Rosie as a UPS

[octillion]

I have a MNROSIE7048-CL200-PW I want to effectively use as a UPS with minimal drain on batteries while in standby. I am running open-loop with the Whizbang Jr (load/charging current is usually small).

Desired setup looks like this:

• 120/240 V utility power will power critical loads (refrigerator, boiler, well pump...).
• While utility power is detected as present, the inverter is shut off to minimize idle power consumption from battery.
• When utility goes down, loads will be supplied from batteries.
• Transfer time is not important, AC input relays may open and inverter may start up at whatever timeframe is required.
• When utility power returns and is stable, sync inverter to utility, bridge AC input to output, then shut off inverter (zero transfer time, beneficial but not required).
• Solar keeps the batteries topped up, but it is a tiny amount of solar until I can permit a better location.
• When battery SoC exceeds 80%, enable inverter and shift load to batteries to consume excess solar beyond keeping batteries charged. Maintaining 80% SoC rather than 100% to minimize wear on batteries.

I have encountered a couple problems:

• If I use power save search and no load is attached and there is no AC input voltage, the typical draw from batteries is a few hundred milliamps. As soon as there is an AC input, the draw is around 1.5 A, whether or not there is a load. This current is excessive, and beyond what my average solar input can overcome. This happens whether I am on "grid" AC input with or without grid assistance, or on "generator" AC input.
• While inefficient, I could utilize the charger to maintain around 80% SoC and overcome the idle draw of powering the inverter in standby. However, I do not see a way to enable the Rosie charger and stop at a particular SoC, I have to charge to 100%. I could reduce the absorb/float voltages as a hack, but this would then throw off reported SoC unless I try to compensate by also reducing the configured battery capacity (100% SoC would actually be 80%, but otherwise would scale correctly). Ideally I could set both a SoC and separate voltage limit (this will prevent overcharging as SoC calibration drifts between full charges), stopping charging when either is hit to maintain a minimum level of charge but leave buffer for solar. When I was running closed-loop with the battery I saw an "Enable Charger SOC" option, but no matter what value I set this to the charger was never enabled or disabled; this option is also not mentioned in the manual, so I have no clue what it is supposed to do.

If I could solve either problem (1) or (2) this would allow my desired setup to function. At the moment I keep the Rosie disconnected from critical loads, have no AC input, and have it standing by in power save search. Solar overcomes the average draw to keep the Rosie powered in this state, and during an outage I manually transfer loads to Rosie. I'll also transfer loads to Rosie when SoC is becoming high to allow it to drain down and utilize excess solar.

One other side oddity: The manual states the power save search delay is adjustable from 10 - 120 seconds. From the MNGP2 I can only set the search delay to "0 S" or "1 S", and either option seems to have no effect, always running on a 10 second search delay.

Thanks

[FNG]

So how I would set it up:

Charger - OFF
AC INPUT select LBX mode and set it for SOC%
SOC% ON GRID set to 80%
SOC% OFF GRID set to 90% (Adjust this to what you want)


What happens now is when the battery is filled by the solar the Rosie will open its relay and ignore the grid until it drops to 80% the it will close its relay and let the grid pass through and go into standby until the solar charges back to 90% than it repeats. I don't believe there is much t save by physically turning the inverter off and if you did it no longer passes through.

The only way I could see to turn it off and power from the grid would be a transfer switch that could be triggered some how from an Aux on SOC% then when triggered it would move the loads to the grid and use a second small relay to drive the Front Panel terminals inside Rosie. I think this save less than 10 ish watts over standby and likely the relay draws and transfer switch would chew that up

[octillion]

Thanks, I had not considered LBX. That would make more efficient use of the battery power, I'll set that up. I forgot to mention, I'm using two EcoWorthy Cubix 100, 48 V LiFePO4 batteries.

I had considered external transfer relays as a last resort, never providing AC power to the Rosie unless I need to charge the batteries through a generator during an extended outage.

I see significant differences in idle battery power draw when AC power is presented to the Rosie. The plot below shows battery consumption when (1) Rosie is isolated from AC power with power save search enabled, (2) Rosie has AC input under "generator" mode, and (3) Rosie has AC input under "grid" mode. In all cases there is no AC load, and the Classics MPPT has been disconnected.

When Rosie has no AC input and utilizes power save search, power draw is very modest, briefly enabling the inverter at a period of 10 seconds to check for loads. The average power draw is only 6.3 W.

When AC input is provided under generator mode the consumption rises significantly to ~32 W. This appears to be because the inverter is running, even though the load is bridged to the AC input. Maybe the topology requires this, I do notice if I manually turn off the inverter the relay connecting AC input to the load disconnects. Ideally the inverter would be able to shut off completely only to wake up when Rosie detects there is no longer a valid AC input.

With AC input provided under grid mode the average power is a bit over 50 W and very noisy. I suspect the noise is related to the inverter tracking grid power. I would expect this mode to have the most consumption. There is no noticeable difference whether grid support is enabled.

So I'm looking for a way to power loads through the Rosie with utility power while keeping the battery draw at/under what I see when no AC is present. If that's not possible I may go the external transfer route.