Victron 712 and State of Charge

[dalford]

Originally Posted by babock

12.9V is much too low for a float voltage. I really doubt its that low. If it is, you need a different converter.


The monitor will sense any current draw. The only thing it can't measure is self discharge of the battery itself which can be 5% a month for a FLA battery.

X2, the manual recommends 13.2V for a 12 volt battery...

[NCBBA11043]

There's 3 stages of charging (from the WFCO website):
Normal (absorbtion) 13.5v
Trickle (float) 12.9v
Fast charge (bulk) 14.3v

I assumed I needed to use the float value. When I was using normal, the system would never synch on it's own. Something else I should look at?

Thanks for replies.

[ScottBrownstein]

Originally Posted by babock

12.9V is much too low for a float voltage. I really doubt its that low. If it is, you need a different converter.


The monitor will sense any current draw. The only thing it can't measure is self discharge of the battery itself which can be 5% a month for a FLA battery.

If you do that the Victron will never get to 100% since the voltage will never drop that low. 13.2 is the generally accepted value for float and it will probably wait until you push in at least 10% more than the bank size.

[babock]

Originally Posted by ScottBrownstein

If you do that the Victron will never get to 100% since the voltage will never drop that low. 13.2 is the generally accepted value for float and it will probably wait until you push in at least 10% more than the bank size.

You don't understand how the BMV works. Once the battery voltage exceeds the charged voltage threshold AND the current is below the tail current AND these occur for the charged detection time, then the BMV sets the 100% charged level.

[babock]

Originally Posted by NCBBA11043

There's 3 stages of charging (from the WFCO website):
Normal (absorbtion) 13.5v
Trickle (float) 12.9v
Fast charge (bulk) 14.3v

I assumed I needed to use the float value. When I was using normal, the system would never synch on it's own. Something else I should look at?

Thanks for replies.

I think you need to check your specs. No way its 12.9V. Have a link?


What is your tail current set to and what is your charge detection time set to? Also, what is the capacity of your batteries and what do you have the capacity set to in your BMV?


Better yet, do a screen shot of your BMV settings and post it.


EDIT: Looks like the WFCO float voltage is 13.2V. Not sure where you saw 12.9. You should set your charged voltage to slightly less than that.

[TitanMike]

Originally Posted by NCBBA11043

I'm also wondering if the unit can sense the parasitic loads while in storage. Battery will drain down, but the amp draw is very low.

It will.

One important item, make sure to perform a "Zero Current Calibration".

Remove negative cable from shunt on the end opposite where the cable from negative terminal is connected (shunt must remain connected to battery negative terminal) Go to Settings, select "Battery" and at the bottom of the screen will be a "Button" next to Zero Current Calibration saying "Calibrate".

By removing the negative cable that connects to the trailer you now have Zero Current flowing with the exception of whatever is being consumed by the Victron itself. I think it's about 200 milliamps. When you reconnect you will now be reading whatever current is being drawn by other appliances, accessories.

I do this every few months although I didn't read anything in the manual that suggested specific intervals.

[NCBBA11043]

Babock,
Yep, you're right....13.2v, 13.6v and 14.4v
Will adjust my settings accordingly.
Thank you.

[NCBBA11043]

Originally Posted by babock

I think you need to check your specs. No way its 12.9V. Have a link?


What is your tail current set to and what is your charge detection time set to? Also, what is the capacity of your batteries and what do you have the capacity set to in your BMV?


Better yet, do a screen shot of your BMV settings and post it.


EDIT: Looks like the WFCO float voltage is 13.2V. Not sure where you saw 12.9. You should set your charged voltage to slightly less than that.

I will post pic tomorrow...

[NCBBA11043]

Originally Posted by TitanMike

It will.

One important item, make sure to perform a "Zero Current Calibration".

Remove negative cable from shunt on the end opposite where the cable from negative terminal is connected (shunt must remain connected to battery negative terminal) Go to Settings, select "Battery" and at the bottom of the screen will be a "Button" next to Zero Current Calibration saying "Calibrate".

By removing the negative cable that connects to the trailer you now have Zero Current flowing with the exception of whatever is being consumed by the Victron itself. I think it's about 200 milliamps. When you reconnect you will now be reading whatever current is being drawn by other appliances, accessories.

I do this every few months although I didn't read anything in the manual that suggested specific intervals.

Wow, thanks. I will try this tomorrow when I have a chance.

[ScottBrownstein]

Originally Posted by babock

You don't understand how the BMV works. Once the battery voltage exceeds the charged voltage threshold AND the current is below the tail current AND these occur for the charged detection time, then the BMV sets the 100% charged level.

I stand corrected. The whole issue of 100% SOC and voltage is a rat's nest. We all know that voltage isn't a good indicator of SOC but a meter needs to calculate some starting point. The parameters of voltage above some low float level and current below some low level and maybe waiting for a while is probably the best indicator that the bank will not accept any more charge. HOWEVER, it is not an indication that you have any specific storage capacity. As the bank ages, SOC will begin to drift since the system assumes that that bank still has the capacity that was originally set. Still the best indicator.

[TitanMike]

Originally Posted by ScottBrownstein

I stand corrected. The whole issue of 100% SOC and voltage is a rat's nest. We all know that voltage isn't a good indicator of SOC but a meter needs to calculate some starting point. The parameters of voltage above some low float level and current below some low level and maybe waiting for a while is probably the best indicator that the bank will not accept any more charge. HOWEVER, it is not an indication that you have any specific storage capacity. As the bank ages, SOC will begin to drift since the system assumes that that bank still has the capacity that was originally set. Still the best indicator.

If one is using a Battery monitor such as the Victron BMV7xx they could merely adjust the ah capacity in the settings.

Observe voltage readings until they reach the 50% level (temperature corrected of course) and then read the amp hours consumed to reach that level. Multiply by 2 and that should be the new amp hour capacity for a degraded battery.

That should bring voltage and SOC % more into sync as battery bank degrades.

Pretty much a non-issue with "Lithium" though. Some of us won't be around long enough for a LiFePo battery bank to degrade to the point this will be an issue at all

[ScottBrownstein]

Originally Posted by TitanMike

Observe voltage readings until they reach the 50% level (temperature corrected of course) and then read the amp hours consumed to reach that level. Multiply by 2 and that should be the new amp hour capacity for a degraded battery.

...and let it sit for at least 4 hours. Yep, could do that. Actually a good SOC meter could do that as well.

[TitanMike]

Originally Posted by ScottBrownstein

...and let it sit for at least 4 hours. Yep, could do that. Actually a good SOC meter could do that as well.

As I understand, most (at least my Victron) calculates SOC and Time Remaining, based on the amp hour capacity you entered in the "Settings" menu.

As pointed out in your previous post this may no longer be accurate as the bank degrades.

Unless the "SOC Meter" has some way of performing this adjustment on it's own I don't see how it can allow for degradation.

In "Smart Batteries" this is done through the performance of regular full discharge/full recharge cycles, that calibrate the "Fuel Gauge".

Pb batteries are certainly not "smart".

[ScottBrownstein]

Originally Posted by TitanMike

...Pb batteries are certainly not "smart".

No they are not. I have a data logger that connects to my Trimetric that continuously measures the settled voltage against the current SOC and attempts to adjust for this. After all we all know that 3 or 4 hours at a low discharge current will give us a decent SOC estimate based on residual voltage. We all know the direction it goes, as a given SOC continually results in a lower and lower resting voltage. It is a slow degradation, but it is always there.

Wish there was a better way, but there isn't.

[TitanMike]

Originally Posted by ScottBrownstein

Wish there was a better way, but there isn't.

I believe that this is one of the appealing features of LiFePo batteries.

An unappealing feature of them however is cost.

As I've related before, "It's now how much you spend, it's how often you have to spend it".

Pb battery life measured in hundreds of cycles, LiFePo batteries measured in thousands. And then there's the weight factor.

In short, there is a better way, just not many are ready to spend the money on it. They still prefer to haul around hundreds of pounds of lead and replace every few years.

[ScottBrownstein]

Originally Posted by TitanMike

I believe that this is one of the appealing features of LiFePo batteries...

Yep, I still lug around 4 FLA batteries...

[Theo]

Originally Posted by TitanMike

{snip}...Pb battery life measured in hundreds of cycles, LiFePo batteries measured in thousands. And then there's the weight factor...{snip}

Add to those factors the ability for a depth of discharge down to about 20% (or lower)! The Renology deal a few days ago was the first time I saw a price under $800.

[ScottBrownstein]

Originally Posted by Theo

Add to those factors the ability for a depth of discharge down to about 20% (or lower)! The Renology deal a few days ago was the first time I saw a price under $800.

Well, let's see. I can get really good Trojans for around $100 each so say 200 AH of lithium only costs what four sets of 440 AH Trojans would be.

I am too old for this, no payback.

[NCBBA11043]

Here's a pic of my settings as requested. I adjusted the charged voltage to 13.0V, as my WFCO uses 13.2V as the float charge. Does it look like I should change any other values?

[babock]

Originally Posted by NCBBA11043

Here's a pic of my settings as requested. I adjusted the charged voltage to 13.0V, as my WFCO uses 13.2V as the float charge. Does it look like I should change any other values?Attachment 210526

What batteries do you have and how old are they?