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Guy Stewart (Victron Community Manager) avatar image

How can you control relays using temperature data?

As lithium batteries become more popular and they are inherently more sensitive to temperature (both hot and cold), there is an increasing need for relay controls to manage it.


These controls should be accessible via Venus and the Multi programming. They should be able to use the various temperature sensors, either provided by the multi's-probe, temp sense connected to VGX, BMV-712 temp sensor, or that communicated from the battery BMS via CANbus.


This relay can then be used to trigger airconditioning, fans, heatpads, alarms or other circuits and contactors.

Each battery has different temperature requirements, so the programming function needs to be flexible, eg on/off at specific degree, minimum time open/closed, option for time based control, also state of charge thresholds (so you don't flatten a nearly empty battery running a heater when it's not needed).

Advanced next level features could include things like only activate when there is surplus solar available, so batteries are not discharged themselves.

Can anyone think of any other elements of importance when thinking about designing a feature like this?

feature requestNode-RED
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1. Easy linkage to 'alert(s)' or 'flags' via VRM and/or local BT/WIFI connected devices to Venus/GX including NMEA2000 or related.

2. User configurable alarm 'label' as there may be a 'generic' alarm relating to more than one instance of application (e.g. over temp / House 2); I could imagine that this functionality would be hijacked or easily transferred for pumps and HVAC temps etc. e.g. pump on / starboard fwd etc).

3. Assume by Alarms coming from CANbus we include NMEA2000?

6 Answers
Pat Davitt avatar image
Pat Davitt answered ·

Guy,

It seems like relays and their control is a hot topic now. Why doesn't Victron create a "Relay Device" with 10 or 20 relay outputs. It could connect to a Venus Device (CCGX, etc.) via USB. You could then use software functionality in the Venus OS to drive the relays high or low based on data received from all Victron equipment that communicates with a Venus Device and use algorithms that are either built-in or customized via Node-Red .

Just a thought,

Pat

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wolfbarnsolar avatar image
wolfbarnsolar answered ·

Why not just use Hydroponics gear

I use heat pads & fans to control the temp of my 60KWH battery box environment

main component is a heat/cool control unit adjustable for temp High/cool to Low/heat

we see temps from -7 to +35C has been working WELL for 3 Years

Multiplus controls the SOC

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kai avatar image
kai answered ·

Not sure which bits of the system you're thinking of. Below are some points relating to the relays themselves if they're to be part of the product.


Size of loads. Are you intending that the relays would drive end devices directly or relays would drive external contactors? Can designer choose different relay types?

Manual override. Can operator force relay open/close if system (incl. software elements that is external to your product) is misbehaving and needs intervention.

Positive confirmation of relay position. For critical circuits/conditions the designer may want to get confirmation that the relay has in fact operated as commanded.

Inductive devices (incl. coils for contactors) can be driven you might want to have an option of an integral shunting diode to increase contact life. Should be an option because there are some circuits that require the diode to be NOT installed (eg gigavac dc contactors).

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Mark avatar image
Mark answered ·

I am also looking for a similar solution - either as added functionality to existing equipment (ideally) or with additional interfacing hardware.

Currently my main want/request is to activate AC OUT 2 based on a few basic inputs from the BMV & MPPT.

Accordingly this would probably be best accomplished using a Venus device, although it may even be possible using a Multi assistant, if the few outstanding parameters were sent to it & available for selection...

I do know that integration of 'node-red' is in progress (which is exciting & promising), but I am a little disappointed because from what I have read on github about this, it will NOT be possible to run node-red on a CCGX device due to insufficient disk space... (and of course I have a CCGX in my system). Is this still the case?


In terms of the logic configuration, the following features would be very important for me;

- Easy to select OR & AND logic conditions (where multiple activation/deactivation parameters exist)

- Time condition that trigger thresholds must be met for before activation/deactivation

- MIN ON time condition

- MAX ON time condition (that could also be used alone for deactivation)


Is there any chance that the CCGX firmware/software could be updated to achieve this direct control over AC OUT 2? (without node-red)

I would think that you could possibly start with a rough duplicate of the automatic generator start/stop logic/layout and link it to triggering AC OUT 2 as the first step, then progress as required from there?


@mvader (Victron Energy Staff) if there is any chance that you could comment on the 'feasibility' of my request it would be greatly appreciated.

I do understand that the quantity of 'feature requests' coming through is probably getting difficult to digest/follow up & prioritise - but "if you don't ask, you don't get", so I am asking... :-)

Regards, Mark


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Boekel avatar image
Boekel answered ·

One feature that would benefit 'dumb' Lithium batteries (like the new Superpack from Victron) is to be able to set charging current to zero (or a low number) based on temperature (5 degrees C is generally specified to be a minimum charging temperature)

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Guy Stewart (Victron Community Manager) avatar image
Guy Stewart (Victron Community Manager) answered ·

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