Legrand MEGALINE 5000 UPS Battery Charging via Solar Charger for Off-Grid Use Feasibility

Welcome esteemed colleagues

I have a small photovoltaic installation with a current capacity is about 1kW
The feeding of energy into the grid via an On-Grid inverter has proven to be a rather problematic issue (without going into details, it is about the ZE electronic meter and one-way metering )

The crux of the matter:
Is it possible to implement additional battery charging in the OnLine UPS Legrand MEGALINE 5000
If I connect a solar charger to the battery and raise the charging voltage a little, I can charge the battery. If I connect the solar charger to the battery and raise the charging voltage slightly, will I force the power to be drawn from the panels and won't the power inverter go crazy?

I am not interested in answers such as : and for what , and why ?

Concrete
Will it work or not , or what upgrades does it require and is it feasible ?

It will work ... .only you need to ensure the whole photovoltaic installation is electrically isolated rather . Often the batteries are at a dangerous potential ( simpler : the poles kick in ) .

And good , then off grid OFF GRID this problem falls away . In my camper I have a battery powered in this way from cells and a turbine and to this a 2 KW inverter . It works .

I see a problem.
If I wanted to do a hybrid , i.e. take some power from the mains and some from the panels then a DC Booster or otherwise a Voltage Booster could be a problem.
It is a kind of DC/DC inverter, which raises the voltage from the batteries.
I do not know if it is possible to force the system to work in parallel ?
.

From the schematic it appears that the batteries are not fed directly from the AC/DC rectifier , only a charger is installed.
To make it funnier an additional more powerful one can be installed .
I would prefer to keep the full efficiency of this UPS with the additional possibility of using PV panels.
I don't know what upgrades this would require though.
Probably the best solution would be to put the voltage from the panels between the AC/DC rectifier and the DC/AC inverter.
alternatively, purchase a UPS that has the batteries supplied directly from the AC/DC rectifier

Incredible Giga Fart !!!
I have a 315W PV cell

At idle it gives about 42,3v
When connected to the UPS I bought ( parallel to the battery.), the UPS switches itself to work with the battery. + cell.
Probably the reason is that it detects an "overcharge" of the battery.

In other words, I have a cheap Off-Grid Hybrid Inverter

There is also a drawback to this behaviour in the UPS
It turns out that when the battery is discharged. , the UPS shuts down

Any ideas on how to get around the problem of the UPS shutting down when the battery is discharged so that it does not shut down but recharges ?

Added after 19 [hours] 48 [minutes]:

After investigating the matter more thoroughly, it turned out that after discharging the batteries and shutting down, the UPS waits about 30s and switches on again returning to normal operation.
The only drawback is this time interval in which there is no power.

Is it possible to set this somehow by software or otherwise ?