One more blathering into the ether (who am I kidding... there will be more)....
I've been having issues with the system allowing VERY LOW current, 0.2-0.7A of current "leaking" into the battery when charging is disabled (low temp charging protection).
This is "software" control. Batrium is telling the GX how to behave based on my safety parameters. In this case, the charging is disabled at 5°C by default. At that time, the Batrium says to limit charging to 0.0A. The GX allows the system to continue to use PV for loads.
I have confirmed:
- Current is physically flowing to the battery. Clamp meter isn't particularly accurate at that level, but I see (+) amps in one direction and (-) when I flip the clamp around. The values are similar to what the shunts report.
- The Batrium is indicating 0.0A to the GX
I have also set the GX is set to restrict charging to 0A.
In all cases, a little current is allowed to flow to the battery. The BMS is pulling power from the load side of the BMV, and the Batrium shunt is between the BMV and the battery, so all loads are accounted for. The Batrium shunt itself pulls power, but that's definitely not a big value - definitely nowhere near the 10-35W the current flow suggests.
Here's a test run where I set the temp cut-off higher:
The box indicates data at the end of the charge restriction section showing 0.5-0.7A between the Batrium and BMV (usually on top of each other). Temp has increased to 45°F. The MPPT is producing 160W to power loads.
I replicated the same behavior by having DVCC restrict charge current to 0A - this will override the BMS limits, so it looks like the issue is what the GX considers to be 0A of charge current. I had my lead-acid batteries restricted to 30A, and I recall seeing them hovering at 29.7A regularly, so I know it can work right. There might be a program logic issue with 0A.
We all know that charging below freezing isn't some binary switch. There's a rate at which Lithium can be charged as temperatures progress lower, but without cell manufacturer data, it's all based on hope. 0.7A is the worst that I've seen and 0.7A/450Ah = 0.0016C, so I'm reasonably confident (hopeful) that no damage is being done. It also helps that temps have barely dipped below freezing, and most of this is happening at the 3-10°C safety level.
As easy as it was to do, that prompted me to accelerate the implementation of the secondary safety on the MPPT - The Batrium Expansion Board Relay 1 is now connected to the MPPT control relay. If closed, MPPT function. If open, MPPT turned off.
New control logic as follows:
Below 8°C, Batrium charging disabled. Sends "0.0A" charge limit to GX. GX uses PV to power loads and leaks 0.2-0.7A to battery.
Below 3°C, Batrium critical condition triggered. Relay 1 opens disabling MPPT completely.
Based on my cheap IR thermometer, the Batrium sensors read about 3°C high.
Note that Critical conditions span multiple criteria. In this case, cell voltage over 4.20V, pack voltage over 58.8V, temp value below 3°C and temp value above 45°C will all disable the MPPT.
I've been threatening to do it, and I had most of the wiring done, but I have had the second Quattro hung on the panel for months - doing nothing. When I looked things over, I realized I was about 20 minutes from being done with installation... I was wrong... it was 15 minutes as the VE.Bus Quick Configure tool is WAY easier than the manual configuration.
So, yep... I now have 120/240VAC split phase. Now each of the 5th wheels get their own inverter to themselves as the 50A to dual 30A splitter each takes one leg.
Sight to behold...
Downright luscious.
'Twas a beautiful weekend for November. Nights were around freezing, but daytime winds and temps were very comfortable with lots of sun. It was quite comforting to look at the big battery's SoC and have no qualms running the 1500W "fireplace" for a couple hours to keep the temps comfortable during a movie.
Spent some time under the 5th wheel to try and find additional points of ingress for the rodents. I sealed off another 5 spots that
might allow access. We've all but eliminated them from the living area, but they are making it into the ceiling. To that end, we opened some foamed holes that they had been previously entering and created a "kill zone". It's an isolated cabinet that only allows entry/ext from the ceiling area. Snap traps, sticky traps and poison bait await. It's probably going to be horrifying, but I can't stand hearing them scurrying around up there. This is the nuclear option.
Also helped the neighbor get suitable gauge wire on his FM80 x2 outputs to battery. His two arrays are capable of nearly maxing out the FM80s, so we installed 2awg (biggest the FM80 could manage) welding cable with 100A breakers (midnite solar) on the output. Also implemented a (-) bus bar to better manage cables between his two inverters and the charge controller. Following day, he saw a total of 130A MPPT out at peak solar and was tickled sh!tless.
Off-grid wins all around!