Activate dumpload before 100% soc

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lief ryan asked Aug 12, '22

Activate dumpload before 100% soc

I have a situation where my batteries reach about 80% soc by 8am on sunny days and the bateies lower thier charge current to say 20A although I may have a potential 100A available, i have a dumpload relay that turns on an immersion heater when the soc reaches 100% and off again when it goes down to 98%, this works well but I know on sunny days I could turn the dumpload on much earlier (at say 75-80% soc) so I was thinking of having the relay triggered by a light intensity sensor connected to an arduino.

Sorry if that was a bit long winded but I'd be interested In hearing people's thoughts or design idea's

Set up is

SmartSolar 150/100

Multiplus 48/3000/35/50

VenusGX

2x pylontech us2000b

8kwp solar

Hot Water Diversion

2 |3000

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Modifications Space

Node Red Space

Answer 1 · 2022-08-12T08:29:00Z

gazza answered · Aug 12, 2022 at 08:29 AM

It is most likely possible... although I would have thought it would be easier to adjust the existing set points that the existing dump relay switches at, based on a voltage or current trigger?
Getting the correct light intensity trigger point may well be time consuming, on part-cloudy days it could be switching on and off a lot..?! At least if you use the data coming out of the MPPT in some way (ie from the Venus) a lot of the smoothing required would be done for you?

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Answer 2 · 2022-08-12T09:39:43Z

Mark answered · Aug 12, 2022 at 09:39 AM

The most reliable way to trigger a dump load, would be to compare the actual battery voltage to the charge voltage limit/setpoint, with the addition of some time delay logic. This will effectively 'test' to see if there is sufficient solar power available at a given interval once the charge voltage limit/setpoint has been achieved.

Consider switching to Venus large image and using NodeRED to easily integrate with all existing parameters and create the required control logic, see: https://www.victronenergy.com/live/venus-os:large.

The ideal control system/setup would be to dynamically vary the power to the dumpload depending on the excess solar power available (as opposed to basic on/off control), but this requires more hardware to modulate the power output.

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lief ryan commented · Aug 22, 2022 at 09:16 AM

thanks, i didn't know about the venus os large.

i do have a PWM diversion load controller but i don't have the option of using a dc dump load as the power shed in 100m away from the house, something like the immersun controller would work if you could get it to respond to battery SOC or voltage?

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