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seandembrosky avatar image

100/20 - 48V system Configuring a dump load for the load port (relay question?)

I have the 100/20 setup to charge a 48V Nissan Leaf battery setup (52V nominal with 7 plates I believe, a friend did the configuring for me)...

The system charges up to 58.1V and then the 810 watts of potential energy coming in don't have anywhere meaningful to go, so I wanted to attach a simple water heating element on the load port and configure the load system to allow the load port on whenever the battery reads over 58V and turn off at 57.5V (so the load only really runs on sunny days when the battery is already topped off).

In an ideal world the load port would skip taking energy from the battery at all and basically just take the excess energy when above the parameters I mentioned and send it all to a heating element.

I understand a relay is necessary since this model only sends 1A on the load port, so where can I find very clear and understandable wiring diagrams or information on how to set this up?

Thanks kindly!

MPPT Controllers
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1 Answer
Jesse avatar image
Jesse answered ·

Hi @seandembrosky

1A is enough to drive most relays, a circuit of one component, connected directly to the output of your MPPT.

You could attach the output of that relay to the remote port of an inverter, or with a bigger relay drive a load directly.

Keeping the battery full while driving a dump load would be much more difficult however, not sure that's possible with the equipment you have. It's very likely to blindly over or under draw.

Also be careful to figure out what the ideal float voltage of your leaf battery is. If 58.1V is needed for a full charge, you shouldn't be keeping it there more than an hour or so usually before letting it drop.

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Thanks for this info...

My plan is to trigger a relay that can divert the entire solar energy to a hot water heating element. When the battery is full the whole system sends its attention to that component, when the battery is used and dips down to 60% SOC the whole system can focus on recharging the battery again. I don't want the load port to be drawing from the battery...

The component I purchased is a zgt-25 DD which is a solid state relay that I thought could help with this process. The challenge is that when the load port is activated at the voltage I want, the voltage coming out of the port is I believe 58V... Super low amps but way too high Voltage for this device from the little I understand... The SSR I invested in has a control of 3-32 Volts. I suspect what is coming out of the load port will be too high a voltage. Seems like I'm stuck here!