State of Charge Question and Charging

[Capebuild]

I have a 100Ah Battleborn Lithium battery (basically new) being charged by a IP67 Victron charger. I just returned from a camping trip the battery had 48% left. When I returned home yesterday I plugged into my "home base shore power" to recharge the battery. The state of charge got up to 87% and now seems to have just settled on that (since yesterday afternoon) and the Victron monitor is reading 13.48 volts.

Any thoughts about why the battery stopped charging at 87% and why the battery voltage is not getting up to around 14 volts? And why the green light on the IP67 charger is just a solid green and not blinking (which it usually does when charging). Even when I unplugged the the shore power the green LED stayed on (on the charger) which I don't recall it doing in the past. All equipment is basically new. There is nothing "on" in the trailer which would be drawing power.

Maybe all is as it should be and I'm just not understanding "how these components work"??

Thanks for any insights. attached are 2 pics which might be a help.
John

[lfhoward]

Hi John,

I think it is a settings issue either in your smartshunt or the charger, and that the battery is actually full. I’ll check my own settings (which I got from Andy on Off Grid Garage) this afternoon for you when I have a chance. Bruce may beat me to it!

[Capebuild]

Thanks Lauren. I'll look forward to hearing any thoughts you may have.

As a follow up, I removed the charging cable disconnecting the shore power. As mentioned in original post, the green LED stayed illuminated on the charger which I was wondering why is that still laminated even though I disconnected the charging cable. I just went and checked the charger and the green LED is now out on the charger..... so maybe it stays lit until it completely discharges any current running through it, even when it's first disconnected.


John

[Pmullen503]

I wish these devices didn't display percentages. Unless you've done a real world test to determine battery capacity, that number is meaningless.

Look at Ah used to recharge. The voltage curve is so flat with Li batteries than using just voltage to determine SOC gets you only a "fully charged, discharged or some where in between" number.

If you want to know what your battery really can do, do a real world test in your camper. Run it down to LVC and charge it to see what it takes to recharge.

[lfhoward]

Hi John,

I pulled up the relevant screens from my Victron battery monitor and my solar charge controller (which can basically stand in for your shore charger because the settings should be similar). My settings came from Andy's Off Grid Garage chanel on YouTube, probably cobbled together from various episodes. I'm interested in keeping my battery viable for as long as possible, so I'm being more conservative than Victron's default settings for LiFePO4, thus it shows up as "User Defined". I started with those defaults though, and then went in and tweaked some things.

Battery Monitor / Smart Shunt:



My battery shows up as 100% at 13.40 volts because that's how I have it programmed.



Charged voltage: 13.8 V-- this should be set to the same value as the absorption charge level on the charger. If it is higher than the absorption voltage of the charger, it will never get to 100% on the meter, even though it is full (what I think is going on with yours).


Solar Charge Controller / Battery Charger:



Note the charger is in Float stage right now. It charged up this morning and went through bulk and absorption before 11 AM. It has been in float ever since. In float, the charger just replaces any current being used, like the 0.5 amps being used by my Venus GX & mobile hotspot (my raspberry pi's).



Absorption: 13.8 V - the highest level I let the voltage charge to (lower than Victron's LiFePO4 default)
Float: 13.4 V - the maintenance voltage the system spends the day in is lower than absorption to not stress the battery out



And in expert mode:
Re-Bulk: 0.10V - how low below Float voltage the battery gets before it shifts back over to bulk charging
Absorption duration: 1 hour - max how long it stays in absorption before going to float
Tail current: 0.8 A - how low the incoming charging amperage is before it goes into float (this usually makes mine change from absorption to float in about 15-20 minutes)

Hope this helps! I can answer any questions later tonight.

Edit: after fixing the charged voltage to equal the absorption voltage, the battery monitor should read 100% after you charge it the next time. It will synchronize itself so you don't have to, or you can press the "synchronize to 100%" button if you know the battery is really full. You should not have to manually reset it on a regular basis.

Edit #2: Andy from Off Grid Garage has shown that the absorption & float voltages of 13.8 and 13.4, respectively, keep the battery in a state where it retains most of its stored energy (more than 90%) at full charge, but doesn't let the battery get up into the steep section of the charging curve. In practice, he (and I) found that charging to 13.8 V instead of 14.2 V sacrifices only a couple of amp hours of total storage at the top end, if even that much. But charging to lower voltage should keep the battery well away from the high voltages where degradation can occur if high voltage happens often (like every day it is charged up by solar). That's also why I reduced the absorption duration and set the tail current, so the battery spends less time hanging out at higher absorption voltages. The difference in practice in terms of battery capacity is negligible to me. The trade off is that battery cell balancing by the BMS needs higher voltages, so normally this step would be done at absorption voltages. But I can tell you my battery's delta is still only 0.001-0.002 V when fully charged, so it has never needed active cell balancing. (This is why I top balanced the cells in the first place before putting the battery into service, and it has stayed perfectly balanced after almost a year.) Andy has tested lower voltages than 13.8 absorption / 13.4 float and it is not worth going any lower than that-- these numbers seem to be the sweet spot for maximizing capacity and minimizing potential degradation.

Edit #3: I see the temperature reading is blank on your BMV/SmartShunt, so I recommend getting one of these to keep your charger from charging the battery below freezing:
https://www.continuousresources.com/col ... 700-series

Edit #4: I am assuming above you created a bluetooth network using your BMV/smartshunt and joined it from the charger. Both devices should be talking to each other and sharing information. :-) On the settings of your devices, choose VE.Smart networking. That way, even though the temperature sensor is plugged into the BMV/smartshunt, the charger can see the temperature too.

[bdosborn]

Your absorption voltage is too low on your charger. Use the app and set it to 14.6V per Battleborn's recommendations. The light stays on because there are capacitors in the charger that store charge. It takes awhile for the LED to discharge them.

https://battlebornbatteries.com/setting-victron-multiplus-compact-battle-born-batteries/

Bruce

[lfhoward]

Your absorption voltage is too low on your charger. Use the app and set it to 14.6V per Battleborn's recommendations. The light stays on because there are capacitors in the charger that store charge. It takes awhile for the LED to discharge them.

https://battlebornbatteries.com/setting-victron-multiplus-compact-battle-born-batteries/

Bruce

Ha ha, I say low and you (and BattleBorn) say high for absorption voltages. I guess it is whatever you are comfortable with.

Either way, be sure the “Charged Voltage” on your battery monitor is set to the same number as the Absorption Voltage on your charger, so that the monitor will synchronize itself to 100% when the battery charges to that level.

[bdosborn]

Yeah, Battleborn runs their cell voltages way higher than I do. I run 13.8v absorbtion for my DIY battery. My cells go crazy out of balance if I go any higher than that. Your meter advise is spot on.
Bruce

[Capebuild]

Thanks Lauren. That's a lot of info and I need to absorb it. And make sure I understand it. And thanks Bruce for your thoughts as well. When I go into the Victron app on my phone I do remember seeing the charger show up (when it was plugged in) but Iv'e not yet programmed anything to it. So when you mentioned setting the "absorption level" on the charger, I haven't done that.... so maybe that is causing the battery to stop charging at 87%. I did (a while ago) go on the Battleborn site and set their recommendations for the BMV712/battery .....so I should probably go and recheck those settings. I need to get a bit more educated with this.

Thanks again.

John

[lfhoward]

That’s it. If your monitor thinks fully charged is 14.6 volts and the charger stops charging at Victron’s default 14.2 volts, it can only get 87% to a full charge.

[featherliteCT1]

This is a great series of posts.

The Battleborn battery is comprised of cylindrical cells whereas the batteries used by lfhoward and bdosborn are comprised of prismatic cells.

I wonder if the cylindrical cells have different charge characteristics.

A battery will charge faster to "full" with a higher charge voltage. I wonder if that is why Battleborn recommends charging at the higher voltage.

Although the charge profile of these Lifepo4 batteries is mostly "flat", the learning curve for me has been pretty "steep".

[bdosborn]

It's all about the LiFePo4 charge curve. The cell voltages go up like crazy at the very end of the charge.



The CALB SE prismatic cells for the van weren't impedance matched very well so the cell voltages diverge a lot when they are almost charged, in the >90% SOC range where the voltage curve goes straight up in the graph. Some cells will go over the maximum recommended voltage of 3.65V if I charge the pack higher than 13.80V. So I limit the absorption voltage to 13.8V as there really isn't much energy going into the battery between 13.8V and 14.7V anyway. I'd rather take it easy on the battery than charge it as full as possible. I'm using CALB CA cells in the trailer and the cell impedances were matched much closer, I can use 14.7V as my absorption voltage without the cell voltages going too high.

I think that Battleborn matches the impedance of their cells well and that's why they can use a higher absorption voltage.
Bruce

[Capebuild]

I've spent a little time going over your previous post, Lauren... and I see I need to tweak some of my settings.
Here's an image of what my current battery settings are configured at:

IMG_7013 Medium.jpeg (36.19 KiB) Viewed 195 times

Here's the image when in absorption mode:

IMG_7009 Medium.jpeg (25.21 KiB) Viewed 195 times

and here's the image when in bulk mode:

IMG_7008 Medium.jpeg (27.02 KiB) Viewed 195 times

In the IP67 Charger there's a few settings I can choose for the "Charge Preset". I chose "li-ion". Hopefully that is correct:
That same page on the charger settings gives an option for the "charge current", either 10A or 25A. I chose 25A. Battleborn says you can charge a 100Ah battery at 50amps but probably not wise to do that all the time and I don't see how you would do that anyway (maybe under the "advanced settings".
Regarding your comment about the temperature setting.... one regret I have is not getting the heated version battery. So you suggestion of getting the temp sensor might be good. I think I remember Battleborn's built in BMS will not allow charging if the temp is under 32 degrees.
Anyway still studying it all.

John

[bdosborn]

You don't need the temperature sensor as the Battleborn has a great BMS that won't allow charging when it's too cold. You can set your discharge floor to at least 10% if you want. The Battleborn BMS will disconnect the battery if you run it down too low. The Battleborn will probably age out before you discharge deeply too often.
From the Battleborn site:

LiFePO4 (Lithium Iron Phosphate) batteries can be continually discharged to 100% and there is no long-term effect. You can expect to easily get 3000 – 5000 cycles at this depth of discharge.

3,000 cycles is roughly a complete discharge a day for 10 years.

Bruce

[Capebuild]

I had contacted Battleborn (via their website) with basically the same question posted in my original post here. Lo and behold a tech person called me this afternoon to help with my inquiry. So, one thing, Battleborn has GREAT customer service.

He walked me through the appropriate settings and did it in a very helpful way. There's a bunch of Victron components listed under a demo tab on the app. I found my components and basically set them up (with his help) and then took a screen shot on my phone of the settings. When I got out to my garage I was able to refer to the screen shot and fine tune the setting on the app on my phone..... setting the absorption voltage(14.4 V) and the float voltage (13.6V) and the storage voltage (13.2V), which I'm not sure I had correctly noted before.

Attached are new images of what the app is now showing me. The charge is up to 100% and the voltage is where it should be (around 14.4 volts). Also attached is a screenshot of the settings in the BMV712.

Thanks for all the help and suggestions.

John