XW 4548 grid-tie and MPPT-60 hunting

[aj164]

I just upgraded the firmware on a grid-tied XW setup. It has 105AH of AGM batteries (48V) and 3.2kW PV array. (The discussion on low battery cap vs PV is in another thread.)

With the latest firmware (from Xantrex website), I noticed the XW hunting between sell back and charge. (The charger on the XW is currently enabled.) We had about 500W of solar power available that evening. The battery amps would slowly alternate between +1.7A and -0.5A with a cycle time of maybe 15 seconds. Loads on the sub-panel were around 125W at the time, and the rest available to sell back or charge the battery.

I also changed the battery charge settings to those recommended by DEKA for their AGM batteries. The voltages are significantly lower than the Xantrex default for AGM, which we had been running. The new values are:

bulk/absorb: 55.2
absorb time: 120min
float: 54.0
eq: 56.4
XW sell voltage: 52.8

I know AGM is not supposed to EQ, but the DEKA EQ voltage is very low, and I think 56.4V was the Xantrex default for bulk/absorb.

We're waiting for a sunny day to see what it does under heavy PV power.

-AJ

[Solar Guppy]

The newer firmware hunts more than the older version, your inadequate battery bank will just make the issue worse. For a 4kw sell, your system requires 400ah battery bank, until you address this you will have issues.