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Simon Phillips avatar image
Simon Phillips asked

Using Programmable relay on Smart Solar controller to switch on 12v DC dump load

Hi New here but I have Victron Multi plus inverter / charger and AGM battery bank . I am looking to up grade my solar using Blue solar panels and Smart solar controller but would like to switch on a dump load to a 12 Volt water immersion heater when batteries are full , Can the programmable output relay I see listed on smart controller be used to switch a bigger relay to do this ? I know Outback and midnite have Aux outputs that can do this but would like to keep everything Victron if possible


Many thanks

smart solar set-up help
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4 Answers
Mark avatar image
Mark answered ·

Yes, it's technically possible (with an additional external relay - rated to the load) and you have a few options to use for control, you could select to engage the dump load based on the charger going into float, high panel voltage or high battery voltage - see image below;

However, that is quite a course method of control and not really ideal. There is no way to combine conditions or of knowing if there is enough 'spare' PV power available to fully power the dump load without drawing on the battery.

So with this type of very simple on/off control method, it's vital that you don't go overboard with the size (power) of the dump load/heater - It's better to go smaller (lower power), so that there is sufficient PV power available to fully cover the dump load more often.


An ideal dump load control system/strategy would include the ability to modulate the power provided to the dump load to suit the 'spare' PV available at the time.


1586947279961.png (59.1 KiB)
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Simon Phillips avatar image
Simon Phillips answered ·

@Mark Many thanks for the answer , that is what I wanted to hear was planning to connect to a 300w 12 water heater element through an external relay . will have 1050 W solar . How would I modulate the power as suggested ? Sorry if dumb question.

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guy-b avatar image
guy-b answered ·

Simon - I have same initial question as your's. I also want to use 300w immersion for dump load - did you ever get the solution and working?

tks Guy

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jkmann avatar image
jkmann answered ·

If you have a BMV712, there is an approach to close a relay based on a battery State of Charge condition, which seems a bit better than switching based on voltage level: https://community.victronenergy.com/questions/22862/bmv-712-relay-switch-condition-charge-status-soc-p.html

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