MSview Modbus Prostar MPPT Lifepo5

Viron · May 2020

I'm in the planning stages of switching to Lifepo4 from AGM. My system is Morningstar PS-MPPT-40M, RD-1 Relay Driver, Samlex PST-3000W 24V pure signwave inverter, and 12ea 100W Renogy PV panels.

Being budget concious I'm considering a Chargery BMS. It has low current outputs to drive relays to drive load and power relays. The relays they sell are power hungry and run hot.

My plan is to use the low current load output to PIN 3 of my PST-3000W inverter. I've proved that works. It draws about 5 milliamps at 24VDC.

Where I need help is using MODBUS via MSview to setup my RD-1 relay driver to signal the PS-MPPT-40M to shut down.

I believe I need to setup the RD-1 to read either 12V
Supply Voltage or Gate Drive Voltage. Then when the Chargery BMS drops current from the low current to the power relay that is actual going to the RD-1, I can set "if voltage less than "x" write to the charge disconnect coil" that tells the PS-MPPT-40M to shutdown via the RJ11 Meterbus port.

Also, I went with Morningstar and Samlex because I am an amateur radio operator and wanted FCC Class B certification to avoid RFI issues. Chargery is an unknown to me but for $150 I'm willing to take a chance.

However, I haven't purchased anything, so if someone has a better low budget low power solution I'm willing to check it out.

I'll probably do CALB 3.2V CA180 cells.

All this is for my portable PV system in my condo in Cocoa, FL so I can have power after a hurricane. I do have fuses, breakers, GFI, switches, etc. Typically I only need 3 to 5 days of power and my normal consumption is 12kWh per day. I already have 18v tool batteries for about 3 days of fan and lights. Also, I have 300W & 500W 12V inverters that can run off my car.

Am I going in the right direction for existing plan? How do I set it up in MSView? Do I use peer to peer or master slave configuration? Do I need to do a different plan with a different BMS because Chargery has RFI noise?

Modbus is new to me. I haven't coded anything in about 20 years. So, if I didn't communicate clearly, or I ask "dumb" questions please forgive me. Nor, do I have any formal electrical training.

mcgivor · May 2020

The Chargery BMS is primarily designed for automotive grid charging applications where the charging is terminated when the batteries are fully charged, not for a solar application where that may be undesirable in that it would physically disconnect the controller. This in turn wouldn't allow the solar to power the loads until it reconnects when the voltage falls to a predetermined value, resulting micro cycles of the battery.

To get around this a bi directional BMS can be used where the battery is bypassed entirely until such time the solar cannot support the loads and the battery supplements it. The settings of the charge controller are important as LiFePo4 have different needs, compared to that of their LA counterparts, for example there should be little to no absorption, no equalization, no temperature compensation and voltage should be limited to provide a maximum cell voltage lower than fully charged, 3.650 volts per cell if in a cyclical application. When dealing with Lifepo4 one needs to think at the cellular level, along with having an accurate meter capable of measuring down to 1 mV, or 0.001 V.

The bidirectional BMS I use was actually less expensive than the Chargery, which I do use as a monitor for a quick reference, though through observation I find the Chargery to be somewhat inaccurate in its voltage display, when verified with 2 Fluke 179's and Fluke 12 meters, but it does offer a basic instant idea of how things are.

My first question would be, did the AGM batteries support your needs? Second, is the capacity of the proposed replacement LFP equal to that of the existing AGM bank? Third, is this a backup as opposed to a cyclical every day use system?

MSview Modbus Prostar MPPT Lifepo5

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