Lithionics and Xantrex: Settings, firmware, and SOC calibration lessons learned

[Steph and Dud B]

Hi, all.

We have the 640Ah Lithionics lithium package and we rarely use even a quarter of that capacity. Winterizing is per the Lithionics manual: kept plugged in with their internal heaters doing their thing. I've noticed a bit of SOC drift, so I decided to do a SOC recalibration by taking the batteries down to low voltage cutoff and recharging per the Lithionics procedure. Learned some stuff. 

I disconnected shore power and let the batteries slowly discharge until they were reading 51 and 61 percent state of charge respectively (there's that drift). Then I turned the inverter on and connected a small 780W space heater to finish the discharge. BUT... The Xantrex inverter cut off with a low battery error when the SOC dropped to only 40 and 50 percent. The Xantrex low battery cutoff was set to 12.1v per Oliver specs and the Xantrex panel reported 12.0V when the inverter cutoff occurred. HOWEVER, the Lithionics BMS were both reporting approx. 12.6v, well above the cutoff point. All battery connections felt tight and cool to the touch. After breaking out the voltmeter and talking with Xantrex this is what I learned: 

1. It is normal to lose some voltage between the batteries and the inverter under load. Just a fraction of a volt, but that matters here. Retesting with a voltmeter showed a drop between .4 and .6 volts under that 780W load. Xantrex support said I could safely change the Xantrex low battery cutoff (LBCO) to 11.5v. That should allow me to draw the batteries down much farther.

2. Lithionics has a firmware update (v9.0.04) that improves SOC calibration by automatically rough calibrating at certain setpoints during discharge: https://lithionics.freshdesk.com/support/solutions/articles/154000127575-what-is-soc-drift-and-how-to-avoid-it-

We've got a bitter cold spell coming, so I'm going to stop playing for now. Recharging the batteries to full today before it gets real cold. I'll install the battery firmware update later and change the Xantrex LBCO setting before I try again.

Always a learning curve...

 

 

Edited yesterday at 03:29 PM by Steph and Dud B
Changed title

[Steph and Dud B]

Update: 

The v9 Lithionics firmware is only available for external BMS batteries at this time, but they say they'll be releasing a similar update for internal BMS batteries soon.

For now, those of us with internal BMS will still need to draw the batteries down to 0% SOC to recalibrate SOC. I'll wait until the new firmware is available...

[jd1923]

1 hour ago, Steph and Dud B said:

It is normal to lose some voltage between the batteries and the inverter under load?

We've got a bitter cold spell coming, so I'm going to stop playing for now. Recharging the batteries to full today before it gets real cold.

Yes, load on the inverter creates a voltage drop. You do not see it as much when you have high SOC and ample LiFe PO4 Ah capacity. When I first tried to run A/C on inverter, back when we had lead-acid batteries, the load of the A/C dropped voltage from 12.8 to 12.1V immediately, hence the inverter started reporting warnings. I would drop your low/shut-OFF setting to 11.9V to start.

Also, if you going into a cold spell and your Oliver is in storage, why recharge now? If they are disconnected, I would leave them at 50-60%. If you are connected and have some parasitic draw, then getting them closer to 100% SOC does make sense. 😎

[Steph and Dud B]

4 minutes ago, jd1923 said:

why recharge now? If you are connected and have some parasitic draw, then getting them closer to 100% SOC does make sense.

Yes, we're connected with the usual parasitic draws plus the internal heaters. Lithionics says leave them on the charger all winter while the internal heaters are being used but I don't like leaving them on the charger 100% of the time, so I've been letting them drop a bit, then bring them back to 100% SOC once every couple of weeks.

[jd1923]

6 minutes ago, Steph and Dud B said:

I don't like leaving them on the charger 100% of the time, so I've been letting them drop a bit, then bring them back to 100% SOC once every couple of weeks.

Yes, good thinking, and don't be afraid to let it go longer to lower SOCs in-between recharging.