New to forum, 3 year old off grid system

[CRJpn]

New to the forum, have an off grid system in our home in Maine that was installed in 2018 and has been working pretty well for past few years. We are living in Switzerland as expats currently, but returning home in the spring.

Looking for any advice to improve or optimize the system, big ones especially:

• Should we start using the FLEXnet DC again - we disconnected it a couple years ago as it was giving poor SOC guidance to the tenant at the time
• Would like to add a 2kW wind turbine to supplement winter solar, we're on top of a mountain and it should do pretty well
• Plan to add more panels, at fixed angle on the end of the house, to supplement winter as well. We are struggling with trees on the adjacent property blocking the existing panels in the winter, adding some on the house about 15' further back than the existing ones should help
• Any advice to further optimize performance and reliability, for example last summer we learned about (and added) a twisted pair to the charge controller to monitor voltage off the battery, we had missed it during install and it made a big improvement for float accuracy.

Appreciate any advice or comments! I'm a mechanical engineer by profession, I struggle a bit with the electrical side and have had the install done professionally, but maintain and update settings on my own.

Thanks and happy new year to everyone!
Christian

[raysun]

Welcome to the forum.

Should we start using the FLEXnet DC again - we disconnected it a couple years ago as it was giving poor SOC guidance to the tenant at the time

It would be interesting to know the details behind this. While the FNDC is designed around lead acid battery chemistry, it works quite well with Lithium batteries. We use one with our SimpliPhi battery with good results.

Would like to add a 2kW wind turbine to supplement winter solar, we're on top of a mountain and it should do pretty well

Whether a wind turbine adds value to a system is dependent on too many variables to make a blanket statement. They tend to be the most expensive power source, the least mechanically reliable, and the most complex to integrate into a renewable energy system.

Plan to add more panels, at fixed angle on the end of the house, to supplement winter as well.

At high latitudes, larger arrays "tuned" to the wide seasonal variation in solar path, and weather, makes good sense. "I have too many solar panels" said nobody, ever.

[ianMc]

Provided you set up the FlexnetDC correctly it is fantastic. The FlexnetDC gets its tits in a tangle when the SOC goes below 50-60%. Obviously, this cannot work as Lithium has a far greater discharge.
What I have done is lie to the system by inflating the size of the battery so that 60% is actually 100% discharge ie
I have 30kw hours of lithium batteries and I have set the FNDC as follows

Battery Ah - 1,450
Charged Voltage - 55 VDC
Charged Time - 1 Minutes
Charged Return Amp- 8 Amps
Charge Factor- 94 Percent

If I login to the mate3 the info returns the SOC and net KW discharge exactly. In effect 60% discharge on the Mate3 is 100% discharge
This works perfectly for me

[raysun]

Provided you set up the FlexnetDC correctly it is fantastic. The FlexnetDC gets its tits in a tangle when the SOC goes below 50-60%. Obviously, this cannot work as Lithium has a far greater discharge.
What I have done is lie to the system by inflating the size of the battery so that 60% is actually 100% discharge ie
I have 30kw hours of lithium batteries and I have set the FNDC as follows

Battery Ah - 1,450
Charged Voltage - 55 VDC
Charged Time - 1 Minutes
Charged Return Amp- 8 Amps
Charge Factor- 94 Percent

If I login to the mate3 the info returns the SOC and net KW discharge exactly. In effect 60% discharge on the Mate3 is 100% discharge
This works perfectly for me

I have a 48V@450AH SimpliPhi battery in my system with an FNDC. I've never had to resort to any sort of "sleight-of-hand" in order to get the FNDC to track the battery State of Charge through discharges as low as 29%.

I also have a Victron BMV700 on the battery. Both it and the FNDC track SoC with good predictability. I find the FNDC reads a bit low, generally in the 2-3% range, during discharge. I attribute that to the Peukert's Constant being set for lead acid battery discharge characteristics.

The battery is regularly recharged to 100%, which of course, automatically syncs the meters. The longest interval at partial state of charge was 21 days. At the end of that time, the FNDC was reading about 5% low.

Current readings from my system. Victron BMV700 via the Victron Connect app on top. FNDC via the Mate3s' internal web service on the bottom.

[CRJpn]

Good advice, thanks all. I will reconnect it and use it when we get home.

Raysun, long story short we had a tenant and communication wasn't great, no feedback at all if I tried to troubleshoot. I can't remember the details, but recall having a few discussions with our installer and making a couple calls to Outback, and finally everyone basically decided it would be better to disconnect it. I think she was getting confused on the SOC%. There were some other configuration issues I ironed out through OpticsRE over the past couple years, and the new firmware has helped some of the configuration resets that were happening. It's running really well now.

I have reviewed the new installer / operating guide for the FNDC (dated 2020), it seems more helpful than the prior one (dated 2007!). The shunts are still installed, so it should be pretty simple to reconnect.

Thanks for the advice, look forward to sharing and participating in the forum and hope everyone has a great 2022.

Regards
Chris

[ianMc]

Hi
When the SOC goes below 60% My Mate3 generates an error message. Is this your experience as well

Regards
Ian

[raysun]

Hi
When the SOC goes below 60% My Mate3 generates an error message. Is this your experience as well

Regards
Ian

Nope.

[raysun]

Raysun, long story short we had a tenant and communication wasn't great, no feedback at all if I tried to troubleshoot. I can't remember the details, but recall having a few discussions with our installer and making a couple calls to Outback, and finally everyone basically decided it would be better to disconnect it. I think she was getting confused on the SOC%

Of course this is strictly my imagination, but I suspect the installer and the support tech agreed that disconnecting the FNDC would stop the confusion.

[CRJpn]

Raysun, long story short we had a tenant and communication wasn't great, no feedback at all if I tried to troubleshoot. I can't remember the details, but recall having a few discussions with our installer and making a couple calls to Outback, and finally everyone basically decided it would be better to disconnect it. I think she was getting confused on the SOC%

Of course this is strictly my imagination, but I suspect the installer and the support tech agreed that disconnecting the FNDC would stop the confusion.

Yes fully agree! Was an adventure with the tenant...never again!