[cknuth]

Richard, I don't have a setup option for float voltage, and there may not be any float in the CC/CV mode.    Below is the Volts/Amps trace from the Magnum remote manual.    It appears that once the constant voltage phase times out (2 hours as I have it now,) the Silent mode lets the batteries fend for themselves until direct 12V and inverted 120V loads pull them down to the Recharge level of 13.3V.  Still, that should take longer than the system is spending in Silent mode currently (maybe 15 minutes?)    I agree with your reasoning, but I can't find the setting to change.   

I'm going to camp out by the monitors and watch charger voltage vs. the battery voltage on the Xantrex.    So right now, we're in the usual Constant Voltage 14.3V mode, with the Xantrex reading 14.22V.    Will check in later with more readings.

   

[cknuth]

Thinking more about what I just wrote, a correction. When on shore power, the Magnum powers its 120V loads off the mains, not by inverted battery power. The only draw on the batteries when in Silent phase would be the 12V house loads. Right?

[cknuth]

“Recharge” is currently set at 13.3V. 

So I watched the monitors go through a cycle.

Time MagnumV XantrexV
3:35 [system entered Silent mode]
3:38 14.2 14.2
3:39 14.1 14.07
3:41 14.0 13.92
3:42 13.9 13.85
3:45 13.8 13.74
3:46 13.7
3:48 13.6
3:51 13.51
3:53 13.5
3:58 13.4
4:02 13.4 13.36
4:04
At this point, Constant Current started, with the Magnum indicating
4:05 13.8V 93A
4:06 14.5V 130A
Then to Constant Voltage
4:07 14.3V 18A
4:10 14.3V   0A

Other observations: the Magnum current during Silent was always 0A; the Xantrex current varied with house 12V loads.  If I turned on some lights, it went up.  Range was 3 – 15A.

It is apparent to me that the CC/CV setting does not supply any float voltage.  I could set the Recharge voltage lower, but it would just take a little longer before the house 12V loads trigger another two-hour constant voltage period.

[cknuth]

That being said, I'm going to lower the recharge setting to 13.0V to see how much longer the small house loads will take to draw the voltage down that far. As has been pointed out, the lithiums need time to settle to 13.2 or so. Watching for the next cycle to come around...

[folivier]

It looks like Magnum is calling Constant Current mode is typically called Bulk by others, Constant Voltage is Absorbtion, and the Maintain mode appears to be the float mode.
My Victron in Bulk mode charges at 14.4 until the amps are full however long it takes, then absorb at constant voltage of 14.4 for my user set time, then goes into float mode at 13.5 volts. But mine does not restart the Bulk charge until the batteries are depleted below my set voltage. Typically the float mode will charge at a few amps to keep the batteries at 13.5 when needed. So the only time it goes into Bulk, Absorb, then float, will be after the batteries are depleted somewhat (don't remember off hand).
I agree with Richard and think you'll end up lowering the recharge voltage. But a call to Battleborn should clear this up for you.

[cknuth]

One more speculation IF I continue using the CC/CV mode: as shown on my timeline, it took less than five minutes to bring the house batteries back to essentially 100%SOC from the Recharge level of 13.3V. Presumably, it will take a little longer from my new setting of 13.0V. But certainly not the two hours called for in the Charge Time recommendations. Is there some other reason for that long "absorb" time?

And if the CC/CV configuration doesn't have a float mode but rather a "freefall" mode, is it healthy to yo-yo the batteries through endless small-percentage charge/discharge cycles?

A lot to talk about with BB.

[Richard]

Good idea on lowereing the recharge voltage. I only commented on float because you listed it in your setup parameters.

So do you have a Magnum inverter or a Xantrex? Not busting your chops but you wrote "Time MagnumV XantrexV".

To avoid the yo yo is why I set mine up a different way.

Yes the only 12V loads when plugged in, or running the generator, are your lights, your thermostats, your Aquahot pumps, and the AmpLStart

I will delve into the CC/CV section of the Magnum manual in the morning. It's late for me here, and I'm not a night person.

[cknuth]

Thanks Richard. My inverter is Magnum and the battery monitor is Xantrex. Which do you have? I watched them both to see if there was any discrepancy - none. Have a good evening!

[Richard]

Good Morning.

Bear with me, for I am a Southern boy born and raised, and we never take the short way to tell anything.

For years after I installed the Lithium pack that I obtained from Forest, I poured over the literature from the manufacturers, and other well versed Lithium installers. I was obsessed with setting the charger to get full use of the batteries without frying my investment. What I discovered was a myriad of opinions on how to do it, and a whole lot of chest pounding over 100ths of a volt. I found a ton of conflicting information and opinions. Then I stumbled into a thread, and a person who seemed to have his head on level made a statement that completely changed my understanding of how to set the batteries up. He said “the batteries will tell you”. What he meant was that if you will take the time to carefully monitor your battery bank through an extended charge and discharge cycle where you intentionally charge into the sharp up curve in voltage and intentionally discharge into the sharp down curve in voltage, then the batteries will tell you where those inflection points are instead of reading tons of conflicting info about where someone thinks they are in theory. The beauty of doing that is that you take out differences in meters, differences in monitoring systems, and differences in wiring. You read the voltages on YOUR system, the one that will be used to maintain and use the bank.

In the short term, I don’t think you need to go that far, but regardless of what you do with charge profiles, you need a critical piece of info from YOUR setup. Turn off the charger and let the batteries go for 8 hrs with normal loads on them. What is the starting voltage when you turned off the charger, and what is the voltage after 8 hours? Since the useful part of lithium setups is flat, the voltage after 8 hours should be very close to YOUR voltage at the flat part of the curve. IF you have the recharge voltage set above that number, then you will continually operate above where the batteries are happiest.

You were correct, with CC/CV, Magnum does not allow a float voltage. They do allow you to hold the batteries at the CV level, but you do not want to hold them that high. So you have a choice to make. You can use the CC/CV setting, but you will always yo yo the batteries since that setup dictates a full charge and recharge when hitting the recharge voltage. OR, you can revert to a custom setup, which allows float, and this eliminates the yo yo. These are your options unless you change to a different charger.

If sticking with the CC/CV setup, I would make two changes to your existing setup parameters. One, I would lower the recharge voltage to 0.3 volts less than the resting voltage determined in the 8 hour test. Two, change the CV Charge Done to amps instead of time. Use 30 amps as the value, since you have a 600 AHr bank, and a good starting point is 5% of the bank size. You can tweak later if you want a higher of lower ending SOC. Again, the End Charge on Amps is based on “the batteries will tell you”. When the batteries stop accepting the higher currents they are nearing full so if you end the charge when the current drops the charger is responding to hints from the batteries that they are full. If you leave the charge done on time, the charger is simply going to hold the voltage for that given time regardless of what the batteries need. That’s not a terrible thing because the amperage will drop, but you run the risk of holding the lithiums at a higher voltage then necessary to get the charge level you desire. On a side note, I ran the CC/CV profile for about a year, but I had the values set conservatively, and I noticed I didn’t seem to have much capacity. That was before I learned about “the batteries will tell you”.

If you want to float the batteries to avoid the constant yo yo of cycling them, then we can set up a Custom profile that will do EXACTLY what the CC/CV does except the charger will go into float when the charge cycle is finished, instead of going into quiet mode. It is obvious that I prefer this option. It has one drawback, that you must be aware of. Depending on where you set the float voltage, it will not hold the battery pack at 90% SOC, probably somewhere between 30 and 70 SOC. If plugged in, I don’t care. However, if I know that I will be off grid for a while, I go to Control and manually start the Charge cycle. No big deal.

I have the Magnum, with the addition of the BMK (battery monitor kit), it allows me to use the Magnum remote to monitor SOC, and it provides more accurate amperage measurements.

Forest handles his a little differently, but he has different equipment with different capabilities than you do. His way works very well also.

Sorry for the treatise. Hopefully it helps when you talk with Battleborn.

[Richard]

If all that didn’t make you nauseated, I can loan you, or you can purchase for about a 100 bucks a data acquisition logger which will generate the purdiest curves of the battery voltages when you run your full cycle test. https://www.dataq.com/products/di-1100/

There are two very good reasons for running a full cycle test. One, it is a great way to baseline the battery bank capacity. Cause five years from now, you will wonder if they are still as good as new. But more importantly the full cycle test identifies the inflection points at the charge and discharge ends of the curve. Knowing those inflection points allows you to set your recharge voltage and your LBCO with a high degree of confidence. And since I have a homegrown battery monitor system for overprotection, I needed to know where to set the alarm and power cut levels to provide protection to the bank.