question

when you hit the minimum ess soc the system dedicates all solar to charging the batteries until it gets near the stop on charge limit set in the schedule.

you can reduce this second limit to allow it to cut back sooner.

Hi @Colin mackay,

That is an ENORMOUS system in a tiny battery.

Your system has the potential to pull 30 kW, that is ~600 A from a 560 Ah battery. This sizing would be ok for a lithium battery, but not for lead acid.

A regular (off grid) system design would be to have 5000 Ah of lead acid battery for such a load. 10 times as much.

A nice, safe, reliable charge and discharge rate for lead acid is C10, or 10% of it's Ah capacity in A.

It is very likely that your battery, if it is engaged at all by the charging (or discharging system) beyond that C10 (55A from a 550Ah battery, or ~2500W) will cause the battery voltage to behave very erratically, spiking high and low.

The system relies on a relatively stable battery voltage to make decisions about when to charge, discharge, load, pass thru power, trigger warnings or alarms.

It is going to be very difficult to make a stable system from this design, with very large potential load demand, PV supply and very small battery. The grid will be doing a lot more work, and will be supplying the system more often than necessary. Also at times, the PV may start to charge the battery, and the voltage will spike up very quickly, leading the PV to quickly back off.

Have a look at the Advanced tab DC battery voltages in VRM to see if you can see the effect I am talking about. If the battery reaches full voltage (~55V) or minimum voltage (~49V) it will adjust its behaviour to to protect the battery, (reducing PV, or preventing discharge from the battery).

These are higher priority triggers and will happen regardless of the reported State of Charge, or the thresholds.

Be sure to turn on the Maximum & minimum view with ~1 minute interval recording on the GX to help see.

These large voltage spikes also might be occurring too quickly to see, so also check the real time view (~2 seconds) around when it is likely to occur.

Have you switched on "DC..."?

Hi all - thanks for your answers.

The current battery is temporary only. We have resolved the issue -- the installer had each inverter connected to a seperate string of batteries -So each inverter was reading and discharging seperate parts of the battery. The system is now working perfectly.

My biggest issue now is the temperature that the MPPTs are running at. The ambient (managed by aircon) is around 23 degrees. The MPPT temperatures range from 42 degrees C to 53 degrees C - is this normal - it seem a little on the high side to me. Any ideas Guy?