Victron Multiplus II 48/5000
Cerbo GX
GX Touch 50
2 x Victron Smartsolar MPPT 250/100
2 x Pylontech US 5000 LiFePo4 batteries
16 x 405 W sola panels at 20° angle (along the roof).
This is installed in a summer cabin in southern Finland on an island not really accessible during the winter.
Last winter (the first winter) I just turned off the inverter for the winter and left the chargers on and the system seemed to survive the six months shutdown just fine, I found the batteries at 100% when I paid the first visit this season.
Now I’m considering a installing a GSM router and a security camera or two.
Obviously it would be nice to be able to let them run all year long.
There is very little (but still some) solar energy available during December/January so I realise there may not be enough energy available to run those, especially as the panels will most likely be covered in snow.
My questions is, is it safe to make an experiment and leave the system on and see what happens?
Will the batteries protect themself from damage if the SOC and/or temperature goes goes too low ?
Maybe this is more of a Pylontech question but I thought I’d start here.
You can configure your own minimum soc. Recommendation for LiFePos is to store them above 60% soc, when unused, to account for some self-discharge happening during the idle period.
So, you could theoretically set the minimum soc to 60% and say: “If we have solar, keep running, when reaching 60%, shut down for idling-purpose”.
Ultimately, before any SEVERE Damage will occur, any system should theoretically protect itself - but that doesn’t mean every other operation state that reaches close to such limits is healthy and desireable.
Depending on the temperatures you reach there, the best / healtiest choice may be to charge the batteries to 80% and move them to a well temperated, dry storage location for the winter and let the gsm / cam only operate when there IS Solar available. (Not sure, if MPPTs will enter operational mode, when battery is disconnected, tho)
Is that SOC limit a feature of the Pylontech internal BMS or Multiplus?
It is difficult to know what temps are reached during winter but the weather is mild in the archipelago, just checked last winter and Decemeber above freezing all through, January was around 0 °C, Feb a few days at -5 °C and March a few more days. Never below -5°C.
The batteries are 40 kg each so I won’t be moving them for storage unless I absolutely have to. I’d rather accept a shorter life time
Physically disconnecting the batteries I do not want to do but if this can be done from the control panel I might consider running the the GSM on solar only but I doubt the Multiplus works if the batteries are disconnected and as you say the same worry applies to MPPTs too.
If you keep your multiplus on and can not use AES or search mode due to the low power then you will have something like 30W for inverter zero power load, 10W for a router, 5W for the GX device and MPPT self consumption and 2 to 5W for cameras depending how many, say 50W continuous load with over half of that to keep the ac power running. I suggest you look into DC powered routers and cameras designed for boats or RVs or most ac powered actually use 9V DC so get some 48V to 9V or whatever converters. Then you are in with a better chance of doing this. My boat has the inverter shutdown but the rest of the system stays live with a DC powered router for monitoring.
I agree with your logic and numbers. I’m checking if the AES or search mode could be utilised, after all I don’t need 24 frames per second video 24 hours a day
Winter time robbery on a remote island over the ice in full view of full time habitants across the water is remote.
But seeing that everything looks alright as far as weather damage is concerned would be nice. And a weather station to monitor the weather would also be entertaining.
So a picture / weather / battery report a few times per hour would suffice I think.
At the same time it would be interesting to learn how much solar power is available. If there is more than the consumption then the batteries will be at 100% and I will not know the excess.
So maybe arrange more load and remotely adjust the AES period if/when the batteries start not reach 100% on a daily bases.
I have a similar issue in a different location (off grid, southern hemisphere, mid winter, gel battery, small system). A low-tech mid-winter solution might be to leave the house power on, use a timer switch for the router and cameras, and run them for an hour or less per day. That provides a window for VRM uploads and to use the security cameras to check the house. In our case, the router (satellite, ~40W) running 24/7 is the largest load when the house is unoccupied.
Thanks. Yes, that is an option and I just understood that the Cerbo will save logs so that sounds feasible to upload them once a day.
Can you elaborate what you mean with ‘leave the house power on’?
The inverter (Multiplus II 5000) idles at 18W so I cannot leave that on. But I don’t know if I need to leave it on, perhaps in the AES or search mode IDK.
I was thinking a step down PSU for the modem and cameras directly from the batteries.
In my case, ‘leave the house power on’ means leave the inverter running (Victron Smart inverter, with low-voltage cut off if the battery gets too low). There should be enough solar to provide minimal power. In your location I assume you get no power at all in winter, so it’s a question of how to ration stored battery power over many months.
Your earlier comment about measuring solar levels when batteries are at 100% was of interest. I’ve been experimenting with Raspberry Pi Pico, light sensors and logging light levels throughout the day. Pico only uses 0.5W.
Thanks.Go it. My experience so far is exactly one winter for which I turned the inverter off. The theoretical non-cloudy no snow on the panels solar power in Dec/Jan is in the ball park of 700 Wh/24 h which is too close for me to rely on that for. I might install a GSM router and do I once a day wake up. This would allow me to monitor the system and if the batteries seem to show signs of depleting I could hike across ice thickness permitting and turn the inverter totally off. Or maybe I could do that remotely?
I think the main obstacle is the temperature as even if I have some solar power the LiFePo4s will not accept any if/when it gets below freezing so I would have have the batteries insulated and heated with a portion of that solar power.
I think overall this is not a project for this winter to deploy as in a few weeks the wether turns nasty and we will go and empty all the water lines and stuff for the winter and the this season is over.
