question

erutan avatar image
erutan asked

Three questions regarding a 300w (100/30 smart controller) solar setup, bmv-712 battery monitor, and VRM.

Overview:

I've had a ~400AH LiFePo4 battery setup charged from the alternator (180A, 14.2V) checking battery levels (very handwavey I know) via voltage level for years and it's worked well but due to c19 I'll need to be inside running an inverter more often, so I'm setting up a solar system. I'm going with 3 100w rigid/fixed solar panels wired in series into a 100/30 smart solar charger. I was thinking of hooking up a bmv-700 (don't need a second bank to be monitored), but having the solar charger monitor my battery temp is key, so then it's the 702 and once I'm there it's a $20 cable or just get a 712 and not have to do another wiring run, so 712 it's looking to be. Having load monitoring seems useful vs just getting the $40 temp/voltage smartsensor.

Questions:

1) Would I have been better off just getting a 100/20? It has low voltage shutoff and output load monitoring, and I'm really not going to be pushing 20A often with 300W, though I did like the ability to add on another panel later. Will I get any significant functionality with a bmv 712 + 100/30 over the 100/20 unit?

2) It looks like I should be able to hook up my SmartSolar 100/30 charger to VRM according to documentation, but the portal only shows the GX controller units as eligible devices, and that'd be overkill for my setup. I assumed it'd sync data from the smartsolar charger to VRM when I was online with my phone/laptop etc connected to it - is that possible? The 30 day limit on VictronConnect for historical data is kind of a shame given how much effort has gone into logging.

3) If 2 isn't possible, does anyone have a decent workflow for archiving the CSV dump info from VictronConnect? It just has relative dates back from the current (0, 1, 2) etc... it'd be nice if those could be put into standard unix datetime when exported by grabbing the date from device (which generally sync to master date/time servers whenever online).

I guess naming the dumps by date, then running a script to parse the csv file by running backwards from the current date and adding in a timestamp field would work (could do a simple personal VRM with a js charting library or something).

BMV Battery MonitorVRMsolar
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3 Answers
spirou avatar image
spirou answered ·

1) without a BMV you're just seeing what comes out of the panels but not what's going in/out of batteries. Not always the same. If I remember correctly 712 has lower self consumption than 702. Also, easier to set up. Probably worth 20€ extra.

You are very unlikely to be seeing 20A in a van scenario unless you're a heavy daytime user and even then the positioning, temperature etc. matter a lot. I was testing my 320Wp setup a few days ago and got to 225W in the middle of a sunny, windy day with clear skies. I had to turn on every single load possible to get there, the battery was full long before that. Also 100/20 is smaller, it might be a factor.

Not sure about that load output and what you think it might do. That's designed for streetlights and such.

2) MPPT/BMV doesn't store a running log for periodic uploads to VRM. You need a ccgx/ venus device for such things, a Rpi is a cheap way to do it but that will have its own self consumption that might not be insignificant especially in winter.

3) I store the 30 day MPPT csv and run it through excel to have a record and a rough idea of what was going on. Obviously a more detailed log would be nice but that's reserved for ccgx/venus. When I want to test stuff I use my phone and VC then make print screens to analyze those short time periods. Not ideal but works.


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erutan avatar image
erutan answered ·

Thanks for getting back to me - this was really helpful!

1) I was just wondering if a 100/20 would fulfill the role of both the 100/30 and bmv-712, which if so I'd redo my setup, but it's not worth returning / re-installing a charger for (not something I'd generally do for a working product, but that'd be > ~$250 savings and a simpler system). I was thinking the load output could be wired though my breaker box and I could measure consumption that way... I don't pull more than 20A at a time on my house batteries.

I've been peaking around 212-222W parked flat for the past 5 days, and that's at 48N in April. I was looking ahead as to whether I'd want to toss another 100w panel for more wintery use at some point, but that's a bit of an edge case. I was ~16A midday, so perhaps the extra overhead has a benefit of allowing a mellower voltage output during bulk in the summer? 13.3*20 is 260W, whereas 14.2*20 is 284... doesn't seem super significant though. I'll just live with my choice and perhaps it'll come in handy later. :)

I have an Engel fridge which is on 24/7, and due to c19 my partner lost her job/housing and is shifting to telehealth, and I who worked remotely before at cafes / librarries / coworking places / etc no longer has that option so we've been turning my camper into a mobile office. Inverter and two laptops running has me on bulk for only 60% of the day, and that's morning in partial shade or less direct sun.

2) That's the conclusion I was coming to... not worth getting a venus or something just for logging on such a simple system.

3) csv into excel would be a simple setup, any templates to work off of floating around to work off of that extend the basic numbers into something visual? It'd also be really nice to have actual dates in there vs just the relative "days ago" it comes with. :/

https://www.victronenergy.com/blog/2016/06/30/victronconnect-1-7-android-6-compatibility-and-more/

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erutan avatar image
erutan answered ·

It'd be interesting to grab lattitude from the phone connected, along with cloud cover from a weather API and record that in the days information.

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