[cknuth]

Good morning Richard! Just read your latest note before coffee, and I'm eager to share my overnight observation that is exactly as you suggest. I lowered the Recharge to 13.0V last night, and that change allowed the batteries to settle at 13.3V in Silent mode. The voltage has held at 13.3 for almost 12 hours at this point. The CHG light on the Magnum remote panel continues to blink, indicating that no float is happening.

My Xantrex monitor, which I refreshed to 100% state of charge after the last charge cycle, is showing about a 3.3A draw, 94.1% SOC and 13.2V. (I plan to replace it with the integrated Magnum BMK.)

Regarding changing the CV Charge Done setting to Amps, you probably know that the manual specifically recommends against this; I had concluded that it was the way to go but was stopped by the voice of authority. But the manual was written long before our batteries were invented, and I accept your voice over theirs. So I'll put in that change now so it's ready for the charge cycle when it comes around.

More reports to come!
C

[bikestuff]

From Richard’s post....

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n 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. 

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This is one of the smartest things I have read on Lithium setups.

I have Battleborns as well and have set them up according to the BB recommendations.   I sit at 100% SOC all the time.....but now believe that I am slowly killing them.   My plan is to follow this strategy and see how my BBs like it.

Bill

[cknuth]

Good to hear from you Bill. What does your system consist of? Amp-hours, type of inverter, usage?
Seems like this thread could result in best practices for folks with similar systems. And maybe some feedback to BattleBorn regarding their customer guidance.

[bikestuff]

I have a Magnum inverter and their integrated BMK.  6 BB 100AH batts.  I set up the Magnum according to the BB recommendations.  My BMK says SOC is always at 100% and I rarely do any dry camping.

Although I found a mis-wired battery tender years ago....I have not really had any battery issues since then. The BBs just sit there and do their thing.

I am going to run Richard’s test soon and will document my results.

One thing to think about whenever playing with lithium  batteries and their settings.....  If you crank the coach with depleted lithium house batteries...the battery isolator will attempt to send current to the house batteries.  Lithium batteries have an almost unlimited ability to accept current.  This can easily overwhelm your isolator.  And when I say “overwhelm” I really mean completely melt.  In my coach I have the super big oil cooled alternator which can put out like 300 amps.  I think the isolator is rated at 200 amps.  If I drove off with empty house batts the alternator will do its job and keep sending current until the regulator tells it to stop.  There is no fancy charge limiting smarts in the Alternator / Isolator circuit.  (Some folks including Richard I believe) have disabled the ability of their alternator to charge their house batteries for this very reason.

What does this mean in the real world?  In practice it is good to make sure that you have charged your lithium’s using the inverters charge circuit before you crank the coach.    Don’t drive off with an empty house battery.  This will put maximum stress on the alternator / isolator./

Cheers,
Bill

[folivier]

Bill the simplest solution to your issue you mentioned above would be to put in a battery switch rated high enough so you can turn the alternator on or off. That way you can use your alternator only when you want to. That's what I did in my Foretravel. But I also have a Victron Orion 30 amp battery to battery charger I'll install soon.

[Richard]

I went to the Magnum manual again, because I did not remember the cautions. The cautions in my manual are really about two lookouts when using End of Charge on Amperage.

One, use a BMK to get a more accurate reading, otherwise the amp reading comes from the charger.
Two, if DC loads come directly off the battery, it could trick the charger into charging too long, since whatever DC loads there are would be subtracted from the Charge End Setting.

Not worried about either, since we are talking about setting the number at 30. Your background drain is 3 to 4 as you noted. And the loss in the battery cables at 30 amps is also minimal.

Now if you are reading another caution, please tell me, since these are the two I found.

I believe that Chuck installed a Sterling battery to battery to work around the fried alternator issue.

[Richard]

Chuck that is great news on your overnight results. Now we know your voltage on the flat part of the curve using your measurement equipment is 13.3 to 13.2. Our ideas about what was happening with the recharge voltage set at 13.4 seem to be accurate.

Don't know if you have seen this https://www.youtube.com/watch?v=v5MADBMKN7Q Battleborns video on setting up a Magnum. Apparently the previous cut and paste was for some other video.

[cknuth]

Status of this little project: after about 36 hours since the latest Silent mode started at 100% SOC, the battery monitor shows:
13.19V
82.4% SOC (105.4 AH used)
3A current
I'm going to leave the lights and other 12V loads on to try and speed up the process. Eager to move on and implement the Custom settings.
Phone tag with BB yesterday - expect to connect today.

[cknuth]

Spoke with Jody at BattleBorn. She confirmed pretty much everything we've been discussing here. Their product is basically flexible and robust enough to deal with the various ways it's being treated in the field. So she didn't have a preference between the CC/CV and Custom settings on the Magnum. But she concurred that I'd need to use the float capability in order to provide sufficient voltage to the Amp-L-Start battery minder.

[cknuth]

After leaving lots of 12V loads on for the morning, I came back to the coach from errands to find the Magnum display showing Constant Charge 14V 123A. So the Silent mode voltage must have finally dipped to 13.0 after almost two days. It went to Constant Voltage after another 10 minutes, indicating 14.1V 120V. Then 15 minutes later, it went to Silent mode and 14.0V 0A, from which it's now settling down. The Xantrex battery monitor shows 99% SOC.

Now that the CC/CV mode has been explored, I'm ready to move on to Custom. The intention is to have the system in Float mode most of the time when it's on shore/generator power, so the battery cycles won't be as deep and so the start battery charger will get the float voltage it needs.