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addvanced asked

Best way to keep my batteries warm, remotely?

My system:

690 Watts of Panels, 150/45 SmartSolar Charger, 1200w Phoenix Inverter, Cerbo GX connected to a 5g router with good reception, and a Smart Shunt attached to 400Ah of self heating LitTime batteries.


Last winter, the batteries did not charge reliably until I insulated them and got them to stay warm (irony!). I'd like to avoid this BS this year, so I'm wanting to install a backup heating system, that ideally would be programmable to run for 10-30 minutes early in the morning, so the batteries are warm enough to begin taking a charger when the sun comes out.

I have purchased some seedling heat mats that take AC.
Current Thoughts:

Option 1: Plug the matts into the inverter directly, and turn the inverter on remotely, maybe program it to come on in the morning.

Option 2: Use something else that can keep track of time/date, like some sort of smart outlet?

I would like to also monitor the temps of my batteries. I am going to build an insulated battery box when I'm out there in a few weeks, and I'm not sure what temperature sensor to get. Does it go into the Cerbo GX or the Smart Shunt?

Temperature Sensor
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3 Answers
elvis avatar image
elvis answered ·

What kind of chemistry are the batteries?

Whats your general location, anticipated temperatures?


I use a small 50W DC powered PTC heater.

An inline snapdisk is used on the power line as a thermostat.

I also use the analog input on the Cerbo for a temperature sensor.


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matt1309 answered ·

Hi @ADDvanced

I'm planning a similar setup soon however my plan was to use shelly smart switches. I believe the shelly 1PM has a temperature addon module that allows you to read temperature from a probe and activate heat pads using this. This could be monitored via home automation system if you have one or via shelly cloud/app if not.

And given it's just a smart switch it could be used with any type of heat pad.

The switches are usually rated for 13a so should be fine for most heat pad scenarios.

I've not got this setup installed yet but this was my planned solution.

You can control shelly devices (using local http API) via node red if you want the victron system to activate the heat pads. I've tested this feature with my excess hot water setup so i know this part of my plan will work.

I generally prefer using Shelly switches controlled via node red on the gx device rather than the built in relays as I feel it gives me a bit for flexibility in terms of load size.


In terms of monitoring the temperature/what activates the switch. My plan was to have 2 ways of starting/stopping the switch as a safety feature. One being in Victron and the other in the shelly switch itself.


Not sure how easy this is but my hope is that in the shelly i can program it to auto turn on if temperature dips before 1 degree Celsius (the lower limit as a backup). But then have node red (using the temperature sensor on my smart shunt which is closest to my battery) to turn on the shelly switch at say 4 degrees.

My concern was my smart shunt is closer to the BMS which will give off some heat so Im hoping i can set it internally in the shelly to also switch on between temp ranges just incase the smart shunt temperature never gets low enough due to BMS keeping it slightly warmer.

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dmsims answered ·

I use a seed germination mat

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Related Resources

Victron temperature sensor disambiguation table - which product supports which sensor