off-grid system :: settings

11.19.2012-Monday

Some fine-tuning has been going on. The battery monitor has been super accurate the past few weeks. I have marked the changes with an asterisk. The charge efficiency factor (CEF) has been adjusted and through trial and error 85% has been reached as the appropriate charger efficiency. This is after trying 74%, 80%, and 95% before arriving at 85%. Current threshold (Ith) was increased to cancel out noise from the 12V timer, garage sensor, and two outside LEDs – we need at least a 1.2A load to register anything other than zero current on the battery monitor. Only when the timer is “ON” and the kitchen lights are on will the current draw register on the battery monitor. Tail current (It) has been increased from 0.5% and should now be about 12A as cut off for charged (when charge current <12A and >13.5V has been achieved monitor registers batteries as “charged”). Charged detection time (Tcd) has been adjusted so the battery monitor more easily registers a charged battery bank as 100% full sooner. Time to go (Tdt) has also been lengthened to 1 minute to more conviently show time remaining to 50% at a one-minute average load. Battery capacity (Cd) has been adjusted for winter – the batteries are cold (25-40°F).

Victron BMV-600s

• *85%-  CEF (charge efficiency factor)
• *1.20A – Ith (current threshold)
• 1.25 – PC (Peukert exponent)
• 13.5V – Vc (charged voltage)
• *850Ah – Cb (battery capacity)
• 50% – DF (discharge floor)
• *0.8% – It (tail current)
• *4 min – Tcd (charged detection time)
• *1 – Tdt (time to go)

3.9.2012 – Friday <PREVIOUS SET POINTS>

The off-grid system is now approaching the two year mark (sine the install date of the solar panels). With a second winter on the way out I’ve had a chance to learn some of the subtleties of our particular battery/inverter set up and have now arrived at a reasonably set list of device settings. A common question I’ve observed from those wanting to install their own system is, “what settings should I use for my charge controller?” From this many more device settings questions arise. The finer points of choosing device settings will rely on manufacturer specifications, particularly those from the battery manufacturer. With that in mind, here is a complete list of the settings I’m using:

 Xantrex C60

• 13.8V – FLOAT (CHG)
• 14.7V – BULK (CHG)

Xantrex MS3000

•  20A – Power Share
• 100% – Max Charge Rate
• 10.5V – Lo DC Volt
• FLA – Batt Type
• 1540Ah – Batt Size
• 85W – Sense Below
• 8s – Sense Interval
• 3 – # Chg Stages
• 15.5V – Egz Volts
• On – Force Charge
• 85V – Lo AC Volt
• 45Hz – Lo AC Freq
• 135V – Hi AC Volt
• 65Hz – Hi AC Freq

Victron BMV-600s

• 74%-  CEF (charge efficiency factor)
• 0.10A – Ith (current threshold)
• 1.25 – PC (Peukert exponent)
• 13.5V – Vc (charged voltage)
• 1500Ah – Cb (battery capacity)
• 50% – DF (discharge floor)
• 0.5% – It (tail current)
• 45 min – Tcd (charged detection time)
• 0 – Tdt (time to go)

CEF (Victron BMV-600s) is a particularly tricky setting. I may return to this post and edit that value from time to time. So far I’ve only been able to determine that 90% is too high, 50% is too low, and 74% is my best guess at this time.