed 80-85 % soc.

 

[the1andonly]

Thanks Raul i am switching the solar off to controller 1 but controller 2 trickle charges the SB. Votronics mppt duo.

 

[the1andonly]

Raul
Eventualy ebay turned this up.

Whist i wait i checked how far out synchronisation was ultramax BT battery 15% bmv 45%.
Any comment on my battery settings.
Solar controllers and b2b are votronics .

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[Raul]

If you charge controller and other sources reach 14,4v, then that’s ok.
I have the same settings, except peukert at 1,04.
Yesterday I charged from ehu as I was 34-37% soc for the last two weeks. And I was pleasantly surprised 3ah out of 400ah. Less than 1%. I think is a bit of both, peukert and charge efficiency that contributes to the deviation. On low discharge/ charge currents peukert is non existing, when you exceed 0,2C it comes into equation.
On the SSR, run a bench test see if operates as intended; , and be pleased if it does not get hot with 50-60A. Try to mount it on a heat sink to help with cooling.

 

[the1andonly]

Thanks Raul , i really appreciate your input.
.will test ssr when eventually arrives.
Currently playng about with another project whilst van disturbed. GLAD i dont change my van every year!