Lithium battery question.

[SCTN]

I have a new smb west built van. I have two inline lithium batteries with the Magnum controller. The battery type is set at “cc/cv” so I can’t set the charge rate. Seems to be about 80% based off of my battery charge indicator.
I have a zamp “suitcase” when boondocking. So not used all the time. My issue with the system is I can’t seem to adjust the battery Managment system from shutting down at around 50% battery life. I was under the assumption that I could safely drain the lithium batteries to around 20%. So my current usable ah is around 30% based off of it charging only to around 80% and bms shuts it down at 50%

I get about 3/4 days of just refrigerator usage at its lowest setting and that while I’m actively driving van. Albeit not very far these days, but almost daily short trips to surf.

Does this sound right? Do I have the magnum adjusted wrong? I don’t have a huge grasp on this battery thing but I get the general idea...kind of

[ShuttlePilot]

Greetings SCTN,



I'm not sure I understand your setup. Do you have lithium batteries permanently mounted in the van that you don't think are working as long as expected? Is the "Magnum controller" a Magnum inverter/charger that you are charging off of shore power? Is the Zamp suitcase a portable solar panel with it's own charge controller? That's what I'm picturing from your post but I'm not sure.



In order to give advise other than "take it to whoever installed it" it would be helpful to know the manufacture and models of the batteries and chargers (solar and/or shore power).


- Eric

[SCTN]

Sorry for confusing, I shouldn’t even brought up solar...but I have a zamp controller.

I have a magnum inverter and controller. Pretty standard Sportsmobile installed set up...but w lithium battery’s. We’re on tight shelter in place here in CA so I can’t take it anywhere. I might just need to be patient but if someone had lithium and my same magnum controller and knew how they set it up so I can discharge battery’s farther than 50% then I would be stoked...or if the system only shuts down after a voltage drop then I have another issue than just my battery management system shutting me down after I drop bellow 50% charge rate. Might be super confusing to everyone, but hopefully someone w smb setup gets it.

[Wowbagger]

The shutdown is controlled by the low voltage cut-out setting on the Magnum, which is a different setting from the CV/CC settings. You can also bump the voltage on the CV/CC settings a tenth of a volt, and that will likely get you that last few percent on charge.



Are they the all-in-one batteries like the BattleBorn, or are they cells + a separate battery management system? I have the latter set up (I designed it myself, and SMB put it in). I don't really trust the Magnum to act as a BMS, as it really doesn't "understand" lithium - the CC/CV setting is a compromise. I have a real LiMnFePO4 BMS that knows my cells, and *it* makes the decision when to cut out.

[SCTN]

Wowbagger. Thanks! After reading the magnum control manual and not seeing anything on lithium I felt maybe it wasn’t the greatest controller either. Do you have a thread on your build I can read?

[Scalf77]

The Magnum inverter/charger is not a BMS, so I wouldn't expect it to act like one. Is it just the inverter shutting down? If so that is a function of the Low Voltage Cut Out as Wowbagger says. You can adjust this to a lower value. Also turn off the inverter when not needed, that will save power.

What batteries do you have and have you checked with them as to what they want the charger settings to be.

-greg

[Lilnuts2]

Magnum does make charger/inverters that can be adjusted to work well with lithium batteries. I have one in our 5th wheel with the battleborn batteries and it works awesome. I cant say enough good things about the lithium batteries.

[SCTN]

Now with some clear direction I was able to find what I was looking for. I was afraid I’d mess something up but I’m going to lower lbco setting to 9.5 and see how it goes. Thank for everyone’s help.

[Scalf77]

I would have concerns on the wire size from batteries to inverter/charger and also for any loose connections. Also your batteries may have a limit on max current they can deliver. Battery info here would help.

-greg

[rsamco]

I also have a SMB-West build with a Magnum MS2000 Inverter/Charger and a Relion RB300 Lithium battery (can also charge off solar and auxiliary alternator). Some points/questions:


* When you say that your battery "cuts out" at 50% SOC do you really mean that there is no voltage? IMO this could only be caused by the battery's BMS (a very unusual behavior) or by a loose battery cable. How are you measuring SOC? Remember it is very difficult (née impossible) to determine SOC by a Lithium battery's voltage. [Or do you mean that this is the point at which the Magnum refuses to invert????]


* I assume that "lbco" is "Low Battery Cut-Off" on the Magnum. The Magnum default is 10V. This is the battery voltage at which the Magnum will stop inverting -- mine is set to 12V and I have no issues.


* Unlike most solar charge controllers and alternator regulators, the Magnum won't start charging the battery until the battery's voltage drops to its programmed "Start CC/CV Charging" voltage level (default 12.0V; mine 13.0V))


My Magnum settings are: