question

Colin Wright avatar image
Colin Wright asked

External load switching via mppt controller

Hi all,

I have an auto load query for mppt controllers.

Firstly our setup us as follows.

We have two arrays:

375 watt with a 100/30 Bluesolar with Bluetooth dongle

460 watt with a 100/50 Smartsolar

We have 720amphour battery bank of 6x 6volt Trojan batteries giving us a 12volt house bank.

My question is, we have a 12volt X 200watt immersion heater for our hot water calorifier on board Emerald.

Is there a way to use the street light function to switch the immersion on at say 14.6volts and off again at 13.6 Volts. As there is no load outlet on the mppt controllers how would we wire it in.

Many thanks for any help you can give. We are trying to use our excess power in the afternoons to automatically heat the water once the batteries are full.

Kind Regards
Colin and Nichola on Emerald
www.yachtemerald.com

MPPT Controllers
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2 Answers
klim8skeptic avatar image
klim8skeptic answered ·

I think it can be done. Look at a demo mode version of your 100/50 in Victron Connect> load output> User def algorithm. This will require a https://www.victronenergy.com/accessories/ve-direct-tx-digital-output-cable and probably a https://www.victronenergy.com/battery_protect/battery-protect

I like KISS. I used a clockwork timer out of a scrapped tumble drier. Similar to this https://www.partmaster.co.uk/timer-clockwork/product.pl?pid=2047309&query=clockwork+timer and a relay.

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Colin Wright avatar image
Colin Wright answered ·

Hi, thanks for this it was really helpful.

I have now sourced and installed the mppt digital tx cable.

Unfortunately the DC/DC solid state relay (SSR) I have used is supposed to switch on between 3v and 50v. However the voltage on the digital tx cable from the mppt gets pulled down to 2.8volts by the relay, so it doesn't trigger. I'm guessing that the relay is taking too many milliamps to trigger.

Can anyone help with the specs of a SSR relay.

It should be DC/DC with an output side of say 12volt and 1amp.

The input side of this relay should trigger from the output of the tx cable on the mppt. I know it is 5volt, but cannot find spec of amps on tx out.

I can then use the output of this smaller relay to trigger the larger load relay this is the easiest work around I can come up with.

I'd be grateful for a part no. and manufacturer of a suitable DC/DC solid state relay, or an Amazon link or similar.

I'm looking for a DC/DC solid state relay that the tx digital out cable on a 100/50 smart solar mppt will trigger.

Kind Regards and many thanks for your time and help.

Best wishes

Colin and Nichola Wright

Yacht Emerald

Cartegena Spain

In virus lockdown.



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