BLITZEN goes Lithium

[Trail Talk]

Our lithium battery (LiFePO4) learning continues...

During our summer travels, we noticed that one of our two Discover Blue 200Ah batteries was consistently discharging faster than the other. Using their BMS Bluetooth app, which reports individual cell voltages and total SOC, we found one was typically reporting 15-20% lower voltage despite checking that all the connections were proper and secure.

So once home I contacted Discover Energy's tech support and "connected" with a really patient technician. Unlike most other support platforms, from internet to insurance, I always deal with the same fellow. Also, unlike those disappearing chat windows, our full communications thread is always there to refer back to.

Recalling the over-voltage protection that was triggered on the same battery (see post #1), and after checking connections and settings, our tech feared the BMS may be bad. Since the BMS is a user-replaceable component with their design, he shipped out another with a link to an installation video.

After the new BMS was installed and both batteries fully charged to the same resting voltage, they went back into the cabin. Access to our battery compartment is through a smallish floor-level access hatch and I'm working on my back mostly so the weight advantage of the lithium over our old AGMs was much appreciated.

Apparently it will take some use and time for the battery app's SOC calculation to sync but I'll continue to rely on the Victron BMV-712 to monitor anyway. VictronConnect is really a fantastic app if you have multiple Victron components.

A bunch of other settings were adjusted as per Discover Blue's specs which were different from the Victron and Xantrex lithium battery defaults; absorption to 13.8V and float to 13.6V, tail current 2.5%, charge efficiency 99%, discharge floor at 15%, and finished by synchronizing the SOC reading to 100%. I also got around to creating a VE.Smart network with with MPPT solar charger so the BMV shares battery temperature and current readings. Annoyingly, for reasons unknown to anyone outside of Victron, they haven't enabled the Orion-Tr "Smart" DC to DC charger for VE.Smart networking!

We haven't travelled since the BMS swap but will do so in the near future. On shore power, the batteries are now maintaining an equal and full charge. I must confess to being a complete noob with electronics and batteries so the generous and patient support I've received from Discover Energy has been a godsend. Still, hoping not to need their services again ;-)

 

[Trail Talk]

No fun having reading a bunch of text so here is picture of the replacement BMS. Comes as a unit with the battery cover and terminal posts.

 

[charlieaarons]

Do you know if those batteries can be mounted on their side?

 

[Trail Talk]

Do you know if those batteries can be mounted on their side?

Manual states any position except upside down.

 

[charlieaarons]

Thanks, just downloaded manual. They seem reasonably priced and have Bluetooth observability.

 

[Trail Talk]

Finally got out for an off-grid overnighter and was able to monitor the batteries as configured. We wanted to observe the aurora borealis but it was cloudy. During a daytime hike we did have a close encounter of the large hairy herbivore kind when a few bachelor bison decided to camp on the trail. We exchanged grunts and huffs and eventually the one closest looked away, signalling we weren't worth the bother, and we skirted by passing within 15 ft. I tried to snap a photo but didn't press the shutter fully so nada (reminder to turn on shutter sounds). FWIW, we would have turned around three months earlier...

We encountered a large herd across the roadway while driving out the next day. It was interesting to watch the bull blocking the road while his harem and calves crossed then finally, with a head toss, he chased off after them. That guy was the reason those bachelors were hiding out about 15 km away. Up north we often came across wandering bachelors, alone or in small groups, looking for better opportunities elsewhere. This photo is from the same time place and time last year, at a much more comfortable distance.



The other "alarming" incident, involving batteries this time, happened when we tried to use an electric kettle, which set off an over-temperature alarm on the Victron BMV-712 battery monitor. Observing the battery app in real time showed normal temps, slightly rising with the current. The battery monitor OTOH showed a rapid rise to the preset alarm threshold. It was a real "D'oh" moment (picture head-slap) when I realized the temperature sensor, sandwiched between two 2/0 battery cables, was passing the current between them and heating up like a toaster element! This was the original set-up with AGM batteries but obviously not suitable for our lithium swap. Moving the sensor to the top of the stack was a quick fix.

 

[Trail Talk]

Recently concluded Ice Ice Baby 2024 and have a couple of issues to add to this thread in hopes it may inform others on the same lithium journey. Or you can get some amusement from my rambling, I'm OK either way ;-)

1. The morning of our departure, aside from having to chip the shore power cord out from under 6" of ice, we found the battery BMS had gone into Charging Under Temperature shutdown even though we leave an electric heater inside the cabin while in storage. The interior thermostat was reading 5C and the BMS protection is 0C. Our batteries, while inside the cabin, are in a compartment with two sides exposed to exterior walls and it had been pretty cold recently. Just sticking my hand inside, it was apparent the temp inside was lower than the main body of the cabin. My solution (before next winter) will be to install vents in the access door to allow that warmer air to circulate around the batteries.

2. We experienced a Low Battery Cut Off alarm from our Xantrex Freedom XC 2000W inverter/charger while camping off-grid. The alarm sounded shortly after I plugged in an electric kettle and allowed us 5 seconds to disconnect the load before the inverter would shut down. Battery SOC had dropped to 50% after three days without driving. While this was the lowest SOC of the trip, it was well within the capabilities of the batteries; its one of the advantages of lithium after all. The inverter cut-off was set to the same value as the battery BMS, 12.0V, so I was puzzled why the inverter sounded an alarm but the BMS didn't. Luckily I had two sources of real-time data to monitor, the inverter's control panel and our Victron BMV-712 battery monitor, while I recreated the problem.

The result was interesting; without a load both sources gave the same voltage but once I switched on the kettle, the inverter's reading consistently dropped 0.4V lower than the BMV-712, triggering the alarm. Confident of the Victron's readings, I adjusted the inverter alarm down to 11.6V for a nominal 12V. It later learned that unequal cable lengths were the likely cause; very short to the Victron shunt but longer to the inverter, thus the voltage drop.

We are planning on upgrading our inverter to 3000W before summer and upsizing the cables to suit. Stuck now on choice; everything else we have is Victron and we love their app and how the components interact seamlessly. The MultiPlus also offers a second 120V output and a 4A truck battery trickle charger output. But man, they are fat bastards!



The Xantrex 3000W Freedom Pro XC has its own Bluetooth interface and doesn't have either a 2nd output or trickle charger BUT its smaller size would probably fit in the existing space so we wouldn't loose any storage.

Still, I'm leaning towards Victron so made a couple of cardboard mock-ups to try and find a suitable place to mount one. Its likely that will be the deciding point between the MultiPlus or MultiPlus II.

 

[gdaut]

Interesting. Why is the BMS and inverter SOC cut-off set at 50%? I understand that is typical for AGM batteries, but as you note, a bid advantage of lithium batteries is they can be regularly discharged to a low SOC. Or at least that is what I understand.

 

[Trail Talk]

Interesting. Why is the BMS and inverter SOC cut-off set at 50%? I understand that is typical for AGM batteries, but as you note, a bid advantage of lithium batteries is they can be regularly discharged to a low SOC. Or at least that is what I understand.

Ah, I was unclear. SOC comment was just to inform. The inverter and BMS cutoffs were set to 12.0V. The BMS is not adjustable but the Xantrex was.

 

[Alloy]

No fun having reading a bunch of text so here is picture of the replacement BMS. Comes as a unit with the battery cover and terminal posts.

View attachment 808832

Where are the temperature sensor(s)?

 

[Trail Talk]

Where are the temperature sensor(s)?

Don't know, they're not identified in the manual. Looking at the photo, my wild-ass guess is the circled part but, if its important, I can ask their Tech Support. What are you thinking?

 

[Alloy]

Don't know, they're not identified in the manual. Looking at the photo, my wild-ass guess is the circled part but, if its important, I can ask their Tech Support. What are you thinking?

View attachment 831025

The BMS will heats up immediately when in use while the cells on/against a cold /floor/wall remain below freezing. Easiest solution is 360° air circulation around the battery(s) and a Bluetooth thermometer.

Some Lithium batteries will have sensors on the BMS - the case - the pos/neg terminals - the bottom or side or between cells.

 

[Trail Talk]

Appreciate that, will investigate

 

[Trail Talk]

View attachment 830891

FWIW, neither fits anywhere convenient within our cabin without giving up a cabinet. Luckily, I can default to She Who Must Be Obeyed for that decision ;-)

 

[NOPEC]

FWIW, neither fits anywhere convenient within our cabin without giving up a cabinet. Luckily, I can default to She Who Must Be Obeyed for that decision ;-)

View attachment 832246

Ah yes, gone but not forgotten, just like Dame Edna and Sir Les Patterson....