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sparkpoint-solar asked

Configuration of 2x Multiplus II 5KVA in parallel (single-phase) ESS system. 5KW appliance is only to be used on battery power when batteries are above 90% SOC and up to 2hrs before sunset.


I'm hoping for some different points of view on how to configure my ESS system so as to arrive at the optimal solution. There is a 5KW appliance(hot tub) that I only want to run on solar power(whenever excess solar power is available) or grid power(when someone manually decides to turn on the appliance).

My thoughts are to configure the ESS through assistants to:

"Power the hot tub through ACOut1 when batteries are above 90% SOC and up to 2/3hrs before sunset." The 2 hrs before sunset is to allow the batteries 2hrs to get up to 100%.

In this case, I would need to also connect the hot tub to ACOut2 so that if a person is to turn on the hot tub and the above conditions are not met, the hot tub would be fed from the mains grid not battery power. A backfeed contactor would first/simultaneously disconnect the hottub from ACOut1 consumption using a relay.

Does anybody have any better suggestions?

The system spec:


2units -Multiplus II 48V 5000KVA (running in parallel mono-phase)

2units - SMART Solar MPPT 250/100 VE CAN

36units - solar panels (11.5KW of generation power, 2x panel arrays of 18 modules)

12units - pylontech US2000 2.4KWh 48V Lithium modules

*Self-consumption only, no feeding back to the mains grid

The goals of the system:

To reduce the monthly electrical bill from mains electric, while still achieving a 12-15 year lifespan for these batteries.

Multiplus-IIbattery chargingESSPylontech
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markus-001 avatar image
markus-001 answered

Assistants in the Multi’s are difficult to tweak as you can’t access them from your smart phone and tweak them in real time. I would go for relay 1 on the Venus set as generator I think it functions the same on the color control You can set the time window the relay will be active for as well as well as voltage set points, current set points and delays, AC load conditions, battery SOC set points and delays. I use this for under floor heating when battery SOC is higher than 90% I switch on UFH when a stove or kettle is switched on (AC load) exceeds set point X for Y seconds and opens the relay. I also switch off the relay when the battery discharge current exceeds x amps for 30 sec. If you have lead acid batteries you get quite a volt drop depending on the load applied which gives you another set point and the ability to open the relay sooner if there is no PV current and a fast volt drop

Eg would be 48 volt system -10amps of current from the battery for 60sec is ok but a voltage of less than 50v, open relay after 2 seconds.

Just keep in mind that you need to swap the wording around for each condition for this to work, so start generator is actually switching off your load or hot tub element and stop generator switches on the load or hot tub element. You can also keep charging the batteries well into the late afternoon by increasing the modulation between on and off so when the relay opens after 30sec of -1000w battery discharge you keep it open for 300 sec to replace more than you took out. Then set the operating time window of the relay to open 1 or 2 hours before sun set. Quite hours would be off hours set the voltages and SOC values way out of scale to make sure the tub stays off when there is no PV available. To manually activate the relay after sunset switch “auto start functionality” to off and the relay closes.

Just to cover my opinion here, as i’m Sure you are aware, drive a suitable contractor from the CCGX relay.

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sparkpoint-solar avatar image
sparkpoint-solar answered

Thank you for your response. I'm not sure what voltage of coil I need for the contactor(what is the voltage of the relay?)... I'm assuming it's 48VDC? Does anyone know?

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