FoxESS Community - Owners & Installers Forum

Noticed an oddity with the Force Charge option over the last few days.
Normally with the battery run down to 20%, it started charging at max inverter ( 5Kw) and stayed
there until its done.

Recently however the first hour approx is only charging at 3Kw , and then it jumps up to 5Kw for the next 2 hrs.
Which is a nuisance as it no longer completely charges during the Octopus Flux cheap 2-5 am window !

Is this something to do with the temperature of the batteries ?
Or is it because the missus has started running appliances at 2am ?

Most likely to be temperature of the batteries, the BMS starts to throttle the charge current below 20C, but you don’t really notice any effect on charging until the batteries have dropped below 15C, they will stop charging altogether at 0C.

When they charge they generate heat and self warm, so depending on the temperature they may be throttled until the batteries are safe to charge at higher current.

Are the batteries located where is it cold ?, if they are exposed to very cold temperatures (like a loft space or unheated garage), it is better to box them in with insulation board or similiar - you’ll find a few posts on this over the last week because of the very low temperatures (this is one here viewtopic.php?t=544 )

I’ve attached the Foxess chart which shows the max charge current for any given temperature - the power will depend on your battery stack and it’s voltage Power = I * V where I = battery charge current, V = battery volts.

Thanks, that looks like a useful chart.
Yes, the batteries are in an unheated garage